File Name: chemical and microbiological analysis of milk and milk products .zip
This study aimed to assess the organoleptic, physico-chemical, and microbial quality as well as the presence of any adulterants in different commercial and local milk samples. Three brands of ultra-high temperature UHT milk, three brands of pasteurized milk, and three raw milk samples were procured and analyzed for different quality tests.
Consumer preference about the milk samples were studied by evaluating the organoleptic properties by a testing panel of 15 panelists.
Physico-chemical, adulteration, and microbial analysis of the milk samples were performed by following different standard methods. From physico-chemical analysis, it was found that raw milk contained the highest amount of moisture All adulteration tests responded negatively for raw samples, whereas commercial milk samples showed positive response only on added sugar test. Total standard plate count and coliform count tests showed that there was no microorganism in a detectable range in commercial milk samples, though raw samples had a significant amount.
Though there were some fluctuations in some parameters of the three milk categories, but this study concluded that the quality of UHT and pasteurized milk were excellent with respect to parameters studied. Milk is known as ideal food with unique quality for nourishment of human being long before recorded history. It is recognized as complete meal because of its wholesome nutrients for all mammals, including human being [ 1 ]. In native conformation, milk shows the apex food value.
It meets the nutritional requirement of the body more perfectly than any other single food as it carries each of the absolutely necessary nutritional components to perform every physiological activities of the body system.
According to Pehrsson [ 2 ], milk has around Former evidence suggests that the people who used to get the most energy of daily requirement from milk and milk products were more prosperous and capable of effective governance and these communities possess the benefit of having complete freedom from many nutritional diseases [ 3 ].
Milk is considered as a highly perishable food because of its higher moisture content and its shelf life is normally 3—5 h as well as it is a great growing medium for microorganism. Before milking, milk is considered as sterile but its quality starts deteriorating during handling, processing and storage [ 5 ]. In addition, microbial contamination is generally happened from different sources.
Common pathogenic microbes in milk include Salmonella sp. Pasteurization, a preservation technique for milk, is mainly performed to destroy or inactive all the harmful or pathogenic microorganisms by using heat treatment [ 5 ]. On the other hand, pasteurization of milk can destroy most of the bacteria but few heat resistant enzymes may remain alive and can result in vital deformity of milk throughout the time of storage [ 7 ].
Food adulteration is a common phenomenon practiced in food processing and marketing sector all over the world. Adulteration of milk has recently become a major issue to be concerned [ 8 ]. According to Moore et al. Azad and Ahmed [ 10 ] reported that milk processing sectors and suppliers add different adulterants and preservative for increasing the shelf life to get rid from the problem of quick deterioration of milk due to its high perishability.
Adulterants added in milk are mainly inferior or cheaper materials which do not affect appearance largely. Raw milk is generally adulterated by using potable water or whey watery part of milk remaining after making of cheese which is known as economic adulteration and is commonly practiced by the supplier mainly to increase the quantity [ 11 ], while the other adulterants include skim milk powder, salt, detergents, cane sugar, urea, formalin, coloring agents, starch, and acids [ 12 , 13 ].
Beside those, adulteration of milk also involves to alter the quality and standard of the processed products from milk [ 14 ]. Thus to get rid from these problems, continuous monitoring the quality and adulteration of milk are so important. Beside those, raw local milk also is found. Quality milk is always getting preference to the consumers. Several articles [ 8 , 15 — 19 ] are available on quality assessment of milk found at several regions of Bangladesh, but more investigations seem to be required for getting updated knowledge about the quality of milk.
Based on these above conditions, this research was carried out to assess the physico-chemical, organoleptic, and microbial quality of the milk and to determine the presence of any added adulterants to the commercial and raw milk found in the markets around Bangladesh Agricultural University BAU , Mymensingh. To perform this study, UHT, pasteurized and raw local milk were chosen and collected from local market of Mymensingh region.
Three UHT milk packets of three different commercial brands were purchased and named based on brand name as A 1 procured from K. Similarly, three commercial branded pasteurized milk packets were purchased and named as B 1 procured from K. Market, BAU. After bringing to the laboratory, the milk containing packs were thoroughly oscillated to mix the inner content properly and opened by using a sterile scissor [ 18 ]. After that microbial analysis was performed immediately and subsequently other analyses were also conducted.
Hedonic rating scale 9-point was used for statistical analysis [ 21 , 22 ]. An evaluation sheet for organoleptic properties is given at Appendix section Appendix-I. Moisture, ash, fat, protein, acidity, total solid TS , SNF, lactose, and specific gravity were analyzed to compare the values among different milk samples. Quantity of moisture, protein, ash, and acidity were determined as per the methods of AOAC [ 23 ].
Amount of fat presence was calculated on accordance to the Gerber method as per described by AOAC [ 23 ]. TS was simply calculated by subtracting the moisture content from Lactometer was used to measure the specific gravity of the milk samples. The milk was mixed thoroughly by avoiding incorporation of air. Enough milk was placed in a cylinder so that the lactometer was placed in the center of the cylinder and reading was recorded within 30 sec after mixing.
Again, the temperature of milk was taken. The lactometer scale was at the top of the milk meniscus. Specific gravity of milk sample was calculated as formula mentioned by Awal et al.
