LACTOSE HYDROLYSIS AND ORGANIC ACIDS PRODUCTION IN YOGURT PREPARED WITH DIFFERENT ONSET TEMPERATURES OF ENZYMATIC ACTION AND FERMENTATION

Abstract The aim of this study was to evaluate lactose hydrolysis between two different initial temperatures of enzymatic and fermentation action to improve the fermentation period by checking the components formed and hydrolysis levels of lactose by HPLC. pH and titratable acidity analysis between treatments - higher initial temperature (HIT), 42 ºC, and lower initial temperature (LIT), 30 ºC - were different (P<0.05) during the fermentation process. HIT obtained lower pH and higher titratable acidity values as 4.6±0.04 and 0.73±0.01 g lactic acid.100 mL-1, respectively, against 4.82±0.01 and 0.64±0.01 g lactic acid.100 mL-1 from LIT. Lactose content was different (P<0.05) between treatments while fermenting; however, at the end of the fermentation, it reached 4.565±0.34 mg.mL-1 and 4.398±0.18 mg.mL-1 for LIT and HIT (P>0,05), respectively. Glucose and galactose remained buoyant during the fermentation period, which indicates its production and consumption at the same time by the lactic acid bacteria involved. The lactic acid concentration in LIT was higher (P<0.05) (18.64±0.62 mg.mL-1) than in HIT (17.56±0.53 mg.mL-1) although citric and acetic acids content decreased throughout the process. In conclusion, the lactase enzyme contributed to reduce the lactose content without affecting the fermentation process. In addition, both treatments obtained lower values of lactose, which is sufficient for the consumption by those who have lactose malabsorption.摘要 本研究旨在对比酶解与发酵作用在两种初始温度下的乳糖水解效果，通过高效液相色谱法（HPLC）检测发酵过程中生成的组分与乳糖水解程度，以优化发酵周期。试验设置两组：较高初始温度组（42℃，Higher Initial Temperature，以下简称HIT）与较低初始温度组（30℃，Lower Initial Temperature，以下简称LIT）。发酵过程中，两组的pH值与滴定酸度均存在显著差异（P<0.05）：HIT组的pH值更低、滴定酸度更高，分别为4.6±0.04与0.73±0.01 g乳酸·100mL⁻¹；而LIT组的对应值为4.82±0.01与0.64±0.01 g乳酸·100mL⁻¹。发酵过程中两组的乳糖含量存在显著差异（P<0.05），但发酵结束时，LIT组与HIT组的乳糖含量分别为4.565±0.34 mg·mL⁻¹与4.398±0.18 mg·mL⁻¹，组间无显著差异（P>0.05）。发酵期间，葡萄糖与半乳糖浓度维持动态平衡，表明参与发酵的乳酸菌可同时合成与消耗这两种单糖。尽管柠檬酸与乙酸含量在发酵全程持续降低，但LIT组的乳酸浓度（18.64±0.62 mg·mL⁻¹）显著高于HIT组（17.56±0.53 mg·mL⁻¹，P<0.05）。综上，乳糖酶可在不影响发酵进程的前提下降低乳糖含量；此外，两组处理的乳糖含量均处于较低水平，足以满足乳糖吸收不良人群的食用需求。