Tropical Roots and Tubers E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: IFST Advances in Food Science
• Sprache: Englisch

Seitenzahl: 1196

Veröffentlichungsjahr: 2016

Beschreibung

Roots and tubers are considered as the most important food crops after cereals and contribute significantly to sustainable development, income generation and food security especially in the tropical regions. The perishable nature of roots and tubers demands appropriate storage conditions at different stages starting from farmers to its final consumers.  Because of their highly perishable nature, search for efficient and better methods of preservation/processing have been continuing alongside the developments in different arena.
This book covers the processing and technological aspects of root and tuber foods, detailing the production and processing of roots and tubers such as taro, cassava, sweet potato, yam and elephant foot yam. Featuring chapters on anatomy, taxonomy and physiology, molecular and biochemical characterization, GAP, GMP, HACCP, Storage techniques, as well as the latest technological interventions in Taro, Cassava, Sweet potato, yam and Elephant foot Yam.

Leseprobe

Table of Contents

Cover

About the IFST Advances in Food Science Book Series

Forthcoming titles in the IFST series

List of Contributors

Preface

Chapter 1: Introduction to Tropical Roots and Tubers

1.1 Introduction

1.2 Roots and Tubers

1.3 Requirements for the Higher Productivity of Tropical Roots and Tubers

1.4 World Production and Consumption

1.5 Constraints in Tropical Root and Tuber Production

1.6 Classification and Salient Features of Major Tropical Roots and Tubers

1.7 Composition and Nutritional Value

1.8 Characteristics of Tropical Roots and Tubers

1.9 Anti‐nutritional Factors in Roots and Tubers

1.10 Applications of Tropical Roots and Tubers

1.11 New Frontiers for Tropical Roots and Tubers

1.12 Future Aspects

References

Chapter 2: Taxonomy, Anatomy, Physiology and Nutritional Aspects

2.1 Introduction

2.2 Taxonomy of Roots and Tuber Crops

2.3 Anatomy

2.4 Physiology of Root and Tuber Crops

2.5 Nutritional Perspective in Root and Tuber Crops

References

Websites:

Chapter 3: Tropical Roots and Tubers: Impact on Environment, Biochemical, Molecular Characterization of Different Varieties of Tropical Roots and Tubers

3.1 Introduction

3.2 Genetic Diversity

3.3 Cassava

3.4 Sweet Potato

3.5 Taro

3.6 Yams

3.7 Future Aspects

References

Chapter 4: Good Agricultural Practices in Tropical Root and Tuber Crops

4.1 Introduction

4.2 Cassava

4.3 Sweet Potato

4.4 Yams

4.5 Elephant Foot Yam

4.6 Taro

4.7 Coleus

4.8 Arrowroot

4.9 Yam Bean

4.10 Future Perspectives

4.11 Summary and Future Research

References

Chapter 5: Fermented Foods and Beverages from Tropical Roots and Tubers

5.1 Introduction

5.2 Food Fermentation

5.3 Summary and Future Perspectives

References

Chapter 6: Storage Techniques and Commercialization

6.1 Introduction

6.2 Problems faced during Storage and their Preventive Measures

6.3 Losses Observed during Various Stages at the Time of Marketing

6.4 Methods employed for Storage of Roots and Tubers

6.5 Commercialization

6.6 Factors affecting Commercialization

6.7 Key Products and Final Markets for Commercialization

6.8 Trends in Commercialization

6.9 Future Research

References

Chapter 7: Good Manufacturing Practices for Processing of Tropical Roots and Tubers

7.1 Introduction

7.2 Good Manufacturing Practices (GMP)

7.3 Key Importance of GMPs for Roots and Tubers

7.4 GMP Components

7.5 GMPs in Low‐income Countries

7.6 Conclusions

7.7 Acknowledgements

References

Chapter 8: Controlling Food Safety Hazards in Root and Tuber Processing: An HACCP Approach

