Factors affecting resistance of banana fruit to compression and impact bruising

Factors affecting resistance of banana fruit to bruising were investigated by estimating the minimum (threshold) compression forces and impact energies (both applied through 8 mm dia balls) required to produce bruises on fruit. In a survey of fruit from 11 sites in St Lucia at altitudes from 4 to 290 m, high thresholds for compression bruising were associated with fruit releasing large amounts of latex at harvest, an indicator of their high turgidity. In experimental work, fruit harvested in early morning (07.45), when their turgidity would have been highest, required 5.49 N compression to cause bruises compared with 4.55 N for later harvested fruit (at both 10.45 and 13.45). Water loss induced by leaving fruit 1 and 2 days at ambient conditions between harvest and application of bruising treatments led to reductions in thresholds for compression bruising from 5.35 to 4.32 and 4.29 N, respectively. The importance of water loss in this effect was confirmed in an experiment in which the initial rate of decline in thresholds for compression bruising was reduced by keeping fruit at high relative humidity. Fruit at 30 degrees C had a lower compression bruising threshold (3.31 N) than those at 13.5, 19 and 24.5 degrees C (4.52, 4.72 and 4.46 N, respectively). In contrast, impact bruising thresholds were affected by delay after harvest and temperature in the opposite direction to compression bruising thresholds, increasing from 93 to 120 microjoules following a 2-day delay after harvest and from 74 to 104 microjoules as a result of elevating temperature from 19 to 30 degrees C. Further work will therefore be necessary to determine which of the two types of influence is most prevalent in the postharvest handling chain before recommendations on modified handling procedures can be made.