ABSTRACT
Chitosan must be dissolved in acid solution to activate its antimicrobial properties. The objectives of present study were to determine whether acetic and lactic acids used to dissolve chitosan would influence its effectiveness to control the native microflora of Butterhead lettuce at harvest and during postharvest storage (7-8 °C, 5 days). Chitosan was applied as a SINGLE DOSE (14, 10, 7, 3 or 0 days previous to harvest) or in SUCCESSIVE DOSES (at 14 + 10 + 7+3 + 0 days prior to harvest). Although chitosan in acetic acid showed antimicrobial activity, treated plants showed dried brown stains which significantly reduced sensorial quality. Chitosan in lactic acid applied in a SINGLE DOSE at harvest or in SUCCESSIVE DOSES reduced microbial counts of all populations at harvest without affecting sensorial quality. After postharvest storage, lettuce treated with SUCCESSIVE APPLICATIONS of chitosan in lactic acid presented significant reductions in the microbial populations compared with untreated sample (-2.02 log in yeast and molds, -1.83 log in total coliforms, -1.4 log CFU g-1 in mesophilic bacteria and -1.1 log in psychrophilic bacteria). In conclusion, replacement of acetic by lactic acid did not affect the antimicrobial activity of chitosan, reducing microbial counts at harvest and after postharvest storage without affecting sensorial quality.
ABSTRACT
UNLABELLED: Samples of butternut squash, potatoes, rice, and wheat flour were analyzed. Bacillus spp. and related species belonging to Paenibacillus and Brevibacillus genera were found in 96% of the samples. In butternut squash, predominant species were Bacillus pumilus and Paenibacillus polymyxa together with other Bacillus spp. species (B. cereus, B. licheniformis, B. sphaericus, and B. subtilis). In all the potato samples, Bacillus species were detected (B. cereus, B. mycoides, and B. licheniformis). Also, Bacillus spp. were detected in 100% of the unhusked rice samples, while incidence in white rice samples was 83%. In total rice samples, B. pumilus, Brevibacillus brevis, and Paenibacillus macerans were the main species and B. cereus, P. polymyxa, B. subtilis, and Brevibacillus laterosporus had the lower percentage. The most important species found in wheat flour was P. polymyxa with colony forming units per gram of about 10(2). As the identified species were potentially causatives of foodborne diseases, attention should be given to sanitary and temperature conditions as critical factors that influence the safety and shelf life of these products. PRACTICAL APPLICATION: Foodborne illness produce by B. cereus have been associated with a wide variety of food. In addition, some other Bacillus species have been related to foodborne disease in humans. Information about the virulence mechanisms of other Bacillus spp. is scanty and their risk is underestimated. Identifying the group of food and the food processes in which Bacillus cereus or other Bacillus spp. would be hazardous for human health is vital for the prevention of foodborne outbreak. In this study, we determined the incidence of Bacillus spp. and related genera in some food items of agriculture origin from Argentina. This research is relevant to identify the presence of potentially pathogen Bacillus species and related genera in this type of food.