8.1 Food Safety

8.2 Food Safety Hazards

8.3 Hazard Analysis Critical Control Point (HACCP)

8.4 Roots and Tubers

8.5 Summary and Future Research

References

Chapter 9: Taro: Technological Interventions

Chapter 9.1: Taro Flour, Achu and Starch

9.1.1 Taro

9.1.2 Versatility of Taro

9.1.3 Processing Constraints

9.1.4 Solutions to Resolve Processing Constraints

9.1.5 Taro Flour

9.1.6 Achu

9.1.7 Taro Starch

References

Chapter 9.2: Bakery Products and Snacks based on Taro

9.2.1 Introduction

9.2.2 Bakeries

9.2.3 Snacks

9.2.4 Conclusion and Future Aspects

References

Chapter 9.3: Other Taro‐based Products

9.3.1 Introduction

9.3.2 Taro Ice Products

9.3.3 Frozen Taro

9.3.4 Preparation of Fermented Taro Paste

9.3.5 Taro Yogurt

9.3.6 Taro Noodles

9.3.7 Taro‐based Baby Food

9.3.8 Preparation of Spherical Aggregate from Taro Starch

9.3.9 Baking and Boiling of Taro Leaves

9.3.10 Taro Flour as a Soup Thickener

9.3.11 Pounded Taro (Achu)

9.3.12 Production of a Taro‐based Spiced Soup: A Case Study

9.3.13 Conclusion and Future Aspects

References

Chapter 10: Cassava: Technological Interventions

Chapter 10.1: Cassava Flour and Starch: Processing Technology and Utilization

10.1 Introduction

10.2 Cassava Flours

10.3 Cassava Starch

References

Chapter 10.2: Other Cassava‐based Products

10.2.1 Introduction

10.2.2 Snacks

10.2.3 Cassava‐based Beverages

10.2.4 Major Popular Meals

10.2.5 Recent Findings and On‐going Studies

10.2.6 Summary and Future Research

10.2.7 Acknowledgements

References

Chapter 11: Sweet Potato: Technological Interventions

Chapter 11.1: Sweet Potato Flour and Starch

11.1.1 Introduction

11.1.2 Sweet Potato Flour

11.1.3 Basic Steps in Production of Sweet Potato Flour

11.1.4 Methods for Production of Sweet Potato Flour

11.1.5 Properties of Sweet Potato Flour

11.1.6 Starch

11.1.7 Basic Steps of Production

11.1.8 Recent Developments for Extraction of Sweet Potato Starch

11.1.9 Physicochemical Properties of Sweet Potato Starch

11.1.10 Pasting Properties of Sweet Potato Starch

11.1.11 Rheological Properties

11.1.12 Morphological Properties

11.1.13 Modified Starches

11.1.14 Utilization

11.1.15 Future Aspects

References

Chapter 11.2: Bakery Products and Snacks based on Sweet Potato

11.2.1 Introduction

11.2.2 Sweet Potato Bread

11.2.3 Sweet Potato Cookies

11.2.4 Purple Sweet Potato Cakes

11.2.5 Instant Nutritious Sweet Potato Chips

11.2.6 Puffed Sweet Potato Food

11.2.7 Airflow Puffed Sweet Potato Chips

11.2.8 Aromatic and Crispy Sweet Potato Chips

11.2.9 Low Temperature Vacuum Fried Sweet Potato Chips

11.2.10 Vacuum Microwave Drying Sweet Potato Chips

11.2.11 Sun Dried Sweet Potato Slices

11.2.12 Summary and Future Research

References

Chapter 11.3: Other Sweet Potato‐based Products

11.3.1 Introduction

11.3.2 Sweet Potato Jelly

11.3.3 Instant Sweet Potato Noodles

11.3.4 Quick‐frozen Sweet Potato Product

11.3.5 Sweet Potato Healthcare Tea

11.3.6 Sweet Potato Shoot‐tip Canning

11.3.7 Sweet Potato Beer

11.3.8 Purple Sweet Potato Juice

11.3.9 Sweet Potato Whole Flour

11.3.10 Sweet Potato Healthcare Food

11.3.11 Sweet Potato Leaf Powder

References

Chapter 12: Yam: Technological Interventions

12.1 Introduction

12.2 Importance of Yam in Tropical Regions

12.3 Yam Production

12.4 Consumption of Yam

12.5 Composition of Yam

12.6 Yam Processing and Utilization

12.7 Effects of Processing on the Quality of Yam

12.8 Technological Application to Yam Processing

12.9 Summary and Future Research

References

Chapter 13:

Amorphophallus

: Technological Interventions

13.1 Introduction

13.2 Habit, Habitat and Distribution

13.3 Nutritional and Anti‐nutritional Factors

13.4 Traditional Processing and Value Addition of EFY

13.5 EFY Processing with Technological Interventions

13.6 A. konjac K. Koch as Industrial Crop

13.7 Processing as Pharmaceutical Supplements

13.8 Summary and Future Perspectives

References

Index

End User License Agreement

List of Tables

Chapter 1: Introduction to Tropical Roots and Tubers

Table 1.1 Origin of tropical roots and tubers

Table 1.2 Annual, biennial and perennial roots/tubers

Table 1.3 World cassava areas, yield and production from 1995–2011

Table 1.4 World leading tropical roots and tubers producers in 2012

Table 1.5 Tropical roots and tubers: salient features

Table 1.6 Comparison of nutritional profile of various tropical roots and tubers

Table 1.7 Comparison of various tropical roots and tubers

Table 1.8 Anti‐nutritional factors in roots and tubers and their mode of elimination

Chapter 2: Taxonomy, Anatomy, Physiology and Nutritional Aspects

Table 2.1 The different edible tubers and root crops of tropical and subtropical regions

Table 2.2 Origin, morphological and genetic composition of Roots and tuber crops

Table 2.3 Taxonomic position of Roots and Tuber crops

Table 2.4 Macro nutrients of major tuber or root crops from tropics

Table 2.5 Minor nutrients ‐ minerals of major tuber or root crops from tropics

Table 2.6 Minor nutrients ‐ vitamins of major tuber or root crops from tropics

Chapter 3: Tropical Roots and Tubers: Impact on Environment, Biochemical, Molecular Characterization of Different Varieties of Tropical Roots and Tubers

Table 3.1 Different molecular markers used for cassava diversity studies

Table 3.2 Various mapping populations used in genome and gene mapping in cassava

Table 3.3 Different molecular markers used for sweet potato diversity studies

Table 3.4 Various mapping populations used in genome and gene mapping in sweet potato

Table 3.5 Different molecular markers used for taro diversity studies

Table 3.6 Various mapping populations used in genome and gene mapping in Taro

Table 3.7 Different molecular markers used for yams diversity studies

Table 3.8 Various mapping populations used in genome and gene mapping in yams

Chapter 4: Good Agricultural Practices in Tropical Root and Tuber Crops

Table 4.1 Major cassava‐producing countries in the world (2013–14)

Table 4.2 Prominent cultivars of cassava and their characteristics

Table 4.3 Fertilizer doses for cassava

Table 4.4 Major sweet potato producing countries in the world (2013–14)

Table 4.5 Prominent genotypes of sweet potato and their characteristics

Table 4.6 Major yam producing countries in the world (2013–14)

Table 4.7 Prominent cultivars of yam and their characteristics

Table 4.8 Major colocasia producing countries in the world (2013–14)

Table 4.9 Prominent cultivars of colocasia and their characteristics

Chapter 5: Fermented Foods and Beverages from Tropical Roots and Tubers

Table 5.1 Microorganisms associated with fermented foods from tropical roots/ tubers crops

Table 5.2 Biochemical composition of wine and medicated wine prepared from sweet potato

Chapter 6: Storage Techniques and Commercialization

Table 6.1 Major causes of loss in roots and tubers

Table 6.2 Conditions for storage of roots and tubers

Table 6.3 Toxicity/microbial spoilage from/in tropical roots and tubers during storage and their preventive measures

Table 6.4 Pest infestation in tropical roots and tubers

Table 6.5 Factors to be taken into consideration at different stages to avoid losses in roots and tubers

Table 6.6 Conditions required for curing of roots and tubers

Table 6.7 Recommended storage conditions for tropical roots and tubers

Table 6.8 Various techniques employed for tropical roots and tubers to enhance quality and shelf life

Chapter 7: Good Manufacturing Practices for Processing of Tropical Roots and Tubers

Table 7.1 Major components of GMP

Table 7.2 Basic requirements of GMP

Table 7.3 Different water quality standards

Table 7.4 Information required for identification of R and T products by labelling

Table 7.5 Different disinfectants for premises for tropical roots and tubers

Table 7.6 Format for complaint report

Table 7.7 Requirements to be put into practice

Table 7.8 Skill requirements in various areas

Table 7.9 Features required for effective layout

Table 7.10 Colour codes of pipelines for processing industry

Table 7.11 Recommended illumination in premises

Table 7.12 Different materials and their properties: A criterion of acceptance/rejection

Chapter 8: Controlling Food Safety Hazards in Root and Tuber Processing: An HACCP Approach

Table 8.1 Examples of some outbreak due to chemical hazards

Table 8.2 Requirements of HQCF and fufu flour

Table 8.3 Quality requirements for HQCF and fufu flour

Table 8.4 Physico‐chemical and microbiological requirements for HQCF and fufu flour

Table 8.5 The level of contaminants for HQCF and fufu flour

Table 8.6 An HACCP plan identifying the control point and critical control points for the production of HQCF

Table 8.7 An HACCP plan identifying the critical control points for the production of

fufu

flour

Table 8.8 Requirements of sweet potato chips

Table 8.9 Physico‐chemical and microbiological requirements for dried sweet potato chips

Table 8.10 Level of contaminants for dried sweet potato chips

Table 8.11 HACCP plan for the production of sweet potato chips

Chapter 9.1: Taro Flour, Achu and Starch

Table 9.1.1 Composition of taro

Table 9.1.2 Anti‐nutritional factors in taro

Table 9.1.3 Various processing constraints in taro and their mode of elimination

Table 9.1.4 Effects of blanching of taro (

Colocasia esculenta

)

