Journal of Food Processing & Technology

Abstract

Inhibiting and Inactivating Effect of Chitosan on Heat Resistant Moulds Responsible for Spoilage of Pasteurized Fruit Products

Manusia SA and Berni E

The antimicrobial properties of chitosan, a deacetylated derivative of chitin, were assessed in a synthetic medium and in a blueberry and red grape juice against six heat resistant moulds (HRM) associated with food spoilage, in order to evaluate its use as a potential food preservative of natural origin. In both synthetic medium and natural substrate, the Minimum Inhibitory Concentration (MIC) of chitosan proved to vary in a wide range, regardless to both fungal genus and medium considered. Although Aspergillus neoglaber, Talaromyces bacillisporus and Aspergillus niger proved most resistant to chitosan (MIC > 5000 mg/L) on both media, a marked difference was detected for other strains tested. On HRM inoculated in MEB, the MIC was equal to 100 mg/L for Byssochlamys fulva or Monascus floridanus, and to 1000 mg/L for Talaromyces macrosporus. On HRM inoculated in blueberry and red grape juice, the MIC was equal to 2500 mg/L for Byssochlamys fulva or Monascus floridanus, and to 5000 mg/L for Talaromyces macrosporus.

If combined with thermal treatment (80°C for 5 min) at a concentration (500 mg/L) that did not prove effective in inhibiting fungal spores, chitosan did not affect spore survival of microorganisms tested, thus allowing the spoilage of tested fruit juice after 5 days at 30°C. Also heat resistance parameters of a selected heat-resistant strain, T. bacillisporus, were not significantly affected by supplementation of blueberry and red grape juice with 500 mg/L of chitosan, D values ranging between 47.6 and 71.4 minutes at 82°C; 13.3 and 23.3 minutes at 85°C; 3.6 and 5.9 minutes at 88°C; 0.9 and 1.8 minutes at 91°C (z=5.2°C to 5.5°C). Since chitosan did not prove effective alone or combined with thermal treatment either to inactivate heat resistant microorganisms tested or to modify heat-resistance parameters of a heat resistant mould such as T. bacillisporus, its use cannot be considered as an interesting strategy to apply milder thermal treatments and to achieve stability of acid products.