Effect of Lactococcus lactis Immobilized Within Pineapple and Yam Bean Segments, and Jerusalem Artichoke Powder on Its Viability and Quality of Yogurt

Lactococcus lactis cells were immobilized within pineapple segments, yam bean segments, and Jerusalem artichoke (JA) powder, and immobilized cells were used separately as adjuncts in producing probiotic yogurt. In parallel, yogurt with free L. lactis cells and yogurt only from starter cultures were also produced. The resulting yogurt samples were stored at 4 °C. Immobilization of cells increased the viability of L. lactis cells compared to free cells during storage of yogurt within pineapple segments, JA powder, yam bean segments, and free cells (43.77 %, 63.62 %, 80.11 %, and 87.14 %, respectively). The pH values of all yogurt samples decreased during storage; however, the pH values of yogurt supplemented with immobilized cells were higher than samples with free L. lactis cells. The increase in lactic acid content during storage was not different among the yogurt samples with added immobilized cells within segments of pineapple, yam beans, and free cells. However, the lactic acid content increase was greater with samples containing immobilized cells within JA powder. The immobilized cells within pineapple segments resulted in a decrease in b * color values (indicating yellowness) and an increase in a * color values (indicating greenness) whereas immobilized cells within yam bean segments resulted in a decrease in b * color values. Immobilized cells within JA powder resulted in a decrease in L * color values (indicating lightness) and an decrease in a * color values when compared to free cells. During storage, the concentration of γ-aminobutyric acid had a tendency to increase, which was not statistically significant. The sensory test revealed that the overall acceptance scores of yogurt with immobilized cells added were quite similar to those of the samples with free cells and controls throughout the storage period of 28 days.