Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar cheese.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Energy sources of non-starter lactic acid bacteria isolated from Cheddar cheese

The range of carbon sources available in cheese curd during maturation that could be used as energy and growth substrates by 60 cultures of non-starter lactic acid bacteria isolated from Cheddar cheese was determined by the detection of tetrazolium salt reduction in Biolog MT1 microplates^™. There were marked inter-species and strain differences in the range of carbon substrates catabolized by the 11 Lactobacillus spp. and 2 Weissella spp. examined. Sugars were used widely among the NSLAB with 90, 100 and 85% of the isolates metabolizing lactose, glucose and galactose, respectively. In addition, ribose, N-acetyl-galactosamine and sialic acid, potentially derived from nucleic acid and casein deglycosylation, were catabolized by 58, 48 and 22% of the isolates, respectively. Lactic acid was also a potential substrate for 15% of the isolates but Tween 80 was not an effective substrate. Although 50% of the NSLAB removed citric acid from the growth medium it was not an independent energy source. Peptides and amino acids were also catabolized by up to 27% of the NSLAB provided that an exogenous source of α-ketoglutaric acid was present to facilitate the aminotransferase-mediated transamination degradative pathway. The MT1 microplate method facilitates the rapid screening for isolates able to establish in the cheese curd and for the detection of specific metabolic activities in isolates undergoing evaluation for use as adjunct cultures in cheesemaking trials.     

Effect of milk pasteurisation temperature on age-related changes in lactose metabolism,pH and the growth of non-starter lactic acid bacteria in half-fat Cheddar cheese

Half-fat Cheddar cheese (∼15%, w/w, fat) was manufactured on three occasions from milk pasteurised at 72, 77, 82 or 87 °C for 26 s, and analysed over a 270 day ripening period. Increasing milk pasteurisation temperature significantly increased the levels of moisture (from ∼45% at 72 °C to 50% at 87 °C), total lactate, and D(−)-lactate in cheese over the 270 day ripening period. Conversely, the cheese pH decreased significantly on increasing pasteurisation temperature. Increasing the pasteurisation temperature did not significantly affect the populations of starter or non-starter lactic acid bacteria during maturation. The use of higher pasteurisation temperatures would appear particularly amenable to exploitation as a means of producing high-moisture (e.g., 40–41%), short-ripened, mild-flavoured Cheddar or Cheddar-like cheeses.     

Selective enumeration of Lactobacillus acidophilus,Bifidobacterium spp., starter lactic acid bacteria and non-starter lactic acid bacteria from Cheddar cheese

Twelve media were evaluated for selective and/or differential enumeration of Lactobacillus. acidophilus, Bifidobacterium spp., starter lactic acid bacteria (SLAB) and non-starter lactic acid bacteria (NSLAB) from Cheddar cheese. All media showed variation in counts and selectivity. Some reported selective media failed to inhibit SLAB and NSLAB. The media that were selective and/or differential and also gave better recovery were Reinforced Clostridium Agar with bromocresol green and clindamycin (RCABC), which was selective for L. acidophilus spp. and Reinforced Clostridium Agar with aniline blue and dicloxacillin (RCAAD), which was differential for Bifidobacterium spp. and SLAB. Reinforced Clostridium Agar with bromocresol green and vancomycin (RCABV) was found suitable for NSLAB. Apart from pure cultures, these media were also tested with commercial Cheddar cheese containing L. acidophilus. Additionally, Cheddar cheese containing L. acidophilus and B. lactis was manufactured and the selected media were used to monitor the initial survival of probiotic bacteria, SLAB and NSLAB present.     

原料乳中干酪非发酵剂乳酸菌的研究

非发酵剂乳酸菌（NSLAB）是天然存在于原料乳中的一类独特的微生物,一般在干酪成熟过程中发挥作用;着重阐述了非发酵剂乳酸菌（NSLAB）的定义、分类状况,分析其对干酪风味形成、质构变化等的影响,提出了研究非发酵剂乳酸菌应注意的问题,为研究干酪的风味多样性提供科学思路。     

Modelling the fate of Listeria monocytogenes during manufacture and ripening of smeared cheese made with pasteurised or raw milk

