Freezing is one of the methods to preserve and guarantee the quality of meat until it reaches the consumer. Even though freezing is classified as a mild form of preservation, it causes meat changes resulting from the formation of ice crystals that subsequently affect the tenderness and functionality of meat. The aim of this study was to evaluate the physicochemical and structural characteristics of chicken half breast submitted to fast freezing (-36 °C for 2 hours) and thawed by five different methods (under refrigeration, in a microwave, in a oven with air circulation, placed in cold water, or at room temperature). After thawing, the following parameters were evaluated: moisture content, drip loss (syneresis), water activity (aw), and shear force. Samples were also histologically evaluated by light microscopy. The results indicated that, despite being submitted to fast freezing, thawing affected (p <0.05) most of the physicochemical and structural properties of the meat, except for aw. Thawing in cold water (packed in low-density polyethylene bags and placed in cold water at approximately 10 °C for 2 hours and 15 minutes) presented the best results due to lesser damage to the cell structure, as shown by the lower drip loss, higher moisture content, and greater tenderness of the samples compared to those thawed using the other methods. Histological examination showed that muscle fiber structural features and organization were maintained. Thawing at low temperatures seems to cause less damage to the meat structure and allows maintaining of its properties. It was concluded that the meat quality is not related only with the freezing method, but also with the method and conditions used in thawing.

No presente trabalho a atividade antioxidante in vitro e a genotoxicidade in vivo de M. dasyclada foi comparada com as espécies de referência M.aquifolium e M. ilicifolia. M. dasyclada mostrou atividade antioxidante in vitro comparável a de M. aquifolium mas inferior a M. ilicifolia, sendo que foi detectada uma correlação de Pearson inversa entre os valores de IC50 por DPPH e o conteúdo fenólico total (–0,932). Em relação ao teor de carbonila, os extratos de M. dasyclada e M. aquifolium promoveram um aumento semelhante na oxidação das proteínas in vivo, ao passo que Maytenus ilicifolia não alterou os níveis de carbonila. O ensaio do cometa demonstrou que as três espécies analisadas promoveram um nível baixo e semelhante de genotoxicidade, o que é compatível com os danos no DNA induzidos por outras plantas medicinais e é parcialmente recuperada por um co-tratamento com a vitamina C. Os dados mostraram M. dasyclada com atividade antioxidante in vitro, e que os seus efeitos genotóxicos e pró-oxidantes in vivo são comparáveis às espécies de referência de Maytenus.

In these work the in vitro antioxidant activity and the in vivo genotoxicity of M. dasyclada was compared to the reference species M. aquifolium and M. ilicifolia. M. dasyclada showed in vitro antioxidant activity comparable to M. aquifolium but lower than M. ilicifolia, being that a inverse Pearson correlation between DPPH IC50 values and total phenolic content was detected (–0.932). The carbonyl content of M. dasyclada and M. aquifolium extracts promoted a similar increase in protein oxidation in vivo, while M. ilicifolia no altered the carbonyl levels. The comet assay demonstrated that the three analyzed species promoted a low and similar level of genotoxicity; which is compatible with DNA damage induced by other medicinal plants and is partially recovered by a co-treatment with vitamin C. The data showed M. dasyclada as antioxidant activity in vitro, and that its genotoxic and pro-oxidant effects in vivo are comparable to the Maytenus reference species.