Received: 30 June, 2010. Accepted: 12 March, 2011. Invited Review Fruit, Vegetable and Cereal Science and Biotechnology ©2011 Global Science Books Process Optimisation of Sweet Potato (Ipomoea batatas) Puree as an Ingredient in a Formulation of Weaning Food Ana Cristina Figueira 1,2 • Olawumi Makinde 1 • Margarida Cortez Vieira 1,3* 1 Food Engineering Department, Instituto Superior de Engenharia, Universidade do Algarve, Campus da Penha, 8005-139 Faro, Portugal 2 Research Center for Spacial and Organizational Dynamics (CIEO), Universidade do Algarve, Campus de Gambelas, 8005-136 Faro, Portugal 3 Center of Investigation in Chemistry of Algarve (CIQA), Universidade do Algarve, Campus de Gambelas, 8005-136 Faro, Portugal Corresponding author: * mvieira@ualg.pt ABSTRACT Sweet potato, a tuber crop widely spread across the World (Africa, Asia, America, Caribbean and Europe) and very affordable, supplies the body with major and vital nutrients (carbohydrates, fat, proteins and vitamins) needed for good body development can be used as an ingredient in weaning food for babies. For this purpose it needs to be boiled and mashed into a paste before being served to babies. The cooking conditions of the Lira variety from a Portuguese region (Aljezur) were studied over a temperature range of 80 to 95°C during 10 to 180 min to evaluate its effects on the physico-chemical properties (texture, non-enzymatic browning and ascorbic acid). From the kinetics modelling study, it was concluded that a fractional conversion first order model fitted well the experimental data for these proper- ties and the kinetic parameters estimated were: texture, (k ref = 0.1611 ± 0.015 min –1 , Ea = 101.13 ± 14.22 KJ/mol with R 2 adj = 0.9719), non-enzymatic browning (k ref = 0.0331 ± 0.004 min –1 , Ea = 389.27 ± 26.86 KJ/mol with R 2 adj = 0.9971) and ascorbic acid (k ref = 0.0244 ± 0.023 min –1 , Ea = 101.70 ± 14.66 KJ/mol with R 2 adj = 0.9905). Based on these findings, the optimization of the cooking conditions to obtain a high quality puree was determined as 90% colour retention, 70% ascorbic acid retention and moderately cooked at 90°C, 7 min; this result was further validated. The team that developed this work was composed by Nigerian and Portuguese researchers and though performed in Portugal and with a Portuguese variety of sweet potato; the goal was to use these results in the industrial development of a weaning food product in Africa, more specifically in Nigeria. _____________________________________________________________________________________________________________ Keywords: ascorbic acid, -carotene, kinetics mathematical modeling, non-enzymic browning, physico-chemical properties, texture and thermal degradation Abbreviations: AA, ascorbic acid; Ea, activation energy; fwb, fresh weight basis; k ref , rate constant; R 2 , determination coefficient; R 2 adj , adjusted determination coefficient CONTENTS INTRODUCTION........................................................................................................................................................................................ 25 SWEET POTATO FROM ALJEZUR (PORTUGAL) .................................................................................................................................. 27 SWEET POTATO PURÉE PROCESSING OPTIMIZATION ..................................................................................................................... 28 PHYSICAL AND CHEMICAL CHARACTERIZATION OF FRESH PRODUCT .................................................................................... 29 MATERIALS AND METHODS .................................................................................................................................................................. 29 RESULTS AND DISCUSSION ................................................................................................................................................................... 30 CONCLUSION ............................................................................................................................................................................................ 32 REFERENCES............................................................................................................................................................................................. 32 _____________________________________________________________________________________________________________ INTRODUCTION Origin, varieties and distribution Over 95% of the global sweet potato crop is produced in developing countries, where it is the fifth most important food crop. China is the largest grower of sweet potatoes, providing about 80% of the world’s supply, followed by Nigeria and Uganda which produce each about 2.5% of the world’s supply, as can be observed in Table 1. Europe has only a very small sweet potato production, mostly in Portu- gal, which is the only European country that produces size- able quantities of sweet potato, at 23,000 tons (International Potato Centre (CIP) 2006). This tuber is very affordable, mainly in Africa as it can be observed in Fig. 1, but excep- tionally it can reach high prices such as the Portuguese one (Fig. 2), due to its special characteristics which deserved a highlight in this review. Nutritional quality of sweet potatoes Depending upon the variety, of which there are about 400, the skin and flesh of the sweet potato may range from almost white through cream, yellow, orange, and pink to a very deep purple, although white and yellow-orange flesh are most common. Sweet potatoes are grouped into two different categories depending upon the texture they have when cooked: 1 st Group - Firm, dry, and mealy; 2 nd Group - Soft and moist. In both types, the taste is starchy and sweet, with different varieties having different unique tastes. Usu- ally sweet potatoes are high in carbohydrates and vitamin A and can produce more edible energy per hectare per day than wheat, rice or cassava (Baybutt et al. 2000). The yel- low-orange flesh varieties also provide vitamins A and C. The plant’s green leaves can also be consumed, providing additional protein, vitamins and minerals (Woolfe 1992). Besides simple starches, sweet potatoes are rich in complex ®