Abstract
This experiment was carried out to investigate the effect of loquat (Eriobotrya japonica Lindley) extract on the acid production and growth of lactic culture in reconstituted skim milk. The supplementation level of loquat extract to reconstituted skim milk was 10％, 15％ and 20％. Reconstitued skim milk containing loquat extract was fermented by single of mixed culture of Streptococcus thermophilus, Lactobacillus acidophilus and Lactobacillus casei. General compositions of loquat extract, changes of viable cell count, pH and titratable acidity during fermentation were determined. Chemical compositions of loquat extract were 91.5％ moisture, 0.2％ crude ash, 8.6$^{\circ}$ Brix soluble sugar, 0.34％ total acid, and 4.11 in pH. Supplementation of loquat extract stimulated acid roduction and growth of lactic acid bacteria. Among supplementation levels, a group that was fermented by a single culture of Str. thermophilus with 10％ loquat extract was shown the highest viable cell count (2.10${\times}$10$\^$9/ CFU/mL) at 12 hours after inoculation. When loquat extract was added to reconstituted skim milk at the level of 10％, all mixed cultures of lactic acid bacteria showed higher acid production and the number of viable cell count than 3 kinds of single cultures. Especially, the growth of mixed culture of Str. thermophilus and Lac. acidophilus was promoted by the addition of 10％ loquat extract. Therefore, it was suggested to manufacture the yoghurt with the addition of 10％ loquat extract and the inoculation of mixed culture of Str. thermophilus and Lac. acidophilus for on the stimulation of growth of the lactic culture.
한국산 비파 과실의 활용도를 높이기 위하여 비파 착즙액을 첨가한 기능성 yoghurt를 개발하기 위한 기초 연구로 비파 착즙액의 농도별(10, 15, 20%) 첨가가 요구르트 균주의 산 생성 및 증식에 미치는 영향을 조사하였다. Str. thermophilus, Lac. acidophilus, Lao. casei를 단독균주 및 혼합군주로 접종하여 배양하면서 생균수와 pH 및 적정산도를 측정하였다. 비파 착즙액의 성분 특성은 수분 91.5%, 조회분 0.2%, 당 8.6$^{\circ}$Brix, 총산 0.34%, pH 4.11이었다. 단독균주의 경우 비파 착즙액의 첨가 농도(10, 15, 20%)를 달리하였을 때 Str. thermophilus는 착즙액 10% 첨가시 배양 12시간에 2.10${\times}$$10^{9}$ CFU/mL로, Lac. acidophilus는 착즙액 10-15% 첨가시 배양 15시간에 1.09${\times}$$10^{9}$-1.14${\times}$$10^{9}$ CFU/mL로 그리고 Lac. casei는 착즙액 10-15% 첨가시 배양 24시간에 1.47${\times}$$10^{9}$-1.54${\times}$$10^{9}$ CFU/mL로 가장 높은 균수를 보였다. 또한 이들 유산균의 산 생성도 비파 착즙액을 10% 첨가하였을 때 가장 많이 증가하였다. 혼합균주의 경우 Str. thermophilus와 Lac. acidophilus, Str. thermophilus와 Lac. casei는 모두 착즙액 10% 첨가구에서 배양 15시간에 각각 1.33${\times}$$10^{5}$ CFU/mL, 1.13${\times}$$10^{5}$ CFU/mL이 증가하면서 최대 균수를 나타내었으며, pH 저하와 적정산도 상승이 뚜렷하였다. 따라서 비파 착즙액 첨가 기능성 yoghurt 제조시 비파 착즙액을 10% 첨가하여 혼합 starter로 Str. thermophilus와 Lac. acidophilus 혼합균주를 사용하는 것이 이들 유산균의 증식에 가장 적합한 것으로 나타났다.타났다.
