Colour of hard cheese 2. Factors of influence and relation to compositional parameters

 Colour properties of hard cheeses, which included mature Vorarlberger Bergk?se (n=141) as well as a set of Emmental cheeses monitored periodically during ripening, were evaluated by tristimulus reflectance measurements. After transformation of the tristimulus primaries into the recently proposed one-dimensional Yellowness index, colour measures were related to selected compositional parameters by multivariate statistical methods. Both multiple regression and principal component regression showed that cheese body colour is mainly affected by qualitative properties of the fat phase which, in turn, are heavily influenced by seasonal deviations. Additional minor sources of variation include the total solids content as well as measures reflecting changes induced by cheese maturation. Received: 15 July 1996     

Colour of hard cheese 2. Factors of influence and relation to compositional parameters

Colour properties of hard cheeses, which included mature Vorarlberger Bergkäse (n=141) as well as a set of Emmental cheeses monitored periodically during ripening, were evaluated by tristimulus reflectance measurements. After transformation of the tristimulus primaries into the recently proposed one-dimensional Yellowness index, colour measures were related to selected compositional parameters by multivariate statistical methods. Both multiple regression and principal component regression showed that cheese body colour is mainly affected by qualitative properties of the fat phase which, in turn, are heavily influenced by seasonal deviations. Additional minor sources of variation include the total solids content as well as measures reflecting changes induced by cheese maturation.     

Judge selection for hard and semi-hard cheese sensory evaluation

During a five month period, 34 potential panellists were subjected to 21 selection tests (triangular test, threshold evaluation, ranking test and stimulus recognition test) based on taste, aroma and textural characteristics of cheese. Standardised available ricotta cheese was used as a substrate in taste and aroma tests, while commercially available cheese was utilised to evaluate candidate performance in textural characteristic tests. A combination of procedures (binomial, sequential and bi-plot) allowed the definition of homogeneous subsets of candidates suitable for different analysis. The binomial approach allowed the last performing candidates to be identified while the sequential procedure enhanced our understanding of their skills. To make the selection criteria more coherent the performance parameters were objectively derived from the array of tests. Candidates were classified into three groups, depending on their capabilities, and the different discrimination power of the tests was highlighted through bi-plots.     

新疆酸凝硬质干酪成熟条件的研究

研究了成熟温度、成熟时间和包装方式等因素对新疆酸凝硬质干酪成熟的影响。分别以干酪中丁二酮质量分数和感官综合评分为指标,确定优化的成熟条件为气调包装、15℃成熟30d。在该成熟条件下,随着干酪成熟时间的延长,干酪中的酯类、醛类、芳香环类、烷烃和烯烃类物质质量分数呈现增加的趋势,而醇类和酸类物质则呈现降低的趋势;在结构方面成熟干酪的分子空穴更大,蛋白质结构变得更加松散。     

Content and distribution of biogenic amines in Dutch-type hard cheese

Content of biogenic amines (BA; histamine, tyramine, tryptamine, putrescine, 2-phenylethylamine, cadaverine, spermidine, spermine) and counts of microorganisms (total aerobic and facultative anaerobic mesophilic microorganisms, TAC; lactic acid bacteria, LAB; coliforms; total anaerobic microorganisms, TAN; yeasts + moulds), were evaluated within the ripening interval of 1–6 months in Dutch-type hard cheese, produced by two different producers (the cheeses designated as R30 and R45) using pasteurized milk and different starter cultures (designated as R30-FD and R30-CH in the case of the R30 cheeses). The cheeses from the two producers differed in their fat content (30% and 45% of fat in dry matter, respectively).     

硬质干酪国家卫生标准修订的研究

根据卫生部“八五”食品卫生工作计划和全国卫生标准分委会制（修）订国家卫生标准项目计划要求,全国乳与乳制品卫生标准制（修）订工作协作组对已颁布实施了１５年之久的硬质干酷国家卫生标准ＧＢ５４２０－８５进行了修订。在感官指标中,取消了百分制评定等级规定;在外观、组织状态、滋气味各项目中进行了规范要求,在理化指标中取消了食盐、汞指标,增加了食品添加剂指标,提出水分指标限值≤４３％,脂肪≥２５％,食品添加剂     

硬质发酵干酪加工设备简述

在简要说明我国发展干酪生产必要性的基础上,以切达干酪加工生产为例,从原奶的预处理、凝块的形成和加工、乳清排放以及质构化和盐化、灌装和压榨、包装和储存等5个方面详细介绍了国内外硬质干酪产品加工设备类型和使用情况,以期推动我国干酪加工设备的国产化进程。     

硬质干酪加工工艺中关键技术参数的研究与优化

以cheddar干酪加工工艺为基础,针对工艺中影响产品质量的工艺参数进行试验分析,找出对产品质量最有影响的关键因素.通过单因素初步试验,进而进行了多因素交叉影响试验,采用LSR法进行多重比较分析.分析结果表明:发酵剂添加量3.0%(质量分数),熟化终止pH值为6.5,保温搅拌温度40℃,保温搅拌时间40 min为适宜的工艺参数,所制得的干酪质量达到统一的标准并且稳定.     