The dynamics of the physicochemical characteristics of foods help to determine the fate of pathogens throughout processing. The aim of this study was to assess the behaviour of Listeria monocytogenes during cheesesmaking and ripening and to model the growth observed under the dynamic conditions of the cheese. A laboratory scale cheese was made in 4 independent replicates from pasteurised or raw cow's milk, artificially contaminated with L. monocytogenes. No growth of L. monocytogenes occurred during raw milk cheese-making, whereas growth did occur in pasteurised milk. During ripening, growth occurred in raw milk cheese, but inactivation occurred in pasteurised milk cheese. The behaviour observed for L. monocytogenes was modelled using a logistic primary model coupled with a secondary cardinal model, taking into account the effect of physicochemical conditions (temperature, pH, water activity and lactate). A novel statistical approach was proposed to assess the optimal growth rate of a microorganism from experiments performed in dynamic conditions. This complex model had an acceptable quality of fit on the experimental data. The estimated optimum growth rates can be used to predict the fate of L. monocytogenes during cheese manufacture in raw or pasteurized milk in different physicochemical conditions. The data obtained contributes to a better understanding of the potential risk that L. monocytogenes presents to cheese producers (growth on the product, if it is contaminated) and consumers (the presence of high numbers) and constitutes a very useful set of data for the completion of chain-based modelling studies.     

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.     

Texture and flavour development in Ras cheese made from raw and pasteurised milk

Texture, proteolysis and flavour development in Ras cheeses made from raw or pasteurised milk with two different thermophilic lactic cultures were monitored during ripening. Results showed that at day 1 of manufacture, the moisture content and pH were lower in raw milk cheese than in pasteurised milk cheeses. Levels of water-soluble nitrogen, casein breakdown, free amino groups and free fatty acids were higher in cheese made from raw milk than in that made from pasteurised milk. Textural characteristics, such as hardness, cohesiveness and chewines, increased in all treatments during the first 60 days of ripening due to the reduction in the moisture level during the second stage of salting (dry salting during the first 60 days of ripening). Cheese made from raw milk received the highest texture and flavour scores by panellists.     

Effect of cook temperature on starter and non-starter lactic acid bacteria viability,cheese composition and ripening indices of a semi-hard cheese manufactured using thermophilic cultures

Semi-hard cheeses were manufactured using Streptococcus thermophilus and Lactobacillus helveticus cultures and their ripening was characterised. During cheese manufacture, curds were cooked to a maximum temperature of 47, 50 or 53 °C, pre-pressed under whey at pH 6.15, moulded, pressed and brined. Increased cook temperature resulted in increased manufacture time, a significantly reduced growth rate of S. thermophilus during manufacture in the order 47≈50 °C>53 °C and in significantly lower mean viable cell counts of S. thermophilus up to 56 d of ripening. Increasing cook temperature had no significant effect on mean viable cell numbers of L. helveticus or non-starter lactic acid bacteria (NSLAB). Cheeses produced from curds cooked to 47 °C had significantly higher levels of moisture in non-fat substances (MNFSs), salt-in-moisture and a significantly lower pH and levels of butyrate compared with cheeses produced from curds cooked to 50 or 53 °C.     

非发酵剂乳酸菌A-3和D-3对半硬质山羊奶干酪成熟的影响

目的获得加速半硬质山羊奶干酪成熟的非发酵剂乳酸菌菌株(non-starterlacticacidbacteria,NSLAB)。方法以前期分离自地中海地区山羊奶干酪中的2株优良NSLAB菌株为研究对象,测定其对干酪成熟过程中组成成分、微生物菌群、蛋白质水解和质构的影响。结果添加NSLAB菌株对干酪组成成分没有显著影响, NSLAB菌株没有影响乳球菌生长,在干酪成熟期间pH 4.6-SN和12%TCA-SN逐渐增加,且添加NSLAB的干酪在成熟30 d后显著增加了pH 4.6-SN和12%TCA-SN含量, 5%PTASN/TN的增加主要是由于乳酸菌中肽酶作用的结果, SDS-PAGE电泳结果说明添加NSLAB菌株的干酪中小分子多肽含量明显比对照干酪多,RP-HPLC分析得出干酪水溶性中肽的数量随着成熟时间增加。添加NSLAB菌株A-3没有改变干酪的硬度,使干酪的弹性增加。结论添加菌株A-3作为NSLAB的干酪样品中微生物自溶率高,蛋白水解程度强,质构性能良好,具有加速干酪成熟的潜力,是山羊奶干酪工业化生产的优良NSLAB。     

