RESUMO
Large amount of pineapple peels (by-products) is left over after processing and they are a potential source for bromelain extraction. Distilled water (DI), DI containing cysteine and ethylenediaminetetraacetic acid (EDTA) (DI-CE), sodium phosphate buffer pH 7.0 (PB) and PB containing cysteine and EDTA (PB-CE) were used as extractants for bromelain from the pineapple peels. The highest bromelain activity was obtained when it was extracted with PB-CE (867 and 1032 units for Nang Lae and Phu Lae cultv, respectively). The PB could maintain the pH of the extract (pH 5.1-5.7) when compared with others. Under sodium dodecyl sulfate polyacrylamide gel electrophoresis, the extract showed protein bands in the range 24-28 kDa. The protein band with a molecular weight of â¼28 kDa exposed the clear zone on blue background under the casein-substrate gel electrophoresis. The effects of the bromelain extract on the protein patterns of beef, chicken and squid muscles were also determined. Trichloroacetic acid soluble peptide content of all the treated muscles increased when the amount of bromelain extract increased. Decrease in myosin heavy chains and actin was observed in all the muscle types when bromelain extract was used. The best extractant for bromelain from pineapple peels was PB-CE. Moreover, bromelain extract could be used as a muscle food tenderizing agent in food industries.
Assuntos
Ananas/enzimologia , Bromelaínas/isolamento & purificação , Aditivos Alimentares/isolamento & purificação , Frutas/enzimologia , Resíduos Industriais/análise , Animais , Bromelaínas/química , Bromelaínas/economia , Bromelaínas/metabolismo , Cisteína/química , Ácido Edético/química , Aditivos Alimentares/química , Aditivos Alimentares/economia , Aditivos Alimentares/metabolismo , Indústria de Processamento de Alimentos/economia , Indústria de Processamento de Alimentos/métodos , Concentração de Íons de Hidrogênio , Hidrólise , Indicadores e Reagentes/química , Resíduos Industriais/economia , Carne/análise , Peso Molecular , Proteínas Musculares/química , Proteínas Musculares/metabolismo , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Frutos do Mar/análise , Especificidade da Espécie , TailândiaRESUMO
Discoloration and lipid deterioration of farmed giant catfish (Pangasianodon gigas) muscle during 14 d refrigerated storage were investigated. Lipid deterioration, lipolysis, and lipid oxidation in both dorsal and ventral muscles increased as storage time increased. A progressive formation of primary lipid oxidation products monitored by the increase in conjugated dienes (CD) was observed (P < 0.05) and the increase in thiobarbituric reactive substances (TBARS), an index of secondary lipid oxidation products, was noticeable throughout the storage (P < 0.05). The pH of both dorsal and ventral muscles tended to increase as storage time continued (P < 0.05). A gradual increase in free fatty acid (FFA) formation was found within the first 10 d of refrigerated storage (P < 0.05), suggesting hydrolysis induced by lipases and phospholipases. However, a sharp decrease in FFA content was observed at the end of storage. Refrigerated storage also resulted in changes in redness index of both dorsal and ventral muscles. These changes were coincidental with the changes in metmyoglobin content. Therefore, the discoloration and lipid changes in giant catfish muscle during refrigerated storage depended on the muscle type and might be related to the difference in composition between dorsal and ventral muscles.
