Dissertation > Industrial Technology > Light industry,handicrafts > Food Industry > The dairy processing industry > Milk

Application of Pulsed Electric Fields on Milk Sterilization and Its Effect on Milk Fat

Author ZhangSha
Tutor YangRuiJin
School Jiangnan University
Course Of Food Science
Keywords Milk HPEF Ascorbic acid Antioxidant capacity Volatile compounds Radicals
CLC TS252.2
Type Master's thesis
Year 2010
Downloads 73
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The high-pressure pulsed electric field (PEF) is one of the hot spots of recent years, research in the field of non-thermal processing of liquid foods, but the majority of its research at home and abroad destroy the enzymes and nutrients of fruit and vegetable juice sterilization of the PEF applications in the study of lipid-rich foods is also relatively small, especially with regard to the impact of the PEF of the lipid component in food is not yet clear. Milk, PEF milk lipid-related quality, and to explore the mechanism of PEF cause lipid oxidation. Determine PEF sterilization process applied to milk and shelf-life, and high-temperature short Pap (75 ° C, 15s) milk comparison. Evaluation of the PEF to deal with the damage of the three main milk bactericidal effect of micro-organisms (E. coli Listeria monocytogenes and Staphylococcus aureus) and generate sub-dead effect. Injury the alkylene dead microorganisms ratio and types of microorganisms, the electric field intensity and treatment time. Staphylococcus aureus resistance on PEF strongest, up the injury Asian dead cells. To study the changes in the PEF process and during storage of the vitamin C content in milk compared with pasteurized milk. PEF role in the loss of vitamin C in the milk processing intensity enhancements increase, and the rate of loss to follow zero-order kinetics equation. The vitamin C content of the PEF milk than pasteurized milk, and shelf life, PEF milk vitamin C loss rate of less than pasteurized milk, the rate of loss to follow first-order kinetics equation. Third, the PEF process and during storage of milk total antioxidant capacity changes. PEF treatment intensity is smaller, the decline in the total antioxidant capacity of the milk is not obvious, but high intensity PEF processing makes milk total antioxidant capacity declines dramatically. PEF milk total antioxidant capacity in the entire shelf life than pasteurized milk. IV milk flavor compounds in the effect of PEF. Solid phase micro-extraction to extract the volatile compounds in the milk, then GC 37 compounds detected in raw milk, pasteurized milk, and milk in PEF. The pasteurized cause an increase in milk content of aldehydes and ketones, and the PEF treatment only results in increasing the content of the aldehyde compound. PEF processing the electric field strength of aldehydes content in milk is more significant. The electric field intensity of the PEF treatment of to 30kV/cm, wherein the content of pentanal and nonanal than pasteurized milk, hexanal, heptanal, and decyl aldehyde content of less than pasteurized milk, but higher than the raw milk. Acids content of pasteurized milk and milk in PEF change significantly in the storage period, the content of aldehydes and ketones has also undergone some changes. Oleic acid emulsion as the research object to investigate the oxidation mechanism of milk fat in the PEF under PEF treatment free radicals. The electron spin resonance experiment results show that the generated hydrogen radicals in the PEF treatment process of oleic acid emulsion, after adding vitamin C, the hydrogen radical disappears, that vitamin C can inhibit the free radicals generated in the PEF treatment process. In addition, for the the PEF role of hydrogen radicals cause milk fat oxidation mechanism was discussed.

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