酶法水解乳糖与热处理偶联对牛乳Maillard反应的影响

旨在探讨乳糖水解程度及热处理方法与Maillard反应的关系,鲜牛乳用中性乳糖酶处理获得不同水解程度的低乳糖牛乳,然后对牛乳进行不同的热处理,处理后的样本进行Maillard反应程度评价。采用葡萄糖氧化酶法测定不同水解时间的牛乳中葡萄糖质量浓度和乳糖水解率,用高效液相色谱法和紫外分光光度法分别测定水解后牛乳经不同热处理后的糠氨酸和5-羟甲基糠醛(5-hydroxymethylfurfural,5-HMF)含量及牛乳褐变程度的OD值。结果表明,随着乳糖水解时间的延长,牛乳中的葡萄糖含量呈增加的趋势,葡萄糖质量浓度从0.00 mg/100 m L增加到1 721.33 mg/100 m L,但增加趋势逐渐变缓;乳糖水解率从0%增加到70.33%,水解时间2.0 h后的牛乳水解率达到了50%以上。糠氨酸含量呈上升的趋势(P0.05),水解时间在3.0 h以上并经75℃、30 min热处理的牛乳,糠氨酸含量超过了190 mg/100 g pro;水解时间为0.5 h及以上并经75℃、15 s热处理的牛乳,糠氨酸含量超过了12 mg/100 g pro。生鲜牛乳和水解后经75℃、30 min热处理的牛乳,均未检测到5-HMF,水解后经75℃、15 s热处理的牛乳,随乳糖水解时间的延长,牛乳中5-HMF含量增加显著(P0.05)。牛乳的褐变程度随乳糖水解时间显著增加(P0.05),且乳糖酶水解后75℃、30 min热处理的牛乳的褐变程度明显高于75℃、15 s热处理的牛乳。本研究结果说明,乳糖经过酶水解后的牛乳,长时间热处理会加重乳Maillard反应,影响乳的蛋白质品质。     

莱茵-埃农氏法和高效液相色谱-示差折光法检测奶粉中乳糖和蔗糖的比较研究

选用市售同种品牌不同年龄段的奶粉,采用莱茵-埃农氏法和高效液相色谱-示差折光检测法对其乳糖和蔗糖进行测定,分析乳糖和蔗糖的差异,并对两种分析方法的结果进行比较,为奶粉中乳糖和蔗糖的检测方法提供依据。结果表明,莱茵-埃农氏法和高效液相色谱-示差折光检测法相比,高效液相色谱-示差折光检测法测定乳糖和蔗糖含量的准确度更高,蔗糖和乳糖的线性范围均为2～12 mg/mL,相关系数分别为0.999 3、0.999 6,精密度实验结果表明,相对标准偏差分别为2.53%、3.81%,平均加样回收率分别为99.70%、101.06%。高效液相色谱-示差折光检测法结果准确、分析时间短、前处理简单,适用于快速测定奶粉中蔗糖和乳糖含量。     

Characteristics of lactose-free frozen yogurt with κ-carrageenan and corn starch as stabilizers

Frozen yogurt is a type of dairy product that is considered to be a more healthful alternative to conventional ice cream due to its lower fat content and the presence of viable lactic acid bacteria. Lactose-free products are a growing trend in the dairy industry, and lactose-free yogurts and ice creams can both be found on the market. However, lactose-free frozen yogurt has not yet reached the market. In this study, we aimed to investigate the effect of adding κ-carrageenan (0.05, 0.1, and 0.15%) and corn starch (1, 2, and 3%) on acidity, texture, viscosity, overrun, melting properties, color attributes, and sensory characteristics of lactose-free frozen yogurts. Lactose was reduced by enzymatic hydrolysis during the fermentation process. The effectiveness of the hydrolysis was measured by HPLC, and lactose was reduced to 0.05% after 80 min of incubation with the enzyme. The addition of stabilizers did not change overrun and melting properties of frozen yogurt, but it did affect pH, titratable acidity, and color parameters. The product with 0.15% κ-carrageenan had the highest hardness and stickiness values. Moreover, κ-carrageenan had a positive effect on sensory attractiveness of lactose-free frozen yogurt, and it reduced the coarse texture in comparison with the control without stabilizers. A lactose-free frozen yogurt with good quality and nutritional characteristics was produced, particularly with the use of κ-carrageenan as stabilizer.     

