Data da Defesa: 24/03/2014



 INTRODUCTION. Nowadays there is an increase in the consumption of minimally processed vegetables (MPV) due to be a product that keeps the freshness of the vegetables in nature combined with the convenience and good nutritional quality. However the increase in consumption along with the minimal processing techniques of MPV, led to an increase occurrence of pathogenic bacteria such as Salmonella spp., Escherichia coli, Staphylococcus aureus and Aeromonas hydrophila, besides the indicators of quality and hygiene processing, such as coliforms, molds and yeasts. Due to this microbial contamination the use of essential oils (EO) of plants and its constituents have been an alternative because they have a broad antimicrobial effect and are defined as GRAS (Generally Recognized as Safe) by the Food and Drug Administration (FDA). The carvacrol, component of Origanum vulgare and Thymus vulgaris essential oils, has been shown to be active against a broad spectrum of microorganisms. A promising trend in the use of EO and its constituents in foods is their incorporation into edible films and coatings, controlling pathogens and extending the shelf life of perishable products such as MPV.
AIMS. The objective of this study was investigate the antimicrobial effect of the carvacrol incorporated into edible film applied in minimally processed pumpkin (MPP), as well as its interference on physical and chemical characteristics.
MATERIAL AND METHODS. To evaluate the in vitro antimicrobial activity, the micro broth dilution method was used according to the protocol established by the document M100-S22/2012, Clinical and Laboratory Standards Institute was used. The bacterial isolates tested were: E. coli ATCC 25922, S. Typhimurium ATCC 14028, A. hydrophila ATCC 7966 and S. aureus ATCC 25923. The edible films were prepared using a suspension at 3 % of cassava starch. The incorporation of carvacrol was taken at concentrations of 312 and 625 mg / mL. Ripe pumpkins (Cucurbita moschata Duch). were minimally processed according to good manufacturing practices. After the minimum processing, pumpkins were immersed in the coating solution of cassava starch and in the coating solution added antimicrobial substance. Two controls (C1 and C2) and two treatments (T1 and T2) were used, which consisted of pumpkin minimally processed (C1); pumpkin coated with cassava starch film without the addition of carvacrol (C2); pumpkin coated with film added to carvacrol at 312 mg / mL (T1) and pumpkin coated with film added to carvacrol at 625 mg / mL (T2). The control and treatment groups were evaluated for survival of bacteria experimentally inoculated and bacteria that naturally occur in MPV, besides the physical-chemical analyzes, for seven days of storage under refrigeration. All microbiological and physico-chemical analyzes were performed according to the official method. Analyses were made in duplicate with two replicates, and the results were expressed as mean and standard deviation. The average results were submitted to analysis of variance (ANOVA) with 5% level of significance, and means were compared by Tukey test.
RESULTS AND DISCUSSION. The minimum inhibitory concentration and minimum bactericidal concentration of carvacrol for S. Typhimurium ATCC 14028, E. coli ATCC 25922, A. hydrophila ATCC 7966 and S. aureus ATCC 25923, was 312 mg / mL. The application of the carvacrol at 625 mg / mL (T2) in minimally processed pumpkin completely inhibited the bacterial growth at all times evaluated. When caravcrol was used at 312 mg / mL (T1), the counts of E. coli and S. Typhimurium were reduced almost 5 log CFU / g at the seventh day. The counts of A. hydrophila were reduced about 8 log CFU / g and S. aureus approximately 2 log CFU / g at the same period. The evaluation of bacteria naturally present in MPV, Coliforms at 35 °C and 45 °C, presented values <3 MPN / g in both treatments, in all days of shelf life. The treatments with the addition of 312 mg / mL and 625 mg / mL of carvacrol presented a significant reduction (p <0.05) in psychrotrophic count, compared to controls C1 and C2. The counts of yeasts and molds also showed a significant reduction (p <0.05) during all days of storage, when compared to treatments with the addition of carvacrol and controls. In the last day, that group of microorganisms was not detected in both treatments. Regarding to physico-chemical parameters, treatments (T1 and T2) and controls (C1 and C2) presented an increase in the values of total tritratable acidity during storage, having significant difference (p <0.05) among treatments T1 and T2 in relation to controls C1 and C2. For pH values there was a significant difference (p <0.05) among T1 and T2 to C1 control at the first and last day of storage. In general there was no significant difference (p <0.05) for the content of Soluble Solids between treatments and controls, showing values ranging from 4.9 to 5.2 °Brix, in the last day of shelf life. In the weight loss test there was a significant difference between treatments and controls. Treatments with carvacrol presented a significant reduction in weight loss (until to 3.73% on the last day of storage, between T2 and C1).
CONCLUSIONS. The results presented in this study showed the efficacy of carvacrol in inhibiting pathogenic bacteria in vitro, in the MIC and MBC assays, as well as in the application on MPP, reducing the count of both pathogenic and spoilage microorganisms without influencing the physico-chemical parameters, reinforcing the idea that the incorporation of compounds with antimicrobial action in edible films for application in MPP is an alternative to improve the microbiological safety and quality of these products.
Key words: Minimally Processed Vegetables; Antimicrobial activity; Phytocompounds; Microbiological Quality.

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