辅助发酵剂加速Provolone干酪成熟的研究

将瑞士乳杆菌6024作为辅助发酵剂添加到Provolone干酪中,加速Provolone干酪成熟,研究了其对干酪游离氨基酸、游离脂肪酸、质构特性、电镜、风味物质的影响。结果表明,瑞士乳杆菌6024作为辅助发酵剂对干酪中游离脂肪酸质量分数没有显著影响,但能显著增加干酪游离氨基酸质量分数,60 d时达到对照组90 d时的质量分数,此时干酪的质构特性、微观结构、风味物质与对照组90 d时差异不显著。由此可知,瑞士乳杆菌6024作为辅助发酵剂可加速Provolone干酪的成熟,缩短成熟时间。     

乳杆菌产X-脯氨酰-二肽酰基-氨肽酶活性对契达干酪抗氧化活性及品质的影响

选取4株(干酪乳杆菌1.0319、瑞士乳杆菌1.0612、鼠李糖乳杆菌1.0911、植物乳杆菌1.0202)具有X-脯氨酰-二肽酰基-氨肽酶(X-prolyl-dipeptide acyl-aminopeptidase,Pep X)活性的乳杆菌,经过3次紫外诱变,诱变出具有高活性Pep X的菌株(UV-C3、UV-H3、UV-R3、UV-P3),将其添加到契达干酪中,分析在干酪成熟期间Pep X活性和抗氧化活性变化,建立二者间的相关性,并研究添加产Pep X乳杆菌对干酪品质的影响。结果表明,乳杆菌所产Pep X活性对契达干酪抗氧化活性及品质具有显著影响,且二者间呈极显著正相关(P0.01)。随着干酪成熟时间的延长,干酪的Pep X活性及抗氧化活性逐渐上升,且在第90天达到最大值,其中,添加UV-R3菌株所产的Pep X活性均显著高于其他组(P0.05),最大值为10.16 U/g,其抗氧化能力(1,1-二苯基-2-三硝基苯肼自由基清除率、羟自由基清除率、还原能力)均显著高于其他组(P0.05),最大值分别为68.43%、67.56%、0.684 3。在120 d后,随着酪蛋白的水解,干酪的苦味肽大量产生,且质构情况显著降低。在第120天时,干酪的风味感官得分达到最大值,均超过9.0分,因此可在成熟120 d后进行食用。     

瑞士乳杆菌对Gouda干酪品质的影响

将瑞士乳杆菌作为辅助发酵剂添加到Gouda干酪中,以未添加瑞士乳杆菌的干酪作为空白对照,观察Gouda干酪在成熟期间的成分、成熟率、蛋白质降解、组织状态的变化情况。同时通过测定氨基酸含量及品尝试验对干酪进行感官评价。结果显示:在120 d的成熟期内两种干酪的蛋白质、脂肪、水分、盐分和灰分含量均未发现明显的差异,而添加瑞士乳杆菌的干酪成熟第30天的成熟率、SDS-PAGE电泳条带数量以及谷氨酸含量均明显高于对照样。添加0.1%的瑞士乳杆菌不仅加快Gouda干酪的成熟,而且提高了干酪的感官品质。     

瑞士乳杆菌对契达干酪成熟期间所产ACE抑制肽的影响及其消化稳定性

为明确瑞士乳杆菌对契达干酪中血管紧张素转换酶（angiotensin-converting enzyme,ACE）抑制肽活性的影响,以蛋白质水解度和ACE抑制率为指标,与干酪乳杆菌组、鼠李糖乳杆菌组和空白组干酪进行对照,研究瑞士乳杆菌对干酪成熟期间蛋白质水解及ACE抑制活性的影响,并对ACE抑制活性最高时期的干酪进行消化稳定性研究。结果表明：成熟期间,3 组益生菌干酪的活菌数无明显差异（P＞0.05）,但均高于空白组;益生菌干酪的蛋白质水解程度和ACE抑制活性显著高于空白组（P＜0.05）,其中瑞士乳杆菌干酪的蛋白质水解程度最强,活性最高（79.71%）。模拟消化后,瑞士乳杆菌干酪活菌数降低14.30%,ACE抑制活性显著增加（P＜0.05）,达到86.06%,多肽质量浓度增加至2.81 mg/mL;研究不同分子质量超滤组分消化后的ACE抑制活性发现,其中大于10 kDa的多肽活性升高,小于10 kDa的活性下降。此外,添加瑞士乳杆菌不影响干酪的整体可接受性。因此,瑞士乳杆菌能促进干酪ACE抑制肽的产生并提高其活性,消化后活性的升高主要与大分子肽的降解有关。     

