Abstract:

Objective: To optimize the Maillard reaction conditions for oyster enzymatic hydrolysates and reducing sugar
based on sensory evaluation of Maillard reaction products (MRPs). Methods: The optimization was carried out using
response surface methodology based on Box-Behnken experimental design. Electronic nose and gas chromatography-mass
spectrometry were employed to analyze the volatile flavor compounds of fresh oyster (FO), oyster enzymatic hydrolysates
(OEH), optimal Maillard reaction products from oyster enzymatic hydrolysates and reducing sugar (OMRPs-OEH). Results:
The optimal reaction conditions were found as follows: extraction time, 29.43 min; temperature, 114.62 ℃; pH, 6.97; and
ratio of enzymatic hydrolysates to reducing sugar (glucose:xylose = 1:2), 1:1. Under these conditions, the experimental value
of sensory evaluation score was 20.88, compared to the predicted value of 20.25. The relative error between the experimental
and predicted values was 3.08%. A total of 30, 36 and 45 components were identified from FO, OEH and OMRPs-OEH by
GC-MS, respectively. The main volatile compounds of OEH were octanal, nonanal, decanal and (Z)-2-decenal, which were
responsible for the unpleasant smells such as fishy, rancid, and oily. After the Maillard reaction, dimethyl disulfide, trimethyl
disulfide and (Z)-4-heptenal became the main volatile compounds, which contributed to the shellfish, meat and seafood
flavors. Meanwhile, pyrazine substances were formed, which were responsible for some nuts-meat flavors. Conclusions: The
Maillard reaction not only can improve fishy odor of OEH, but also can develop a new oyster flavoring agent, which has
highly economic and social value.

Key words: oyster, Maillard reaction, response surface methodology, electronic nose, gas chromatography-mass spectrometry (GC-MS)