Effect of conventional dipping and twin-nozzle electrostatic spray coating methods on the shelf-life quality parameters of Apples (Rich Red): A comparative study
Akanksha Singh, Sakshi Gumber, Aamir Sohel, Raj Rani, S. P. S. Saini, Manoj K. Nayak, M. Patel, Koushik Mazumder
Abstract
• Electrostatic spraying (ESC) was used to apply AX-SABG-based composite coating on apples. • The physiochemical properties of AX-SABG indicated its superiority over the commercial coating for the ESC application. • The ESC application provided better homogeneity and lesser thickness of the coating material on the fruit surface. • AX-SABG-based composite coating was effective in maintaining the shelf life of apples with dipping (DP) and electrostatic spray (ESC) coating. • The type of coating application did not have a significant influence on the performance of the coating material. Apples are climacteric fruits that are in high demand; however, improper postharvest management leads to a loss of 20–30 % of the total produce before reaching consumers. The objective of this study was to compare the effectiveness of edible coatings from biopolymers namely arabinoxylan (AX), and stearic acid ester of β-glucan (SABG) coating material with dipping (DP) and electrostatic spray (ESC) methods at 22 ± 2 °C. The viscosity, conductivity, surface tension, contact angle, and charge-to-mass ratio of AX-SABG (1–2 %) were 0.49–0.99 kg/cm 3 , 2.27–2.96 mS/cm, 36.15–34.01 mN/m, 52.22- 45.78 (θ), and 1.67–1.71 mC/kg respectively. AX-SABG with a higher charge-to-mass ratio proved to be a better alternative for ESC application compared to the commercial coating shellac. SEM analysis and microscopic studies indicated that the ESC method resulted in a homogenous and thinner coating on the fruit surface compared to DP. The coated (AX-SABG and Shellac, 1–2 %, DP and ESC) apples significantly reduced weight loss (%), ripening index, decay incidence, enzyme activities, preventing color degradation, maintaining higher firmness and anthocyanin content compared to uncoated fruits. However, AX-SABG exhibited a more prominent effect in reducing weight loss (%), respiration and ethylene production rate, decay incidence, enzymatic activity, and retaining anthocyanin content in the coated apples compared to shellac-coated fruits. The study advocates that ESC can be used at the industrial scale for the surface coating of fruits.