The kinetics of astaxanthin degradation and lipid oxidation in shrimp oil from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) as affected by storage temperature were studied. When shrimp oil was incubated at different temperatures (4, 30, 45 and 60 °C) for 16 h, the rate constants (k) of astaxanthin degradation and lipid oxidation in shrimp oil increased with increasing temperatures (p < 0.05). Thus, astaxanthin degradation and lipid oxidation in shrimp oil were augmented at high temperature. When shrimp oils with different storage conditions (illumination, oxygen availability and temperature) were stored for up to 40 days, astaxanthin contents in all samples decreased throughout storage (p < 0.05). All factors were able to enhance astaxanthin degradation during 40 days of storage. With increasing storage time, the progressive formation of primary and secondary oxidation products were found in all samples as evidenced by the increases in both peroxide values (PV) and thiobarbituric acid reactive substances (TBARS) (p < 0.05). Light, air and temperatures therefore had the marked effect on astaxanthin degradation and lipid oxidation in shrimp oils during the extended storage.

Shrimp oil is one of the important sources of n-3 fatty acids, which have been known for health benefit. The incorporation of shrimp oil into food emulsion has gained increasing interest. Since shrimp oil is rich in unsaturated fatty acids, it is susceptible to oxidation, leading to development of off-odor and loss in nutritive value. Thus, this study aimed to investigate the oxidative stability shrimp oil-in-water emulsion (pH 3.6) incorporated with various antioxidants at different levels during the storage at 30°C for 12 days. With increasing storage time, progressive formation of hydroperoxide was found in all samples as evidenced by the increase in peroxide values (PV) (p < 0.05). The lower PV was found in those added with antioxidants; however PV values varied with different antioxidants added. Sample added with 200 ppm α-tocopherol alone had the higher PV than others (p < 0.05). The increase in thiobarbituric acid reactive substances (TBARS) of the control, sample added with 200 ppm α-tocopherol and that containing 500 ppm lecithin were noticeable when storage time increased (p < 0.05). Slight increases in TBARS were found in samples added with mixed antioxidants including 50 ppm EDTA + 100 ppm tannic acid, 50 ppm EDTA + 200 ppm α-tocopherol, 50 ppm EDTA + 100 ppm tannic acid + 200 ppm α-tocopherol or 50 ppm EDTA + 100 ppm tannic acid + 500 ppm lecithin + 200 ppm α-tocopherol throughout 12 days of storage (p < 0.05). This was concomitant with the decreased formation of volatile compounds and rancid off-odor in emulsion containing mixed antioxidants, especially 50 ppm EDTA + 100 ppm tannic acid and 50 ppm EDTA + 100 ppm tannic acid + 500 ppm lecithin + 200 ppm α-tocopherol. Thus, the use of EDTA in combination with tannic acid could retard the lipid oxidation in the shrimp oil-in-water emulsion more effectively, compared to other combinations of antioxidants tested.