| Summary: | 碩士 === 國立屏東科技大學 === 動物科學與畜產系所 === 106 === Natural or synthetic antibacterial and antioxidant agent can retard microbial growth and lipid oxidation while adding to meat products during storage. Mountain pepper (Litsea cubeba (Lour.) Persoon), also called Maqaw, is a natural ingredient which can retard microbial growth and lipid oxidation for food adding. The aim of this study was to investigate the antioxidant characteristis of mountain pepper powder it’s effects on the shelf life of marinated duck tenderloin during cold storage.
The native mountain pepper was bought in Taitung, Taiwan. After well cleaned, the mountain pepper was dried for 24, 48 and 72 hours at 40 and 60°C separately and then powdered. Mountain pepper powders were extracted by distilled water and evaluated the total phenolic content (TPC), DPPH radical-scavenging activity (DPPH), and ferrous ion chelating activity (FICA) for selecting the best during condition with the best overall antioxidation ability. The result demonstrated that the extract of mountain pepper powder dried in 60°C for 48 hours contained the highest TPC content (112.41 mg/ml); the treatment group of 60°C for 24 hours showed the highest DPPH (80.42%) ability and the 60°C treatment for 72 hours showed the highest FICA rate (79.40%) in all treatments. Therefore the water-extracted mountain pepper dried in 60°C for 48 hours had the best antioxidant ability in TPC and a good characteristis in DPPH and FICA.
Experiment 2 was carried out to evaluate the proximate composition, pH value, color value (L*, a* and b*), 2-thiobarbituric acid reactive substances (TBARS) value, volatile basic nitrogen (VBN) value, microbial count (Total plate counts and lactobacillus counts), and sensory evaluation of duck tenderloin marinated in (0.5 and 1.0 % w/w) mountain pepper powder dried in 60°C for 48 hours during 4°C dark storage. The analysis were carried out every 2 days during storage.
Experiment 2 has shown, Both 0.5 and 1.0% added amounts of mountain pepper powder in marinated duck tenderloin had no effect on proximate composition, The pH value between all treatments tended to decrease had no significant differences during storage. The control and the black pepper group showed significant increasing L* value during storage, the rest group tended to decrease without significant differences instead. The a* and b* value of all treatments decreased during storage. The TBARS of control showed the highest value in all treatments, and the treatment with 1.0% mountain pepper is the lowest one. The VBN values of 0.5%, 1.0% mountain pepper and 0.5% lemongrass treatments were significantly lower than the control. Especially the 0.5% and 1.0% mountain pepper treatments in 6th and 8th day storage showed significantly lower VBN value than the control, 0.5% rosemary and 0.5% black pepper treatments. The numbers of total bacteria and lactic acid bacteria counts of all treatments increased during storage. In 6th and 8th day of storage, the numbers of bacteria and lactic acid bacteria in 0.5% and 1.0% mountain pepper treatment were significantly lower than the other treatments. In the result of the sensory evaluation, the marinated duck tenderloin which stored on the 2nd day of storage, the mountain pepper treatment showed higher sensory evaluation scores than all other treatments. On the 4th day of storage, all scores of all treatments were slightly lower than the scores than on the 2nd day. However, the mountain pepper treatment still had higher scores with the total acceptance.
Results showed that the water extraction of mountain pepper that dried in 60°C for 48 hours had better antioxidant ability. Both 0.5 and 1.0% added amounts of mountain pepper powder in marinated duck tenderloin had no effect on proximate composition, pH value and sensory evaluation of cooked marinated duck tenderloin during cold storage. Compared with the control, the mountain pepper treatment product showed better effect of inhibiting on lipid oxidation and microbial growth. Therefore, it is inferred that the mountain pepper can effectively reduce the oxidation and rancidity of the food, and can achieve the antibacterial effect.
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