Study on the effects of different sterilization methods and storage conditions on milk quality

Abstract

Milk is processed in different ways. Milk may be heated, frozen, or condensed as it is excreted in raw milk or in order to kill pathogenic microorganisms and increase shelf life. Its protein and fat content may change. Lactose is hydrolyzed, homogenized, cholesterol is removed, or fermented cultures are added to it, and its calcium levels are increased. Some special processing operations are performed to meet the consumer's needs and the specific market situation. Due to its characteristics such as relatively long shelf life, the use of UHT sterilized milk has always been associated with the suspicion among consumers that this type of milk contains preservatives or its nutritional value is greatly reduced by applying high temperatures. In this article, while briefly referring to the nutritional value of milk, the effect of pasteurization and sterilization heat on the milk components is compared. Milk is the only food known in nature that can meet the body's basic needs for nutrients in a balanced way. Milk contains a very valuable set of proteins, sugars, fats, various minerals, especially calcium and phosphorus, and a variety of vitamins. Due to its special composition, this valuable nutrient is a very suitable environment for the multiplication of pathogenic microorganisms and the transmission of diseases from animals to humans.

Effects of cold storage and freezing on sheep’s milk

“…This microbial group in sheep's milk showed no major variations during refrigerated storage, since the average count between producers was 6.02 log CFU/mL (n = 12) in the first day and 6.09 log CFU/mL (n = 12) in the fourth day under refrigeration (Munieweg et al, 2017). Psychrotrophic group includes potentially proteolytic bacteria that can affect the quality of raw milk and dairy products such as Pseudomonas, Bacillus, and Listeria, as well as lactic acid bacteria such as Lactococcus, Leuconostoc, and Lactobacillus (Forsythe, 2019;Khayrullin & Rebezov, 2023), with spoilage and pathogenic microorganisms. Brazilian legislation does not set up a limit for S. aureus in raw milk, but this microorganism is a well-known cause of clinical and subclinical mastitis in sheep (Bishop & Morris, 2007) and a potentially harmful bacterium (Basanisi et al, 2016), emphasizing the importance of the results observed in the present study (Figure 1C).…”

“…The acidification of milk causes the destabilization of the emulsion, leading to economic losses to the producer and to the industry (Fava et al, 2014). Changes in the pH and acidity may affect the coagulation process as well as the water retention capacity of the mass, influencing the size of the formed clot granules, the draining process, the texture, and the microbial growth in cheese (Khayrullin & Rebezov, 2023;Park et al, 2006).…”