Influence of Raw Milk Quality on Fluid Milk Shelf Life

Abstract

Pasteurized fluid milk shelf life is influenced by raw milk quality. The microbial count and somatic cell count (SCC) determine the load of heat-resistant enzymes in milk. Generally, high levels of psychrotrophic bacteria in raw milk are required to contribute sufficient quantities of heat-stable proteases and lipases to cause breakdown of protein and fat after pasteurization. Sanitation, refrigeration, and the addition of CO2 to milk are used to control both total and psychrotrophic bacteria count. It is not uncommon for total bacterial counts of raw milk to be < 10,000 cfu/mL. In the past, fluid milk processors have not focused much attention on milk SCC. Increased SCC is correlated with increased amounts of heat-stable protease (plasmin) and lipase (lipoprotein lipase) in milk. When starting with raw milk that has a low bacterial count, and in the absence of microbial growth in pasteurized milk, enzymes associated with high SCC will cause protein and fat degradation during refrigerated storage, and produce off-flavors. As the ability to kill, remove, or control microbial growth in pasteurized refrigerated milk continues to improve, the original milk SCC will be the factor limiting the time of refrigerated storage before development of an off-flavor in milk. Most healthy cows in a dairy herd have a milk SCC < 50,000 cell/mL. Bulk tank SCC > 200,000 cell/mL are usually due to the contribution of high SCC milk from a small number of cows in the herd. Technology to identify these cows and keep their milk out of the bulk tank could substantially increase the value of the remaining milk for use in fluid milk processing. To achieve a 60- to 90-d shelf life of refrigerated fluid milk, fluid processors and dairy farmers need to work together to structure economic incentives that allow farmers to produce milk with the SCC needed for extended refrigerated shelf life.

Relationship between haptoglobin and serum amyloid A in milk and milk quality

“…The casein content but also the degree of casein degradation affects the processing properties of the milk and the yield and quality of the dairy products. Some properties that will be affected is the heat stability, sensory properties and texture, e.g., in the production of yoghurt and cheese (Lynch et al, 1995;Barbano et al, 2006;Kelly et al, 2006;De Noni et al, 2007 No relationship between APP and proteolysis was observed in this study. One reason for this could be that the fluorescamine method is not sensitive enough to detect small differences in proteolysis (Harayani et al, 2003).…”

Estudo da vida útil de queijo Minas

“…Estes microrganismos produzem enzimas extracelulares (lipases e proteases) as quais, por reações bioquímicas, produzem compostos alterando o produto e limitando a vida de prateleira (MOURA, 1997, FRANK;CHRISTEN;BULLERMAN, 2005). Geralmente o alto número de bactérias psicrotróficas reflete uma quantidade suficiente de proteases e lipases para causarem a quebra das proteínas e gordura (BARBANO; MART;SANTOS, 2006). O desenvolvimento dos microrganismos psicrotróficos lipolíticos e proteolíticos (Tabela 1) poderá, eventualmente, ocasionar alterações físico-químicas com o passar dos dias ficando visíveis e perceptíveis as mudanças quanto às características organolépticas do queijo.…”

Quality indicators of tank milk in different production systems of tropical regions

“…Also, due to the formation of scar tissue in the alveolar region replacing the secretory tissue, high SCC is also associated with production losses (BARBANO et al, 2006). Cinar et al (2015) concluded that high SCC negatively affects not only the yield, but also the composition and quality of milk, and suggests that monthly monitoring is the most effective method to monitor and evaluate changes in the production and quality of milk caused by the presence of mastitis in the herd.…”