离子色谱电化学测定牛奶中的乳糖和乳果糖

本方法成功地对牛奶中的乳糖和乳果糖进行了分离和测定。以CarboPacPA1色谱柱,5mmol/LNaOH+1mmol/LCH3COONa等梯度淋洗,脉冲安培检测,该方法具有良好的重现性、线性关系(r2>0.9989)和较低的检测限。乳糖和乳果糖的检测限分别是:0.012、0.02mg/L;样品测定的回收率为95%～102.8%。     

抗乳糖不耐受添加剂的研究

对产乳糖酶的三株乳酸菌进行协同发酵制成抗乳糖不耐受添加剂,冻干的乳糖酶在4℃贮存三个月活性基本不变,确立抗乳糖不耐受添加剂乳酸菌添加浓度为107/L。     

Enhanced β-galactosidase production by supplementing whey with cauliflower waste

Among the five Kluyveromyces marxianus strains tested for β-galactosidase production, K. marxianus NCIM 3465 showed maximum enzyme activity of 1.62 IU mg⁻¹ dry weight. Different levels (5–25%, w/v) of dried cauliflower waste were incorporated into whey to evaluate the effect of its supplementation on enzyme production. Although a marginal increase in enzyme production was seen by incorporating 5% and 10% cauliflower waste in whey, nearly 15% increase in β-galactosidase production was observed when cauliflower waste level was increased to 20% compared with whey alone. Supplementing whey with 20% cauliflower waste also decreased the production time. Lactose concentration in whey, mainly responsible for increasing the biological oxygen demand load of the effluent water, decreased from 4.2% to nearly 0% at 24 h. Thus, this study demonstrated that both these by-products/residues could be effectively used for β-galactosidase production at commercial scale.     

Evolution of available lysine and lactose contents in supplemented microencapsulated fish oil infant formula powder during storage

In this work we report the evolution of available lysine, lactose and lipid hydroperoxide contents as indicators of food quality and stability of two types of infant formula powder stored at 25° and 37 °C for 12 months. The first type was supplemented with microencapsulated fish oil (MFO), made of little powder particles in a food starch‐coated matrix of caseinate and saccharose to prevent the oxidation of polyunsaturated fatty acid (PUFA). The second type was not supplemented and was used for reference. MFO might not be stable during storage and affect negatively the quality of the formula in two ways: by oxidation of PUFA, which may also easily react with lysine upon oxidation, blocking lysine, or by hydrolysis of saccharose, producing reducing sugars and increasing the Maillard reaction. Slight changes were observed in lysine and lactose evolution. By comparing the two formulae, this study shows that the MFO material did not negatively affect the studied parameters, indicating therefore acceptable stability in the conditions tested.     

生物转化乳糖酸的研究

乳糖酸(Lactobionicacid)是乳糖氧化的产物,具有多种生理功能。目前,欧美等发达国家乳糖酸的生产是通过化学合成法,生产成本高,且有大量副产物生成。研究采用具有葡萄糖氧化酶的菌株BurkholderiacepaciaNo.24细胞培养物进行生物转化生产乳糖酸,55g湿重/1000mL细胞可将浓度为193mmol/L的乳糖转化成188mmol/L的乳糖酸,转化率可达99.8%,且转化液经薄层色谱层析和高效液相色谱检测证明在转化过程中没有副产物生成;同时,该菌株还具有广泛的底物专一性,能将葡萄糖、麦芽糖等糖类转化成相应的糖酸。     

Substitution of sodium chloride by Morton Lite Salt or Mineral Salt in mayonnaise

The effect of substituting Morton Lite Salt or Mineral Salt for sodium chloride in neutral emulsion and in mayonnaise was evaluated by using 1.00% sodium chloride, 1.25% Morton Lite Salt and 1.40% Mineral Salt of the emulsion weight. None, 1.00%, 2.00% and 3.00% of lactose were used to mask the bitter taste associated with potassium chloride. A triangle test using twelve to fifteen panelists was used. Results indicated that both Morton Lite Salt and Mineral Salt had a significant different taste (P ≤ 0.01) as compared with sodium chloride when they were used with none and 1.00% of lactose. Samples which had 2.00% or 3.00% lactose showed no significant taste difference between Morton Lite Salt or Mineral Salt and sodium chloride. It was concluded that a bitter masking agent such as lactose is needed when Morton Lite Salt or Mineral Salt is used to substitute sodium chloride in mayonnaise.     

低乳糖酸奶的研制

研究了低乳糖酸奶产品的配方组成及其生产工艺条件等。结果表明，该产品除具备有普通酸奶的营养丰富全面、口味酸甜爽口纯正以及凝固性能良好和无褐变等特点外，其乳糖的水解率高达70％以上，可以有效的预防人体乳糖不耐症的发生。