Author : Jun Su
Publisher :
ISBN 13 :
Total Pages : 145 pages
Book Rating : 4.:/5 (13 download)
Book Synopsis Impact of Psychrotrophic Bacteria in Raw Milk on the Stability of Dried Milk Powder and Added Vitamin D by : Jun Su
Download or read book Impact of Psychrotrophic Bacteria in Raw Milk on the Stability of Dried Milk Powder and Added Vitamin D written by Jun Su and published by . This book was released on 2017 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Psychrotrophic bacteria are of special concerns in dairy industry. They can grow in cold, and produce heat-resistant enzymes that cause quality defects in dairy products. On the other hand, lipids and added vitamin D are important nutrients of milk and milk products. This study was to investigate how these microorganisms affect the stability of dried milk powders and added vitamin D during storage. The microbiology of raw milk was studied via observation of psychrotrophic bacterial growth and preliminary study of raw milk bacterial community profiling. The milk powder samples were prepared by cold incubation, followed by homogenization, pasteurization, vitamin D fortification, and freeze drying. Chemical analysis was conducted by monitoring the lipid oxidation status and vitamin D content of milk powders during storage. The effects of pasteurization and storage temperature were also considered. Psychrotrophic bacterial population expanded rapidly during raw milk holding. Several lipase-producing psychrotrophic bacteria including Pseudomonas, Serratia, Acinetobacter, Aeromonas, Bacillus, and Moraxella were found in raw milk samples that had been incubated in cold (7°C) for two to four days. The low peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) suggest that all milk powders remained at an early stage of lipid oxidation during the sixmonth storage. It was noted that besides TBARS assay, the gas chromatography (GC) analysis of hexanal might also be applied for secondary oxidation product determination. The liquid chromatographymass spectrometry (LC-MS) based quantification of vitamin D3 in milk powders was achieved with high accuracy and reproducibility. A decrease in vitamin D3 content was observed over the four-month storage. However, no sufficient evidence in this study suggests that the lipase-producing psychrotrophic bacteria found in cold-incubated raw milk would have an effect on the stability of lipid content and added vitamin D in dried milk powders during long-term storage.
