title: The Development of Expanded Snack Product Made from Pumpkin Flour-Corn Grits: Effect of Extrusion Conditions and Formulations on Physical Characteristics and Microstructure.
abstract: Pumpkin products confer natural sweetness, desirable flavours and β-carotene, a vitamin A precursor when added as ingredients to extruded snacks. Therefore, a potential use for dried pumpkin flour is as an ingredient in ready-to-eat (RTE) snack foods. Growth in this market has driven food manufacturers to produce a variety of new high value snack foods incorporating diverse ingredients to enhance the appearance and nutritional properties of these foods. Ready-to-eat snacks were made by extruding corn grits with 5%, 10%, 15% and 20% of pumpkin flour. Snacks made from 100% corn grits were used as control products for this work. The effect of formulation and screw speeds of 250 rpm and 350 rpm on torque and specific mechanical energy (SME, kWh/kg), physical characteristics (expansion ratio, bulk density, true density and hardness) and the microstructure of the snacks were studied. Increasing the screw speed resulted in a decrease of torque for all formulations. When pumpkin flour was added the specific mechanical energy (SME) decreased by approximately 45%. Increasing the percentage of pumpkin flour at the higher screw speed resulted in a harder texture for the extruded products. X-ray tomography of pumpkin flour-corn grit snacks showed that increased levels of pumpkin flour decreased both the bubble area and bubble size. However, no significant differences (p> 0.05) in bubble wall thickness were measured. By understanding the conditions during extrusion, desirable nutritional characteristics can be incorporated while maximizing expansion to make a product with low bulk density, a fine bubble structure and acceptable organoleptic properties.
authors.affiliation: Foodservice Department, Faculty of Hotel and Tourism Management, Universiti Teknologi MARA (UiTM), Pulau Pinang, 13500 Permatang Pauh, Penang, Malaysia. norfezah420@ppinang.uitm.edu.my.
authors.forename: Norfezah Md
authors.initials: NM
authors.lastname: Nor
authors.affiliation: Institute of Food, Nutrition and Human Health, College of Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. A.J.Carr@massey.ac.nz.
authors.forename: Alistair
authors.initials: A
authors.lastname: Carr
authors.affiliation: Institute of Food, Nutrition and Human Health, College of Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. a.hardacre@massey.ac.nz.
authors.forename: Allan
authors.initials: A
authors.lastname: Hardacre
authors.affiliation: Department of Wine, Food and Molecular Biosciences, P.O. Box 84, Lincoln University, Lincoln 7647, Christchurch, New Zealand. Charles.brennan@lincoln.ac.nz.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Brennan
keywords: extrusion; feed rate; physical characteristic; pumpkin; screw speed