Study on the changes of approximate composition and physical parameters of nugget of silver carp (Hypophthalmichthys molitrix) during the initial frying in several vegetable oils at different temperature levels

Value added products are defined as a set of products that are made up of the primary food with the help of different types of human or mechanical processing, and vary in appearance, texture, flavor and odor with their primary substance. One examples of value added products is battered and breaded products. Nuggets are products which are made of mixing mince or surimi with flavored and additive ingredients. The mixture is prepared after battering and being coated with toasted flour. It is then primary fried in oil and after freezing, packaged and stored. Therefore, the consumer only uses the final baking step, which usually involves frying in oil, consuming the product after thawing. Deep fat frying is a common cooking method in which fat is used as a heat transfer medium, during which foods with unique characteristics are produced in terms of taste, texture and appearance. During the frying process, along with shifting and moving the temperature, transferring and moving the material happens. Usually, with increasing frying time, the amount of oil absorption increases, but there is no linear relationship between. The amount of oil absorption depends on several factors such as oil quality, frying time, oil and food temperature, food form, porosity and chemical composition, especially the initial moisture content of the product.In general, fried foods at temperatures between 175 and 190°C have good brittle properties. Temperatures above 175°C may be associated with acrylamide formation, which is a carcinogenic substance. Therefore, the purpose of this study was to investigate the effect of frying medium (different vegetable oils) and temperature on the variations in the approximate composition and physical parameters of the fried silver carp nugget.
In order to produce fish nuggets, 87% of minis were mixed with additive and flavoring ingredients, 5% breadcrumbs, 5% onions, 1% garlic, 1.5% salt and 0.5% spices. The mixture was shaped into round shapes and immersed in the glaze with a specific formulation and after dripping the extra glaze was covered with toasted flour. Then, nuggets were prepared using sunflower, olive, canola and sesame oil for 30 seconds at temperatures of 150, 170 and 190 degrees of celsius preheated by frying deep frying and after cooling to room temperature was packed in zipper bags and was frozen at -20°C. After a day, the nuggets were removed from the freezer and after de-damping at ambient temperature, chemical (including approximate analysis, pH measurements, water holding capacity) and physical tests (including viscosity, yield of product, shrinkage, Colorimetric and sensory analysis) were performed on fish nuggets. For physical tests and sensory analysis, nuggets were deep fried in sunflower oil for 3 minutes at 180°C.
The findings showed that fried nugget in sunflower oil and sesame oil contained moisture content, yield and high red color index, and oil absorption and yellowness index were less than fried nugget in olive oil and canola. From the temperatures of 150, 170 and 190°C in the primary frying, the temperature of 170°C had the highest moisture content and yield, and the average value of the brightness and redness index was 150 and 190°C. The temperature of 150°C showed lower oil absorption than 170°C and 190°C. According to the sensory evaluation, the sensory indexes of color, taste, smell, fat sensation in the mouth, texture, juiciness and general acceptance of the treatments in different oils and different temperatures of the initial frying were the same and did not show any significant difference. The priority was to select the panel of fried nugget panels in olive oil and prefer the initial frying temperature of 170 and 190°C. According to the results of this study, in terms of physical factors and the rate of absorption, fried nuggets in sunflower and sesame oil were more effective. Between the different temperatures of the initial frying, temperatures of 170°C for all of the measured indexes yielded better results than temperatures of 150 and 190°C.