契达酶改性干酪的研制

选择中性蛋白酶、风味酶以及脂酶Lipase R,将其添加到新鲜干酪浆中,水解到一定程度以生产出具有契迭风味的酶改性干酪.首先添加中性蛋白酶和风味酶,根据蛋白水解程度和感官评价,确定出具有最佳风味的初级水解产品.之后向此初级产品中分别添加Lipase R进行脂解以获得最终的EMC.最后将生产出的EMCs产品与新鲜干酪、天然成熟契达干酪进行比较,比较内容包括理化成分、蛋白水解程度、感官评价等.     

复合风味蛋白酶与脂肪酶制作酶改性干酪

研究使用复合风味蛋白酶和脂肪酶制作酶改性干酪的最佳工艺,确定乳化盐种类及添加量、酶解反应温度、反应时间及酶添加量等工艺条件.采用pH4.6水溶性氮与5%磷钨酸可溶性氮表示蛋白水解度,铜皂法测定游离脂肪酸来表示脂肪水解度.结果表明:新鲜契达干酪凝乳与水以2:1的比例混合,添加1.5%的乳化盐(焦磷酸钠:三聚磷酸钠1:1)后,以复合风味蛋白酶0.02%和脂肪酶1%的添加量,在50℃下水解8h,即得到风味适宜的酶改性干酪.     

酶改性干酪工艺初探

本文以游离脂肪酸(FFA)为指标,结合感官品评,通过单因素实验和正交实验,优化了脂酶酶解工艺:45℃下添加0.4%的(按干酪质量计)Palatase20000L,调整体系pH至7.5,搅拌酶解6h,得到游离脂肪酸(FFA)为31.97%,比原料干酪高了25.51%;以pH4.6可溶性氮(pH4.6-WSN)和12%三氯乙酸(TCA)溶解氮(12%TCA-SN)为指标,结合感官品评,通过单因素实验和正交实验,优化了蛋白酶酶解工艺:添加0.1%的蛋白酶(以干酪质量计),在50℃下水解4h,在此工艺下得到的酶解产物pH4.6-WSN为37.19%,比原料干酪高了13.16%,12%TCA-SN为31.99%,比原料干酪高了13.18%。     

复合风味蛋白酶与脂肪酶制作酶改性干酪

研究使用复合风味蛋白酶和脂肪酶制作酶改性干酪的最佳工艺,确定乳化盐种类及添加量、酶解反应温度、反应时间及酶添加量等工艺条件。采用pH4.6水溶性氮与5%磷钨酸可溶性氮表示蛋白水解度,铜皂法测定游离脂肪酸来表示脂肪水解度。结果表明:新鲜契达干酪凝乳与水以2∶1的比例混合,添加1.5%的乳化盐(焦磷酸钠∶三聚磷酸钠1∶1)后,以复合风味蛋白酶0.02%和脂肪酶1%的添加量,在50℃下水解8h,即得到风味适宜的酶改性干酪。      

蛋白质酶解产物苦味的形成及脱除的研究进展

蛋白质酶解物苦味的苦味是长期困扰其应用的问题，本文对苦味肽的产生、化学组成及脱除苦味的方法进行了综述。     

干酪的成熟,风味与微生物及其酶的关系

本文对干酪的成熟、风味与微生物及其酶的关系进行了综述；讨论了如何缩短干酪的成熟期并改善干酪的风味；另外，本文也报道了干酪工艺学的新理论和新进展。     

干酪风味影响因素的论述

本文对影响干酪风味的众多因素进行了论述,包括乳的来源、成分,干酪的盐含量、结构和酸度变化,干酪中的相变化带来的影响,以及基因和风味的联系,发酵剂和附属发酵剂的影响。从而为控制干酪的风味形成,获得稳定一致的风味物质,制作特征性风味的干酪奠定基础。     

干酪的成熟,风味与微生物及其酶的关系

本文对干酪的成熟、风味与微生物及其酶的关系进行了综述；讨论了如何缩短干酪的成熟期并改善干酪的风味；另外，本文也报道了干酪工艺学的新理论和新进展。     

分步酶解法制备酶改性切达干酪粉

介绍了一种分步酶解法制备酶改性干酪粉(EMC)的方法。第一步,用不同的蛋白酶与肽酶混合酶对切达干酪浆进行蛋白水解,筛选出最佳水解产物。第二步,用不同的脂肪酶对最佳水解产物进行脂肪水解。将得到的酶解液喷雾干燥获得两种粉末状的EMC产品A和B,并与商品切达EMC进行比较分析。本研究获得的两种EMC产品的总游离氨基酸及总游离脂肪酸质量分数均比商品EMC高,各种游离氨基酸质量分数也普遍高于商品EMC。EMC产品A感官指标得分较高,不同链长的脂肪酸比例与商品EMC接近。     

