Influence of an autochthonous starter culture and a commercial starter on the characteristics of Tenerife pasteurised goats’ milk cheese

Two batches of Tenerife cheese were produced from pasteurised goats’ milk, one with a commercial starter and another with an autochthonous starter consisting of three selected strains of lactic acid bacteria isolated from artisanal Tenerife cheese. Influence of starter on the characteristics of the cheeses was evaluated. Owing to the composition of the starters, lactobacilli and leuconostocs varied significantly between both cheeses. However, the type of starter did not significantly affect the physicochemical and proteolytic properties of the cheeses. In general, cheeses made with autochthonous starter received higher scores for sensory attributes, especially for aroma, than those made with commercial starter.     

不同发酵剂对牦牛乳硬质干酪品质的影响

以新鲜牦牛乳为原料,分别添加嗜温、嗜热和混合(嗜温∶嗜热=1∶1)三种发酵剂制作硬质干酪,研究在1~180 d成熟过程中,不同类型发酵剂制作的干酪中蛋白降解和ACP(酸性磷酸酶)对其品质的影响。结果表明:牦牛乳硬质干酪成熟过程中发挥作用的ACP主要来自发酵剂,且干酪中蛋白降解受ACP影响显著,ACP与PPN(多肽氮)呈强正相关性(r=0.720),与CN(酪蛋白氮)和PN(蛋白氮)呈强负相关性。三种干酪PPN在60~120 d均保持稳定状态。不同类型的发酵剂对干酪蛋白降解强弱不同,过强或过弱均会影响到干酪的品质,嗜温发酵剂对干酪蛋白降解最弱,该干酪风味比较清淡;嗜热发酵剂对干酪蛋白降解能力最强,该发酵剂制作的干酪苦味较重,但组织状态较好;混合发酵剂对蛋白降解适中,该干酪发酵风味浓郁,组织状态较佳。      

凝固型芝士风味发酵乳的制备

以生牛乳、白糖以及芝士酱为主要原料,以酸度和感官评价为检测指标,通过单因素试验和正交试验确定凝固型芝士风味发酵乳的最佳发酵工艺条件。结果表明,凝固型芝士风味发酵乳的最佳发酵工艺条件为白砂糖7.5%、芝士酱0.9%、发酵温度43 ℃,发酵时间5.5 h。在此优化条件下,成品感官评分为91分,酸度为78.9 °T,产品组织细腻均匀,无乳清水析出,酸甜适中,口感嫩滑,且具有芝士酱特有的风味。     

Improvement of sensory quality of lowfat kefalograviera-type cheese by using commercial special starter cultures

Two commercially available special starter culture systems, Alp DIP and a mixture of Alp DIP D and Joghurt V1, were compared with one commercial regular starter culture, CH-1, for their effects on the compositional, sensory and textural characteristics of lowfat (9.5%) high moisture (49.6%) Kefalograviera-type cheese during aging. A full-fat control Kefalograviera cheese (30.8% fat, 37.8% moisture) was also made with the regular starter culture. The results indicated that the type of starter did not affect the composition (moisture, fat, protein, salt and pH) of the lowfat cheese. Sensory analysis showed that the lowfat cheeses made with the special cultures received greater body and texture scores and significantly higher flavor scores than the lowfat control cheese after aging for 90 and 180 d. Moreover, the former cheeses received body and texture and flavor scores not significantly different from those of the full-fat cheese. Texture profile analysis by Instron showed that there were no significant differences in the textural characteristics (force and compression to fracture, cohesiveness, springiness, gumminess and chewiness) between lowfat cheeses made with the special cultures and that made with the regular starter, except for hardness which was significantly lower in the former cheeses.     

