THE INFLUENCE OF VACUUM PRESSING ON THE TEXTURE OF CHEDDAR CHEESE*

A study was made of the influence of several factors on the texture of young and mature vacuum-pressed rindless cheese. Pressures greater than 26 lb/in² were required for maximum improvement in texture. A vacuum of 15 in was less effective than a vacuum of 25 in. Vacuum pressing of ‘dressed’ cheese for 5 min was almost as effective as vacuum pressing for 17 h; vacuum pressing after dressing was more effective than before dressing; transfer of vacuum-pressed cheese to a normal press for the completion of pressing did not affect texture. Vacuum treatment of curd before hooping and pressing in the normal way had no beneficial effect on texture; vacuum pressing improved the texture of cheese made with mixed-strain starters although this cheese was not as close as vacuum-pressed cheese made with single strain starters. The distinct improvement in cheese texture which resulted from some combinations of vacuum pressing condition was confirmed in commercial scale trials involving 2,540 rindless cheese. This improvement was evident when cheese were graded at two weeks and when regraded at maturity.     

Quality and ripening changes of Ras cheese made by direct acidification

Trials were carried out to produce Ras cheese of good quality without the use of starter. Cheese was made from pasteurized cow's milk acidified with lactic acid or citric acid to pH 5.8 alone or coupled with mixing the curd with glucono δ lactone (4.5 g/kg curd). Control cheese was made from milk ripened with a starter culture of S. lactis. Resultant cheeses showed poor body and texture, weak flavour intensity and low levels of soluble nitrogen compounds and free volatile fatty acids. Incorporation into the cheese curd of mixtures containing Fromase 100 (fungal protease) and Piccantase B (fungal lipase) or Fromase 100 and Capalase K (animal lipase) enhanced flavour intensity, improved body characteristics and accelerated the formation of both soluble nitrogen compounds and free volatile fatty acids. The organoleptic properties of the experimental cheeses with added enzymes were comparable to those of the control cheese.     

Improving the quality of Ras cheese made without starter

Trials were carried out to produce Ras cheese of good quality without the use of starter. Cheese was made from cows' milk, pasteurized and acidified with lactic acid or citric acid to pH 5·8; cheese was also made after adding 4·5 g glucono-δ-lactone per kg to the acidified curd. Control cheese was made by the traditional method.The cheese had poor body and texture, weak flavour intensity, and low levels of soluble nitrogen compounds and free volatile fatty acids.Incorporation into the cheese curd of mixtures containing Fromase 100 (fungal protease) and Piccantase B (fungal lipase) or Fromase 100 and Capalase K (animal lipase) enhanced flavour intensity and body characteristics and accelerated the formation of both soluble nitrogen compounds and free volatile fatty acids. The organoleptic properties of the experimental cheese with added enzymes were comparable to the control cheese.     

Manufacture of process cheese products without emulsifying salts using acid curd and micellar casein concentrate

Process cheese products (PCP) are dairy foods prepared by blending dairy ingredients (such as natural cheese, protein concentrates, butter, nonfat dry milk, whey powder, and permeate) with nondairy ingredients [such as sodium chloride, water, emulsifying salts (ES), color, and flavors] and then heating the mixture to obtain a homogeneous product with an extended shelf life. The ES, such as sodium citrate and disodium phosphate, are critical for the unique microstructure and functional properties of PCP because they improve the emulsification characteristics of casein by displacing the calcium phosphate complexes that are present in the insoluble calcium-paracaseinate-phosphate network in natural cheese. The objectives of this study were to determine the optimum protein content (3, 6, and 9% protein) in micellar casein concentrate (MCC) to produce acid curd and to manufacture PCP using a combination of acid curd cheese and MCC that would provide the desired improvement in the emulsification capacity of caseins without the use of ES. To produce acid curd, MCC was acidified using lactic acid to get a pH of 4.6. In the experimental formulation, the acid curd was blended with MCC to have a 2:1 ratio of protein from acid curd relative to MCC. The PCP was manufactured by blending all ingredients in a KitchenAid blender (Professional 5 Plus, KitchenAid) to produce a homogeneous paste. A 25-g sample of the paste was cooked in the rapid visco analyzer (RVA) for 3 min at 95°C at 1,000 rpm stirring speed during the first 2 min and 160 rpm for the last min. The cooked PCP was then transferred into molds and refrigerated until further analysis. This trial was repeated 3 times using different batches of acid curd. MCC with 9% protein resulted in acid curd with more adjusted yield. The end apparent viscosity (402.0–483.0 cP), hardness (354.0–384.0 g), melting temperature (48.0–51.0°C), and melting diameter (30.0–31.4 mm) of PCP made from different acid curds were slightly different from the characteristics of typical PCP produced with conventional ingredients and ES (576.6 cP end apparent viscosity, 119.0 g hardness, 59.8°C melting temperature, and 41.2 mm melting diameter) due to the differences in pH of final PCP (5.8 in ES PCP compared with 5.4 in no ES PCP). We concluded that acid curd can be produced from MCC with different protein content. Also, we found that PCP can be made with no ES when the formulation uses a 2:1 ratio of acid curd relative to MCC (on a protein basis).     

