Development of Freshness Index of Eggplant

Surface gloss, stiffness, and density were considered prime contributors to the freshness of eggplant fruit (Solanummelongena L.). An index to measure freshness was defined as the ratio of product of relative spectral reflectance (surfacegloss) and stiffness ratios to the density ratio. Surface gloss was measured in terms of relative spectral reflectance using acomputerized spectral radiometer system. Stiffness was determined as an initial slope of force deformation curve obtainedby uniaxial compression tests. Weight and volume for computing eggplant density were determined by standard methods.These parameters were changed to consumers acceptable limit by storing the eggplants for different periods at 25.2.Ctemperature and 905 % relative humidity. Experiments were replicated five to eight times, and the average values were usedto compute dimensionless ratios (values at any time divided by initial value) that were later used to determine a freshnessindex. Various forms of equations were tested for best fitting the data to establish the best relationship with price variation in local market. The freshness index of eggplant fruit decreased exponentially with storage period while it varied in form of power equationof weight and density ratios. It attained the lowest value (5.6%) at acceptable limit of weight ratio of about 0.87. Freshnessindex correlated linearly with stiffness ratio and quadratically with surface gloss (correlation coefficient 0.99). Price ofeggplant varied linearly with the freshness index with good correlation coefficient (0.98), which indicated that the developedfreshness index might be useful in estimating the price of eggplants.