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Browning inhibition and microbial control in fresh-cut persimmon (diospyros kaki 'Rojo Brillante') by apple pectin-based edible coatings

Sanchis, E., Ghidelli, C., Palou, L., Perez-Gago, M. B., Gonzalez, S., Sheth, C., Mateos, M.
Acta horticulturae 2015 no.1079 pp. 335-341
Diospyros kaki, antioxidants, apples, aqueous solutions, astringency, bacteria, calcium chloride, carbon dioxide, catechol oxidase, citric acid, coatings, color, edible films, enzymatic browning, fresh-cut foods, microbial growth, nisin, off flavors, pectins, persimmons, potassium sorbate, shelf life, sodium benzoate, yeasts
‘Rojo Brillante’ persimmons can be commercialized as a fresh-cut commodity after removing natural fruit astringency by applying high levels of CO2. However, the shelf life of minimally-processed fruit is rather limited due to enzymatic browning and microbial growth. The aim of this study was to develop new edible coatings based on apple pectin with a combination of antioxidants and antimicrobial agents. Treatments included one of the following antimicrobials, i.e., potassium sorbate (PS) at 0.2 or 0.4%, sodium benzoate (SB) at 0.4%, or nisin (NI) at 500 IU/ml, added to 1% apple pectin coatings containing 1% citric acid and 1% calcium chloride (CaCl2) as antioxidants. Persimmon slices were dipped in the coatings, the aqueous antioxidant solution or water (control), and were packed under normal atmosphere and stored at 5°C for 9 d. Color, polyphenoloxidase (PPO) activity, visual quality, overall flavor and microbial growth were measured after 2, 5, 7 and 9 days of storage. Coated samples and those dipped in the antioxidant aqueous solution presented lower a* and higher b* values than the control samples, indicating browning inhibition. These results correlated with the lower PPO activity of treated samples compared to the control samples. The persimmon slices treated with coatings containing PS and SB reached the limit of marketability after 7 days of storage. Addition of antimicrobial agents to apple pectin coatings slightly affected the initial overall fruit flavor. After 2 days of storage, off-flavors disappeared and samples were ranked above the limit of acceptability by the judges. The antimicrobial coatings inhibited the growth of mesophilic aerobic bacteria, and those containing SB and NI were the most effective. No growth of molds, yeasts and psychrophilic aerobic bacteria during storage was monitored.