Table 9.1.5 Chronological progression for the production of taro flour

Table 9.1.6 Proximate composition, colour values and functional properties of flours from different botanical sources

Table 9.1.7 Comparative visco‐elastic characteristics of traditional and reconstituted‐flour achu

Table 9.1.8 Some physicochemical and textural properties of traditional and reconstituted achu

Table 9.1.9 Fractional analysis of carbohydrate content of taro corm

Table 9.1.10 Chronological progression of the recent developments for the extraction of taro starch

Chapter 9.2: Bakery Products and Snacks based on Taro

Table 9.2.1 Mixture design plan for the preparation and some characteristics of taro‐wheat‐gum blend flour

Table 9.2.2 Alveographic characteristics of wheat taro composite dough as affected by the level of taro flour, Ibo coco variety

Table 9.2.3 Formulation of the snap taro cookie

Table 9.2.4 Some physical characteristics of taro‐wheat composite biscuits

Chapter 9.3: Other Taro-based Products

Table 9.3.1 Comparative cooking, textural and sensory properties of dough made from wheat flour and 50% blends with taro and sweet potato

Table 9.3.2 Yields, protein and carbohydrate compositions of some extracted taro mucilage

Table 9.3.3 Coded and actual values (g/L) of

D glomerata

,

X parviflora

and

S zenkeri

used in the Central Composite Rotatable Designs

Table 9.3.4 Antioxidant properties of individual ingredients that composed Oxisoup

Table 9.3.5 Predicted optimum level of spices for use in the preparation of Oxisoup

Chapter 10.1: Cassava Flour and Starch: Processing Technology and Utilization

Table 10.1.1 Description of technological effect of processing steps during CF manufacture

Table 10.1.2 The types of cassava products studied by previous authors

Table 10.1.3 Standards for CF

Table 10.1.4 Pasting properties of some flour from root and tuber crops

Table 10.1.5 Standard for cassava starch

Table 10.1.6 Food and non‐food utilization of CS

Chapter 10.2: Other Cassava-based Products

Table 10.2.1 Physicochemical properties of gari

Table 10.2.2 Specification of gari from selected African Standard and Codex

Table 10.2.3 Proximate composition of gari and lafun

Chapter 11.1: Sweet Potato Flour and Starch

Table 11.1.1 Composition of sweet potato

Table 11.1.2 Chronological progression for the production of sweet potato flour

Table 11.1.3 Problems encountered during storage of sweet potato flour

Table 11.1.4 Comparison of characteristics of sweet potato starch with other starches

Table 11.1.5 Chronological progression of the recent developments for the extraction of sweet potato starch

Table 11.1.6 Amylose content, water absorption capacity and oil absorption capacity of sweet potato starch

Table 11.1.7 Swelling power and solubility of sweet potato starch

Table 11.1.8 Pasting properties of sweet potato starch

Table 11.1.9 Pasting properties of sweet potato starch

Table 11.1.10 Rheological properties of sweet potato starch

Chapter 11.2: Bakery Products and Snacks based on Sweet Potato

Table 11.2.1 Formulation of sweet potato cookies

Table 11.2.2 The formulation of purple sweet potato cake

Table 11.2.3 Effect of water and oil addition on puffing

Table 11.2.4 Effect of rice and millet addition on puffing

Table 11.2.5 Quality standards of the puffed sweet potato food

Table 11.2.6 Optimum processing parameters for air puffed sweet potato chips

Table 11.2.7 The parameters for vacuum microwave drying technology

Chapter 11.3: Other Sweet Potato-based Products

Table 11.3.1 Effect of ingredient content (%) on the quality of sweet potato jelly

Table 11.3.2 Optimum processing conditions of enzymatic (amylase) hydrolysis

Table 11.3.3 Optimum processing conditions of the secondary enzymatic hydrolysis

Table 11.3.4 Amino acid composition of protein derived from sweet potato variety 55‐2

a

Table 11.3.5 Essential amino acid composition of SSP compared to the WHO “ideal protein”

Chapter 12: Yam: Technological Interventions

Table 12.1 Cultivated areas (`000 ha) and yield (t/ha) of yam in 2005–2013 in yam zone

Table 12.2 World‐wide and African consumption (1000 ton) of yam in year 2005–2011

Table 12.3 Composition of yam tuber

Table 12.4 Composition of pounded yam

Table 12.5 Composition and brown index of stiff dough

Table 12.6 Proximate composition of instant yam flour

Table 12.7 Pasting properties of flour from

Dioscorea

species

Table 12.8 Effect of processing on the functional properties of yam flour

Table 12.9 Starch shape and average granule size

Table 12.10 Effect of processing on the nutrients in yam

Table 12.11 Effect of processing on anti‐nutrients composition in yam

Chapter 13:

Amorphophallus

: Technological Interventions

Table 13.1 Proximate biochemical composition of EFY (on dry weight basis)

Table 13.2 Summary of nutritional aspects of konjac Glucomannan (KGM)

List of Illustrations

Chapter 1: Introduction to Tropical Roots and Tubers

Figure 1.1 Post‐harvest handling stages in the storage of tropical roots and tubers.

Figure 1.2 Various tropical roots and tubers.

Figure 1.3 Commodity value scheme for tropical roots and tubers.

Chapter 2: Taxonomy, Anatomy, Physiology and Nutritional Aspects

Figure 2 (2.1) Desert yam flower (2.2) Desert yam tuber (2.3) Potato tuber (2.4) Sweet potato roots (2.5) Cassava (2.6) Yautia. Desert yam photographs were reproduced with permission from Barry Filshie and the Australia & Pacific Science Foundation and The Royal Botanic Gardens Sydney. Link: http://www.apscience.org.au/projects/APSF_04_3/apsf_04_3.htm Cassava photographs were reproduced with permission from Jesse, Link: http://tongatime.com/tag/yam/. Photographs of Yautia were reproduced with permission from Andrew Grygus, Link: http://www.clovegarden.com/ingred/am_arum.html

Figure 2 (2.7) Taro (2.8) Elephant Ears (2.9) Dioscorea (yams) (2.10) Wild yam (2.11) Arracacha (2.12) Parsnip. Photographs of Taro were reproduced with permission from Andrew Grygus, Link: http://www.clovegarden.com/ingred/am_arum.html. Elephant Ears photographs were reproduced with permission from Jesse, Link: http://tongatime.com/tag/yam/. Photograph of Yams (Dioscorea) was reproduced with permission from Nandan Kalbag, Link: http://gardentia.net. Wild mountain yam photograph was reproduced with the permission from Alan Carter, Link: https://scottishforestgarden.wordpress.com

Figure 2 (2.13) Celeriac (2.14) Parsley (2.15) Pignuts or Earthnuts (2.16) Skirret (2.17) Carrot (2.18) Arrowroot. Celeriac photographs were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/Ce‐Ch.html. Photograph of Pignuts and Skirret were reproduced with the permission from Alan Carter, Link: https://scottishforestgarden.wordpress.com

