Microbiological quality of enzymatically peeled persimmon fruit for fresh-cut slices

The microflora was analyzed on persimmon fruit ('Tone-wase') that had been peeled enzymatically and sliced for fresh-cut product and compared with those hand-peeled and sliced manually with a knife. The enzymatic peeling process involved porous treatment of the peel with a needlepoint holder allowing the penetration of a pectolytic enzyme solution under the peel, followed by heating at 100°C for 45 s to inactivate the substances in the peel that inhibit the pectolytic enzyme, cooling in tap water, infusion of 3% protopectinase (Pectinase-IGA) at 37°C for 3 h, and rinsing under running tap water to remove the peel and any residual enzyme. Peeled fruit was cut radially into four sections using a sanitized knife. The peel of persimmon fruit had microbial counts ranging from 3.0 to 3.3 log CFU g^-1 and a wide diversity of fungal flora. After the fruits were submerged in hot water at 100°C for 45 s, the microbial counts in the peel and flesh were reduced to levels below the limit of detection. After the enzyme infusion followed by gentle rinsing with tap water, microbial counts of enzyme-peeled fruit remained undetectable. When microbial contamination of enzyme-peeled and hand-peeled fresh-cut slices were compared, bacterial counts were >0.5 logs higher in hand-peeled slices than in enzyme-peeled slices which were below the detection level. The diversity of bacterial and fungal flora was less in enzyme-peeled slices than in hand-peeled slices. Surface lightness of enzyme-peeled slices was lower than that of hand-peeled slices, but other color indexes, pH, and texture were not affected by enzymatic peeling. These results indicate that enzymatic peeling could be an alternative to hand peeling of persimmon fruit for fresh-cut product to achieve effective peeling and microbial safety.