What is the effect and application of different breading powders in fried chicken nuggets?

Deep-fried food is very popular because of its special flavor and texture, and most of them are deep-fried with coated powder. Problems that may easily occur in coated fried food include: poor adhesion between the base material and the coated powder, easy to fall off, high oil absorption rate, poor taste and so on.
Wheat flour is one of the main raw materials for coating powder, which can provide suitable viscosity to stabilize the various ingredients in the coating powder and avoid layering of the coating paste. Modified starch is also widely used in the coating powder, the higher the proportion of straight chain starch in the coating powder, the higher the oil resistance and water resistance of the coating powder layer, and the better the crispiness of the food.
Adding proteins (soybean isolate protein, egg yolk, skimmed milk, fish scale collagen, whey collagen, wheat gluten protein, etc.) to the breading powder can help to reduce the fat content of deep-fried breaded food and improve the texture of the food.
The addition of edible gums (xanthan gum, carrageenan, gelatin, guar gum) to the breading powder can increase the adhesion of the breading powder, thus improving the texture of the food. Cellulose in the coating powder can strengthen the thermal stability and adhesion of the coating layer, prevent the moisture of the substrate from escaping, significantly reduce the oil content of the food, and increase the crispiness of the food. The addition of bulking agent in coating powder will make the food form a porous, spongy organization, which is easy to be digested and absorbed, avoiding the loss of nutrients.
Breading Powder and Battering Powder Ingredients
Breading powder ingredients: Flour, tapioca starch, HPMC and 10:0, 9.5:0.5, 9:1, 8.5:1.5, 8:2 octenyl succinate amylopectin-corn alkyd proteins complexes (OZ1, OZ2, OZ3, OZ4, OZ5, respectively) as a single breading powder for deep-fried chicken nuggets.
Ingredients: 50 g of flour, 40 g of tapioca starch, 6 g of soy protein, 3 g of salt, 0.50 g of compound phosphate, 0.50 g of HPMC, and 210 g of deionized water; mixed well to form a coating slurry.
Preparation process of deep-fried chicken nuggets: chicken nuggets thawing → cutting → marinating → on the coating powder → on the slurry powder → on the breadcrumbs → pre-frying → cooling → packaging → freezing → re-frying → finished product.
Results and analysis
1, the adhesion of the coating powder The adhesion of the coating powder is closely related to the water-absorbing ability of the starch/hydrophilic colloid in it. As can be seen from Fig. 1, there was no significant difference in the adhesion between tapioca starch and flour; the adhesion of HPMC and the complex was significantly higher than that of tapioca starch and flour, which may be due to the fact that HPMC has a high viscosity in the presence of a small amount of water, and the maize alkyd-soluble proteins in the complex can bind with the proteins and lipids on the surface of the chicken meat to improve its adhesion.

Fig. 1 Adhesion of different coating powders
2, Battering rate of chicken nuggets From Figure 2, it can be seen that the highest battering rate of fried chicken nuggets was 48% when the breading powder was HPMC. There was no significant difference between the battering rates of flour and the five complexes (31%-36%); tapioca starch had the lowest battering rate of 27%.
HPMC is a thermoreversible gel, which has good water solubility at room temperature, and its viscosity increases after absorbing water from the surface of the substrate material, which leads to an increase in its coagulation rate. The complexes had higher viscosity relative to tapioca starch, which resulted in higher coagulation rate of the products, and OZ2 and OZ3 coagulation rates were relatively high in the complexes.

Fig. 2 Battering rate of chicken nuggets with different coating powder
3, the fat content of fried chicken nuggets When the coating powder was flour and OZ1, the fat content of the internal matrix of fried chicken nuggets was higher, which was 5.83% and 5.46%, respectively; the fat content of the internal matrix of fried chicken nuggets coated with compound powder was lower (2.63%~5.46%).
The oil content in the outer batter layer of fried chicken pieces was highest when the coating powder was tapioca starch, reaching 28.81%; the oil content in the outer batter layer of fried chicken pieces coated with OZ1 and OZ2 was lower (20.97%~21.06%). This may be due to the strong gel structure and high viscosity of the complexes, which can reduce the formation or enlargement of the pores of the outer batter layer to a certain extent, and thus reduce the adsorption of oil and grease in the outer batter layer.