Figure 2 (2.19) Ginger (2.20) Chufa tuber in soil (2.21) Oca (2.22) Different colored Ulluco (2.23) Beet (2.24) Mauka. Chufa tuber photographs were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/Ch_2.html. Photographs of Oca were reproduced with the permission from Alan Carter, Link: https://scottishforestgarden.wordpress.com. Photographs of different colored ulluco and Mauka were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/Ulluco.html and http://home.scarlet.be/∼fk392454/mauka.html

Figure 2 (2.25) Jicama (2.26) Hogpotato (2.27) Earthnut Pea (2.28) Mashua (2.29) Turnip (2.30) Radish. Photographs of Jicama were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/I‐J.html. Photographs of Hogpotato and Earthnut Pea were reproduced with the permission from Alan Carter, Link: https://scottishforestgarden.wordpress.com. Photographs of Mashua were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/Mashua.html

Figure 2 (2.31) Daikon (2.32) Maca (2.33) Jerusalem Artichoke (2.34) Salsify (2.35) Chicory root (2.36) Burdock. Photograph of Jerusalem Artichoke, Salsify and Burdock were reproduced with permission from Andrew Grygus, Link: http://www.clovegarden.com/ingred/am_arum.html. Photographs for Chicory root were reproduced from Wikimedia Commons and the credited to by Rasbak at nl.wikipedia (seriously color balanced),licensed under Creative Commons Attribution‐ShareAlike v3.0 and Michel Chauvet distributed under license Creative Commons Attribution‐Share Alike 3.0 Unported., respectively, and obtained with help of Andrew Grygus. Photograph of Maca was reproduced from Wikimedia Commons and credited to “Maca”. Licensed under Public Domain via Wikimedia Commons ‐ http://commons.wikimedia.org/wiki/File:Maca.gif#mediaviewer/File:Maca.gif

Figure 2 (2.37) Yacon (2.38) Dandelion (2.39) Chinese Artichoke (2.40) Daylily roots (2.41)

Amorphophallus Konjac

(2.42)

Amorphophallus paeoniifolius

. Photographs of Chinese Artichoke were reproduced with the permission from Alan Carter, Link: https://scottishforestgarden.wordpress.com. Photographs of Yacon and Dandelion were reproduced with permission from Frank van Kiersbilck, Link: http://home.scarlet.be/∼fk392454/yacon.html and http://home.scarlet.be/∼fk392454/D‐E.html. Photograph of Amorphophallus konjac was reproduced from Wikimedia Commons and the credited to “Amorphophallus konjac knolle” by Sebastian Stabinger ‐ http://de.wikipedia.org/wiki/Bild:Amorphophallus_konjac_knolle_155gramm.jpg. Licensed under CC BY‐SA 3.0 via Wikimedia Commons ‐ http://commons.wikimedia.org/wiki/File:Amorphophallus_konjac_knolle.jpg#mediaviewer/File:Amorphophallus_konjac_knolle.jpg”. Photographs of Daylily were “Reproduced with permission from Catherine Herms and Ohio State Weed Lab Archive, The Ohio State University. Photograph of Amorphophallus paeoniifolius was “Reproduced from Wikimedia Commons and the credited to “” by Original uploaded by Aruna (Transferred by sreejithk2000) ‐ Original uploaded on ml.wikipedia.LicensedunderCCBY‐SA3.0viaWikimediaCommons. Link: http://commons.wikimedia.org/wiki/File:%E0%B4%9A%E0%B5%87%E0%B4%A8.JPG#mediaviewer/File:%E0%B4%9A%E0%B5%87%E0%B4%A8.JPG”.

Figure 2 (2.43) Garlic and (2.44) Onion.

Figure 2 (2.45) (A) Anatomical structure of Root. (B) Cross‐sectional view of Dicot and Monocot roots. (C) Anatomical structure of stem. (D) Plant cells and structural components of xylem and phloem. (E) Leaf anatomical structure. Courtesy: Dr. G.R. Kantharaj, Principal Scientist (Retd.), Genetic Engineering Lab, IAHS, Bangalore, India.

Figure 2 (2.46) Physiological changes accompanying Storage root formation.

Figure 2 (2.47) Physiological changes accompanying Tuberization.

Chapter 5: Fermented Foods and Beverages from Tropical Roots and Tubers

Figure 5.1 Novel fermented products prepared from sweet potato at RC‐CTCRI, Bhubaneswar: (a) anthocyanin rich wine; (b) herbal wine; (c) beer; (d) lacto juice: (e) curd; and (f) lacto pickle.

Chapter 6: Storage Techniques and Commercialization

Figure 6.1 Effect of temperature on lesion diameter in root slices of sweet potato cultivar

Yanshu 1

inoculated with post‐harvest pathogens,

Botryodiplodia theobromae, Rhizopus oryzae

and

Rhizopus stolonifer

and incubated for 24 hours.

Chapter 7: Good Manufacturing Practices for Processing of Tropical Roots and Tubers

Figure 7.1 GMPs as common matrix in food safety programme.

Chapter 8: Controlling Food Safety Hazards in Root and Tuber Processing: An HACCP Approach

Figure 8.1 The seven HACCP principles.

Figure 8.2 The decision tree (Source: NACMCF, 1997).

Figure 8.3 Origin of some root and tuber crops.

Figure 8.4 An example of good layout for food processing.

Figure 8.5 Identification of Critical Control Points (CCPs) for HQCF (Obadina

et al.,

2014).

Figure 8.5 Identification of Critical Control Points (CCPs) for

fufu

flour.

Figure 8.6 Identification of critical control points (CCPs) for instant yam flour (Obadina

et al.,

2014).

Figure 8.7 Identification of CCPs for sweet potato chips.

Chapter 9.1: Taro Flour, Achu and Starch

Figure 9.1.1 Taro corm.

Figure 9.1.2 Schematic representation of taro flour production.

Figure 9.1.3 Production of taro flour.

Figure 9.1.4 Flow diagram for the production of TTA, TFA and TCA.

Figure 9.1.5 Gelatinization curves of fresh taro macerate and processed taro flour (Njintang, 2015a).

Figure 9.1.6 Traditional and reconstituted achu (Njintang, 2015).

Figure 9.1.7 Wet milling process for taro starch extraction.

Chapter 9.2: Bakery Products and Snacks based on Taro

Figure 9.2.1 Effect of incorporation of

Grewiamollis

gum and taro flour on firmness of composite bread.

Figure 9.2.2 Effect of incorporation of

Grewiamollis

gum and taro flour on overall acceptability of composite bread.

Figure 9.2.3 Whiteness of the crust (A) and crumb (B) of composite bread as affected by the levels of Grewiamollis gum and taro flour.

Figure 9.2.4 Some pictures of bread as affected by level of taro and gums in the composite: (A) 100% wheat; (B) 70% wheat, 30% taro and 0% gum; (C) 65% wheat, 30% taro and 5% gum.

