Effect of ultrasound combined with edible coating based on guar gum on the physicochemical quality and texture of fried zucchini slices.

Edible coating (EC) can reduce excessive oil absorption in deep-fat fried food products. Ultrasound is an efficient pretreatment to preserve the quality characteristics of fried samples. The impact of guar gum based EC and sonication on the quality parameters of fried zucchini slices was investigated. The frying time, moisture percent, oil absorption, texture hardness, surface area change, crust color parameters (lightness, redness, yellowness, and total color change), and sensory attributes were assessed after the frying process. EC with guar gum and ultrasonic pretreatment significantly increased the frying time of the slices (p < 0.05). Ultrasonic power (75 or 150 W) did not have a significant impact on changing the frying time and moisture content of fried zucchini pieces (p > 0.05). The guar gum based EC and sonication process reduces the oil absorption in samples by reducing water evaporation. The highest (17.87%) and lowest (12.19%) oil absorption were for the uncoated and coated-high-power-sonicated (150 W) fried zucchini slices, respectively. The high-power ultrasound pretreatment significantly decreased the hardness of fried zucchini pieces (p < 0.05). High-intensity ultrasonic pretreatment (150 W) significantly decreased the crust area change of fried zucchini slices (p < 0.05). The maximum lightness (82.54) and yellowness (41.25) indexes, the minimum redness (-7.24), and total color change (10.68) indexes were for the coated and high-power sonicated (150 W) slices. The highest appearance, odor, texture, flavor, and overall acceptance were for the coated and low-power sonicated (75 W) sample. PRACTICAL APPLICATION: Ultrasound can induce various physicochemical effects, which can modify the structural properties of food products. Ultrasound (5 min, ultrasound bath 40 kHz and 75 W) with guar gum dispersion (1%, w/v) was an efficient treatment for maintaining the quality attributes of fried zucchini slices. The combined edible coating-sonication method can be used to reduce oil absorption, improve the physical properties of fried zucchini slices, and produce better quality product properties than traditional frying.