益生菌干酪的工艺研究

将植物乳杆菌MA2及Kefir发酵剂应用于益生菌干酪生产中,并对干酪的理化指标、感官进行了测定、评价,结果显示:成熟45 d后,相比于普通干酪,添加了植物乳杆菌MA2及Kefir的新型益生菌干酪的可溶性氮及不饱和脂肪酸的含量显著升高;并且具有良好的风味和质地,其中MA2干酪具有明显的酸奶味,提高了干酪的适口性,更加符合国人的口味习惯,具有良好的生产开发前景;而Kefir干酪具有Kefir发酵乳的特有风味,带有适宜的酒香味,可以被开发成个性化干酪,丰富了干酪的品种。     

花生牛乳复合软质干酪的研制

为开发适合中国消费者口味的干酪,选取花生乳部分代替牛乳,进行了复合乳软质干酪的研究。结果表明:花生乳添加比例为15%、瑞士乳杆菌接种量4%、凝乳酶用量0.002%、CaCl2添加量0.03%时,复合干酪风味、质地最佳。     

益生性植物乳杆菌对切达干酪挥发性风味形成的影响

将分离自西藏灵菇的益生性植物乳杆菌1-2通过在杀菌乳中添加活菌数8.0、9.0（lg（CFU/mL））和在排乳清后添加于凝乳块8.0（lg（CFU/g））的方式分别加入到切达干酪中,考察植物乳杆菌活菌数量、添加方式和成熟时间对干酪挥发性风味物质组成的影响。利用固相微萃取和气相色谱-质谱联用技术检测出对照组干酪的风味物质26种,益生菌干酪组风味物质30种,添加植物乳杆菌1-2可产生乙苯、十二烷、己醇和丙酮4种挥发性风味物质。成熟时间对干酪风味的影响最大,随成熟时间的延长,益生菌干酪组中苯含量显著增加,而对照组干酪在成熟12周时才检测到苯。益生菌添加量和添加方式对干酪挥发性风味的影响相似,丁酸受益生菌活菌数和添加方式的影响最大,益生菌干酪组成熟12周时,丁酸含量最高达对照组的3.96倍（P＜0.05）。在杀菌乳中添加益生菌活菌数8.0（lg（CFU/mL））组和9.0（lg（CFU/mL））组干酪中挥发性风味物质含量有显著差异,但在杀菌乳中添加高活菌数9.0（lg（CFU/mL））和在排乳清后添加低活菌数8.0（lg（CFU/g））于凝乳块中对干酪挥发性风味的形成具有相似的影响。本研究结果为改进益生菌干酪的加工工艺和风味品质提供了实验依据。     

益生菌对契达干酪成熟过程中抗氧化性变化的影响

为确定益生菌对契达干酪抗氧化性变化的影响,在菌株具备良好耐酸、耐盐性,适用于干酪生产前提下,以水解性和抗氧化性为指标,分别筛选出水解能力和抗氧化能力较强的菌株,并将其添加到契达干酪中,不添加益生菌的干酪为空白组,对干酪成熟过程中活菌数和抗氧化性进行分析。结果表明,9?株益生菌中,瑞士乳杆菌（Lactobacillus helveticus）1.0612和鼠李糖乳杆菌（Lactobacillus rhamnosus）1.0911分别具有较强的水解能力和抗氧化能力。在成熟过程中,添加L. helveticus 1.0612和L. rhamnosus 1.0911的两组干酪活菌数无显著差异,但均显著高于空白组。3?组干酪抗氧化能力均先升高再降低、最后趋于平缓,1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基和羟自由基清除能力均在第4个月达到最大,还原能力在第5个月达到最大,且添加水解能力强的L. helveticus 1.0612干酪各项抗氧化能力的最大值（DPPH自由基、羟自由基清除能力和还原能力分别为51.05%、49.97%、0.66）均显著高于添加L. rhamnosus 1.0911的干酪（47.30%、46.19%、0.56）（P＜0.05）。因此,在契达干酪中添加水解能力较强的菌株,相比于添加本身具有良好抗氧化活性的菌株,可能会加剧干酪的蛋白水解,生成具有抗氧化能力的短肽和氨基酸,从而提高干酪的抗氧化活性。     

