Abstract
(1) Background: Multiple attempts have been conducted to correlate milk keeping quality with chemical, physical or bacteriological parameters. These methods only measure the chemical changes in milk produced by bacteria. Headspace solid-phase micro-extraction (HS-SPME) is an economic and recent method used to measure both volatile compounds and microbial load in milk, also allowing to keep the quality of the milk product. (2) Methods: The present study was conducted to identify and measure the off-flavoring volatile compounds through gas chromatography coupled with flame ionization detector (GC-FID) and the microbial load of pasteurized fluid milk stored at different temperatures, as a possible indicator of its keeping quality. (3) Results: The highest results were obtained to acetone, followed by butanone, pentanal and ethanol. These mean values were significantly enhanced from the 0 to 19th day of storage, at 10 °C. At day 19th, the minimum score for aroma, flavor and overall acceptability were also recorded as 4.33 ± 0.17, 4.02 ± 0.06, 4.00 ± 0.04, respectively. Likewise, maximum values for standard plate count (Log10 CFU 15.54 ± 0.40 mL−1) and total psychotroph count (Log10 CFU 11.67 ± 0.30mL−1) were reported at 10 °C and 4 °C. (4) Conclusion: HS-SPME/GC-FID methodology revealed to be very sensitive and capable to be applied in volatile compounds quantification in pasteurized milk produced during the storage period at different temperatures.
Highlights
It has been demonstrated that it is more difficult to objectively quantify milk spoilage than organoleptically
Available pasteurized milk with 3.25% standardized fat content with the same date of production was purchased from Walmart Superstore of Darigold company brand
PDMS/DVB coated fiber proved to be superior for analysis of volatiles in pasteurized milk samples
Summary
It has been demonstrated that it is more difficult to objectively quantify milk spoilage than organoleptically. With a standard plate count of 106 CFU/mL, are perfectly palatable, whereas others have become unpalatable. It is even more difficult to estimate “keeping quality”, the number of days between manufacture and spoilage [1]. Keeping quality is essentially determined by the rate of production of off-flavors and off-tastes. It is only indirectly related to the bacterial quality of milk. A bacterial strain which produces more off-flavors will obviously cause spoilage at a lower count than one which produces lesser off-flavors [2]. Off-flavor production may vary with temperature, storage time and substrate availability, which itself may be produced by other bacteria [3]
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