Microbiological and biochemical properties of canestrato pugliese hard cheese supplemented with bifidobacteria

Canestrato Pugliese cheeses from ewe milk were produced according to a traditional protocol and by adding 7.0 log10 cfu of fresh cells per gram of Bifidobacterium bifidum Bb02, Bifidobacterium longum Bb46, or both species. The traditional technology was modified slightly to favor the survival of probiotic microorganisms. After 56 d of ripening, the survival of B. bifidum Bb02 and B. longum Bb46 was 6.0 and 5.0 log10 cfu/g, respectively. After 19 d cheeses contained ca. 7.0 log10 cfu/g of bifidobacteria. Compared to traditional cheese, the addition of bifidobacteria seemed to support the growth and survival of mesophilic lactobacilli and Streptococcus thermophilus, used as starter, during ripening. No significant differences were observed in the main chemical composition, and only a slightly higher concentration of acetic acid was found in cheeses with bifidobacteria added. On the contrary, alpha- and beta-galactosidase activities were markedly more pronounced in the presence of bifidobacteria, especially with B. bifidum Bb02. In contrast with traditional cheese, the lactose was completely hydrolyzed in cheeses made with bifidobacteria. Urea-PAGE electrophoresis of the pH 4.6-soluble and pH 4.6-insoluble N fractions did not show appreciable variations. Only the reversed-phase-HPLC analysis of the pH 4.6-soluble N showed a slightly more complex profile in the presence of bifidobacteria. This finding was in agreement with the higher value of the pH 4.6-soluble N/total N ratio and with the more pronounced amino-, imino-, and dipeptidase activities found in all the cheeses with the bifidobacteria added, especially B. bifidum Bb02. No differences were found in the free amino acid and free fatty acid contents. The amino acids glutamic acid, valine, proline, leucine, and lysine and the fatty acids butyric, caproic, capric, and oleic acids were found at the highest concentrations. The sensory evaluation did not show significant differences, and Canestrato Pugliese cheeses were characterized by small and uniformly distributed eyes, were pale yellow, had an elastic consistency and a Pecorino-like smell, were very salty, and tended to be moderately piquant.     

Acceleration of cheese ripening at elevated temperature. An estimation of the optimal ripening time of a traditional Argentinean hard cheese

The effect of elevated ripening temperature on physicochemical, biochemical and sensory characteristics in Reggianito Argentino cheese was evaluated to determine the optimal time for cheese ripening at 18 °C that ensures typical cheese characteristics. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months. Seventy-eight variables (as determined by urea-PAGE, RP-HPLC of the water-soluble at pH 4.6 fraction, free amino acids, free fatty acids and sensory analysis) were considered for the principal component analysis. The statistical analysis allowed determination of the optimal time for ripening Reggianito Argentino cheese at 18 °C, which was ranged between 2 and 3 months. In conclusion, the results obtained were not only useful in characterising the ripening of an Argentinean hard cheese, but also in evaluating the effect of an increase of ripening temperature on the main physicochemical, biochemical and sensory changes of Reggianito Argentino cheese.     

发酵剂添加量和成熟时间对牦牛乳硬质干酪脂肪氧化的影响

为研究发酵剂添加量和成熟时间对牦牛乳硬质干酪中脂肪氧化的影响,试验以添加不同发酵剂质量分数(1%、2%、3%)制得的牦牛乳硬质干酪为材料,对其90 d成熟期内的氧化指标和理化指标进行测定。结果表明:发酵剂添加量和成熟时间对牦牛乳硬质干酪的理化指标和脂肪氧化程度均有显著性影响(P <0. 05),且随发酵剂添加量的增加,干酪中酸度值(acidity value,ADV)、过氧化值(peroxide value,POV)、羰基价(carbonyl value,CV)、硫代巴比妥酸值(thiobarbituric acid value,TBA)增加;随成熟时间的延长,ADV、CV、TBA值增加,POV值先增加后降低。发酵剂添加量为3%时,能够显著增大干酪中脂肪的氧化程度(P <0. 05),同时随成熟时间的延长,脂肪氧化持续进行并且氧化程度也在不断加深。该研究将发酵剂添加量和成熟时间相结合,探讨牦牛乳硬质干酪中脂肪氧化的变化规律,以期从脂肪的氧化机制调控干酪的品质,为实现工业化生产提供理论依据。     

