**3. Milk processing techniques and their harms to milk**

Rapid development of our society in the past few decades and careless use of large amount of agricultural services are appearing to be a burden over human health [3]. The hunger of the increasing population cannot be satisfied with fresh milk due to unequal production and utilization system. In the past 15 years, the dairy industry has evolved with newer techniques of production, products, and processing [3]. But there are several harms to the soundness of milk associated with processing techniques in terms of quality and quantity losses.

### **3.1 Pasteurization**

 Diseases associated with the consumption of milk are common due to microbial contamination. To keep milk safe from such microbial contaminants, primarily largescale techniques (like pasteurization) are adopted to every milk production system. For this purpose, collected milk from dairy farms is sent to a reservoir of processing units for processing, where a large amount of milk is stored [50]. Transportation of milk in such a way may cause a source of spreading viruses and bacteria. That milk is usually pasteurized and assuming that heat treatment has demolished appropriately [51]. However, some bacteria remain intact due to microbial biofilm within the distribution line and unhygienic behavior of employees [52]. While repeated or prolonged heat treatment causes protein denaturation and binding of denatured whey protein with casein micelles leads to migration of soluble calcium and phosphate to the colloidal stage and mollify of the enzymes. Research shows that the available amount of lysine, iodine, folate, and vitamins B12, C, B6, and B1 in milk decreases after pasteurization [53]. Heat treatment reduces α-la (α-lactalbumin) and PGRP (peptidoglycan recognition protein) in the case of camel milk [54]. Extreme pH, removal of bound Ca2+, addition of denaturant agents, or cleavage of disulfide bridges can denature α-lactalbumin in several ways [55]. Among vitamins, vitamin C is the most important that can be quickly destroyed when milk is heated [56].

Treatment at elevated temperatures reduces the quality of milk supply, as many nutrients are thermally unstable [2]. The second most parameter is aroma of dairy products, which critically affects consumer acceptance, shelf life, and other attributes. When thermal treatment is employed to reduce or destroy the microbial load and enzyme activity to ensure safety and to increase shelf life, the aroma of the milk changes and differs from that of raw milk [57]. Ultra-pasteurization (UP) and ultra-high temperature (UHT), high temperature/short time (HTST), DSI-UP, or IND-UP are widely used thermal treatments for extended shelf life of milk. These processing techniques affect color due to various reactions during thermal processing or storage. These key changes in flavor during thermal processing of milk are associated with Maillard reactions [58].

### **3.2 Ultra-high temperature (UHT)**

The contents of flavored milk are sweeteners such as natural sugar, sucrose, fructose, glucose syrup, or a sweetener without calories depending upon the

*Reconnoitering Milk Constituents of Different Species, Probing and Soliciting Factors… DOI: http://dx.doi.org/10.5772/intechopen.82852* 

 manufacturer and the consumer demand [59]. As a result of heat treatment, the basic constituents like proteins, carbohydrates, and vitamins of flavored milk undergo chemical and biochemical modifications [60]. Some of these modifications include lactulose and acid formation through lactose degradation. It promotes dehydroalanine development by side chains of amino acids through β-elimination. It is a compound that reacts readily with lysine yielding lysinoalanine and the denaturing of whey proteins [61].
