Effects of Soaking with Natural Additives in Combinations with Vacuum or Modified Atmosphere Packaging on Microbial Populations and Shelf Life of Fresh Truffles (Chinese Tuber Indicum)

Abstract

The objective of this study was to evaluate the relative effects and interactions of combined soaking treatment using citric acid (CTA) and apple polyphenol (APP) at mild heating temperatures for the inactivation of the external and internal microflora (mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi) in Chinese Tuber indicum, as well as to analyze the microbiological and sensory changes under modified atmosphere packaging (MAP)- and vacuum atmosphere packaging (VAC)-packed Chinese T. indicum stored at 4 °C for up to 55 d. Chinese T. indicum was soaked with CTA and APP alone or in combination for 10, 20, and 30 min at 35, 45, and 55 °C. A disinfection method using CTA and APP (3% CTA + 3% APP for 20 min at 45 °C) was obtained. Under this set of combination, the experimental values of microbial counts of mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi were 2.31 ± 0.4 log CFU/g, <1.0 log CFU/g, and <1.0 log CFU/g, respectively. Through the analysis of sensory qualities and microbial populations for MAP- or VAC-packed Chinese T. indicum, the shelf life of soaked truffles was prolonged to 45 or 40 d, respectively. The synergistic effect of CTA and APP may provide valuable insight into the reduction of microorganisms on fresh truffles.

Microbiological evaluation of whole, sliced, and freeze‐dried black truffles (Tuber melanosporum) under vacuum packaging and refrigerator storage

“…Each microbial count (expressed as log CFU/g) was calculated based on the mean of three samples. 29 Ten bacterial colonies on the respective agar (except Bacillus colonies which were below the quantification limit) were isolated and tested for oxidase and catalase reactions 30,31 before they were Gram-stained (Fluka, Australia). 6,32,33 Spore staining was performed for Bacillus spp.…”

“…6 The variations in the microbial counts between studies could be due to differences in collection season, maturity, origin, geographical location, soil microbiology, and postharvest packaging. 29,37,38 Pseudomonadaceae are psychrotrophic (cold-tolerant) bacteria that can proliferate even at 2-5 C [39][40][41] and can contribute to food spoilage particularly in food with a high water activity. 42,43 Sorrentino et al 8 reported that Pseudomonas spp.…”