The effect of edible coating based on sodium caseinate and propyl gallate on the shelf life of minimally processed fennel during storage

This research aimed to study the effect of an active edible coating based on sodium caseinate (SC) and propyl gallate (PG) on the quality of minimally processed (MP) fennel during storage. The respiration rate (RR) of the MP fennel coated with SC of different concentrations (8 %, 10 % and 12 %) and without coating was evaluated at 10 °C to determine the best SC concentration. Thereafter, MP fennel without coating, with 8 % SC coating and with 8 % SC coating enriched with PG (0.13 mg mL−1) was evaluated for their effect on the microbial count and microbiota composition, weight loss, pH, total acidity (TA), total soluble solids (TSS), colour, total polyphenols content and antioxidant capacity during storage (0, 7 and 15 days) at 4 °C. In addition, sensory analysis was performed to discriminate fresh samples from samples at different levels of visual quality. The results showed that 8 % SC coating decreased the RR to 20 %. During storage at 4 °C, weight loss increased up to 2% after 15 days of storage for all samples, whereas the pH, TA and TSS of MP fennels did not change significantly. The presence of the active coating affected the microbiota composition of the MP fennels, inhibiting some Enterobacteria species, thus leading to the predominance of Pseudomonas spp., which agrees with culture-based results. As the active compound has a positive impact on the total polyphenol content and antioxidant capacity, in the absence of the active compound, the coating did not influence these parameters. A ΔE value of 3.7 was found to be the critical level of the quality index for MP fennels, as demonstrated difference from reference sensory test. Moreover, this research highlights that the browning process is the limiting factor for the product's shelf life.