酶解方式对黄油酶解物风味物质的影响

采用SPME和GC-MS方法比较了不同酶解方式对黄油酶解物中风味物质的影响。黄油单酶酶解物、双酶酶解物中分别鉴定得到12种、16种,14种（同时加酶）和16种（顺序加酶）风味物质;黄油酶解物中的主要风味物质为酮类、脂肪酸类物质。两种酶解方式的双酶酶解物中的主要风味物质相似,均为中、短碳链的脂肪酸,但含量有所不同。因此,不同酶解方式获得的黄油酶解物中风味物质的种类与含量差别较大。      

酶改性干酪的生产技术

目前获得有营养的、经济的和持续的干酪风味产品的方法主要是酶改性干酪(Enzyme Modified Cheese,EMC)。生产EMC所需的技术包括水解干酪/凝乳使用的酶(蛋白酶、肽酶、脂肪酶和酯酶),在可控条件下,水解直到得到所需的风味。EMC的风味最高可达天然干酪风味的30倍,使用这种方法可以生产出许多不同种类的干酪风味产品。主要介绍EMC风味产生的概况,以及生产EMC所需的酶及技术等。     

Ultrafiltered milk reduces bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide-producing culture

The objectives were to reduce bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide (EPS)-producing culture and study relationships among ultra-filtration (UF), residual chymosin activity (RCA), and cheese bitterness. In previous studies, EPS-producing cultures improved the textural, melting, and viscoelastic properties of reduced-fat Cheddar cheese. However, the EPS-positive cheese developed bitterness after 2 to 3 mo of ripening due to increased RCA. We hypothesized that the reduced amount of chymosin needed to coagulate UF milk might result in reduced RCA and bitterness in cheese. Reduced-fat Cheddar cheeses were manufactured with EPS-producing and nonproducing cultures using skim milk or UF milk (1.2×) adjusted to a casein:fat ratio of 1.35. The EPS-producing culture increased moisture and RCA in reduced-fat Cheddar cheese. Lower RCA was found in cheese made from UF milk compared with that in cheese made from control milk. Ultrafiltration at a low concentration rate (1.2×) produced EPS-positive, reduced-fat cheese with similar RCA to that in the EPS-negative cheese. Slower proteolysis was observed in UF cheeses compared with non-UF cheeses. Panelists reported that UF EPS-positive cheese was less bitter than EPS-positive cheese made from control milk. This study showed that UF at a low concentration factor (1.2×) could successfully reduce bitterness in cheese containing a high moisture level. Because this technology reduced the RCA level (per g of protein) to a level similar to that in the control cheeses, the contribution of chymosin to cheese proteolysis would be similar in both cheeses.     

Production of fresh Cheddar cheese curds with controlled postacidification and enhanced flavor

Cheddar cheese in curd form is very popular in eastern Canada. It is retailed immediately after cheese manufacturing and can be maintained at room temperature for 24 h to provide better texture and mouthfeel. Subsequently, the cheese curds must be stored at 4°C. The shelf life is generally 3 d. In this study, Cheddar cheese curds were produced by adding a high diacetyl flavor-producing strain (Lactococcus diacetylactis) to a thermophilic-based starter. The objective was to achieve both postacidification stability to increase the shelf life and enhanced flavor. The addition of L. diacetylactis increased processing time but did not affect cheese composition or the evolution of proteolysis and texture. During cheese manufacturing, streptococci became the dominant microflora in all cheeses, whereas populations of Lactococcus cremoris and L. diacetylactis decreased. During cheese storage, viable counts of L. diacetylactis and Streptococcus thermophilus increased but the counts of L. cremoris decreased. During cheese manufacturing and storage, the concentrations of lactic acid and diacetyl increased rapidly in cheeses produced with L. diacetylactis. Citric acid and galactose contents remained high in cheese made without L. diacetylactis. Sensory evaluation indicated that cheeses containing the L. diacetylactis strain were more flavorful and also had less sourness and could be stored at 4°C for up to 7 d.     

Effect of free and encapsulated recombinant aminopeptidase on proteolytic indices and sensory characteristics of Cheddar cheese

The recombinant aminopeptidase of Lactobacillus rhamnosus S93 in free or encapsulated form was used in production of Cheddar cheese. The effects of these enzymes on the proteolytic indices as well as sensory characteristics have been investigated during Cheddar cheese ripening. An extrusion method was used to encapsulate the enzyme in alginate beads coated with chitosan. The free or encapsulated aminopeptidase were added at the renneting or salting stage at three different concentrations (50, 500, 2000 units per 18 L of milk). Indices of secondary proteolysis were enhanced by increasing the enzyme concentration. Cheeses with the highest concentration of the encapsulated enzyme had significantly higher concentrations of soluble nitrogen in phosphotungstic acid and total free amino acids and received the highest mean scores for the sensory characteristics.     