干酪加工中的牛奶内源酶和非发酵剂乳酸菌

介绍了干酪加工中起作用的牛奶内源酶及微生物，包括血浆酶、组织蛋白酶D、半胱氨酸蛋白酶、脂蛋白脂肪酶和非发酵剂乳酸菌及它们的作用机制和特性。     

Fermentation of carbohydrates from cheese sources by non-starter lactic acid bacteria isolated from semi-hard Danish cheese

Carbohydrate fermentation of 45 isolates of non-starter lactic acid bacteria from Danish semi-hard cheeses was studied using BioScreen C equipment. Thirty-nine of the isolates were identified as Lactobacillus paracasei/casei/rhamnosus, 2 as Lb. curvatus and 4 as a new species, Lb. danicus, using ITS-PCR. A specially designed carbohydrate-restricted medium supplemented with one of nine carbohydrates was used to evaluate potential carbohydrate sources in cheese–milk-fat globule membrane (MFGM), glycomacropeptide (GMP), or lysed cells. Lb. paracasei strains grew well on the carbohydrates from MFGM, GMP and bacterial cell wall peptidoglycan. The highest growth rates were observed on N-acetylglucosamine (NAG) (0.32–0.56 h⁻¹) and the lowest on ribose (0.12–0.23 h⁻¹, if ribose was fermented at all). Lb. danicus strains grew better on carbohydrates from lysed bacterial cells than on carbohydrates from MFGM or GMP, and it was the only species with a shorter lag-phase on ribose or NAG after being pre-incubated on ribose.     

Terpene profiles in Cantal and Saint‐Nectaire‐type cheese made from raw or pasteurised milk

Terpene profiles in cheese can be considered a ‘terroir’ fingerprint as the information contained in it should enable the pastures on which the animals were fed to be recognised. Yet a certain elasticity of the signature must be taken into account when determining authentication strategies, since products acknowledged as containing a common signature may have undergone certain procedures, such as cheese making and milk pasteurisation, that could have potentially altered their terpene profiles. In this study, Cantal and Saint‐Nectaire‐type cheeses were made from both raw and pasteurised milk from the same herd of dairy cows that had been grazed on natural grassland. Cheeses from raw and pasteurised milk were made from the same milking on the same days. Cantal and Saint‐Nectaire‐type cheeses were made on 4 different days, alternatively over four weeks. The terpenes in the cheese fat were analysed by dynamic headspace/gas chromatography/mass spectrometry. A great diversity of monoterpenes, sesquiterpenes and oxygen‐containing derivatives were identified. The major terpenes identified in most cheeses were β‐caryophyllene, α‐ and β‐pinene and limonene. Milk pasteurisation did not induce changes in the terpene profile of the cheese. Significant differences (p < 0.001) were observed between Cantal and Saint‐Nectaire cheeses: α‐pinene, β‐myrcene and β‐phellandrene were, respectively, three, five and five times more abundant in Cantal cheese, while tricyclene, α‐phellandrene and geraniol were found exclusively in Cantal cheese. In contrast, unidentified sesquiterpenes with retention indices (KI) = 1342 and 1511, α‐cubebene, longifolene and γ‐elemene were more abundant or exclusively found in Saint‐Nectaire cheese. A significant relationship with the date of milking (p < 0.01) was observed for α‐pinene and tricyclene in Cantal, for β‐myrcene, δ‐3‐carene, p‐cymene and α‐terpinene in Saint‐Nectaire cheese. Copyright © 2005 Society of Chemical Industry     

Proteolysis during ripening of Manchego cheese made from raw or pasteurized ewes' milk. Seasonal variation

Changes in nitrogen compounds during ripening of 40 batches of Manchego cheese made from raw milk (24 batches) or pasteurized milk (16 batches) at five different dairies throughout the year were investigated. After ripening for six months, degradation of p-kappa- and beta-caseins was more intense in raw milk cheese and degradation of alpha(s2)-casein in pasteurized milk cheese. Milk pasteurization had no significant effect on breakdown of alpha(s1)-casein. Hydrophobic peptide content did not differ between raw and pasteurized milk cheese, whereas hydrophilic peptide content was higher in raw milk cheese. There were no significant differences between seasons for residual caseins, but hydrophobic peptides were at a higher level in cheese made in autumn and winter and hydrophilic peptides in cheese made in winter and spring. Raw milk cheese had a higher content of total free amino acids and of most individual free amino acids than pasteurized milk cheese. The relative percentages of the individual free amino acids were significantly different for raw milk and pasteurized milk cheeses. The relative percentages of Lys and lie increased, while those of Val, Leu and Phe decreased during ripening. There were also seasonal variations within the relative percentages of free amino acids. In raw milk cheeses, Asp and Cys were relatively more abundant in those made in autumn, Glu and Arg in cheeses made in winter, and Lys and Ile in cheeses made in spring and summer. Biogenic amines were detected only in raw milk cheese, with the highest levels of histamine, tryptamine and tyramine in cheeses made in spring, winter and spring, respectively.     

