RESUMO
Fresh produce have a more limited shelf life than processed ones. Their sensory attributes such as appearance and surface texture are important features in consumer perception and liking. The decomposition of fresh produce, which is caused by enzymes, chemical reactions, and microbial infections, often caused by Colletotrichum species, is inevitable. However, it can be slowed down. Several materials have been developed for this purpose, with an emphasis on active coatings using nanomaterials. In this study, the protective effects of a zein coating containing chitosan nanowhiskers (CSW) for the maintenance of fruit quality were investigated using guava (Psidium guajava L.) as a model fruit. CSW were previously characterized, and their antifungal effects against distinct Colletotrichum species (Colletotrichum asianum, Colletotrichum tropicale, Colletotrichum gloeosporioides, and Colletotrichum brevisporum) were proven. Coatings were characterized by thermogravimetric analysis, optical profilometry, and mechanical properties. Total soluble solids, pH, mass loss, and visual inspection of uncoated and coated guava fruits were also verified during 9 days. Results show that CSW length and aspect ratio decreased for longer extraction times. A similar behavior was found for x-ray diffraction in which peak intensity decreases under the same conditions. CSW degradation (ca. 250-400°C) also depends on extraction time in which more crystalline whiskers are the most thermally stable ones. The addition of CSW did not significantly (p < 0.05) modify the homogeneity and continuity of coating but prevented microbial growth assuring fruit quality during storage. In summary, coatings protected guava fruits from post-harvest spoilage while preserving quality and extending shelf life. PRACTICAL APPLICATION: Fresh foods such as fruits and vegetables have a more limited shelf life than processed ones.
Assuntos
Quitosana , Filmes Comestíveis , Zeína , Antifúngicos/farmacologia , Frutas/química , Quitosana/química , Zeína/análise , Conservação de Alimentos/métodosRESUMO
During the shelf-life of fresh meat, physical, chemical, microbiological, and sensory changes may occur. To avoid such changes, the combination of vacuum-packaging and use of edible coatings make a good strategy. This study aimed to evaluate the physicochemical characteristics of vacuum-packaged lamb meat combined with different zein-based edible coatings containing different vegetable oils (pink pepper, rosemary, olive oil, and the combinations of olive oil + pink pepper or rosemary), stored at 5 ± 1 °C. Parameters including pH, instrumental color, water holding capacity (WHC), shear force, and thiobarbituric acid reactive substances (TBARS) were analyzed every seven days, for 29 days. Significant differences (P<0.05) were observed in coating effects and storage time. The combination of olive oil and pepper oil (OLPP) exhibited higher color stability, while the coatings containing rosemary (RO), rosemary and olive oil (OLRO), and pink pepper oil (PP) exhibited the highest oxidative stability in 29 days. The pH, WHC, and shear force parameters did not appear to have been affected by the coatings. In summary, as appearance is an important purchasing factor, the coating containing olive oil and pink pepper oil is very promising as an alternative for maintaining vacuum-packaged lamb meat quality.(AU)
Durante a vida de prateleira da carne fresca podem ocorrer mudanças físico-químicas, microbiológicas e sensoriais indesejadas. Para evitar tais mudanças a combinação da embalagem tradicional à vácuo com revestimentos comestíveis é uma alternativa. O objetivo deste estudo foi avaliar o efeito do uso de diferentes revestimentos comestíveis à base de zeínas em combinação com diferentes óleos vegetais (óleos de: pimenta rosa, alecrim, azeite e combinação de azeite + óleo de pimenta rosa ou alecrim) nas características fisico-químicas da carne ovina, embalada à vácuo e armazenada à temperatura 5±1 °C. Foram realizadas análises de pH, cor instrumental, capacidade de retenção de água (CRA), força de cisalhamento, substâncias reativas ao ácido tiobarbitúrico (TBARS) a cada sete dias, no período de 29 dias. Foram observadas diferenças significativas (P<0,05) para o efeito de revestimentos e o tempo de armazenamento. A combinação de azeite mais óleo de pimenta (OLPP), apresentou maior estabilidade de cor, enquanto que os revestimentos contendo alecrim (RO), alecrim mais azeite (OLRO) e óleo de pimenta (PP) foram os que apresentaram maior estabilidade oxidativa no período de 29 dias. Os parâmetros pH, CRA e força de cisalhamento não parecem ter sido afetados pelos revestimentos. Tendo em vista que aparência é um importante fator de compra, o revestimento contendo azeite e óleo de pimenta rosa foi o mais promissor para ser utilizado na manutenção da qualidade de carne ovina.(AU)
Assuntos
Produtos da Carne/análise , Embalagem de Alimentos/métodos , Zeína/análise , Óleos de Plantas/análise , Fenômenos Químicos , OvinosRESUMO
Two high lysine maize endosperm mutations, opaque-5 (o5) and opaque-7 (o7), were biochemically characterized for endosperm protein synthesis and lysine metabolism in immature seeds. Albumins, globulins, and glutelins, which have a high content of lysine, were shown to be increased in the mutants, whereas zeins, which contain trace concentrations of lysine, were reduced in relation to the wild-type lines B77xB79+ and B37+. These alterations in the storage protein fraction distribution possibly explain the increased concentration of lysine in the two mutants. Using two-dimensional polyacrylamide gel electrophoresis of proteins of mature grains, variable amounts of zein polypeptides were detected and considerable differences were noted between the four lines studied. The analysis of the enzymes involved in lysine metabolism indicated that both mutants have reduced lysine catabolism when compared to their respective wild types, thus allowing more lysine to be available for storage protein synthesis.
Assuntos
Lisina/metabolismo , Mutação , Proteínas de Plantas/genética , Zea mays/genética , Eletroforese em Gel Bidimensional , Genótipo , Proteínas de Plantas/análise , Proteínas de Plantas/biossíntese , Sementes/metabolismo , Zea mays/metabolismo , Zeína/análise , Zeína/genéticaRESUMO
A study is presented on the protein composition of the Venezuelan corn cultivars Venezuela-1, Arichuna, Obregón and Venezuela-1 Opaque-2. The proteins were isolated and analyzed for their molecular weight and lysine and tryptophan content. Protein fractionation showed significant differences between normal corn cultivars and Opaque-2. The latter showed a low level of zein and a high content of alcohol-insoluble reduced glutelins (AIG), albumins and globulins in relation to the normal kernel. The relative increase of these protein fractions, rich in lysine and tryptophan, results in a higher concentration of these amino acids in the Opaque kernel, as revealed by the analysis of these compounds carried out in different cultivars. Electrophoretic analysis showed only small differences in the number and intensity of bands from the protein fractions of the maize cultivars under study.