Effects of starter culture combinations using isolates from traditional cheese on the quality of Turkish white cheese

Four types of Turkish white cheese with good curd and acid formation properties were produced, one by using commercial starter culture and the other three by using different combinations of isolates from traditional cheese with no starters added. The effects of using these combinations on quality were determined. Starter culture combinations did not influence the chemical properties of cheese significantly. However, one cheese type produced from combinations of isolates of rural cheese was found to be comparable to the samples produced from commercial starter cultures in terms of sensory and microbial quality. This combination could have promise for white cheese production.     

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.     

Invited review: Microbial evolution in raw-milk,long-ripened cheeses produced using undefined natural whey starters

The robustness of the starter culture during cheese fermentation is enhanced by the presence of a rich consortium of microbes. Natural starters are consortia of microbes undoubtedly richer than selected starters. Among natural starters, natural whey starters (NWS) are the most common cultures currently used to produce different varieties of cheeses. Undefined NWS are typically used for Italian cooked, long-ripened, extra-hard, raw milk cheeses, such as Parmigiano Reggiano and Grana Padano. Together with raw milk microbiota, NWS are responsible for most cheese characteristics. The microbial ecology of these 2 cheese varieties is based on a complex interaction among starter lactic acid bacteria (SLAB) and nonstarter lactic acid bacteria (NSLAB), which are characterized by their different abilities to grow in a changing substrate. This review aims to summarize the latest findings on Parmigiano Reggiano and Grana Padano to better understand the dynamics of SLAB, which mainly arise from NWS, and NSLAB, which mainly arise from raw milk, and their possible role in determining the characteristics of these cheeses. The review is presented in 4 main sections. The first summarizes the main microbiological and chemical properties of the ripened cheese as determined by cheese-making process variables, as these variables may affect microbial growth. The second describes the microbiota of raw milk as affected by specific milk treatments, from milking to the filling of the cheese milk vat. The third describes the microbiota of NWS, and the fourth reviews the knowledge available on microbial dynamics from curd to ripened cheese. As the dynamics and functionality of complex undefined NWS is one of the most important areas of focus in current food microbiology research, this review may serve as a good starting point for implementing future studies on microbial diversity and functionality of undefined cheese starter cultures.     

High-Pressure Treatment and Freezing of Raw Goat Milk Curd for Cheese Manufacture: Effects on Cheese Characteristics

High-pressure treatment of raw goat milk curd was investigated as an alternative to thermal treatment of milk in cheese manufacture, and curd freezing as a procedure to surmount the seasonality of goat milk production. Experimental cheeses were made by mixing (70:30) fresh cow milk curd with frozen curd from pasteurized goat milk (PGC), frozen curd from raw goat milk (RGC), or frozen pressurized curd from raw goat milk (PRGC). Control cheese was made from a mixture (70:30) of pasteurized cow and goat milk. RGC cheese showed the highest counts of staphylococci, Gram-negative bacteria and coliforms, whereas PRGC cheese had maximum aminopeptidase activity, esterase activity, and overall proteolysis. Control cheese exhibited the highest dry matter content and peptide levels, the lowest concentration of free amino acids, the highest concentration of volatile compounds such as free fatty acids, alcohols and esters, and the firmest texture. Differences in sensory characteristics between experimental and control cheeses were of minor importance. High-pressure treatment of curd allowed the production of cheese of bacteriological quality similar to that of control cheese made using pasteurized milk, while curd freezing did not alter the sensory characteristics of experimental cheeses with respect to control cheese.     

