Study On Identification And Control Technology Of Off-flavor Components In Frozen Strawberry Juice

Ultra-high pressure （UHP） sterilization of strawberry juice is becoming more andmore popular in the international and domestic markets, since its unique and freshtastes, also the products are nutritious as the fresh material. Though UHPsterilization of strawberry juice can maintain natural flavor and nutrients in thelargest degree, unpleasant off-flavor had generated during frozen storage.Qualitative spectral scan method of GC-MS and internal standard method ofisoamyl alcohol was used to analyze the diversity of the main aroma and theirrelative contents. The main components of off-flavor were determined by thecomparison of differences between fresh and frozen strawberry juice. The relatedfactors and control measures of off-flavor were also studied then. Main researchfinding was following:1. Fresh strawberry juice processed by ultra-high pressure could produce a slightoff-flavor during frozen storage as a result of the productions of hydrogensulfide and isooctyl alcohol. The content of isooctyl alcohol came up to11.23mg/l, outstrip the odor detection threshold of isooctyl alcohol, which hassignificant influence on the off-flavor of frozen strawberry juice. Sensoryevaluation indicated that effect of hydrogen sulfide on aroma is much strongerthan effect of isooctyl alcohol. The synergic action of hydrogen sulfide andisooctyl alcohol made off-flavor more stimulating.2. The content of H₂S increased gradually along with the frozen storage timeincreases, and the increasing tended to be stable in the eighth week. Thecontent of H₂S is relatively small with the decreasing of freezing storagetemperature. Isooctyl alcohol exhibit similar trends, the increasing tended tobe smooth in the twelfth week. High and low freezing temperatures arefavorable to the generation of isooctyl alcohol, frozen storage temperature of-18℃had a certain extent in the inhibition of isooctyl alcohol production. Thecontent of hydrogen sulfide and isooctyl alcohol were decreased during thefrozen storage as a result of vacuum deoxidizing.3. The aroma of fresh strawberry juice and0.2%（v/v） strawberry essence wereadded to the degassed frozen strawberry juice, strawberry juice with better quality of aroma can be obtained. Strawberry was subjected to ultra-highpressure processing before frozen storage could reduce the content ofoff-flavor, the quality of frozen strawberry juice was optimistic improved.