Impact of Microfiltration on Particle Size Distribution, Volatile Compounds and Protein Quality of Pasteurized Milk during Shelf Life

Abstract

The effects of microfiltration on particle size, volatiles, protein quality and proximate compositions in pasteurized milk were studied over 7 days at 4°C. Changes in proximate compositions, pH, particle size, amino acids and volatile compounds of microfiltered and pasteurized milk (MPM) and pasteurized milk (PM) were evaluated. The MPM had lower values of proteins and total solids, and possessed higher particle size compared with PM. The D10 and D50 in MPM were individually reduced by 8.3% and 3.1% from day 0 to 7, and there were no differences for the D90. Sixty-one and 65 compounds were identified in the MPM and PM, respectively. The total contents of aliphatic hydrocarbons and alcohols in MPM decreased with storage length, while those of hydrocarbons, ketones, phenols, nitrogenous compounds and sulfide in PM increased with storage time. Other compounds clearly started to increase on day 4 and were reduced markedly by day 7. After 7 days, aliphatic hydrocarbons and alcohols decreased by 21.8% and 47.3% in MPM, while hydrocarbons, ketones and sulfide increased by 57%, 5.4% and 35.4% in PM, respectively. At the same storage time, the hydrocarbons, alcohols, aldehydes, acid and ketones were less in MPM than in PM. MPM had higher EAAI, BV and ePER values. These highlighted that microfiltration changes the compositions of volatiles and improves protein quality and stability during MPM shelf life.

Characterization of volatile compounds and organic acids in ultra-high-temperature milk packaged in tetra brik cartons

“…Similarly, Vegas and Roussis [13] reported an increase in butanoic, hexanoic, octanoic, and decanoic acids in pasteurized milk compared to raw cow milk. Acids identified in this study have previously been found in milk pasteurized by microfiltration and ultrapasteurized milk with dominance of hexanoic and octanoic acids, respectively, [18,29,44] who indicated that pasteurization with microfiltration caused a greater increase in acids than pasteurization only. Although the fat content of commercial UHT milk samples analyzed is standardized to values of ≤3% and <3.5% as UHT whole milk, the values of free fatty acids showed a wide variation from brand to brand, ranging from 25.78 to 87.96%.…”

“…This could be attributed to the different process technology, quality of initial raw milk and the high storage temperatures since the contents of free fatty acid are increased in UHT milk produced from the raw material with the largest number of psychrotrophic bacteria and stored at the high temperatures [54] and also in milk pasteurized by microfiltration. [18,29,44] Although ethanol was found in all the samples at trace levels, 2-furan methanol, 2-pentanol, and 2-ethyl-1-hexanol were determined in some UHT milk samples as the major alcohols. These alcohols may be formed by the reduction of aldehydes, were previously identified in milk powder.…”

“…This compound has previously been found in micro-filtered pasteurized milk as dominant VOC, [18] and also in ultrapasteurized milk packaged in polyethylene terephthalate containers [29] and reconstituted milk. [44] Oximes are may be formed by reaction aldehydes or ketones with a nitrogen-containing reducing agent in a weakly acidic medium during the high heat treatment and/or homogenization since aldehydes were detected in UHT milk samples at trace levels and samples with low ketone percentages had a high level of oxime-methoxy phenyl.…”

Effects of UV-C and single- and multiple-cycle high hydrostatic pressure treatments on flavor evolution of cow milk: Gas chromatography-mass spectrometry, electronic nose, and electronic tongue analyses

“…The volatile compounds were determined in triplicate by GC-MS as described previously. [7] Briefly, samples were extracted from milk using the SPME technique that was performed using an autosampler (GC Sampler 80, Agilent, Santa Clara, CA, USA). A milk sample (10 mL), 2 μL of the internal standard solution (0.1 mg/mL 2,4,6-trimethylpyridine in methanol), and 3.7 g of sodium chloride were placed in an annealed 20-mL brown glass vial with screw cap.…”

“…[3] The flavor properties of cow milk and its products vary depending on cow species, daily diet, environment, age, biological factors, processing, packaging material, and storage conditions. [2,3,[5][6][7] Traditionally, heat treatments, particularly ultra-high temperature (UHT) processing, have been used to eliminate potential pathogens and spoilage organisms in milk. However, they produce thermally derived-off flavor compounds such as aldehydes, methyl ketones, and various sulfur compounds.…”