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Abstract In this study, the effects of hot water temperature on clarity, total soluble solids, polyphenol oxidase (PPO) and color of banana juice during hot water extraction were discussed based on the theory in which heat treatment might induce the pectin and protein in banana pulp to form insoluble products. The results showed the hot water temperature had a significant effect on the formation of insoluble polymers in banana pulp from pectin and protein. In 75 °C water, the pectin and protein in banana pulp were most inclined to form insoluble products. Under this condition, the clarity of banana juice was also highest. The light transmittance at 660 nm was close to 90%. In the banana juice, extracted by 75 °C water, the pectin and protein contents were lowest, and they were lower than 7.3 mg/100 ml and 12.9 mg/100 ml respectively. The 75 °C water could not inactivate completely the pectin in banana pulp due to its high heat resistance, Therefore, 0.05% L-cysteine or ascorbic acid needed to be added into banana pulp to inhibit the browning of juice induced by residual PPO.
Key words Clear banana juice; Hot water extraction; Polyphenol oxidase; Pectin; Protein
Banana has the largest trade in the world 's fresh fruit trade. Its yield is second only to citrus, ranking second in the world. Our country is the main banana-producing country. Its planting area and yield are all ranked highest in the world. Banana is a kind of comprehensive nutritional fruit. It contains almost all vitamins and minerals. These nutrients are easy to digest and absorb. Regular consumption can prevent high blood pressure and obesity. Besides, banana has the functions of clearing heat, moistening the intestines and detoxifying. It is a rare popular fruit111. However, banana is a typical climacteric fruit. It is storage-intolerant, and is easy to degenerate. Once in faced with high yield but unmarketable case, the banana will undergo serious loss. The best way to solve this problem is to vigorously develop the banana post-yielding processing121. At present, the foreign deeply processed product of banana mainly is banana puree, and other processed products of banana are rare131. Although there are a lot of researches about banana processed products in China, such as banana wine,...