适于大豆干酪加工的乳酸菌发酵剂研究

以豆浆为发酵底物,对8株乳酸菌的凝乳性能进行了研究,检测了凝乳的黏度、酸度、双乙酰、胞外多糖和pH值为4.6可溶性氮含量,采用混合权重法对结果进行统计分析,得出凝乳性能的排序结果为Lb2→La→St1→Lb1→Sl→St2→Sc→Lc。此外,对8株乳酸菌的α-低聚半乳糖代谢能力进行了研究,乳杆菌代谢能力显著高于乳球菌。最后,优选出适于大豆干酪加工的乳酸菌发酵剂为St1和La。     

Effect of the lactoperoxidase system on the activity of mesophilic cheese starter cultures in goat milk

The effect of goats’ milk lactoperoxidase (LP) system on the activity of commercially available mesophilic cheese starter cultures was investigated. The growth and acid production of the starter cultures were measured at 2 h intervals for 8 h in goats’ milk kept at 30°C. Most of the starter cultures examined were found to be sensitive to the LP system, but varied in their susceptibility to inhibition. The activity of the mixed starter cultures CHN11, CHN22, CHN19, DCC240 and Flora Danica Normal was strongly inhibited by the LP system. However, the mixed starter culture LL 50C showed resistance to the LP system. The single strain culture Lactococcus lactis subsp. lactis NCDO 605 was inhibited by the LP system. However, the cultures Lactococcus lactis subsp. diacetylactis NCDO 176 and Leuconostoc mesenteroides subsp. cremoris ATCC 33313 were insensitive to the LP system. The results of this study indicate the need for routine screening of starter cultures for resistance to the LP system before using them for cheesemaking from goats’ milk preserved by the LP system.     

发酵乳制品中苯甲酸的来源及水平

论述了发酵乳制品酸牛乳、干酪中苯甲酸的来源及水平,对分析、预测发酵乳制品中苯甲酸自然形成量,并有效控制产品的安全质量提供参考。     

脱脂乳的不同热处理对其酸奶凝胶流变学性质的影响

研究了复原脱脂乳经不同加热处理后其酸奶凝胶形成过程中流变学特性的变化,复原脱脂乳经７０～９０℃处理１０～２５ｍｉｎ,用Ｄ－葡萄糖－δ－内酯酸化成胶,用流变学方法动态监测凝胶性能。并监测酸化过程和成胶时间,结果显示,不同条件下自理后的脱脂乳在酸化过程中,ｐＨ值并未改变,但产储存模量（Ｇ′）和损失模量（Ｇ″）随受质变程度的增加而增加,只是当加热温度为９０℃时反而随加热时间的延长而降低,在８５℃加热２５     

发酵剂对牦牛乳硬质干酪成熟过程中生物胺的影响

乳酸菌产生物胺的能力具有菌株特异性,因此,为了探究不同种类发酵剂对牦牛乳硬质干酪中生物胺形成的影响,该试验利用高效液相色谱对3种不同发酵剂制作的硬质干酪成熟过程中生物胺进行了测定和分析。结果表明,嗜热和嗜温发酵剂牦牛乳硬质干酪中检测出2-苯乙胺、腐胺、尸胺、组胺和酪胺,混合发酵剂干酪中检测出腐胺、2-苯乙胺、尸胺和酪胺。各生物胺之间呈现正相关性。3种不同发酵剂干酪在1～6个月成熟过程中,其各生物胺整体呈现增加趋势,嗜热、嗜温和混合发酵剂干酪中总生物胺最高含量分别为(448.3±9.6)、(456.8±58.4)、(293±24.5)mg/kg。组胺和酪胺是2种毒性相对高的生物胺,嗜热发酵剂干酪中组胺和嗜温发酵剂干酪中酪胺最高,其最高含量分别为(20.8±7.9)、(92.9±6.7)mg/kg,混合发酵干酪中未检测出组胺,酪胺含量次之,3种不同发酵剂干酪中组胺、酪胺含量均低于推荐安全剂量50 mg/kg和100 mg/kg。这为合理选择发酵剂和控制干酪中生物胺形成提供了依据。     

Effect of starter cultures on properties of soft white cheese made from camel (Camelus dromedarius) milk

