Abstract:
A beverage was prepared from pineapple, carrot and ginger juices
using Response Surface Methodology to form a refreshing nutritional drink.
Three independent variables were used to prepare the beverage: pineapple-tocarrot juice ratio (75/25-90/10), fibre size distribution (0.6-1.2 mm) and ginger
concentration (2-5%). The effects of the variables were investigated and
represented using quadratic models on pH, total soluble solids, beta-carotene
and sensory attributes as responses. Responses for independent variables and
responses were optimized by setting goals to optimize the beverage. The
optimized beverage was obtained at pineapple-to-carrot juice ratio, fibre size
distribution and ginger concentration of 80/20, 0.6 mm and 3% respectively.
Optimized unpasteurized beverage was prepared and stored at -24, -10 and 4
oC and quality changes studied every five (5) days for 40 days. Significant
decrease in ascorbic acid, beta-carotene, total antioxidant activity, total soluble
solids was observed at the end of storage while total phenolic content
remained almost unchanged. Minimal quality changes occurred in frozen
samples. In another experiment, pasteurized (80 oC, 15 mins) optimized
beverage was treated with 0.1% sodium benzoate and 0.1% citric acid and
stored at 4, 28 and 38 oC and quality changes studied every 15-days for 90
days. Significant decrease in total phenolic, ascorbic acid, beta-carotene and
total antioxidant activity were observed at the end of storage at rates
depending on storage temperature. Frozen storage, therefore, can help slow the
degradation in the quality of fresh unpasteurized beverage, while storage at
low temperature can slow quality degradation in pasteurized beverage.
