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Yukari Murakami, Yoshihiko Ozaki and Hidemi Izumi

The microbiological quality and shelf life of enzyme-peeled fresh-cut persimmon slices were evaluated during storage in a high CO2 controlled atmosphere (CA) and active modified atmosphere packaging (MAP) at 10 °C. Microbial counts of the enzyme-peeled slices were lower in high CO2 atmospheres (10%, 15%, and 20%) than in air during CA storage for 6 days at 10 °C with the 20% CO2 atmosphere being most effective. High CO2 atmospheres did not affect the number of bacterial and fungal species detected in the persimmon slices. The surface color, expressed as C* values, of the peeled side of enzyme-peeled slices was lower in high CO2 than in air after 6 days of CA storage. In contrast, C* values at the cut side were higher for slices stored in 20% CO2 than in air on Day 6. High CO2 atmospheres did not affect other quality of enzyme-peeled slices such as texture, pH, sugar content, and total ascorbic acid content. Based on the optimum 20% CO2 concentration in a CA, enzyme-peeled slices were stored in a MAP flushed with either air or 20% CO2 for 4 days at 10 °C. The CO2 concentration approached an equilibrium of either 5% or 10% after 3 days of storage in packages flushed with either air or 20% CO2, respectively, and the O2 decreased to ≈10% in both packages. Adding 20% CO2 to the MAP was effective in reducing the growth of mesophiles and coliforms but not fungi in enzyme-peeled persimmon slices throughout 4 days of storage. The diversity of bacterial and fungal flora was partially similar between packages flushed with air and 20% CO2. Texture, pH, surface color, sugar content, and total ascorbic acid content of enzyme-peeled persimmon slices were unaffected by air or 20% CO2 as the flushing gas, except that C* values of the enzymatically peeled side on Day 4 were lower for slices flushed with 20% CO2 than air. A 20% CO2 atmosphere is recommended for reducing the microbial population of enzyme-peeled persimmon slices stored at 10 °C and the shelf life of persimmon slices in an active MAP with 20% CO2 is 4 days at 10 °C.

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Yukari Murakami, Yoshihiko Ozaki and Hidemi Izumi

Enzymatic peeling of ‘Fuyu’ and ‘Tone-wase’ persimmon fruit was conducted for production of fresh-cut slices, and the microbiological and physicochemical quality of enzyme-peeled fresh-cut slices was compared with that of slices manually peeled with a knife. The enzymatic peeling process involved a porous treatment of the peel, heating at 100 °C for 45 s, infusion with 3% protopectinase at 37 °C for 3 h, and rinsing under running tap water. Initially, the peel of ‘Fuyu’ persimmon fruit had microbial counts ranging from 3.9 to 4.2 log cfu·g−1 and a diverse microflora. The heating treatment before the enzymatic peeling process reduced the microbial counts in both the peel and flesh of all fruits to levels below the lower limit of detection. After the enzyme infusion followed by gentle rinsing with tap water, microbial counts of enzyme-peeled fruit were close to or below the level of detection. When microbial contamination of enzyme-peeled and knife-peeled ‘Fuyu’ and ‘Tone-wase’ persimmon slices was compared, the bacterial counts and diversity of bacterial and fungal flora were less in enzyme-peeled slices than in knife-peeled slices. With ‘Tone-wase’ slices, the color index, pH, and texture were unaffected by enzymatic peeling, except for surface lightness, which was lower in enzyme-peeled slices than in knife-peeled slices. These results indicate that enzymatic peeling could be an alternative to knife-peeling of ‘Tone-wase’ persimmon fruit for fresh-cut production from the point of microbiological and physicochemical quality.