Survival of Listeria monocytogenes during manufacture, ripening and storage of soft lactic cheese made from raw goat milk

Soft lactic cheeses were manufactured with raw goat milk inoculated with Listeria monocytogenes. The physico-chemical and microbiological characteristics of curds and cheeses were determined after each processing step as well as during ripening and refrigerated storage. The fate of Listeria monocytogenes was evaluated by enumeration on PALCAM agar and by a qualitative detection after a double selective enrichment procedure. The results showed that the physico-chemical and microbiological characteristics of lactic cheeses caused a decrease of Listeria monocytogenes counts. However, this decrease did not lead to the complete disappearance of the pathogen and Listeria monocytogenes was able to survive in soft lactic cheeses made with raw goat milk.     

Survival of some non-starter bacteria in naturally ripened and enzyme-accelerated Cheddar cheese

Effects of the addition of a proteinase (Neutrase 1-5S) and a peptidase (aminopeptidase DP-102) as agents for accelerating the ripening of Cheddar cheese on the survival of some non-starter bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and a Salmonella sp.) were studied throughout a 4-month ripening period. The enzymes were found to have no significant effect on the survival of the Gram-positive bacteria but some significant effects were observed, at some stages of the ripening period, with the Gram-negative bacteria in that lower levels were recovered from cheeses treated with the enzyme system.     

新疆哈族奶酪中产蛋白酶非发酵剂乳酸菌的筛选及其系统发育分析

以采集10份新疆塔城地区哈萨克族牧民自制的奶酪为原料,用改良的ROGOSA和MRS两种培养基对其分离纯化,共筛选出43株菌种,其中球菌32株,杆菌11株。对筛选出的菌株进行产蛋白酶和菌株自溶能力测定,结合生理生化特性和16S rDNA序列同源分析和建立系统发育树分析,对挑选出的10株优势菌进行了菌株分子生物学鉴定,鉴定结果表明：菌株R6-6自溶度最高,为42.32%;而自溶度最低的菌株为R4-4,达到6.21%;菌株R2-2、R4-2、R4-7为表皮葡萄球菌（Staphylococcus epidermidis）;菌株R3-5、R10-6为乳酸片球菌（Pediococcus acidilactici）;菌株R3-2为戊糖片球菌（Pediococcus pentosaceus）;菌株R6-6为干酪乳杆菌（Lactobacillus casei）;菌株R9-5、R9-6为鼠李糖乳杆菌（Lactobacillus rhamnosus）。其中产蛋白酶的最优势非发酵剂乳酸菌（NSLAB）菌株为乳酸片球菌（P. acidilactici）。     

Microbiological and biochemical characteristics of Kashkaval cheese produced using pasteurised or raw milk

Microbiological quality and biochemical changes of Kashkaval cheese manufactured using sheep's raw milk without starter addition or pasteurised milk with an added commercial starter were studied. Mature cheeses had pH values 5.0–5.3, salt content 2.1–2.7%, protein content 23.3–25.1%, moisture content 36.8–39.5%, fat content 28.0–32.2%, and ash content around 5.0%. In raw milk cheeses, mesophilic non-starter lactobacilli prevailed followed by enterococci. In pasteurised milk cheeses Lactococcus lactis starter prevailed. All cheeses were safe according to the criteria in Regulation (EC) 1441/2007. The proteolysis index was around 20%. Butyric, myristic, palmitic, stearic and oleic were the principal free fatty acids in both cheeses. Ketones were abundant in pasteurised milk cheeses and esters in mature raw milk cheeses. Pasteurisation did not affect (P > 0.05) the physicochemical composition and the proteolysis of cheeses. Raw milk cheeses showed higher levels (P < 0.05) of lipolysis than pasteurised milk cheeses.