• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.9
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• pp.1316-1323
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• 2016

The aim of this study was to evaluate proteolytic and antioxidant activities of fresh pineapple and kiwi juices extracted using a slow-speed masticating household juicer during low temperature storage. While over 90% of vitamin C and total polyphenols in both juices were retained after storage for 30 days at $-20^{\circ}C$, reduction of 56.8% for vitamin C and 31.9% for total polyphenols in pineapple juice were detected after storage at $4^{\circ}C$. In the case of kiwi juice, 32.9% of vitamin C and 22.4% of total polyphenols were lost. A high initial content of vitamin C in kiwi juice resulted in a slower reduction rate than that for pineapple juice. A similar result was obtained for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Proteolytic activities of both juices were maintained efficiently with less than 10% loss during storage for 30 days at $-20^{\circ}C$. Protease stability of pineapple juice was better than that of kiwi juice during storage at $4^{\circ}C$, and the same result was obtained when boiled chicken breast was used as a substrate. From these results, when storing pineapple and kiwi juices, which are widely used as a natural meat tenderizer and digestive aid, cold storage at $-20^{\circ}C$ seemed to be more suitable for maintaining antioxidant and proteolytic activities than cold storage at $4^{\circ}C$.

• Korean Journal of Food Science and Technology
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• v.11 no.3
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• pp.171-175
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• 1979

Thermal properties of crude papain and crude peroxidase from domestic papaya were investigated. The crude extract of papaya was inactivated at the temperature range of $60^{\circ}{\sim}90^{\circ}C$ at pH 7.0 and the rest of the activities of papain and peroxidase were determined, respectively. The heat inactivation of papain and papaya peroxidase was biphasic at low temperature. For the thermal inactivation of papain extract, the enthalpy of activation was 91.4 kJ/mol, the entropy of activation, -49.6 J/mol K, and the free energy of activation, 108.5 kJ/mol. The activation energy for the inactivation of papaya peroxidase was 168.5 kJ/mol, the entropy of activation, $200.4\;J/mol{\cdot}K$ and the free energy of activation, 99.7 kJ/mol. The thermal stability of papain showed that it has a possibility for use as a meat tenderizer. It was also discussed that papaya peroxidase could be more suitable as a biochemical criteria for heat treatment than papaya catalase.

• Journal of Animal Science and Technology
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• v.45 no.2
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• pp.309-318
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• 2003

In order to improve the quality of low-grade seasoned ribs, kiwi powder, pear powder and phosphates were studied. To seasoned ribs, 0.1%, 0.3% or 0.5% of kiwi powder was added and their MFI(Myofibrillar Fragmentation Index) values were 341.4, 368.3 and 405.1, respectively. As the amount of kiwi increased, MFI value increased(p<0.001). Also, when 0.5%, 1.0% or 3.0% of pear powder was added to seasoned ribs, their MFI values were increased as the addition levels of pear powder increased. As the amount of kiwi and pear powder were increased, WHC(Water Holding Capacity) decreased(p<0.001). On the other hand, as the amount of phosphates added increased, WHC increased. In drip loss, as the amount of kiwi and pear powder increased, it increased. However, drip loss was decreased as the amount of phosphates increased. For meat color, ‘L’ values of pear treatment groups were similar to those of control and ‘a’ values were higher in the treatment groups of 0.1${\sim}$0.3% kiwi powder, 0.5${\sim}$1.0% pear powder and 0.3${\sim}$0.5% phosphate than those of control. In sensory evaluation, treatment group of 0.3% kiwi powder and 0.5% phosphate showed the highest values in juiciness, tenderness and acceptability among the treatments(p<0.01).