高产3-甲基丁醛乳酸乳球菌对切达干酪风味的影响

为研究高产3-甲基丁醛乳酸乳球菌YN2-1对切达干酪风味的影响,将其作为附属发酵剂加入切达干酪中,通过感官定量描述分析、气相色谱-质谱联用技术(GC-MS)、气相色谱-离子迁移谱联用技术(GC-IMS)及电子鼻技术对比分析不同切达干酪样品的香气特征及其挥发性化合物的差异。首先在对样品的定量描述性分析和喜好度评价中发现,添加乳酸乳球菌YN2-1的切达干酪与未添加该菌的样品具有显著的香气差异,添加YN2-1的奶酪坚果风味、奶香风味及肉汤风味香气强度更高,其喜好度得分也更高。经GC-MS测定发现:添加乳酸乳球菌YN2-1并成熟60 d和120 d的干酪样品中3-甲基丁醛的含量分别为18.43 μg/kg和13.96 μg/kg,显著高于对照组,表明该菌株在切达干酪中具有高产3-甲基丁醛的特性。利用GC-IMS指纹图谱直观地区分添加乳酸乳球菌YN2-1的切达干酪与对照样品风味物质间的差异,其中2,3-丁二酮、2-戊酮 D、2-壬酮、2-甲基丁醛、正丙醇、乙酸丁酯、丁酸丁酯、2,5-二甲基吡嗪、2-乙烷基-3,5-二甲基吡嗪等物质含量在成熟60 d或120 d的样品中显著增加。不同样品间电子鼻雷达图轮廓不重叠、判别因子(DFA)的区分度较高,表明添加YN2-1菌株的干酪样品与对照样品之间具有明显差异,验证了GC-MS与GC-IMS的分析结果。结论:该菌株的加入除了能够提高3-甲基丁醛含量外,还有助于干酪中其它风味物质含量的增加,对切达干酪的坚果香、奶香及果香具有明显改善作用,具有良好的应用潜力。     

契达干酪浆中使用热激瑞士乳杆菌的研究

在食品加工中添加酶解干酪比添加天然干酪更加营养、经济、有效。为了改善酶解干酪的风味,研究经优化热激(67℃/20s,68℃/15s,69℃/10s)条件处理与未处理的瑞士乳杆菌对干酪浆蛋白水解的影响。研究结果表明,经过5d成熟时间,蛋白水解产生肽段的数量增加,疏水性肽对亲水性肽的比率降低。感官评价结果显示,在适当条件下热激组的干酪浆滋气味显著增加,酸味降低,硬度减小。     

Ripening of cheddar cheese with added attenuated adjunct cultures of lactobacilli

We made Milled curd Cheddar cheese with Lactococcus starter and an adjunct culture of Lactobacillus helveticus I or Lactobacillus casei T subjected to different attenuation treatments: freeze shocking (FS), heat shocking (HS), or spray drying (SD). Proteolysis during cheese ripening (0 to 6 mo), measured by urea-PAGE and water-soluble nitrogen, indicated only minor differences between control and most adjunct-treated cheeses. However, there were significant differences in the effect of Lactobacillus adjuncts on the level of free amino nitrogen in cheese. Cheeses made with FS or HS Lb. helveticus adjunct exhibited significantly greatest rates of free amino group formation. Lipolysis as measured by total free fatty acids was consistently highest in adjunct-treated cheeses, and FS Lb. casei-treated cheeses showed the highest rate of free fatty acid formation followed by FS Lb. helveticus treated cheeses. Mean flavor and aroma scores were significantly higher for cheeses made with Lb. helveticus strain. Freeze-shocked Lb. helveticus-treated cheeses obtained the highest flavor and aroma scores. Sensory evaluation indicated that most of the adjunct-treated cheeses promoted better texture and body quality.     

Starter strain related effects on the biochemical and sensory properties of Cheddar cheese

A detailed investigation was undertaken to determine the effects of four single starter strains, Lactococcus lactis subsp. lactis 303, Lc. lactis subsp. cremoris HP, Lc. lactis subsp. cremoris AM2, and Lactobacillus helveticus DPC4571 on the proteolytic, lipolytic and sensory characteristics of Cheddar cheese. Cheeses produced using the highly autolytic starters 4571 and AM2 positively impacted on flavour development, whereas cheeses produced from the poorly autolytic starters 303 and HP developed off-flavours. Starter selection impacted significantly on the proteolytic and sensory characteristics of the resulting Cheddar cheeses. It appeared that the autolytic and/or lipolytic properties of starter strains also influenced lipolysis, however lipolysis appeared to be limited due to a possible lack of availability or access to suitable milk fat substrates over ripening. The impact of lipolysis on the sensory characteristics of Cheddar cheese was unclear, possibly due to minimal differences in the extent of lipolysis between the cheeses at the end of ripening. As anticipated seasonal milk supply influenced both proteolysis and lipolysis in Cheddar cheese. The contribution of non-starter lactic acid bacteria towards proteolysis and lipolysis over the first 8 months of Cheddar cheese ripening was negligible.     