Effect of polyphenolic ingredients on physical characteristics of cheese

A novel cheese product developed based on the incorporation of various polyphenolic compounds was evaluated for its texture characteristics. Single phenolic compounds including catechin, epigallocatechin gallate (EGCG), tannic acid, homovanillic acid, hesperetin and flavone, along with natural crude compounds such as grape extract, green tea extract and dehydrated cranberry powder, were added as functional ingredients during the cheese-making process. Cheese curds containing polyphenolic compounds at a concentration of 0.5 mg/mL showed a decrease of curd moisture content (CMC) while the gel strength (GS) was not affected. Structural differences were observed when crude polyphenolic compounds were added to the cheese, resulting in rough and granular structures. Physical properties of the cheese product were evaluated after adding bioactive phenolic compounds to the cheese curd. We fully expect to apply this approach to other dairy products in the future.     

Proteolysis, lipolysis, volatile compounds, texture, and flavor of Hispánico cheese made using frozen ewe milk curds pressed for different times

Hispánico cheese is manufactured in Spain from a mixture of cow and ewe milk. Production of ewe milk varies throughout the year, with a peak in spring and a valley in summer and autumn. To overcome this seasonal shortage, curd from spring ewe milk may be frozen and used for cheese manufacture some months later. In the present work, ewe milk curds pressed for 15, 60, or 120 min were held at −24°C for 4 mo, thawed, cut to 1-mm pieces, and mixed with fresh cow milk curd for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same (80:20) proportion. Cheeses, made in duplicate experiments, were analyzed throughout a 60-d ripening period. No significant differences between cheeses were found for lactic acid bacteria counts, dry matter content, hydrophilic peptides, 47 out of 68 vol.tile compounds, texture, and flavor characteristics. On the other hand, differences of minor practical significance between experimental and control cheeses, unrelated to the use of frozen ewe milk curd or the pressing time of ewe milk curd, were found for pH value, aminopeptidase activity, proteolysis, hydrophobic peptides, free amino acids, free fatty acids, and the remaining 21 vol.tile compounds. It may be concluded that the use of frozen ewe milk curd in the manufacture of Hispánico cheese does not alter its main characteristics.     

花生乳牛乳新鲜干酪加工工艺优化

用花生乳代替部分牛乳生产新鲜干酪,对花生乳添加比例、氯化钙添加量、凝乳酶添加量3个因素对凝乳效果的影响分别进行单因素试验,确定各自合适比例后,再采用L9(33)正交试验,确定花生乳牛乳新鲜干酪最佳生产工艺。结果表明花生乳添加量20%、氯化钙添加量0.06%、凝乳酶添加量0.002%时制作出的新鲜花生乳牛乳干酪成品呈乳白色、柔软、有弹性、具有花生风味,产品出品率为16.33%。     

干法磨粉对荞麦豆皮品质影响研究

为考察干法磨粉工艺对荞麦豆皮粉粉质特性及荞麦豆皮产品品质的影响,选用了万能和超微2种不同仪器对混合原料进行磨粉,用传统湿法工艺作为对照,通过分析荞麦豆皮粉的粒径分布、白度、糊化特性等粉质特性,并结合荞麦豆皮的质构特性和感官评分,以筛选出粉质特性和产品口感均较好的干法磨粉工艺。研究结果表明:超微磨粉粒径最小,白度最高,糊化特性较好,荞麦豆皮质构适中,感官评分高,各项参数接近或优于传统湿磨,而普通万能磨粉粒径较大,白度也低,荞麦豆皮质构较超微和湿磨硬,感官评分也低于超微和湿磨。综上所述,超微磨粉工艺得到的粉与普通磨粉工艺相比,具有很好的加工性能,可以用来制得荞麦豆皮品质优良的预制粉,能够改良传统的荞麦豆皮制作工艺。     