This experiment was conducted to investigate the effect of starter cultures on the physicochemical properties, texture, and consumer preferences of soft white cheese (SWC) made from camel (Camelus dromedarius) milk. The experiment was laid out in a completely randomized design with 5 treatments [starter cultures; i.e., 1 thermophilic (STI-12), 2 blended (RST-743 and XPL-2), and 2 mesophilic (R-707 and CHN-22) cultures]. Starter cultures STI-12 and RST-743 were inoculated at 37°C, whereas XPL-2, R-707, and CHN-22 were inoculated at 30°C. Camel milk inoculated using STI-12 and RST-743 cultures resulted in faster acidification than XPL-2, R-707, and CHN-22 cultures. Camel milk SWC made using STI-12 and CHN-22 cultures gave lower pH (4.54) and titratable acidity (0.59), respectively, whereas R-707 culture resulted in high cheese yield (13.44 g/100 g). In addition, high fat (20.91 g/100 g), protein (17.49 g/100 g), total solids (43.44 g/100 g), and ash (2.40 g/100 g) contents were recorded for SWC made from camel milk made using RST-743 culture. Instrumental analysis of cheese texture revealed differences in resistance to deformation in which camel milk SWC made using RST-743 culture gave higher firmness (3.20 N) and brittleness (3.12 N). However, no significant difference was observed among camel milk SWC adhesiveness made using different starter cultures. Consumer preference for appearance, aroma, taste, and overall acceptances of SWC were affected by inoculation of starter cultures. Considering curd firmness, cheese yield, compositional quality, and textures using STI-12, RST-743, and R-707, these cultures were found to be better for the manufacture of camel milk SWC.     

Isolation of lactic acid bacteria from Lighvan cheese, a semihard cheese made from raw sheep milk in Iran

The lactic acid bacteria contributing to Lighvan cheese ripening during the different stages of production were investigated. Isolated strains from different culture media were identified phenotypically to species and subspecies level. In total, 413 strains were isolated from raw milk, 1-day-old cheese and fully ripened cheese. The most abundant species belonged to Enterococcus faecium (87 isolates), Lactococcus lactis ssp. lactis (68 isolates), Enterococcus faecalis (55 isolates) and Lactobacillus plantarum (48 isolates). E. faecium, Lc. lactis and Lb. plantarum were the predominantly isolated strains from ripened cheese. Therefore, they may contribute considerably to the aroma and flavour development of Lighvan cheese.     

Production and properties of a semi-hard cheese made from soya milk

Summary A semi-hard soya cheese, with mean moisture content 61.5%, crude protein 21.8% and fat 2.6%, was produced from reconstituted soya-milk powder using a starter culture of Streptococcus thermophilus and Lactobacillus fermentum . The physical properties of the cheese, as determined with a Texture Profile Analyser , were similar to a cheese made to the same compositional standards from bovine milk. A taste panel of Far Eastern subjects did not find the flavour of the fresh soya cheese acceptable but, when cubes of the cheese (1 cm³) were deep-fried in corn oil, the hedonic rating improved significantly. It is suggested that the cheese could be used as a protein-rich component of a meal, e.g. to replace meat in a stew, or as a 'snack food'.     

Kinetics of available lysine in stored commercial skim milk powder at moderate temperatures

Kinetics of lysine blockage, as an early step of the Maillard reaction, was investigated in commercial skim milk powder to understand the extent of the reaction, specifically after packages are opened and during the subsequent storage. Samples were stored at six conditions including three temperatures (30, 32.5 and 35 °C) and two relative humidities (43% and 52%) for 30 days, the period in which the product is recommended to be consumed after opening. The reaction rate was determined using a dye‐binding method. Based on our findings, decrease in available lysine follows first‐order reaction kinetics model. Small changes in temperature (2.5 °C) caused significant increase in the reaction rate constants. Relative humidity affected temperature dependency of the reaction, and activation energies were estimated to be 142.5–170.8 kJ mol^?1. This study aims to increase the awareness of the significance of storage quality in relation to the nutritional status of the products.     

