Mechanisms Underlying Off-flavor Production in UHT-enabled Wall-breaking Pine Pollen during Storage
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Abstract:
The changes in the essential nutrients, common oxidation indices and volatile constituents, along with the causes of odor generation and the main off-flavor components, were investigated during the storage of ultra-high temperature instantaneous sterilization (UHT)-enabled wall-breaking pine pollen. The results showed that after a 30-day storage, the contents of crude fat and unsaturated fatty acids decreased by 31.37% and 14.03%, respectively, and the relative contents of free fatty acids and saturated fatty acids increased by 38.78% and 32.34%, respectively, with the contents of crude proteins, total sugars and amino acids remaining unchanged. In the early stage of storage, the content of free fatty acids in the UHT-enabled wall-breaking pine pollen was lower, but increased sharply after 8 days and reached 9.53 mg/kg at the 30th day. The peroxide value and thiobarbituric acid value increased first and then decreased with the prolongation of storage, and reached the maximum, 6.09 meq/kg and 34.52 mg/kg, respectively, at the 3rd day and 5th day. In addition, the main volatile components of the UHT-enabled wall-breaking pine pollen increased steadily during storage, with the changes of hexanal and hexanoic acid being the most significant (reaching 12.69 μg/g and 10.51 μg/g, respectively after 5 days). These results indicated that the off-flavor of UHT-enabled wall-breaking pine pollen was produced mainly via lipid oxidation during storage, and the oxidation was more severe in the early stage of storage. Hexanal and caproic acid, the secondary oxidation products of oil oxidation, were the main volatile components of the wall-breaking pine pollen during storage, which also accounted for odor generation.