An attempt to produce ras cheese by direct acidification

Ras cheese was made from cow's milk acidified with either lactic or citric acid to pH 5·8 with and without the addition of GDL to the resultant curd from each acidulant. Also, control Ras cheese was made using lactic starter culture. The cheese made from the direct acidified milk showed slightly higher moisture and salt contents compared with the control. This was associated with slightly lower fat and acid contents. Also, the cheese made by direct acidification contained lower levels of SN, NPN, AN and TVA compared with the control cheese. The direct acidified cheese was characterized by poor body, crumbly texture and weak flavour intensity. Cheese made from citric acid-acidified milk was more acceptable than that made from milk acidified with lactic acid.     

Effect of high-pressure treatment of ewe raw milk curd at 200 and 300 MPa on characteristics of Hispánico cheese

Hispánico cheese is a semihard variety made from a mixture of cow and ewe milks. Production of ewe milk declines in summer and autumn. To surmount the seasonal shortage of ewe milk and prevent the inactivation of milk enzymes by pasteurization, curd made in spring from ewe raw milk was pressurized at 200 and 300 MPa and stored frozen for 4 mo. Thawed ewe milk curds were added to fresh curd made from pasteurized cow milk for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same proportions as those used for experimental cheeses. Experimental cheeses exhibited lower dry matter content, higher aminopeptidase activity and total free amino acid concentration, and higher levels of acetic and propionic acids, aldehydes, alcohols, and esters compared with control cheese. In contrast, the concentration of total free fatty acids and ketones and the levels of textural parameters were significantly higher in control cheese. The use of ewe raw milk curd pressurized at 200 and 300 MPa, stored frozen and thawed for Hispánico cheese manufacture, was generally beneficial for cheese characteristics and increased cheese yield because of the lower dry matter content of experimental cheeses.     

Effect of liquid whey protein concentrate–based edible coating enriched with cinnamon carbon dioxide extract on the quality and shelf life of Eastern European curd cheese

Fresh unripened curd cheese has long been a well-known Eastern European artisanal dairy product; however, due to possible cross-contamination from manual production steps, high moisture content (50–60%), and metabolic activity of present lactic acid bacteria, the shelf life of curd cheese is short (10–20 d). Therefore, the aim of this study was to improve the shelf life of Eastern European acid-curd cheese by applying an antimicrobial protein-based (5%, wt/wt) edible coating. The bioactive edible coating was produced from liquid whey protein concentrate (a cheese production byproduct) and fortified with 0.3% (wt/wt, solution basis) Chinese cinnamon bark (Cinnamomum cassia) CO₂ extract. The effect of coating on the cheese was evaluated within package-free (group 1) and additionally vacuum packaged (group 2) conditions to represent types of cheeses sold by small and big scale manufacturers. The cheese samples were examined over 31 d of storage for changes of microbiological (total bacterial count, lactic acid bacteria, yeasts and molds, coliforms, enterobacteria, Staphylococcus spp.), physicochemical (pH, lactic acid, protein, fat, moisture, color change, rheological, and sensory properties). The controlled experiment revealed that in group 1, applied coating affected appearance and color by preserving moisture and decreasing growth of yeasts and molds during prolonged package-free cheese storage. In group 2, coating did not affect moisture, color, or texture, but had a strong antimicrobial effect, decreasing the counts of yeasts and molds by 0.79 to 1.55 log cfu/g during 31 d of storage. In both groups, coating had no effect on pH, lactic acid, protein, and fat contents. Evaluated sensory properties (appearance, odor, taste, texture, and overall acceptability) of all samples were similar, indicating no effect of the coating on the flavor of curd cheese. The edible coating based on liquid whey protein concentrate with the incorporation of cinnamon extract was demonstrated to efficiently extend the shelf life of perishable fresh curd cheese, enhance its functional value, and contribute to a more sustainable production process.     

