RESPONSE SURFACE METHODOLOGY OPTIMISATION OF GOLD KIWIFRUIT-APPLE LEATHER

Response surface methodology was used to investigate the effects of sugar, apple level and drying temperature on the L* value (lightness), chroma, water activity and puncturing force of the gold kiwifruit-apple leather at a moisture content range of 21.5±1% (dry basis) and to determine the optimised conditions for producing gold kiwifruit leather. The L* value of gold kiwifruit-apple leather increased with decreasing drying temperature regardless of the sugar level while it slightly increased as the sugar level increased. The apple level has no effect on the L* value of the product. The chroma of the gold kiwifruit-apple leather is higher at the lower temperature. But the effects of sugar and apple levels on the chroma of the product were not significant. The water activity of the gold kiwifruit-apple leather is higher at the middle to high sugar levels due to the quadratic effect and regardless of apple level and drying temperature. The puncturing force of the gold kiwifruit-apple leather was lower at the middle and high levels of sugar regardless of apple level and drying temperature. Both the apple level and drying temperature have interaction effects on the water activity and puncturing force of the product. The use of 13.575-15.000% sugar level, 12.15-15.00% apple pulp level and 60oC drying temperature in processing of gold kiwifruit-apple leather resulted in 50.29-50.67 L* value, 32.70-33.46 chroma, 0.55-0.56 water activity and 0.01-0.17 kg puncturing force.