The effects of processing variables on physical and chemical characteristics of sweet potato flours

Abstract

Sweet potatoes are well known for their high nutritional values such as vitamins, minerals and bioactive compounds. However, the consumption of sweet potatoes has declined in the past several decades. This decline is attributed to difficulties in availability, storage, and handling for food processors as well as limited choices of sweet potato products for consumers beyond the raw root. Thus, one way to expand sweet potato consumption is to develop different processed products. In product development, the final quality of the product is highly dependent on the quality of the raw ingredients used. Most of the researcher focused on the development of new products adding with sweet potato flour. However, they didn’t emphasis the flour quality. Therefore, the main purpose of this study was to prepare flour from sweet potatoes using different pretreatments and drying methods. Flours were prepared from peeled and unpeeled yellow color sweet potatoes using hot air drying with sulfite treatment. Sulfite treated peeled and unpeeled flour had higher JE values, swelling capacity, ascorbic acid, and total phenolic contents than untreated peeled and unpeeled flour. However, flour from yellow color sweet potato treated with calcium chloride had higher amounts of ascorbic acid and B-carotene than that treated with sodium hydrogen sulfite for both hot air drying and freeze drying. On the other hand, maltodextrin-added flours from purple color sweet potato using hot air drying had higher AE values, water soluble index, total phenolic, and anthocyanin contents than those of untreated flours.However, during spray drying, flours treated with amylase and amylase with maltodextrin had higher anthocyanin and total phenolic contents than control or maltodextrin treated flours. Therefore, the overall study concluded that sweet potato flour could be produced using different pretreatments and drying methods that can be used to enhance the nutritional properties of functional food ingredients.