Figure 9.2.5 Effect of variety and level of taro flour incorporation on soluble proteins of biscuits.

Figure 9.2.6 Effect of variety and level of taro flour incorporation on soluble sugars of biscuits.

Figure 9.2.7 Typical surface plot for the effect of digestion time and level of taro flour on the

in vitro

carbohydrate digestibility of biscuits (

Egg‐like

variety).

Figure 9.2.8 Effect of variety and level of taro flour incorporation on water absorption capacity of biscuits.

Figure 9.2.9 Effect of variety and level of taro flour incorporation on water solubility index of biscuits.

Figure 9.2.10 Some idioblasts identified in taro corm. (a) raphide idioblast with one end ejection; (b) raphide idioblast with two end ejection; (c) druse idioblast; (d) inoffensive idioblast.

Figure 9.2.11

Colocasia esculenta

corm, ecotype

Ibo coco

.

Chapter 9.3: Other Taro-based Products

Figure 9.3.1 General flow sheet for formulation and preparation of weaning foods from taro and soy blend.

Figure 9.3.2 Scanning electron microscopy of natural occurring compound starch in taro corms (Njintang, 2003).

Figure 9.3.3 Achu and yellow soup in Cameroon (a) and served form in the West Africa (b).

Figure 9.3.4 Proposed flow diagram for the production of instant achu powder.

Figure 9.3.5 Typical surface plot for the effect of [

D. glomerata

] vs [

X. parviflora

] (a) and [

S. zenkeri

] (b) on flavonoids content of Oxisoup.

Chapter 10.1: Cassava Flour and Starch: Processing Technology and Utilization

Figure 10.1.1 Production of cassava between 2000 and 2013 (source: FAO, 2014).

Figure 10.1.2 Some mobile micro scale cassava processing units (a) mobile cassava graters; (b) mobile batch mechanical press (source: Fieldwork, 2010).

Figure 10.1.3 Typical smoke drying facility for dying fermented cassava mash in West Africa (source: Shittu

et al

., 2005).

Figure 10.1.4 Flash dryer (source: Sanni

et al.

, 2006).

Figure 10.1.5 Water vapor adosprtion isotherm of fufu, pupuru and lafun flours at 27°C (source: Shittu

et al

., 2015a).

Figure 10.1.6 Composite bread sample by substituting 10% of WF with flours from different cassava genotypes bread by IITA (98/0002, 99/6012, 98/0002, 92b/0061, 82/00058) grown with or without NPK fertilizer (source: Shittu, 2007).

Figure 10.1.7 Starch extraction process from cassava roots.

Chapter 10.2: Other Cassava-based Products

Figure 10.2.1 Process flow for agbeli kaklo production.

Figure 10.2.2 Process flow for ayigbe biscuit production.

Figure 10.2.3 Process flow for ready‐to‐prepare abacha production and preparation.

Figure 10.2.4 Process flow for fried cassava chips production.

Figure 10.2.5 Process flow for akara‐akpu production.

Figure 10.2.6 Process flow of tapioca production.

Figure 10.2.7 Process flow for Nigerian fufu.

Figure 10.2.8 Process flow for gari and kpokpo gari production.

Figure 10.2.9 Process flow for

attieke

and

attoukpou

processing.

Figure 10.2.10a Process flow for kokonte flour production.

Figure 10.2.10b Process flow for kokonte preparation.

Figure 10.2.11 Process flow for the production

of

agbelima.

Photograph 10.2.1 Packaged agbeli kaklo for sale.

Photograph 10.2.2

Ayigbe

biscuit purchased from a local seller.

Photograph 10.2.3a Ready‐to‐prepare abacha.

Photograph 10.2.3b Abacha /African salad.

Photograph 10.2.4 Fried cassava chips.

Photograph 10.2.5 Akara‐akpu as served at home.

Photograph 10.2.6a Tapioca grits as sold in a Ghanaian market.

Photograph 10.2.6b Value‐ added tapioca from Benin.

Photograph 10.2.7 Cassava bankye ampesie with pepper sauce and egg.

Photograph 10.2.8a Lady pounding fufu.

Photograph 10.2.8b A bowl of pounded fufu (cassava and plantain).

Photograph 10.2.8c Fufu as served at home.

Photograph 10.2.9 Nigerian fufu served with bitter leaf soup.

Photograph 10.2.10a Packaged gari sold at a local market.

Photograph 10.2.10b Eba and agushi soup.

Photograph 10.2.10c Dumped gari and “shito” with sardine.

Photograph 10.2.10d Gari soakings with roasted groundnuts.

Photograph 10.2.11 Attieke served at home.

Photograph 10.2.12 Attoukpou sold on the market.

Photograph 10.2.13a Packaged kokonte sold at a local market.

Photograph 10.2.13b Ball of kokonte served with groundnut soup at a local restaurant.

Photograph 10.2.14 Ball of placali prepared at home.

Photograph 10.2.15 Agbelima sold at a local market.

Chapter 11.1: Sweet Potato Flour and Starch

Figure 11.1.1 Schematic representation of sweet potato flour production.

Chapter 11.2: Bakery Products and Snacks based on Sweet Potato

Figure 11.2.1 Technological process of sweet potato bread.

Figure 11.2.2 Sweet potato bread.

Figure 11.2.3 Bread with sweet potato stuffing.

Figure 11.2.4 Technological process for sweet potato cookies.

Figure 11.2.5 Impact of amount of added sweet potato on cookie property (cited from Li

et al.

, 2008).

Figure 11.2.6 Sweet potato cookies.

Figure 11.2.7 Purple sweet potato cookies.

Figure 11.2.8 Ready to use sweet potato flour.

Figure 11.2.9 Sweet potato cake.

Figure 11.2.10 Purple sweet potato cake.

Figure 11.2.11 Technological process for instant nutritious sweet potato chips.

Figure 11.2.12 Instant sweet potato chips.

Figure 11.2.13 Double screw extrusion machine.

Figure 11.2.14 Preparation of crisp and delicious puffed sweet potato food.

Figure 11.2.15 Extrusion puffed sweet potato crisps.

Figure 11.2.16 Airflow explosion puffing machine.

Figure 11.2.17 Processing steps of airflow puffed sweet potato chips.

Figure 11.2.18 Airflow puffed sweet potatoes.

Figure 11.2.19 Processing steps of aromatic and crispy sweet potato chips.

Figure 11.2.20 Aromatic and crispy sweet potato chips.

Figure 11.2.21 Technological process of low temperature vacuum fried sweet potato chips.

Figure 11.2.22 Low‐temperature vacuum frying machine.

Figure 11.2.23 Low temperature vacuum fried sweet potato chips.

Figure 11.2.24 Vacuum microwave drying equipment.

Figure 11.2.25 Processing steps of vacuum microwave dried sweet potato chips.

Figure 11.2.26 Vacuum microwave dried sweet potato chips.

Figure 11.2.27 Sun curing of the sweet potato slices.

Figure 11.2.28 Sweet potato slices covered with sugar icing.