Comparison of Fascal cheese produced with natural,commercial or autochthonous cultures

Lactic acid bacteria were isolated from raw ovine milk and Fascal cheese and used as two alternative inoculants for production of this Brazilian cheese. Microbiological counts and moisture of these cheeses were comparable to those observed in cheese made with a commercial starter. All cheeses showed absence of Salmonella spp., tolerable counts of coliforms, but coagulase‐positive staphylococci counts exceeded the standard values. Cheeses produced with Lactobacillus plantarum LCN 28 and Lactobacillus rhamnosus LCN 43 showed better results than those observed for the other experimental combinations. Autochthonous cultures could be beneficial to the manufacture of high quality typical raw milk cheese.     

Influence of heat impact in reconstituted skim milk on the properties of yoghurt fermented by ropy or non‐ropy starter cultures

The paper describes studies on the influence of heat impact in reconstituted skim milk on chemical and functional properties of yoghurt products. Reconstituted skim milk was heated for 20 min at 85°C, 90°C, or 95°C. Ropy (producing exopolysaccharides, EPS) or non‐ropy strains of S. thermophilus and L. delbrueckii subsp. bulgaricus were used as starter culture for yoghurt manufacture. The studies have shown that the fermentation times decreased with increasing heat impact when the ropy starter culture was used, while they remained to a far extent unchanged if the non‐ropy starter culture was applied. The lactic acid contents of the yoghurt products were in the same range when the milk was heated at 85°C or 90°C, while they were different when milk was heated at 95°C. There was a tendency visible that an increase in preheating leads to increased L (+)‐ and decreased D (–)‐lactic acid contents if the non‐ropy culture was applied. Using the ropy culture, it was vice versa. A slightly decrease in proteolysis with increasing heat impact was to be noted with both starter cultures. Concerning the relation of proteolysis to acidification, the fermentation process could be subdivided into three sections with different slopes if the non‐ropy starter culture was used, while a linear relation was found if the ropy starter culture was applied. Regarding final product characteristics it was found that the functional properties of yoghurt decreased with increasing heat impact when the ropy starter culture was applied, while they remained to a far extent unchanged when the non‐ropy starter culture was used. It can be concluded from these studies that a preheating of milk at a temperature of 85°C (20 min) is optimal in regard to final yoghurt product characteristics.     

超高效液相色谱串联质谱法检测奶粉中苯甲酸的含量

目的 建立一种超高效液相色谱-串联质谱(ultra performance liquid chromatography-tandem mass spectrometry, UPLC-MS/MS)检测奶粉中苯甲酸(benzoic acid)含量的分析方法。方法 样品经水提取后, 选用Waters Acquity UPLC BEH C18色谱柱(2.1 mm×50 mm, 1.7 μm), 以甲醇和0.1%氨水作为流动相进行梯度洗脱, 电喷雾离子化(electrospray ionizatio, ESI-)及多反应监测模式(multi-reaction monitoring, MRM)进行测定, 外标法定量。结果 苯甲酸在0.04~2.00 μg/mL浓度范围内, 线性关系良好(r2=0.9996), 样品加标回收率为94.92%~109.31%, 定量限为0.06 μg/g, 结果的相对标准偏差为1.69%~6.90%。结论 该方法前处理简单, 稳定性和可靠性好, 具有良好的定性和定量分析能力, 适用于奶粉中苯甲酸含量的检测。     

Comparison of casein micelles in raw and reconstituted skim milk

During the manufacture of skim milk powder, many important alterations to the casein micelles occur. This study investigates the nature and cause of these alterations and their reversibility upon reconstitution of the powders in water. Samples of skim milk and powder were taken at different stages of commercial production of low-, medium-, and high-heat powders. The nature and composition of the casein micelles were analyzed using a variety of analytical techniques including photon correlation spectroscopy, transmission electron microscopy, turbidity, and protein electrophoresis. It was found that during heat treatment, whey proteins are denatured and become attached to the casein micelles, resulting in larger micelles and more turbid milk. The extent of whey protein attachment to the micelles is directly related to the severity of the heat treatment. It also appeared that whey proteins denatured during heat treatment may continue to attach to casein micelles during water removal (evaporation and spray-drying). The process of water removal causes casein and Ca in the serum to become increasingly associated with the micelles. This results in much larger, denser micelles, increasing the turbidity while decreasing the viscosity of the milk. During reconstitution, the native equilibrium between colloidal Ca and serum Ca is slowly reestablished. The reequilibration of the caseins and detachment of the whey proteins occur even more slowly. The rate of reequilibration does not appear to be influenced by shear or temperature in the range of 4 to 40°C.     

