Submitted to: Sweetpotatoes: Post-harvest Aspects in Food, Feed and Industry
Publication Type: Book / chapter
Publication Acceptance Date: 5/22/2009
Publication Date: 5/1/2010
Publication URL: http://hdl.handle.net/10113/44182
Citation: Truong, V., Avula, R.Y. 2010. Sweetpotato purees and powders for functional food ingredients. In: Ray, R.C., Tomlins, K.I., editors. Sweetpotatoes: Post-harvest Aspects in Food, Feed and Industry. New York: Nova Science Publishers, Inc. p. 117-161. Interpretive Summary: The chapter is a part of the book entitled “Sweetpotatoes: Post-harvest Aspects in Food, Feed and Industry”, edited by R. C. Ray and K. I. Tomlins, Nova Science Publishers, Inc., New York. The review covers: 1) technical aspects of processing sweetpotatoes into purees and dehydrated forms, and 2) effects of processing on product quality, storability, nutritional values and functionalities. The article does not intend to be a comprehensive review of available literature on this subject but it focuses on recent innovations such as microwave-assisted processing and aseptic packaging for shelf-stable and high quality purees, different drying methods, and chemical modifications to produce sweetpotato powders with specific functionality. Applications of these ingredients to impart desired textural properties and enhance the levels of phytonutrients such as beta-carotene and anthocyanins in processed foods are discussed.
Technical Abstract: Processing technologies have been developed in various parts of the world to convert sweetpotatoes into purees and dehydrated forms that can be used as food ingredients in numerous food products. This article reviews the processing operations involved in these technologies and their effects on quality, storability, nutritional values and rheological properties of sweetpotato purees and powders/flours. For purees, the processing steps include peeling, cutting/grinding, and pre-cooking/finish-cooking with temperature-time program suitable for starch conversion by endogenous amylolytic enzymes to obtain the products with targeted maltose levels and viscosities. The purees can be subsequently preserved by refrigerated and frozen storage, canning or aseptic packaging. However, poor product quality due to excessive thermal treatments in canning, high cost of investment associated with frozen products and limited package sizes of these preserved forms are the main hurdles for widespread applications of sweetpotato purees in the food industry. These problems can be overcome by a new process using a continuous flow microwave system for rapid sterilization and aseptic packaging to produce shelf-stable purees with consistently high quality. Sweetpotato purees can be further processed into drum- or spray-dried powders. In many countries, solar drying and mechanical drying in cabinets and tunnels are common in producing sweetpotato dried chips which are pulverized into flours. Extrusion technology and chemical treatments are also applied to produce sweetpotato powders for specific functionality. With high levels of carbohydrates, beta-carotene (orange-fleshed varieties) and anthocyanins (purple-fleshed varieties), sweetpotato purees and dehydrated forms can be used as functional ingredients to impart desired textural properties and phytonutrient content in processed food products.