Streptococcus thermophilus in cheddar cheese--production and fate of galactose

The behaviour of Streptococcus thermophilus in combination with Lactococcus lactis subsp. cremoris or subsp. lactis mesophilic starters in experimental Cheddar cheese is reported. In a standard manufacturing procedure employing a 38 degrees C cook temperature, even very low levels (0.007%) of Str. thermophilus combined with normal levels of the mesophilic starter (1.7%) resulted in increased rates of acid production, the formation of significant amounts of galactose (approximately 13 mmol/kg cheese), and populations nearly equivalent to those of the mesophilic lactic starter in the curd before salting. At a 41 degrees C cook temperature, the Str. thermophilus attained a higher maximum population (approximately log 8.2 colony forming units (cfu)/g) than the Lc. lactis subsp. cremoris (approximately log 6.8 cfu/g) and formed more galactose (approximately 28 mmol/kg). Lactobacillus rhamnosus, deliberately added to a cheese made using Str. thermophilus starter and which contained 24 mmol galactose/kg at day one, utilized all the galactose during the first 3 months of cheese ripening. Adventitious non-starter lactic acid bacteria had the potential to utilize this substrate too, and a close relationship was demonstrated between the increase in this flora and the disapearance of the galactose. Some possible consequences for cheese quality of using Str. thermophilus as a starter component are discussed.     

Development and use of a defined strain starter system for Cheddar cheese

Out of 210 strains of Streptococcus cremoris and Streptococcus lactis screened, 35 were suitable for inclusion in multiple strain starters for Cheddar cheese. The use of various combinations of these 35 strains and bacteriophage-insensitive mutants isolated from some of them as cheese starters over six seasons is described. All cheese graded well for body, texture and flavour, with <1% being downgraded due to starter failure. The system is now being used in all Cheddar cheese plants in Ireland producing ˜60,000 tonnes a year. The problems encountered in phage monitoring are also discussed.     

不同发酵剂对切达干酪成熟期间品质的影响

应用乳酸乳球菌乳酸亚种LA、乳酸乳球菌乳脂亚种LC以及不同比例混合菌(LA∶LC=1∶1,LA∶LC=1∶2,LA∶LC=2∶1)制作切达干酪,研究这5种发酵剂在干酪成熟过程中对其质构、感官、风味物质形成及蛋白水解程度等方面的影响。结果表明:3种不同比例组合菌株发酵剂的蛋白水解能力适中,生产出的干酪口味清淡,其中按1∶1接种制作的干酪具有良好的成熟度、质地和风味,具有一定的商业应用价值,可将其用于切达干酪的生产。     

Effect of homogenisation of cheese milk and high‐shear mixing of the curd during cream cheese manufacture

The role of the homogenisation pressure of cheese milk (0, 25, 100 MPa) and high‐shear mixing of cheese curd at different speeds (750, 1500, and 3000 r.p.m.) and times (2 and 4 min) in improving the texture of medium‐fat cream cheese was investigated independently. Homogenisation resulted in small fat globules and firmer texture, while increasing speed and mixing times resulted in a decrease in curd particle size and an increase in the spreadability of the cheese. All curd samples from both the trials exhibited shear‐thinning behaviour. Unhomogenised milk and high‐shear mixing of the curd showed a low coefficient of friction (better lubrication property).     

开菲尔直投式发酵剂在益生菌干酪生产中的应用研究

该研究主要将开菲尔粒制备成直投式发酵剂应用于干酪的生产。 以FD-DVS R-704商业干酪发酵剂制作的干酪为对照,对其 理化指标、挥发性香气成分、质构特性和感官指标进行测定与评价。 结果表明,与对照干酪相比,开菲尔干酪的水分含量、pH4.6-可溶 性氮（SN）及12%三氯乙酸（TCA）-SN的含量极显著增高（P＜0.01）,pH值极显著低（P＜0.01）,而粗脂肪比例和总游离氨基酸（TFAA） 含量无显著差异（P＞0.05）,不饱和脂肪酸（UFA）含量显著增高（P＜0.05）;醇类和酯类物质的种类增多;硬度和咀嚼性极显著降低（P＜0.01）,胶黏性极显著增大（P＜0.01）,内聚性和弹性无明显差异（P＞0.05）;开菲尔粒益生菌干酪呈乳白色,表面有光泽,不仅具 有干酪特有的滋味和气味,且具有开菲尔发酵乳的特有风味,带有适宜的酒香味。