Compositional factors associated with calcium lactate crystallization in smoked Cheddar cheese

Previous researchers have observed that surface crystals of calcium lactate sometimes develop on some Cheddar cheese samples but not on other samples produced from the same vat of milk. The causes of within-vat variation in crystallization behavior have not been identified. This study compared the compositions of naturally smoked Cheddar cheese samples that contained surface crystals with those of samples originating from the same vat that were crystal-free. Six pairs of retail samples (crystallized and noncrystallized) produced at the same cheese plant on different days were obtained from a commercial source. Cheese samples were 5 to 6 mo old at the time of collection. They were then stored for an additional 5 to 13 mo at 4°C to ensure that the noncrystallized samples remained crystal-free. Then, the crystalline material was removed and collected from the surfaces of crystallized samples, weighed, and analyzed for total lactic acid, l(+) and d(−) lactic acid, Ca, P, NaCl, moisture, and crude protein. Crystallized and noncrystallized samples were then sectioned into 3 concentric subsamples (0 to 5 mm, 6 to 10 mm, and greater than 10 mm depth from the surface) and analyzed for moisture, NaCl, titratable acidity, l(+) and d(−) lactic acid, pH, and total and water-soluble calcium. The data were analyzed by ANOVA according to a repeated measures design with 2 within-subjects variables. The crystalline material contained 52.1% lactate, 8.1% Ca, 0.17% P, 28.5% water, and 8.9% crude protein on average. Both crystallized and noncrystallized cheese samples contained significant gradients of decreasing moisture from center to surface. Compared with noncrystallized samples, crystallized samples possessed significantly higher moisture, titratable acidity, l(+) lactate, and water soluble calcium, and significantly lower pH and NaCl content. The data suggest that formation of calcium lactate crystals may have been influenced by within-vat variation in salting efficacy in the following manner. Lower salt uptake by some of the cheese curd during salting may have created pockets of higher moisture and thus higher lactose within the final cheese. When cut into retail-sized chunks, the lower salt, higher moisture samples contained more lactic acid and thus lower cheese pH, which shifted calcium from the insoluble to the soluble state. Lactate and soluble calcium contents in these samples became further elevated at the cheese surface because of dehydration during smoking, possibly triggering the formation of calcium lactate crystals.     

Proteolysis development in enzyme-modified Cheddar cheese using natural and recombinant enzymes of Lactobacillus rhamnosus S93

Proteolysis in enzyme-modified cheese was investigated with natural crude enzyme or recombinant aminopeptidase, both derived from Lactobacillus rhamnosus S93 in the presence of a commercial proteinase, Neutrase. For production of enzyme-modified cheeses, a cheese slurry was produced and pre-incubated with Neutrase. Natural enzyme or recombinant aminopeptidase (50 units 200 g⁻¹ slurry) was added alone or in combination to the cheese slurries, which were then incubated anaerobically under vacuum at 37 °C for 1, 3 and 6 d. The greatest levels of phosphotungstic acid soluble nitrogen and free amino acids were observed in the enzyme-modified cheese containing natural enzyme followed by the one treated with a combination of the natural enzyme and recombinant aminopeptidase. The enzyme-modified cheese containing the recombinant aminopeptidase alone resulted in the complete disappearance of proline after 1 d of maturation time.     

Consumer perception of smoked Cheddar cheese

Consumer perception of smoked cheese was evaluated through focus groups, surveys, and central location testing. Three focus groups (n = 29) were conducted with consumers of smoked cheese. Subsequently, 2 online surveys were conducted. The purpose of the first survey (n = 1,195) was to understand types of smoked cheeses consumed and if consumers associated specific wood smokes with smoked cheese. Next, an adaptive choice-based conjoint (n = 367) was designed to evaluate consumer perception of different attributes of smoked cheese. Maximum difference scaling and familiarity questions were also included in the adaptive choice-based conjoint survey. Following the surveys, a central location test (n = 135) was conducted with cheeses smoked with 3 different woods at a low and high intensity (6 cheeses total). Hierarchical Bayesian estimation, 1-way ANOVA, agglomerative hierarchical clustering, and 2-way ANOVA (smoke type × intensity level) were used to interpret the collected data. Results from the focus groups indicated that smoked cheese was perceived as an artisan, high-end product and that appearance and price were strong purchase factors. In general, consumers were not aware of how smoked flavor was imparted to cheese, but when informed of the processes, they preferred cold-smoked cheese to the addition of liquid smoke flavor. Results from both surveys confirmed focus group observations. Consumers perceived flavor differences among different wood smokes and smoked products. Method of smoking, smoke intensity, type of wood, and type of cheese were the most important attributes for purchase of smoked cheese. When tasting, consumers differentiated smoke aroma and flavor among cheeses and preferred cherry wood smoked cheeses over apple wood or hickory smoked cheeses. Understanding consumer perceptions of smoked cheese will give insight into the desired experience that consumers expect when purchasing smoked cheese.