Chapter 11.3: Other Sweet Potato-based Products

Figure 11.3.1 Sweet potato jelly.

Figure 11.3.2 Processing steps of sweet potato jelly.

Figure 11.3.3 Instant sweet potato noodles.

Figure 11.3.4 Technological process of preparing quick‐frozen sweet potato.

Figure 11.3.5 Quick‐frozen sweet potato products.

Figure 11.3.6 Preparation of sweet potato healthcare tea.

Figure 11.3.7 Sweet potato healthcare tea.

Figure 11.3.8 Technological process of preparing sweet potato shoot‐tips.

Figure 11.3.9 Sweet potato beer.

Figure 11.3.10 Technological process of preparing sweet potato beer.

Figure 11.3.11 Preparation of purple sweet potato juice.

Figure 11.3.12 Purple sweet potato juice.

Figure 11.3.13 Sweet potato whole flour. (a) Purple sweet potato whole flour. (b) Yellow flesh sweet potato whole flour.

Figure 11.3.14 Sweet potato protein.

Figure 11.3.15 Technological process of protein recovery from sweet potato starch waste water by foam separation.

Figure 11.3.16 Schematic representation of the foam separation apparatus.

Figure 11.3.17 Technological process of extracting dietary fiber from sweet potato residues by the thermostable α‐amylase method.

Figure 11.3.18 Production line for sweet potato dietary fiber.

Figure 11.3.19 Production line for sweet potato pectin.

Figure 11.3.20 Extraction procedure of sweet potato pectin.

Figure 11.3.21 Purple sweet potato anthocyanins under different pH conditions.

Figure 11.3.22 Extraction procedure of sweet potato anthocyanins.

Figure 11.3.23 Extraction procedure of polyphenols from sweet potato leaves.

Chapter 12: Yam: Technological Interventions

Figure 12.1 Yam tubers.

Figure 12.2 Yam porridge.

Figure 12.3 Flow chart of processing of yam tuber into porridge.

Figure 12.4 Processing of yam tuber into pounded yam.

Figure 12.5 Yam tuber processing into dried yam chips.

Figure 12.6 Yam chips dried at road side.

Figure 12.7 Yam chips of different thickness.

Figure 12.8 Processing of fried yam cake.

Figure 12.9 A typical morphological structure of trifoliate yam starch using light microscopy (LM) (×800) (a) and scanning electron microscopy (SEM) (×3000) (b).

Figure 12.10 Fabricated drum dryer.

Chapter 13:

Amorphophallus

: Technological Interventions

Figure 13.1 Structure of

Amorphophallus paeoniifolius

(var. Gajendra) plant (a) with tuber insert (b) of two years old.

Figure 13.2 Preparation of crude

EFY

flour (CEF) from fresh corm material (adapted from Chua

et al.

(2012).

Figure 13.3 The isolation and preparation of RS from EFY (updated from Reddy

et al.

(2014).

Figure 13.4 The chemical structure of a selection of GM; G, glucose or acetylated glucose at 6th position; M, mannose.

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Tropical Roots and Tubers

Production, Processing and Technology

Edited By

Harish K. Sharma

Food Engineering and Technology Department, Sant Longowal Institute of Engineering and Technology, India

Nicolas Y. Njintang

Department of Biological Sciences, Faculty of Sciences; and National School of Agro Industrial Sciences (ENSAI), University of Ngaoundere, Cameroon

Rekha S. Singhal

Food Engineering and Technology Department, Institute of Chemical Technology, India

Pragati Kaushal

Food Engineering and Technology Department, Sant Longowal Institute of Engineering and Technology, India

This edition first published 2016 © 2016 by John Wiley & Sons, Ltd

Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK

Editorial offices: 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell.

The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.

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Limit of Liability/Disclaimer ofWarranty: While the publisher and author(s) have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Library of Congress Cataloging-in-Publication data applied for.

ISBN: 9781118992692

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover image: GettyImages/Roel Smart

About the IFST Advances in Food Science Book Series

The Institute of Food Science and Technology (IFST) is the leading qualifying body for food professionals in Europe and the only professional organzation in the UK concerned with all aspects of food science and technology. Its qualifications are internationally recognized as a sign of proficiency and integrity in the industry. Competence, integrity and serving the public benefit lie at the heart of the IFST philosophy. IFST values the many elements that contribute to the efficient and responsible supply, manufacture and distribution of safe, wholesome, nutritious and affordable foods, with due regard for the environment, animal welfare and the rights of consumers.

IFST Advances in Food Science is a series of books dedicated to the most important and popular topics in food science and technology, highlighting major developments across all sectors of the global food industry. Each volume is a detailed and in-depth edited work, featuring contributions by recognized international experts, and which focuses on new developments in the field. Taken together, the series forms a comprehensive library of the latest food science research and practice, and provides valuable insights into the food processing techniques that are essential to the understanding and development of this rapidly evolving industry.

The IFST Advances series is edited by Dr Brijesh Tiwari, who is Senior Research Officer at Teagasc Food Research Centre in Ireland.

Forthcoming titles in the IFST series

Emerging Technologies in Meat Processing

, edited by Edna J. Cummins and James G. Lyng

Ultrasound in Food Processing: Recent Advances

, edited by Mar Villamiel, Jose Vicente Garcia-Perez, Antonia Montilla, Juan Andrés Cárcel and Jose Benedito

Herbs and Spices: Processing Technology and Health Benefits

, edited by Mohammad B. Hossain, Nigel P. Brunton and Dilip K Rai

List of Contributors

Adebayo B. Abass

, International Institute for Tropical Agriculture, Regional Hub for Eastern Africa, Dar es Salaam, Tanzania.

Olufunmilola A. Abiodun

, Department of Home Economics and Food Science, University of Ilorin, Kwara State, Nigeria.

Ifeoluwa O. Adekoya

, Department of Biotechnology and Food Technology, University of Johannesburg, Johannesburg, South Africa.

Rahman Akinoso

, Department of Food Technology, University of Ibadan, Oyo State, Nigeria.

Buliyaminu A. Alimi

, Department of Bioresources Engineering, School of Engineering, University of Kwazulu‐Natal, Pietermaritzburg, South Africa.

Sudhanshu S. Behera

, Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, India; Department of Biotechnology, College of Engineering and Technology (BPUT), Bhubaneswar, India.

Ashok K. Dhawan

, National Institute of Food Technology, Entrepreneurship and Management (NIFTEM), Sonepat, India.

Maninder Kaur

, Department of Food Science and Technology, Guru Nanak Dev University, Amritsar, India.

Pragati Kaushal

, Department of Food Engineering and Technology, Sant Longowal Institute of Engineering and Technology, Sangrur, India.

Marion G. Kihumbu‐Anakalo

, Department of Food Science, Egerton University, Egerton, Kenya.

Agnes W. Kihurani

, School of Agriculture and Biotechnology, Karatina University, Karatina, Kenya.

Kuttumu Laxminarayana

, Regional Centre, ICAR – Central Tuber Crops Research Institute, Bhubaneswar, India.