Fate of Listeria innocua during production and ripening of smeared hard cheese made from raw milk

The fate of 2 different Listeria innocua strains was analyzed during the production and ripening of smeared raw milk Greyerzer cheese (Gruyère). These strains were used as surrogates for the pathogenic Listeria monocytogenes, as they are physiologically very similar. Bacterial cells were added to the cheese milk at levels of 10⁵ cfu/mL. During the first 24 h of cheese making, the number of the test strains decreased to a level of below 10² cfu/g. Obviously, the cooking temperature of 56°C and the subsequent slight temperature decrease to 50°C within 70 min contributed to a distinct reduction of Listeria counts. The counts in the cheese cores did not exceed 10³ cfu/g within 12 wk of cheese ripening and Listeria was not detectable after 24 wk. In contrast to the cores of the cheeses of the 4 batches in this study, their rinds always contained a high listerial load of approximately 10⁶ to 10⁸ cfu/g throughout the entire ripening period. The smeared surface showed an increase of pH to alkaline values, corresponding to smear microbiota development. Coryneforms and Staphylococcus counts were stable at >10⁷ cfu/cm² over 175 d, whereas yeast counts decreased to about 10⁵ cfu/cm² at the end of ripening. The study shows that the smear culture had no noticeable anti-listerial potential. When removing the rind or portioning such smeared cheese loaves with a cutting device, a postprocess contamination of the core might occur, thus presenting a major hygienic risk.     

Effects of somatic cells on the protein profile of hard ovine cheese produced from different breeds

Bulk tank ewe's milks with low (<500,000 ml(-1)), medium (1,000,000-1,500,000 ml(-1)) and high (>2,500,000 ml(-1)) somatic cell counts (SCC) from three breeds were used to manufacture hard ewes'-milk cheese. Physico-chemical analysis and capillary electrophoresis of fresh cheeses and cheeses that had been ripened for 1, 2, 3 and 6 months were carried out. The results showed that high SCC levels in milk affected the moisture content of only freshly made cheeses and the pH, fat content and fat acidity of ripened cheeses. Regarding proteolysis, the levels of all β-CNs in freshly made cheeses were significantly lower as the SCC values increased and the Castellana breed was the most affected by SCC levels because a significant decrease in all α-CNs was also observed as SCC levels rose. Analysis of the casein profile by principal component analysis (PCA) revealed that there were no clear differences according the SCC up to the third month. However in the third and sixth months cheeses with low levels of SC were closely grouped and characterised by the highest levels of intact caseins. Regarding the effect of breed, the results point to a more intense proteolytic activity in the Assaf breed, whose more matured cheeses showed the highest content of casein proteolytic fragments.     

Streptococcus thermophilus 580 produces a bacteriocin potentially suitable for inhibition of Clostridium tyrobutyricum in hard cheese

A strain of Streptococcus thermophilus that inhibits Clostridium tyrobutyricum has been isolated from raw milk. The active compound produced disappears after a treatment with protease. However, unlike most bacteriocins, it is not thermoresistant, and the activity is completely lost after 1 h at 60 degrees C. Its inhibitory spectrum is limited to other thermophilic streptococci, Brochothrix, and sporulated gram-positive rods. So this bacteriocin could be different from those already described. This bacteriocin-producing strain could be used in thermophilic starter for hard cheese making because the bacteriocin is not active against thermophilic lactobacilli. It is produced in M17 medium during the decreasing temperature phase of the hard cheese-making process temperature cycle and is also produced in milk. Moreover, when Streptococcus thermophilus was cocultured with a Lactobacillus delbrueckii subsp. lactis starter strain, it seems to enhance the bacteriocin production. However the level of activity always decreases drastically during the stationary phase. But inhibition of Clostridium tyrobutyricum spores can be obtained in small-scale curds.     

Proteolysis and texture of hard ewes' milk cheese during ripening as affected by somatic cell counts

Ewes' milk samples with low (<500,000 ml(-1)), medium (1,000,000-1,500,000 ml(-1)) and high (> 2,500,000 ml(-1)) somatic cell counts (SCC) were used to manufacture hard ewes' cheese using the Zamorano cheese manufacturing protocol. Cheeses that had been ripened for 1, 2 and 3 months were used to obtain isoelectric ovine casein that was analysed by capillary electrophoresis. The texture of the cheeses during ripening was determined instrumentally using the Warner-Bratzler maximum shear force and assessed for sensory qualities by consumers using hedonic tests. The study revealed that the pH value and the lactose content of the milk were affected by high SCC and that the coagulation properties were dependent on the somatic cell content. The protein and moisture contents of the cheeses were unaffected by SCC but a significant increase of pH with ripening time were observed in high-SCC cheeses. The results also pointed to a significant increase in proteolysis related to SCC levels, showing that intact casein, both alphas1 and beta-casein, decreased as the SCC of milk increased, and that the proteolytic fragments, mainly I-alphas1, increased with SCC levels. Significant differences in texture were found among the samples, the cheeses made with high levels of SCC being significantly less compact at each ripening time. The differences in texture were detected by the consumers, who reported defects in cheeses made with high levels of SCC. Indeed, high SCC cheeses were significantly less well accepted.     

