Physicochemical and Functional Properties of Chemically Pretreated Ndou Sweet Potato Flour

Abstract

Sweet potato (Ipomoea batatas Lam) is a nutritious crop abundant in calories and bioactive compounds such as beta-carotene, ascorbic acid, polyphenols, and dietary fibre. This study investigated the effect of pretreatments on the physicochemical and functional properties of Ndou sweet potato (NSP) flour. Flour samples were prepared by randomly assigning NSP slices to two treatments (citric acid and sodium metabisulphite) at 5, 10, and 15 g/L concentration for 10 min. Distilled water was used as control. The moisture content (7.70%) of NSP flour treated with citric acid was significantly (p<0.05) higher than that of the flour treated with sodium metabisulphite (5.54%) as the concentration level increased. The treatments did not significantly (p<0.05) affect the protein and fat contents of the NSP flour and protein increased from 2.54 to 2.82%, while fat decreased from 0.69 to 0.61%. Sodium metabisulphite treated samples had a higher L∗ value, ash, and pH level than citric acid treated samples. However, pH was slightly decreased by both treatments from 6.05 to 5.09. Citric acid treated samples had higher a∗ and b∗ values than sodium metabisulphite treated samples. In terms of the functional properties of NSP flour, the treatments significantly (p<0.05) affected the water absorption capacity, viscosity, swelling power, solubility index, and thermal properties although the bulk density and least gelation concentration were not significantly (p>0.05) affected. Sodium metabisulphite was very effective in improving physicochemical and functional properties of NSP flour as compared to citric acid. The findings of this study show the possibilities of using NSP flour in food systems as gelling agent, fat replacer, and thickeners.

Functional properties of sweet potato flour and its role in product development: a review

“…The loose bulk density is the lowest attainable density without compression. [11] A value of 0.80 to 0.87 g/ mL was reported by Ngoma et al [21] for chemically (sodium metabisulphite and citric acid) pretreated sweet potato flours. After chemical treatments a slight change in the bulk density of the flour was displayed, compared to the control, where the gelatinization process occurred, which increased the bulk density of the flours.…”

“…The bulk density indicates the relative volume of packaging material that plays an important role in the storage, transport, marketing and wet food processing industry. [12,21,28] It also provides information on a product's porosity that can affect package choice and design. [15,21] The processing methods are reported to affect bulk density of the flours.…”

“…[12,21,28] It also provides information on a product's porosity that can affect package choice and design. [15,21] The processing methods are reported to affect bulk density of the flours. Patria et al [35] studied the effect of steaming time and drying method on physically modified sweet potato flour and obtained an average bulk density of 0.46 g/mL to 0.48 g/mL.…”

“…Conversely, flours with high bulk density are not suitable in packaging and it is doubtful to result in cost savings as it will require more packaging materials. [21] High bulk density flours have been known to be good for mixing purposes, whereas those with lower bulk density can find better use in the infant food industry. [28] On the other hand, the lower the value of bulk density, the higher the number of flour particles that can stay together [11] that makes these flours valuable for food products required higher energy values.…”

Development and Quality Characteristics of Cookies from Sprouted Sorghum, Pigeon Pea and Orange Fleshed Sweet Potato Flour Blends

“…The most commonly obtainable sweet potato varieties have purple, yellow, and white root tubers because of the distinct contents of phenolic compounds and pigments in their root tubers [8,9]. Processing of sweet potato can be used as one of the ways to address the challenges faced with storing and transporting the raw sweet potato roots in developing countries [10]. Orange fleshed potato is a naturally bio-fortified crop that has a great potential for global fight against vitamin A. Vitamin A is an essential micronutrient for normal immune function of the body, it is essential for good health and eye sight.…”