Peng‐Gao Li

, Department of Nutrition and Food Hygiene, School of Public Health, Capital Medical University, Beijing, P.R. China.

Carl M.F. Mbofung

, National School of Agro Industrial Sciences, University of Ngaoundere, Adamaoua, Cameroon.

Sanjibita Mishra

, Regional Centre, ICAR – Central Tuber Crops Research Institute, Bhubaneswar, India.

Chokkappan Mohan

, Division of Crop Improvement, Central Tuber Crops Research Institute (ICAR), Trivandrum, India.

Tai‐Hua Mu

, Institute of Agro‐Products Processing Science and Technology, Chinese Academy of Agricultural Sciences, Key Laboratory of Agro‐products Processing, Ministry of Agriculture, Beijing, P.R. China.

Aswathy G.H. Nair

, Division of Crop Improvement, Central Tuber Crops Research Institute (ICAR), Trivandum, India.

Nicolas Y. Njintang

, Faculty of Sciences, University of Ngaoundere, Adamaoua, Cameroon; National School of Agro Industrial Sciences, University of Ngaoundere, Adamaoua, Cameroon.

Adewale O. Obadina

, Department of Food Science and Technology, Federal University of Agriculture, Abeokuta, Nigeria.

Ibok Nsa Oduro

, Department of Food Science and Technology, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana.

Sandeep K. Panda

, Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Johannesburg, South Africa.

Vidya Prasannakumary,

Division of Crop Improvement, ICAR‐Central Tuber Crops Research Institute, Trivandum, India.

Ramesh C. Ray

, ICAR ‐ Central Tuber Crops Research Institute (Regional Centre), Bhubaneswar, India.

Kawaljit Singh Sandhu

, Department of Food Science and Technology, Chaudhary Devi Lal University, Haryana, India.

Lateef O. Sanni

, Department of Food Science and Technology, Federal University of Agriculture, Abeokuta, Nigeria.

Joel Scher

, Laboratoire d'Ingenierie des Biomolecules (LIBio), Université de Lorraine, France.

Harish K. Sharma

, Department of Food Engineering and Technology, Sant Longowal Institute of Engineering and Technology, Sangrur, India.

Anakalo A. Shitandi,

Kisii University, Kisii, Kenya.

Taofik A. Shittu

, Department of Food Science and Technology, Federal University of Agriculture, Abeokuta, Nigeria; Department of Bioresources Engineering, School of Engineering, University of Kwazulu-Natal, Pietermaritzburg, South Africa.

Bahadur Singh

, Food Engineering and Technology Department, Sant Longowal Institute of Engineering and Technology, Sangrur, India.

Lochan Singh

, National Institute of Food Technology, Entrepreneurship and Management (NIFTEM), Sonepat, India.

Sarita Soumya

, Regional Centre, ICAR – Central Tuber Crops Research Institute, Bhubaneswar, India.

Hong‐Nan Sun

, Institute of Agro‐Products Processing Science and Technology, Chinese Academy of Agricultural Sciences, Key Laboratory of Agro‐products Processing, Ministry of Agriculture, Beijing, P.R. China.

Ashutosh Upadhyay

, National Institute of Food Technology, Entrepreneurship and Management (NIFTEM), Sonepat, India.

Bashira Wahab

, Department of Food Science and Technology, Federal University of Agriculture, Abeokuta, Nigeria.

Preface

Tropical roots and tubers occupy an important place in the global commerce and economy of a number of countries and contribute significantly to sustainable development, income generation and food security, especially in the tropical regions. Researchers have demonstrated the importance of tropical roots and tubers to human health, contributing an important source of carbohydrates and other nutrients. The perishability and post‐harvest losses are the major constraints in their utilization and availability, therefore they demand appropriate storage conditions at different stages and value addition. The objectives of this book are therefore to provide a range of options from production and processing to technological interventions in the field, in a comprehensive form at one place.

This book focuses on all the major aspects related to tropical roots and tubers. With a total of 18 chapters, contributed by various authors with diverse expertise and background in the field across the world, this book reviews and discusses important developments in production, processing and technological aspects. Individually, taro, cassava, sweet potato, yam and elephant foot yam are mainly discussed and covered. The chapters in the book describe and discuss taxonomy, anatomy, physiology, nutritional aspects, biochemical and molecular characterization, storage and commercialization aspects of tropical roots and tubers. Good agricultural practices and good manufacturing practices are also given special emphasis. The HACCP approach in controlling various food safety hazards in processing of tropical roots and tubers is also discussed. Technological interventions, brought out in different tropical roots and tubers, constitute a major focus and it is expected that this book will find a unique place and serve as a resource book on production, processing and technology.

This book is designed for students, academicians, industry professionals, researchers and other interested professionals working in the field/allied fields. A few books are available in this field but this book is designed in such a way that it will be different and unique, covering production, processing and technology of lesser publicized tropical roots and tubers. The text in the book is standard work and therefore can be used as a source of reference. Although best efforts have been made, the readers are the final judge.

Many individuals are acknowledged for their support during the conception and development of this book. Sincere thanks and gratitude are due to all the authors for their valuable contribution and co‐operation during the review process. The valuable input from Wiley and the assistance by publishing and copy‐editing departments is gratefully acknowledged. Sincere efforts have also been made to contact copyright holders. However, any suggestions or communications with respect to improving the quality of the book will be appreciated and the editors will be happy to make amendments in the future editions.

Harish K. Sharma

Nicolas Y. Njintang

Rekha S. Singhal

Pragati Kaushal

Chapter 1Introduction to Tropical Roots and Tubers

Harish K. Sharma and Pragati Kaushal

Department of Food Engineering and Technology, Sant Longowal Institute of Engineering and Technology, Sangrur, India

1.1 Introduction

Roots and tubers are considered as the most important food crops after cereals. About 200 million farmers in developing countries use roots and tubers for food security and income (Castillo, 2011). The roots and tubers contribute significantly to sustainable development, income generation and food security, especially in the tropical regions. The origin of tropical roots and tubers along with their edible parts is presented in Table 1.1.

Table 1.1 Origin of tropical roots and tubers

Tropical roots and tubers

Origin

Edible part

Sweet potato

Central/South America

Root, leaves

Cassava

Tropical America

Root, leaves

Taro

Indo‐Malayan

Corm, cormels, leaves and petioles

Yam

West Africa/Asia

Tuber

Elephant foot yam

Southeast Asia

Tuber

Individually, cassava, potato, sweet potato and yam are considered the most important roots and tubers world‐wide in terms of annual production. Cassava, sweet potato and potato are among the top ten food crops, being produced in developing countries. Therefore, tropical roots and tubers play a critical role in the global food system, particularly in the developing world (Amankwaah, 2012). The leaders, policy‐makers and technocrats have yet to completely recognize the importance of tropical tubers and other traditional crops. Therefore, there is a need to focus more on tropical roots and tubers to place them equally in the line of other cash crops.

