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7'. ____ _-(x/} t / '/ > . SWEET POTATO w/, o anz untappedfood resource JENNIFER A. WOOLFE Published in collaboration with the International Potato Center, Peru ~~The ,Kht 4~the I" pritadfl I/,-,t 1711' MnIJ4 - i TAl l.n..T , Ah 'l'' ~pl"llW e;/.;4 CAMBRIDG;' UNI VItSITY PRtl-.SS Cambrkige New York Port Chester Melbourne Sydney Published by tIc Press SYtidicatc of tl Lttivcrsity oI' CattI)ridge The Pitt Building, *I rumpington Stret, (atI)ridgc (:B2 IRP 41) West 2(th Street, Ncw York, NY I1I 1-4211, [S\ I) Stamford Road, Oaklcigh, Victoria 316, Australia (:mlbridg I tnivcrsity Press 1992 First ptllishILd V)'-'2 Printed in Great Britain at the University press. Cambridge British I .irary aials.guhn, in punb/iatiwn data \ot lli'In.n iicr A. SweetIpotato. 1. Potatoes I. Title 641.3522 Libra' ol ConVress; ataliguin.9 in pilh-ation dala Woolfi, .Jcnnifcr .\. Sweet potato : an untapped food resource / Jennifer A. Woolfc. p1. clt. Includes bibliographical rcferenccs and index. ISBN 0)521 40295 6 (tardcovcr) 1. Swcct potato products. I. Title °'IP444.S94W66 1991 664'.80522 dc20 91-10460 CIP ISBN 1 521 40295 6 hardback The sweet potato is at present grown in more than 100 of the in dependent countries of the world. Most of the producer nations are situated in the tropical developing world where a Ihlihproportion of the poorest people live. Increasing recognition ofthe exciting potential which sweet potato holds fo rcombating food shortages and m:nut rition) has resulted in intensified research eflrts to enhance production and consump tion. This ook reviews the current knowledge about the varied aspects of the sweet potato as a human food and animal feedstuff. 'When you have rice to eat, don't forget sweet potatoes. (Chinese saying) CONTENTS Acknowledgements xiii Abbreviations for organizations xiv Introduction 1 References 13 I Sweet potato - past and present 15 Origin and history 15 The sweet potato in developing countries 18 General description of the plant and its cuLivation 24 References 38 2 Chemical composition 41 Roots 41 Tops 92 Summary 104 References 105 3 The nutritional value of sweet potato roots and leaves 118 Roots 121 Tops 165 Summary 178 References 179 4 Toxic and anti-nutritional factors 188 Toxic strcss metabolites 188 Trypsin inhibitors 203 Flatulence factors 209 Rcfecrnces 213 ix C 0 N I1 N TS 5 Postharvest procedures: I. Storage and cooking 219 A. Curing and storage 221 Methods and improvemcnt s 221 Quality and nutritional changes 245 B. Domestic cooking 262 Ncth(lods 262 Quality and nutritional changes 267 Rteferences 282 6 Postharvest procedures: II. Processing 292 A. Processing for direct use as human food 294 Techiti hgy 294 Further pr()ducts froni prinary processes 333 Other protlucts 350 B. Nutritional value of processed products 352 Roots 352 Tops 363 C. Alternative or derived sweet potato products for human food 366 Starch manutfacture 366 Secondar' products frot starch 371 By-products frin starch wastes 378 Alcoholic beverages 379 Enz'mes 384 Pectin 385 Pigments 385 L.ipids 387 Leaf pro)tein c(),ncentrates 387 Single cell protein 389 D. Overview 389 References 397 7 Livestock feeding with sweet potato roots and vines 409 Agronomic aspects 415 Pigs 417 Poultry 436 Cattle and other ruminants 445 Aquaculture 454 FermcntLd I'Ceds and the use of sweet potato wastes as livestock feed 454 Sunniary 459 References 464 x (() NT E.S 8 Consumption and utilization patterns and trends 473 A tyl)(i]EL v Eff SwCect -1p)atEE C011SLllflpti(li 475 lnfi rt( itrfll MI Co)l SUIlipt iE 1Mad utili;ui. n 477 DifrI'crInCCS a m111C1O,guI tit's 480 I)iffcrcnces withim CEEtEtrics 483 Case studies 484 (China 486 •11alan 504 lihc Philippincs 521 Papua Ncw (muinca 539 Randaiant] t gianda 548 Plru 558 Survey results on consumption and utilization 575 Factors influencing consumption and utilization 582 RI(mts 583 "E"ES 595 Rcfcrcrnccs 597 Appendix: A selection of sweet potato dishes from around the world 603 Index 622 Xi To the one who always believes in me my husband and best friend ACKNOWLEDGEMENTS 1 owe a particular debt of gratitude to those who have read my manuscript so painstakingly and have contributed with immensely helpful comments and suggestions. My thanks are especially due to Professor Stanley Kavs, who reviewed almost the entire manuscript. I am also extremely grateful, for reading of individual chapters, to the following: Dr J. Howard Bradbury, Dr l)ouglas lorton, Mr Dennis Morgan, Professor Ikuzo Uritani and Nis I£rica Wheeler. Niy thanks go to the many scientists all over the world with whom I have corresponded, and who supplied me with information, translations and encouragement. ()utstanding among these is Professor Ikuzo liritani, who has given so generousl\ of his time and knowledge to me through crrespondence and also during my visit to Japan. I would also especially like to thank the ilowing people for the help they have so kindly given in ,'arious ways towards the preparation of this book: Ms Marisela Benavides, Dr \Wanda (llins, Professor Barry Duell, is Jane l-arland, Nis Paulette Foss, Professor Niachiko ()no, is Linda Peterson, Dr Satoshi Sakamoto, Dr Truong Van Den and Dr Yoshiki Umemura. This work was carried out through the auspices of the International Potato Center. I would finally like to thank the Center's Director, Dr Richard Sawyer, for giving me the chance to write this book and Dr Douglas Horton for his constant support and encouragement through out its preparation. xiii ABBREVIATIONS FOR ORGANIZATIONS ACIAR: Australian Centre for International Agricultural Research AFRC: Agriculture and Food Research Council (UIK) AVRDC: Asian Vegetable Research and Devclopment Center CARICOM: Caribbcan ComniUnitv CGIAR: Consultative G(roup for International Agricultural Research CIAT: Centro Internacional de AgricultuRa rro)pical (Colombia) CIP: Centro Internacional de la Papa (international Potato Center) CSIR(): Centre for Scientific and lndu,strial Research (Australia) CSP\X'(;: Caril bean Sweet Potato \W(orking Group 1)SIR: Department of Scientific and Industrial Research (New Zealand) F.C: I'iropean l'conomic ((M11mIu~tnit\ I*MBRAP'\: Fmpresa BrasilCira dC Pesluisa AgrOpCcuaria I'NCA: I'1ncuCsta Nacional de (C)nsum)de Alimentos FAO: Food and Agriculture ()rganization of the United Nations FONAGR(): Fondo de Fomento Agro)pCcuaria (Chincha,Peru) HITAIIR: Hawaii institute of Tropical \griculture and Ilunan Resources iC'AR: Indian Council of Agricultural Research IDRC: International Development Rcsearch Centre IITA: International Institute of Tropical Agriculture (Nigeria) I LRAD: International L.aboratory for Research on Animal Diseases INCAP: Institute of Nutrition of Central America and Panama I NIAA: Instituto Nacional de Investigacion Agraria yAgroindustrial xiv