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Title: Biochemical Changes in Protein and Lipid Fractions of Ultra-High Temperature Treated Milk and Dairy Drinks at Different Stages of Processing and Storage
Authors: Ajmal, Muhammad
Keywords: Veterinary Sciences
Dairy Technology
Issue Date: 2019
Publisher: University of Veterinary and Animal Sciences, Lahore.
Abstract: This study is comprised of five experiments, in the first experiment chemical changes taking place in lipid fraction of pasteurized milk was studied. Raw milk from the same source was at once cooled down to chilling temperature and in second instance it was put on the lab shelf for two hours at ambient temperature and then chilled to same temperature, followed by pasteurization and chilled storage. In the second experiment, samples of UHT milk were tested for chemical characteristics and lipid oxidation. In third experiment, impact of UHT treatment (142oC for 2 sec) and 90 days ambient storage (30-35oC) on protein and amino acid profile of UHT milk and sedimentation was investigated. In fourth experiment, samples of UHT Treated products were stored for 90 days. Transition in antioxidant capacity, vitamin A, E, fatty acid profile was studied. Transition in protein profile, Maillard reaction products and lipid oxidation of flavored UHT treated milk was investigated. In fifth experiment, Samples of mango flavored UHT milk 200 ml pack (475 Nos.) were purchased from the market and stored at ambient temperature for the duration of 90 days. Proteolysis, hydroxyl methyl furfural furosine, Nε-carboxymethyl lysine, FAP, FFA, PV and sensory characteristics were studied at 0, 45 and 90 days of storage. It was observed that chemical characteristics and storage stability of raw milk in the second instance was different from the milk cooled at once. Therefore, it is recommended that milk collection system in the developing countries should be improved to avoid any delay in between milking and chilling of raw milk. The results of the second experiment disclosed that fatty acid and triglyceride profile were not affected till 60 days with a steady increase in lipase activity. Strong correlations between peroxide value and induction period were established. For the anticipation of oxidative stability of UHT milk, induction period can be used. After UHT treatment, β-lactoglobulin, β-lactalbumin, immunoglobulin and serum albumin decreased by 12.1%, 15.4%, 10.6% and 10.2% with no effect on casein fractions. Sedimentation was comprised of 14.9% αs1-casein, 3.42% αs2-casein, 9.88% β-casein, 2.27% κ-casein, 4.36% β-Lactoglobulin, 1.88% β-lactalbumin, 1.84% immunoglobulin and 0.61% Serum Albumin. Out of 80% casein and 20% whey, 38.5% and 8.7% became the part of sedimentation. Tyrosine content of flavored UHT milk increased during the storage. Tyrosine content of flavored UHT milk at 0, 45 and 90 days of storage were 3.5, 6.9 and 15.2 µg tyrosine/ml. HMF content of UHT milk at 0, 45 and 90 days of storage were 1.56, 4.18 and 7.61 (µmol/L). Furosine content of flavored UHT milk at 0, 45 and 90 days of storage intervals were 278, 392 and 561 mg/100g protein.
Gov't Doc #: 18953
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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