Definition of the sensory properties of hard cheese: A collaborative study between Scottish and Norwegian panels

Twelve samples of hard cheese were subjected to sensory analysis by a Scottish and a Norwegian panel of judges. The Scottish panel comprised 12 judges who had received no training, but who were experienced in evaluation of hard cheese. In contrast, the Norwegian panel of 10 professional judges was carefully selected and highly trained but inexperienced in evaluation of cheese. Samples were presented in a manner which allowed estimation of effects due to order of presentation. The cheeses were rated according to predetermined vocabularies that comprised terms encompassing odour, flavour and texture. The trained Norwegian panel performed significantly better than the Scottish panel in terms of consistency and repeatability. Despite this difference in sensory acuity, sensory space maps constructed after Principal Component Analysis of the data from each panel of judges were very similar.     

1H nuclear magnetic resonance relaxometric characterization of fat and water states in soft and hard cheese

The aim of this work was to study the spin spin (T2) relaxation components of one hard cheese and three soft cheeses to characterize fat and water states. NMR signals were measured at 6 degrees C with a 0.47 T NMR device. The transverse relaxation decay was fitted using the Marquardt method. The T2 relaxometric behaviour of the cheeses under consideration was characterized by four relaxation components. To understand the chemical composition of each NMR component, we studied anhydrous milk fat extracted from each cheese analysed. At 6 degrees C, the fat was 60% crystalline. In cheese, the solid fat was found mainly in the shorter relaxation component with a T2 of 17 micros. The intensity of the NMR relaxation with a T2 > 1 ms was explained by the amount of water, liquid fat and proteins, and the associated relaxation time varied as a function of the process used. The composition of each relaxation component was confirmed by the temperature effect and the influence of the fat content on the NMR cheese signal. NMR relaxometry was able to provide information on water behaviour (i.e. the quantity and level of interactions with proteins) and on the solid:liquid ratio of anhydrous milk fat in the cheese.     

Potential use of presumptive enterococci and staphylococci as indicators of sanitary condition in plants making hard Italian-type cheese

Raw milk, pasteurized milk, unripened cheese (1 day old), and partially ripened cheese (3 months) from 42 milk lots at a plant making hard Italian-type cheese were analyzed for presumptive enterococci using kanamycin esculin azide agar pour plates. Fully ripened (> or =10 months) cheeses, derived from other milk lots, were also tested. Numbers of presumptive staphylococci (Baird-Parker agar [B-P]) were determined in the partially and fully ripened cheeses. Presumptive enterococci were ubiquitous in raw milk, usually at levels of 2.1 to 3.0 log CFU/ml. Enterococci were detected in 11 (26%) of 42 pasteurized milk samples. Enterococci and staphylococci were detected in 39 (93%) and 6 (14%) of unripened cheeses and in 33 (80%) and 4 (10%) of partially ripened cheeses, respectively. Only eight and five samples of enterococci-positive unripened and partially ripened cheese, respectively, were made from pasteurized milk in which presumptive enterococci were detected. Of 42 samples of fully ripened cheese, 35 (83%) and 8 (19%), respectively, contained presumptive enterococci and staphylococci. Results suggest either that low numbers of presumptive enterococci survive pasteurization and cheese ripening or that contamination of cheese by enterococci occurs after pasteurization. Biochemical testing confirmed 63% of presumptive enterococci isolates. None of the 20 presumptive staphylococci isolates produced colonies typical of Staphylococcus aureus on B-P agar; the isolates were identified as 1 Staphylococcus epidermidis, 1 Staphylococcus xylosus, 2 Staphylococcus saprophyticus, 1 Staphylococcus warneri, 5 Kocuria spp., and 10 unidentified gram-positive, catalase-positive cocci. Three staphylococci isolates decreased in numbers by more than 3.0 log CFU/ml in 9.9 ml of skim milk heated 30 min in a 62.8 degrees C water bath. This finding suggests that most presumptive staphylococci detected may have been prepasteurization contaminants. Unless specificity of the kanamycin esculin azide and B-P media is improved, use of presumptive enterococci and staphylococci as indicators of postpasteurization sanitation in plants making hard Italian-type cheese cannot be recommended.