Document Type : Research Article
Authors
Department of Food Science and Technology, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
Abstract
Introduction: The main part of the further-processed foods especially fish, seafood, poultry, cheese and vegetables market is constituted of battered and breaded products. The annual consumption of battered and breaded products in some countries such as Europe, Japan, and Oceania is approximately 2 billion pounds. Frying of battered and breaded products is used to improve their quality factors which are mainly crispness, texture, moisture and oil contents, porosity, color and appearance, flavor and nutrition. Crispy outer layer and the moist and juicy interior as pleasant textural characteristics are created in fried foods. Chicken nugget which is made from chicken meat is breaded or battered, then deep-fried or baked and finally is quick frozen. Chicken nugget is composed of four layers including paste, pre-dust, batter and breaded layers. Amaranth is one of the pseudo-cereal grains which belongs to the Amaranthaceae family. The color of amaranth seed varies from milky white to yellow, golden, red, brown, and black. This plant has high nutritional and biological value. Amaranth seed contains starch (61/4%), protein (16/5%), unsaturated fats (5/7%), fiber (20/6%), vitamins (E, B2 and C), minerals (calcium, magnesium, zinc and iron) and phenolic compounds. The purpose of this study was to replace wheat flour with amaranth flour in order to reduce wheat grain dependence, improve the nutritional value of nuggets as well as explore the production possibility of a new product for celiac disease.
Materials and methods: In order to investigate the effect of replacing of wheat flour by amaranth flour in nugget formulation, amaranth flour was used at 0, 50 and 100% levels separately in chicken paste, batter dough, and all layers of nugget (chicken paste, predust, and batter dough). Then, the chemical composition and pH of chicken nugget, chicken paste emulsion stability, cutting force, oil absorption, porosity, cooking loss, degree of oxidation, color and sensory characteristics of produced nuggets were evaluated.
Results and discussion: Results showed that increasing the substitution percent would increase the nutritional value of nuggets. The pH of all produced nuggets containing amaranth flour was higher than the control sample and pH reduction occurred slower in them during 13 days of storage at 4 ° C. Emulsion stability was also affected by the replacement rate and reached the maximum content at full replacement. Samples with 100% incorporation of amaranth flour had the highest emulsion stability due to the presence of polar lipids and globulin in amaranth flour which are surface active agents. However, 50% substitution of wheat flour with amaranth flour in chicken paste significantly decreased emulsion stability as this sample had the lowest emulsion stability. It seems that the interaction of amaranth albumin proteins with wheat gluten proteins reduced soluble proteins, which caused emulsion stability reduction of chicken paste containing both amaranth flour and wheat flour. Also the presence of amaranth flour in nuggets significantly increased oil absorption, porosity, cutting force and cooking loss. Oil absorption of nuggets increased by increasing the amount of amaranth used in nugget production, as the control nuggets had the lowest oil absorption. Albumin proteins which are present in amaranth flour have high oil absorption capacity. Amaranth flour has low viscosity in gelatinization owing to the low amylose content of amaranth starch, which decreases the absorption of batter dough to the chicken paste and as a result cooking loss will increase. Porosity of nuggets increased by increasing the amount of amaranth flour in prepared nuggets. Globulin which constitutes about 20% of amaranth proteins is a good foaming agent. Entrapment of air bubbles by globulin caused porosity increase in nuggets. In addition, the results of moisture content of nuggets showed moisture removal of nuggets containing amaranth flour after frying. Steam pressure of evaporated water caused porous tissue in samples. Hardness, chewiness, gumminess, springiness, and cohesiveness of nuggets containing amaranth flour increased. The cutting force was increased significantly as a result of the amount of amaranth flour of nuggets as was expected. About the oxidation, increasing the substitution rate reduced the amount of malonaldehyde in the early days and reduced the oxidation process in 13 days of storage at 4 ° C. High amounts of phenolic compounds were found in amaranth flour, which could reduce lipid oxidation and spoilage of nugget. Amaranth flour darkened nuggets and by increasing amaranth content, that amount of L (brightness), a (redness) and b (yellowness) declined. Lightness of the outer layer of nuggets decreased by increasing the amaranth amount of nugget, due to the presence of bran and betacyanin pigment in amaranth flour which make it darker than white flour. Wheat flour could be substituted with amaranth flour in nugget production, increasing the nutritional value of product by increasing protein, fiber and minerals levels, with no undesirable effect on total acceptance of consumers.
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