Physico Chemical, Antioxidant and Pasting Properties of Pre-heated Purple Sweet Potato Flour

Siti Nurdjanah

doi:10.11648/j.jfns.20170504.11

Abstract

Purple sweet potatoes contain anthocyanins which could function as a natural food colorant, and an antioxidant. One of the problems in handling the fresh roots is their susceptibility during storage, and to extend their uses, fresh purple sweet potato could be processed into flour. However, during flouring process, the properties of the purple sweet potato may undergo some changes such as partial gelatinization of the starch and discolorization. Therefore, the purpose of this study was to investigate the effect of pre-heating treatment during flouring process on degree of gelatinization, the anthocyanin content, the antioxidant activity and the total phenolic content of heat treated purple sweet potato flour. Other objectives were to observed the changes in the starch properties such as rheological properties, granular appearance of the heat treated- purple sweet potato flour. Pre-heating treatment of purple sweet potato flour was prepared by heating grated purple sweet potato in a single rotary drum cooker at 90°C for 15, 30, 45, 60 and 75 min, followed by drying in a cabinet dryer at 60°C for 8 h. The results showed the longer pre-heating time at 90°C had caused increase in the degree of gelatinization, increase in total phenolic and anthocyanin retention. In addition, differences in gelatinization temperature, maximum viscosity, paste stability and retrogradation, and differences in scanning electron microscope (SEM) of granular appearance were also observed. The overall results indicated that pre-heating treatment can be used for modifying the physical, chemical and rheological properties to suit various applications and preserving functional properties of purple sweet potato flour.

Highlights

Sweet potato (Ipomoea batatas (L.) Lam), a fairly droughttolerant crop, is widely grown throughout the world, primarily in the tropics and subtropics
In this paper we reported study on physicochemical, functional, and rheological properties of physically modified purple sweet potato flour processed through pre-heating treatment
The longer the preheating time had caused the higher degree of gelatinization (Table 1). This finding indicates that preheating treatment of Purple sweet potatoes (PSP) in a rotary drum cooker without addition of water before flouring process has caused partial gelatinization of the flour

Summary

Introduction

Sweet potato (Ipomoea batatas (L.) Lam), a fairly droughttolerant crop, is widely grown throughout the world, primarily in the tropics and subtropics. It has various skin and flesh color from white to yellow, orange, light purple to deep purple. The annual sweet potato production accounts up to more than 105 million metric tons [1]. In Indonesia, the trend with respect to utilization of sweet potato is changing from domestic consumption to use in various commercial products such as flour, starch, pectin, and dietary fiber [2]. Purple sweet potatoes (PSP) contain relatively high acylated anthocyanins, with mainly cyanidin or peonidin as the aglycone [3]. Studies proved anthocyanin provide physiological functions such as antihyperglycemic [4], antiinflamatory and anticarcinogenic [5] and antioxidant [6]

Objectives

Methods

Results

Conclusion