Litchi fruit and fresh litchi juice are highly appreciated in south part of China and many countries in the world. China is the largest production country of Iitchi fruit, and more than half of all of litchi production in China are in Guangdong province. Among various litchi cultivars, Feizhixiao, is the most prized for its wonderful flavor and aroma, and it is also the most popular fruits to be processed to other value-added products such as litchi juice or litchi wine. However, the delicate litchi aroma and flavor are altered during the thermal sterilization process used in litchi juice production. The thermal process of litchi juice causes the decrease of pleasant litchi aroma and gives rise to the distinct cooked-vegetable off-flavor, which impeded the commercialization of litchi juice and the growth of litchi industry. It is important to understand the flavor change of litchi juice during thermal processing. In this study, the aroma profiles of fresh and heat-treated litchi juices were investigated using aroma extract dilution analysis (AEDA), followed by isotope dilution based quantitation, and odor activity value (OAV) comparison. Both the AEDA and OAV results suggested that cis-rose oxide, geraniol, phenylacetaldehyde, citronellol and linalool were the most important aroma-active compounds in fresh litchi juice. The heating process affected many odor-active compounds in the litchi juice. The heating process dramatically decreased geranial, cis-rose oxide, phenylacetaldehyde, citronellol, and linalool, while significantly increased dimethyl sulfide (DMS), methional, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 3-methylbutanal and 2,4-dithiapentane, which could be responsible for the cooked cabbage/potato, garlic/onion and sulfurous off-flavor perceived in processed juice. The reconstitution and omission experiment further proved that DMS, methional, DMTS and DMDS were the main contributors to the cooked off-flavor in heated litchi juice.

Effect of thermal sterilization on the aroma profile of Lychee (<i>Litchi chinensis </i> Sonn.) juice

2019 Fall National Meeting

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Effect of thermal sterilization on the aroma profile of Lychee (Litchi chinensis Sonn.) juice