Avaliação dos efeitos de revestimentos naturais na conservação de carne bovina resfriada e embalada a vácuo

Abstract

Brazil is the world’s second largest producer and exporter of bovine fresh meat, what in 2014 accounted for about US$23.31 billion in Gross Value of Production (GVP) in a market of US$62.97 billion per year, generating about 7 million jobs. The most evaluated parameters about meat, can be divided into physical-chemical like temperature (T), water activity (Aw), redox potential (Eh), hydrogen ion potential (pH), maturation or tenderization, cooking method and sensorial like color, softness, texture, juiciness and flavor - combination of aroma and taste. As 75% of muscle composition is water, in the muscle conversion into meat there is a release of 2 to 5% of this total water, due evaporation and exudation, characterizing a high Aw value. This obtained solution is rich in amino acids, peptides, nucleotides, sugars and although the vacuum packaging is considered an efficient way to preserve in natura chilled beef, a serious problem, known as blown pack may occur if microbial contamination is significant or not respect the cooling minimum temperature (4 ± 2 °C). Therefore, the reduction of microbial proliferation in food is necessary. The goal of this work was to use a coating based on chitosan at 1% (w/w) and glycerol at 0.5% (w/w) which can be applied to food protection, especially as edible films and coatings. In parallel, was evaluated the effects of extract (PEE) and propolis nanoparticles (PNs) on some bacterial genders commonly found in fresh meat in natura. The permeability of the film produced in this work, respectively to O2 and CO2 gases was 1.53 ± 0.73 • 10-15 g•m•(Pa•s•m2) -1 and 1.20 ± 0.06 • 10-12 g•m•(Pa•s•m2) -1, relatively larger, when compared to literature. This film has relatively high moisture content and low solubility, what is interesting for application in meat, because it keeps its barrier property and integrity, even under high humidity and possible high Aw. Regarding the color (Hue) of meat samples (Longissimus dorsi) used in this experiments, on the 7th day presented a small disadvantage of coated and vacuum samples relative to that were not vacuum. However, on the 14th day, brightness (Chroma) of the samples in this condition was better than the other samples and, there was no significant difference in color. Therefore, this condition yet can be considered more advantageous when we wish to extend the shelf life time. The coating developed in this work, improved water holding capacity (WHC) of meat samples, which helps the desired juiciness of the product. Besides that, this film inhibits the growth of enterobacteria, lactic acid bacteria (LABs) and total psychrotrophic, which certainly can increase the shelf life of the product. The used PEE has a relatively high phenolic content and antioxidant capacity. For all tested concentrations of PEE and PNs with all bacterial species, better results were obtained with PNs.