Optimization of active pectin coating formulation and its effect on surface morphology and shelf-life of white button mushroom (Agaricus bisporus)

The present work aimed to optimize an active pectin-based coating to preserve microbial and enzymatic stability and maintain the quality parameters of white button mushrooms (WBM), thus increasing their shelf stability. d-optimal mixture design was implemented to study the effect of pectin (X₁), ascorbic acid (X₂), and ethylene-diamine-tetra acetic acid (EDTA) (X₃) on polyphenol oxidase (PPO) inhibition, browning index, and total phenolic content. The optimal coating was a mixture of 2.55% w/v pectin, 0.67% w/v ascorbic acid, and 0.78% w/v EDTA. Further, the optimally coated WBM was stored for 6 days at 20 ± 1 °C. The coating on WBM significantly prevented the growth of natural microflora in the sample. Similarly, a maximum of 84% PPO inhibition was achieved at the end of the storage period. A minimum browning index (BI) of 66 was observed after six days of storage, significantly lower than that of the uncoated sample with a BI of 72.72 ± 0.90. Maximum phenolic content of 10.23 mgGAE/g WBM (dry basis) was preserved till day 6, while the antioxidant capacity was 7.16 ± 0.20 mg GAEAOC/g WBM (dry basis). Based on microbial safety and overall quality parameters, the optimal pectin-based ascorbic acid and EDTA-enriched coating led to a shelf-life of 4 days against 2 days for uncoated mushrooms at 20 °C. The optimized coating of mushrooms resulted in competitive inhibition of PPO. Fourier transform infrared (FTIR) spectroscopy revealed that EDTA and optimized coating modulated the secondary structure conformation in the amide I region. Microstructural analysis of the mushroom cap surface through scanning electron microscopy (SEM) showed that the optimized coating formed a homogeneous protective barrier on the mushroom surface, leading to the closure of intercellular spaces on the surface. The optimized coating can help mitigate postharvest losses due to the high perishability of white button mushrooms and provides a valuable solution for the industry to enhance product quality and safety.