Tropical root and tubers are the most important source of carbohydrates and are considered staple foods in different parts of the tropical areas of the world. The carbohydrates are mainly starches, concentrated in the roots, tubers, corms and rhizomes. The main tropical roots and tubers consumed in different parts of the world are taro (Colocasia esculenta), yam (Dioscorea spp.), potato (Solanum tuberosum L.), sweet potato (Ipomoea batatas), cassava (Manihot esculenta) and elephant foot yam (Amorphophallus paeoniifolius). Yams are of Asian or African origin, taro is from the Indo Malayan region, probably originating in eastern India and Bangladesh, while sweet potato and cassava are of American origin (Table 1.1). Naturally suited to tropical agro‐climatic conditions, they grow in abundance with little or no artificial input. Indeed, these plants are so proficient in supplying essential calories that they are considered a “subsistence crop” (www.fao.org). Because of their flexibility in cultivation under a mixed farming system, tropical roots and tubers can contribute to diversification, creation of new openings in food‐chain supply and to meet global food security needs.

The perishability and post‐harvest losses of tropical roots and tubers are the major constraints in their utilization and availability. The various simple, low‐cost traditional methods are followed by farmers in different parts of the world to store different tropical roots and tubers. The requirements of storage at different stages during the post‐harvest handling of tropical roots and tubers are presented in Figure 1.1. The perishable nature of roots and tubers demands appropriate storage conditions at different stages, starting with the farmers to their final utilization (consumers). Therefore, an urgent requirement exists to modernize the traditional methods of storage at different levels, depending upon the requirements of keeping quality.

Figure 1.1 Post‐harvest handling stages in the storage of tropical roots and tubers.

The various interactive steps involved in post‐harvest management of any tropical root or tuber, if not controlled properly, may result in losses. To prevent these losses, several modern techniques such as cold storage, freezing, chemical treatments and irradiation may be widely adopted. Roots and tubers not only enrich the diet of the people but are also considered to possess medicinal properties to cure various ailments. So the role of roots and tubers in functional products can also be investigated in the light of medicinal properties. An immense scope exists for commercial exploitation in food, feed and industrial sectors. Since tropical roots and tubers crops are vegetatively propagated and certification is not common, the occurrence of systemic diseases is another problematic area. Some of these root and tuber crops remain under‐exploited and deserve considerably more research input for their commercialization.

1.2 Roots and Tubers

1.2.1 Roots

The root is the part of a plant body that bears no leaves and therefore lacks nodes. It typically lies below the surface of the soil. Edible roots mainly include cassava, beet, carrot, turnip, radish and horseradish. Roots have low protein and dry matter compared to tubers. Moreover, the major portion of dry matter contains sugars. The major functions of roots include absorption of inorganic nutrients and water, anchoring the plant body to the ground and storage of food and nutrients.

1.2.2 Tubers

Tubers are underground stems that are capable of generating new plants and thereby storing energy for their parent plant. If the parent plant dies, then new plants are created by the underground tubers. Examples of tubers include potatoes, water chestnuts, yam, elephant foot yam and taro. Tubers contain starch as their main storage reserve and contain higher dry matter and lower fiber content compared to roots. Various tropical roots and tubers are presented in Figure 1.2.

Figure 1.2 Various tropical roots and tubers.

The production of roots and tubers can be grouped into annuals, biennials and perennials. The perennial plants under natural conditions live for several months to many growing seasons, as compared to annual or biennial. The main points of difference among annuals, perennials and biennials are presented in Table 1.2. The perennials generally contain a greater amount of starch as compared to biennials.

Table 1.2 Annual, biennial and perennial roots/tubers

Life cycle

Limiting aspects

Benefits

Annual

Takes 1 year to complete its life cycle.

Growth can be a limiting factor in excess/scarcity of water for annual plants. Insect and disease problems are of minor concern.

Lesser benefits as compared to perennials and biennials.

Biennial

Takes 2 years to complete its life cycle.

Early growth and quality is affected by late‐season moisture stress.

Provides lesser benefit as compared to perennials in agriculture.

Perennial

Takes more than 2 years to complete its life cycle.

No specific period for growth. But by providing early and modified irrigation practices, production can be improved.

They can hold soil to prevent erosion, do not require annual cultivation, reduce the need for pesticides and herbicides, and capture dissolved nitrogen.

1.3 Requirements for the Higher Productivity of Tropical Roots and Tubers

The factors that need to be focused upon to meet the objectives of food security, sustainable farming and livelihood development are farming systems, pest and pathogen control systems, genetic systems and strategies for improvement, together with marketing strategies and the properties of the products and constituents.

1.3.1 Farming Systems

Tropical roots and tubers are generally grown in humid and sub‐humid tropics, which are not suited for cereal production. Significant differences exist in the farming system perspectives of tropical root and tuber crops, varying from complex systems of production to intercropping farming systems. These systems are important to consider when studying the variation of different crop farming systems. The increasing production in the Pacific region has depended largely on farming more land rather than increasing crop yields. This is contrary to the projections of FAO that the 70% growth in global agricultural production required to feed an additional 2.3 billion people by 2050 must be achieved by increasing the yields and cropping intensity on existing farmlands, rather than by increasing the amount of land brought under agricultural production (Hertel, 2010).

Farming systems need to be carefully looked after, by protecting and raising the production of tropical roots and tubers. For this purpose, various changes in attitudes and agricultural practices are desirable. Additional investments are required to reduce the impact of climate change and to overcome the disastrous effects of soil erosion. Diversity in the production of tropical roots and tubers and increasing production surface area may be adopted for higher productivity and better quality of tropical roots and tubers. Proper organization among small farmers, effective investment in mechanization, and improved storage and processing facilities can improve the productivity of tropical roots and tubers.

1.3.2 Pest and Pathogen Systems

The pest and pathogens of different tropical roots and tuber crops are varied. Roots and tubers are generally produced by small‐scale farmers, debarring a few exceptions using traditional tools and without the adequate input of fertilizers or chemicals for pest and weed control. Therefore, the correct use of less expensive and effective dosages of pesticides and fertilizers is important to increase the productivity of these crops. Moreover, the activities need to be designed to reduce environmental degradation. Biochemical approaches need to be followed to reduce the damage due to pests and pathogens. The assessment of loss caused by pests and pathogens cannot be overlooked, which otherwise affects the production of tropical roots and tubers. In addition, pest and pathogens are of particular concern because of their direct effect on human and animal health. The effect of climatic conditions on the damaging action of pests and pathogens needs to be highlighted. Therefore, proper crop protection, involving different management practices, needs to be followed to reduce the damage due to pests and pathogens and to enhance the productivity of tropical roots and tubers.

1.3.3 Genetic Systems and Strategies for Genetic Improvement

The genetic system of roots and tubers widely differs, so the strategies for genetic improvements also differ. The breeding of root and tuber crops is primarily done sexually. The fact is that the different genetic systems suffer from many breeding complications along with limited opportunities for genetic development and further modifications (Mackenzie, 1995).