To check the presence of any adulteration, several tests were performed. The tests were mainly involved titration of sample with different reagents. Added sugar and starch existence were determined on according to the method as mentioned by Sharma et al.
Salt and skim milk powder test were conducted on according to Awan et al. In addition, clot on boiling COB test and alcohol test were conducted according to Tessema and Tibbo [ 27 ]. Microbiological tests like standard plate count SPC and total coliform count TCC were performed to know the microbial status of the milk samples.
The evaluated scores for organoleptic properties of the UHT, pasteurized and raw milk samples are shown in Table 1. The analysis was performed to compare the acceptability of the three milk categories to the consumer. From the Table 1 , it is seen that there was a significant difference of score values for color, flavor, and texture of UHT and pasteurized milk samples.
But all the samples were not differed significantly from each other. In the most of the cases, one sample was differed significantly from others and rest two was equally acceptable.
On the other hand, the raw milk samples were equally acceptable in case of color and flavor while significant difference was found for texture value. Taste is an important organoleptic parameter and evaluation on it showed that UHT, pasteurized and raw milk samples were got same acceptance to the panelists. The overall acceptability values revealed that A 2 sample was the mostly acceptable among three UHT milk samples as well as in case of pasteurized milk while the raw collected milk samples were equally acceptable to the panelists.
Arafat et al. They also noticed that the quality of the samples were equally acceptable based on sensory parameters. However in this study, the samples were differed significantly in case of few sensory parameters. This difference might be happened due to acceptance criteria of panelists.
The raw and processed milk samples were evaluated for their physico-chemical properties, such as moisture, ash, protein, fat, lactose, acidity, SNF, TS, and specific gravity. The average data of the analyses are shown in Table 2.
The percentage of moisture content obtained from different milk samples are shown in Table 2. Three raw samples C 1 —C 3 contained more than All the heat-treated milk contained water lower than the raw samples. UHT milk samples contained water in the range of Mixing of water with the native milk may cause in increasing the moisture content of the raw milk samples, whereas the industrial processed milks are usually standardized and the values in this case were in satisfactory level.
The amount of ash in the raw milk samples were in the range of 0. But, the determined ash values of this study in case of raw milk were reasonably higher than the ash values mentioned by Elmagli and Zubeir [ 31 ] as ranged as 0. On the other hand, the pasteurized milk samples had the ash content of 0. The UHT milk samples had ash content in the range of 0. However, among all the milk samples UHT milk sample A 3 contained the lowest amount of ash content.
The raw milk samples had the protein content in the range of 3. Hossain et al. All the three pasteurized milk samples contained a minimum of 3. BSTI [ 32 ] fixed up standard protein content of minimum 3. Thus, the results obtained for pasteurized milk samples were met up the standard protein content as per as BSTI [ 32 ]. The UHT milk samples can be attributed as good quality in terms of protein content as all of the samples had above 3. Milk fat is granted as the most desirable and important nutrient available in milk.
From this study, 3. On the other hand, any pasteurized milk should have at least 3. Similar observation was depicted by Hossain et al. Low fat content in raw milk or due to withdrawal of fat from the raw milk during processing without following the standards provided by BSTI and FDA may cause in lowering the fat content of the pasteurized milk [ 34 ]. All the heat-treated samples had the lactose content in the range of 4. Titratable acidity measures the freshness, bacterial activity, and taste of milk and acknowledged as an indicator of milk quality.
In this study, the highest acidity value was found as 0. Popescu and Angel [ 35 ] stated that the high quality milk should have maximum acidity of 0.
From this study, it was found that the pasteurized milk samples had the acidity ranges from 0. The standard of BSTI [ 32 ] permits less than 0. Highest SNF 8. Dilution of milk using water can cause in lowering the TS content.
Ranging from raw milk to frozen dessert milk samples, the Dairy Lab examines for the presence of indicator organisms, antibiotic residual testing, determination of the pasteurization process, and microscopic examination of somatic cells. The laboratory analyzes dairy samples derived from cow, goat, and sheep origins. Individual analysts are certified for milk product analysis by participation in a yearly proficiency test scheme, and a triennial on-site evaluation.
This study aimed to assess the organoleptic, physico-chemical, and microbial quality as well as the presence of any adulterants in different commercial and local milk samples. Three brands of ultra-high temperature UHT milk, three brands of pasteurized milk, and three raw milk samples were procured and analyzed for different quality tests. Consumer preference about the milk samples were studied by evaluating the organoleptic properties by a testing panel of 15 panelists. Physico-chemical, adulteration, and microbial analysis of the milk samples were performed by following different standard methods. From physico-chemical analysis, it was found that raw milk contained the highest amount of moisture
Горячий пар пробивался через люк подобно вулканическим газам, предшествующим извержению. Проклиная себя за то, что не забрала у Стратмора беретту, она пыталась вспомнить, где осталось оружие - у него или же в Третьем узле. Когда глаза Сьюзан немного привыкли к темноте, она посмотрела на дыру, зияющую в стеклянной стене. Свечение мониторов было очень слабым, но она все же разглядела вдали Хейла, лежащего без движения там, где она его оставила.
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