Woranong Thongsombat, Anchalee Sirichote, and Suganya Chanthachum

pp. 187 - 196

Abstract

The production of guava juice fortified with soluble dietary fiber as pectin extracted from guava cake (peel, pulp, seeds) was conducted. The waste guava cake from juice processing plant was used for pectin extraction using sodium hexametaphosphate method followed by pectin precipitation using acidified
ethanol method. A yield of 30.50±0.34% crude pectin was achieved. Crude pectin also contained 4.71±0.18% moisture, 0.34±0.21% protein, 0.68±0.00% ash, 20.70±0.16 g (%dwb) soluble dietary fibers. pH of crude pectin was 3.06±0.02. The L* a*and b* values were 81.17±0.21, 4.76±0.04 and 15.43±0.07, respectively. Water holding capacity and bulk density were 0.90±0.01 g.water/g.solid and 0.96±0.05 g/ml, respectively. This study found that the optimum conditions for guava juice extraction using pectinase at 45o
C were 0.10 % v/v pectinase concentration and 2½ h incubation time. Under these optimum conditions, production of guava juice with different ratios of total soluble solids (^oBrix) to acid as citric acid content (%) including, 24.0, 28.0, 32.0, 35.0 and 40.0 oBrix-acid ratio, and product sensory evaluation were also conducted. By the consideration from the greatest perceived scores of all sensory evaluation attributes including color, turbidity, odor, flavor and overall acceptability, the oBrix-acid ratio of 40.0 was selected for guava juice processing. The clarified guava juice was then fortified with pectin powder extracted from previous experiments using various pectin concentrations: 0, 0.25, 0.50 and 0.75% (w/w). It was found that the perceived scores of the overall acceptability attribute decreased (p<0.05) with increasing of pectin concentration. The greatest perceived score of the mouthfeel attribute was observed from the use of 0.25% pectin. Therefore, the optimum concentration
of 0.25% soluble dietary fiber as pectin for guava juice fortification is selected for further guava juice processing.