Antioxidant activity of Cheddar cheeses at different stages of ripening

The aim of the study was to evaluate the changes in the antioxidant properties of Cheddar cheese at different stages of ripening using different assays: 2, 2'-azinobis (3 ethyl benzothiazoline)-6-sulphonic acid, 2, 2-diphenyl 1, picryl hydrazyl and superoxide radical scavenging activity. Cheddar cheese was prepared with Lactobacillus casei ssp. casei 300 and Lactobacillus paracasei ssp. paracasei 22 and without adjunct cultures. The antioxidant activity of water-soluble extracts of Cheddar cheese was dependent on the ripening period. The changes in the antioxidant activity were related to the rate of formation of soluble peptides (proteolysis) in all the samples of cheeses up to fourth month of ripening.     

Impact of liposome-encapsulated enzyme cocktails on cheddar cheese ripening

Cheddar cheese proteolysis and lipolysis were accelerated using liposome-encapsulated enzymatic cocktails. Flavourzyme, neutral bacterial protease, acid fungal protease and lipase (Palatase M) were individually entrapped in liposomes and added to cheese milk prior to renneting. Flavourzyme was tested alone at three concentrations (Z1, Z2 and Z3 cheeses). Enzyme cocktails consisted of lipase and bacterial protease (BP cheeses), lipase and fungal protease (FP cheeses) or lipase and Flavourzyme (ZP cheeses). The resulting cheeses were chemically, rheologically and organoleptically evaluated during 3 months of ripening at 8 °C. Levels of free fatty acids and appearance of bitter and astringent peptides were measured. Certain enzyme treatments (BP and ZP) resulted in cheeses with more mature texture and higher flavor intensity in a shorter time compared with control cheeses. No bitter defect was detected except in 90-day-old FP cheese. A full aged Cheddar flavor was developed in Z3 and ZP cheeses, while treatment BP led to strong typical Cheddar flavor by the second month and did not exhibit any off-flavor when ripening was extended for a further month.     

Evolution of Free Amino Acids during the Ripening of Cheddar Cheese Containing Added Lactobacilli Strains

Cheddar cheese was produced with different lactobacilli strains added to accelerate ripening. The concentration of proteolytic products was determined as free amino acids in the water-soluble fraction at two, four, seven and nine months of aging and at two different maturation temperatures (6°C, 15°C). All amino acids increased during ripening and were higher in the Lactobacillus- added cheeses than in the control cheese, and higher in cheeses ripened at 15°C than at 6°C. Glutamic acid, leucine, phenylalanine, valine and lysine were generally in higher proportion in all cheeses. The cheeses with added L. casei-casei L2A were classified as having a “strong Cheddar cheese” flavor after only seven months of ripening at 6°C.     

Determination of regional flavor differences in U.S. Cheddar cheeses aged for 6 mo or longer

ABSTRACT:  Cheddar cheese is a widely popular food in the United States. This product is produced in facilities across the United States and often marketed based on region of manufacture, implying that regional differences in flavor character of the cheese exist. This study was conducted to determine if regional differences in flavor exist in the aged U.S. Cheddar cheeses. Three times per year for 2 y, triplicate 18-kg blocks of Cheddar cheese (< 60 d old) were obtained from 19 manufacturing facilities located in 4 major cheese- producing regions/states: California, Northwest, Midwest, and Northeast. A trained sensory panel documented the flavor characteristics of cheeses after 6-, 9-, 12-, 18-, and 24-mo ripening at 7 °C. Regional differences were observed for specific flavors for cheeses manufactured in the Northwest, Midwest, and Northeast across ripening ( P < 0.05), but the specific flavors responsible for these effects were not consistent across ripening. Similarly, cheese make procedure effects were also observed for specific flavors across ripening ( P < 0.05), but these differences were also not consistent across ripening. The impact of region and cheese make procedure on flavor of the aged Cheddar cheeses was small in comparison to consistently documented, facility-specific flavor differences ( P < 0.0001). Flavor profiles of aged Cheddar cheeses were most strongly influenced by practices specific to manufacturing facility rather than region of manufacture.     

Influence of starter culture ratios and warm room treatment on free fatty acid and amino acid in Swiss cheese

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.