Master of Science (MS)
School of Nutrition and Food Sciences
Green tea (Camellia sinensis) extract (GTE) is rich in polyphenolic compounds, especially catechins that are potent antioxidants. The antioxidant property of GTE may make it ideal for use as a glazing solution for suppressing lipid oxidation in shrimp (Litopenaeus setiferus) during frozen storage. In this study, GTE was evaluated as a glazing material for shrimp frozen by air-blast (BF) and cryogenic freezing (CF). Two percent, three percent and/or five percent green tea extract solutions (2GTE, 3GTE, 5TGE) were used for glazing. Distilled water glazed (GDW) and non-glazed (NG) shrimp were used as controls. The GTE was characterized by measuring color, pH, &176;Brix, total phenols, % antiradical activity and the individual catechins were identified by HPLC. The freezing time, freezing rate and energy removal rate for freezing shrimp by both freezing processes was estimated. The frozen shrimp samples were stored in a freezer at -21&176;C for 180 days. Samples were analyzed at 1, 30, 90 and 180 days for pH, moisture content, glazing yield, thaw yield, color, cutting force and thiobarbituric acid reactive substances (TBARS). The HPLC analysis of the GTE revealed the presence of catechin and its isomers and the total polyphenol content determined by HPLC was 148.1 ± 2.49 g/l. The freezing time for air-blast and cryogenic freezing was 48.67 ± 2.30 min and 4.83 ± 0.29min respectively. Cryogenic freezing had an energy removal rate (836.67 ± 78.95 J/s) nearly ten times higher than blast freezing (80.26 ± 3.82 J/s). The pH of all samples increased with increase in frozen storage time and there was no significant difference among treatments. Glazed samples had higher moisture content compared to NG shrimp after 180 days storage. Glazing improved the thaw yield of shrimp. GTE was effective in controlling lipid oxidation in shrimp. Cryogenically frozen shrimp glazed with 5 % green tea extract (CF5GTE) had the lowest lipid oxidation at the end of 180 days. Glazing with GTE affected a* and b* values, but had no significant effect on the L* values of shrimp. The cutting force of all NG shrimp was significantly lower than that of glazed shrimp. This study showed that green tea extract could be successfully applied as an antioxidant glaze for frozen storage of shrimp.
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Sundararajan, Srijanani, "Evaluation of green tea extract as a glazing material for shrimp frozen by cryogenic and air-blast freezing" (2010). LSU Master's Theses. 652.