Metabolička aktivnost termorezistentnih mikroorganizama

Abstract

Termorezistentni mikroorganizmi, zahvaljujući otpornosti na termičke tretmane koji se primenjuju u industriji mleka, kao i mogućnostima rasta i metaboličkim aktivnostima u uslovima čuvanja gotovih proizvoda, imaju značaja kao mikroorganizmi kvara. Ova osobina definiše tehnološki značaj termorezistentnih mikroorganizama. Među populacijom termorezistentnih mikroorganizama, Bacillus spp. pokazuju značajnu proteolitičku aktivnost, a s obzirom na njihovo svojstvo razlaganja kazeina, potencijal njihove proteolize može se uspešno koristiti u koagulaciji mleka i zrenja sireva. Veliki značaj imaju proteinaze Bacillussubtilis, čiji se proteolitički enzimi uspešno primenjuju u proizvodnji Chedar, Munster i Camembert sira. Suprotno ovome, aktivnost proteina za Bacillus spp. u sterilisanom mleku, u uslovima ne - adekvatnog čuvanja dovodi do slatkog grušanja ili pojave gorkog ukusa mleka, kao rezultat nastanka gorkih peptida, dok preterana aktivnost proteinaza bacila pri proizvodnji Chedar sira uslovljava gruš mekše konzistencije, veći sadržaj proteina i masti u surutki, što dovodi do smanjenog randmana sira za 10%. Oslobađanjem nižih masnih kiselina delovanjem lipolitičkih enzima poreklom od mikroorganizama, razvija se neprijatan ukus i miris, što predstavlja manu poznatu pod imenom hidrolitička užeglost. Od termorezistentnih mikroorganizama, sposobnost hidrolize masti pokazuju mikroorganizmi roda Bacillus. Cilj ovog rada bio je da se ispita sposobnost termorezistentnih mikro organizama izolovanih iz mleka da razlažu proteine, masti i skrob, što dovodi do kvara mleka i proizvoda od mleka. Od ukupno 80 izolata termorezistentnih mikroorganizama, proteolitičku aktivnost je ispoljilo 35 (43,75%) izolata u uslovima inkubacije pri 30°C/72h i 30 (37,50%) izolata u uslovima inkubacije pri 20±2°C/72h, dok nijedan izolat nije ispoljio proteolitičku aktivnost u uslovima inkubacije pri 10±1°C/10 dana. Amilolitička aktivnost je utvrđena kod 16 (20,0%) izolata u uslovima inkubacije pri 30°C/72h i 15 (18,75%) izolata u uslovima inkubacije pri 20±2°C/72h. Amilolitička aktivnost termorezistentnih mikroorganizama izostaje u uslovima inkubacije pri 10±1°C/10 dana. Ispitivani izolati termorezistentnih mikroorganizama nisu pokazali lipolitičku aktivnost, bez obzira na primenjene različite uslove inkubacije.

Heat-resistant microorganisms, thanks to their resistance to thermal treatments are applied in the dairy industry, and growth opportunities, as well as metabolic activity in the conditions of storage of Ninal products, are important as spoilage microorganisms. This attribute deNines technological signiNicance of heat-resistant microorganisms. Among a population of heat-resistant microorganisms, Bacillus spp. showes a signiNicant proteolytic activity, and due to its caseolytic activity, proteolytic potential can be successfully applied in the coagulation of milk and cheese ripening.Proteinases produced by Bacillus subtilishas great importance and aresuccessfully used in the production of Chedar, Munster and Camembert cheese. However, the activity of proteinase Bacillus spp. in sterilized milk in inadequate storage conditions, leads to the sweet coagulation, or occurrence of sweet or bitter taste of milk as a result of the formation of bitter peptides, while excessive activity oNbacillus proteinases in production process of Chedar cheese causes soft curd consistency, a higher content of proteins and fat in the whey, which leads to reduced dressing of cheese for 10%.Release of low fatt acids due to activity of lipolytic enzymes from a microorganisms, develops an unpleasant taste and odor, which is a foible known as hydrolytic rancidity. Among heat-resistant microorganisms, bacteria of the genus Bacillusshow the ability to hydrolyse fats. The aim of this study was to examine the ability of heat-resistant microorganisms, isolated from milk to degrade proteins, fats and starches, which can lead to spoilage of milk and milk products. Out of 80 isolates of heat-resistant microorganisms, proteolytic activity showed 35 (43.75%) isolates in condition of incubation at 30°/72h and 30 (37.50%) isolates under coditions of incubation at 20 ±2°C/72h, while neither isolate showed proteolytic activity under conditions of incubation at 10±1°C/10 days. Amylolytic activity was found in 16 (20.0%) isolates under conditions of incubation 30°C/72h and 15 (18.75%) isolates under conditions of incubation at 20±2°C/72h. The heatresistant microorganisms did not show amylolytic activity under conditions of incubation at 10±1°C/10 days.Investigated thermoresistant bacteria did not show lipolytic activity, regardless of the applied different incubation conditions.