Figure 4 Oil content of fried chicken nuggets
Moisture content of deep-fried chicken nuggets The moisture in food has a great influence on its taste, color and flavor, and is also very likely to lead to the deterioration of food quality. Tapioca starch has the lowest moisture content of 22.33%; OZ5 has the highest moisture content of 29.98%; and there is no significant change in the moisture content of the internal matrix of deep-fried chicken nuggets with different coating powders.
The high moisture content of the internal matrix and the moderate moisture content of the external batter layer in the battered food products would result in a crispy texture on the outside and tenderness on the inside. If the moisture content of the external batter layer was too high, it would result in sticky teeth and lack of crispy texture during consumption; if the moisture content was too low, it would cause the external batter layer to be too hard, which would lead to a decrease in the quality of the food.

Table 1 Moisture content of deep-fried chicken nuggets
5. Textural properties of fried chicken pieces The hardness and chewiness of the outer breading layer of fried chicken pieces coated with HPMC were lower than those of fried chicken pieces coated with flour, tapioca starch and complex.
Although there was no significant difference between the hardness, elasticity and chewiness of the outer breading layer of flour, tapioca starch and complex, for the complex, it showed a tendency to decrease with the increase in the amount of corn alkyd soluble protein added.
On the one hand, during the process of gel formation, zeinolysin would hinder the rearrangement of starch molecules and weaken the interaction between starch molecules; on the other hand, part of starch molecules in the composite system was replaced by zeinolysin, which reduced the total content of starch molecules, and so the hardness of the outer coating layer decreased.
The elasticity of the internal matrix with HPMC as the coating powder was smaller than that of the internal matrix of deep-fried chicken nuggets with flour, tapioca starch and the composite system, which indicated that the presence of starch in the external coating batter would have a certain effect on the textural properties of the matrix food within the batter, and the starch absorbed water and swelled during the frying process to make the coating batter layer elastic, and the starch viscosity was increased after the paste was pasted, and at the same time blocked the pores in the batter layer, so that the deep-fried chicken nuggets had a better Elasticity.
6, the color of fried chicken pieces of fried food attractive golden yellow is mainly caused by non-enzymatic browning, including caramelization reaction, Melad reaction and other reactions. Research shows that the factors affecting the color of deep-fried chicken nuggets are mainly the main components of the batter, frying temperature, frying time, raw material processing methods. The red and yellow color of the outer surface of deep-fried chicken nuggets increased most significantly, which can give consumers an attractive and pleasant feeling.
The deep-fried chicken nuggets coated with powder as HPMC had the lowest red and yellow color and the brightest color; there was no significant difference in the color of deep-fried chicken nuggets coated with powder as substance, and the color of deep-fried chicken nuggets was golden yellow when the complex was coated with powder. This may be due to octenyl succinic acid starch ester and corn alcohol soluble protein in the deep-frying process occurred in the Melad reaction, so that the deep-fried chicken nuggets show attractive golden yellow color.
7. The sensory scores of deep-fried chicken nuggets with flour and tapioca starch as coating powder had lower sensory scores. Although the deep-fried chicken nuggets coated with tapioca starch and flour had the attractive flavor of deep-fried food, the adhesion between the outer coating layer and the base chicken nuggets was poor, or even completely detached, with a greasy feeling.
OZ2 was the highest sensory score of fried chicken nuggets coated with flour, which not only had an attractive golden color and special flavor of fried food, but also had clear cut surface layers, moderate thickness of the outer batter layer and close adhesion with the base chicken. When flour, tapioca starch, HPMC and the complex were used as the coating powder, the differences in the adhesion status with the base chicken pieces were larger, and the better water retention and oil resistance of the complex helped to improve the sensory quality of the fried chicken pieces.