Production of low-fat Chanco cheese using homogenized milk and adjunct lactic culture

The objective of this study was to determine the effect of the partial homogenization of milk and the use of an adjunct lactic culture on the processing, quality and yield of low-fat Chanco cheese.
  Treatments were: T1 normal-fat control and T2 low-fat control. The low-fat treatments were: T3 using homogenized milk, T4 with adjunct lactic culture and T5 both variables.
   It was concluded that the homogenization slightly increased the time of rest after cutting of the curd, and the addition of adjunct lactic culture increased the acidity of whey during a second agitation. Nevertheless, the total time and pH at the end of the process were normal and without significant statistical difference ( P  > 0.05) between treatments. When using homogenized milk the losses of fat in whey decreased by 50% with respect to the low-fat control and nearly 80% in relation to the full fat control. Consequently, the yield was increased. The physical and chemical characteristics of the Chanco cheese were not affected by the studied variables. With respect to the sensory evaluation, significant differences in colour and aroma did not appear, but there were statistically significant differences (P <  0.05) in taste, hardness, adhesiveness, cohesiveness and elasticity between the full-fat control and all the low-fat treatments. In the case of general acceptance, the treatment with adjunct lactic culture was similar to the full-fat control. In addition, it showed the least difference (mild) in elasticity and taste in relation to this control .     

Studies on the development of beverages using fruit juice/pulp, separated milk and reconstituted skim milk

Studies were carried out on the development of beverages using fruit juice/pulp, separated milk and reconstituted skim milk. Beverages were prepared by blending juice/pulp from apples, bananas, guavas, litchis and mangos at four different concentrations (100, 200, 300 and 400 g/L) with separated and reconstituted skim milk. Organoleptic evaluation of the beverages showed that apple juice and guava pulp could be blended at up to 300 and 100 g/L in milk products, respectively. Banana and mango pulp could also successfully be used at up to 200 g/L in separated milk and reconstituted skim milk. Litchi juice could be blended up to 300 g/L in separated milk and 200 g/L in reconstituted skim milk.     

Seasonal variation in conjugated linoleic acid and vaccenic acid in milk fat of sheep and its transfer to cheese and ricotta

The seasonal variation in conjugated linoleic acid (CLA) and vaccenic acid (VA) concentrations in sheep dairy products and the extent of their transfer from milk fat to cheese and ricotta fat were investigated. Samples were collected from 2 sheep milk processing plants in North Sardinia (Italy) every 2 wk from March through June. Concentrations of fatty acids (FA) in fresh cheese and ricotta fat were primarily dependent on the fatty acid content of the unprocessed raw milk. The content of c9,t11-CLA averaged 1.73, 1.69, and 1.75 mg/100 mg of FA methyl esters (FAME), respectively, for milk, cheese, and ricotta, and differed significantly between cheese and ricotta. The content of VA averaged 3.40, 3.33, and 3.43 mg/100 mg of FAME, respectively for milk, cheese, and ricotta. The FA composition of dairy products was markedly affected by period of sampling: the mean c9,t11-CLA and VA concentration decreased from March (2.20 and 4.52 mg/100 mg of FAME) to June (1.14 and 1.76 mg/100 mg of FAME) in all dairy products. No differences in c9,t11-CLA and VA concentration of dairy products were observed between the 2 dairy companies obtaining milk from the same geographical origin. The seasonal changes in CLA and VA in milk fat were probably related to changes in pasture quality.