Effect of reverse osmosis and ultra-high-pressure homogenization on the composition and microstructure of sweet buttermilk

Buttermilk (BM), the by-product of butter making, is similar to skim milk (SM) composition. However, it is currently undervalued in dairy processing because it is responsible for texture defects (e.g., crumbliness, decreased firmness) in cheese and yogurt. One possible way of improving the incorporation of BM into dairy products is by the use of technological pretreatments such as membrane filtration and homogenization. The study aimed at characterizing the effect of preconcentration by reverse osmosis (RO) and single-pass ultra-high-pressure homogenization (UHPH) on the composition and microstructure of sweet BM to modify its techno-functional properties (e.g., protein gel formation, syneresis, firmness). The BM and RO BM were treated at 0, 15, 150, and 300 MPa. Pressure-treated and control BM and RO BM were ultracentrifuged to fractionate them into the following 3 fractions: a supernatant soluble fraction (top layer), a colloidal fraction consisting of a cloudy layer (middle layer), and a high-density pellet (bottom layer). Compositional changes in the soluble fraction [lipid, phospholipid (PL), protein, and salt], as well as its protein profile by PAGE analysis, were determined. Modifications in particle size distribution upon UHPH were monitored by laser diffraction in the presence and absence of sodium citrate to dissociate the casein (CN) micelles. Microstructural changes in pressure-treated and non-pressure-treated BM and RO BM particles were monitored by confocal laser scanning microscopy. Particle size analysis showed that UHPH treatment significantly decreased the size of the milk fat globule membrane fragments in BM and RO BM. Also, pressure treatment at 300 MPa led to a significant increase in the recovery of total lipids, CN, calcium, and phosphate in the BM soluble fraction (top layer) following ultracentrifugation. However, PL were primarily concentrated in the pellet cloud (middle layer), located above the pellet in BM concentrated by RO. In contrast, PL were evenly distributed between soluble and colloidal phases of BM. This study provides insight into the modifications of sweet BM constituents induced by RO and UHPH from a compositional and structural perspective.

Effect of lactose standardization of milk using low-concentration factor ultrafiltration: Effect of reducing the lactose-to-casein ratio on the properties of milled-curd Cheddar cheese

The pH of cheese is determined by the amount of lactose fermented and the buffering capacity of the cheese. The buffering capacity of cheese is largely determined by the protein contents of milk and cheese and the amount of insoluble calcium phosphate in the curd, which is related to the rate of acidification. The objective of this study was to standardize both the lactose and casein contents of milk to better control final pH and prevent the development of excessive acidity in Cheddar cheese. This approach involved the use of low-concentration factor ultrafiltration of milk to increase the casein content (∼5%), followed by the addition of water, ultrafiltration permeate, or both to the retentate to adjust the lactose content. We evaluated milks with 4 different lactose-to-casein ratios (L:CN): 1.8 (control milk), 1.4, 1.1, and 0.9. All cheesemilks had similar total casein (2.3%) and fat (3.4%) contents. These milks were used to make milled-curd Cheddar cheese, and we evaluated cheese composition, texture, functionality, and sensory properties over 9 mo of ripening. Cheeses made from milks with varying levels of L:CN had similar moisture, protein, fat, and salt contents, due to slight modifications during manufacture (i.e., cutting the gel at a smaller size than control) as well as control of acid development at critical steps (i.e., cutting the gel, whey drainage, salting). As expected, decreasing the L:CN led to cheeses with lower lactic acid, residual lactose, and insoluble Ca contents, as well as a substantial pH increase during cheese ripening in cheeses. The L:CN ratio had no significant effect on the levels of primary and secondary proteolysis. Texture profile analysis showed no significant differences in hardness values during ripening. Maximum loss tangent, an index of cheese meltability, was lower until 45 d for the L:CN 1.4 and 0.9 treatments, but after 45 d, all reduced L:CN cheeses had higher maximum loss tangent values than the control cheese (L:CN 1.8). Sensory analyses showed that cheeses made from milks with reduced L:CN contents had lower acidity, sourness, sulfury notes, and chewdown cohesiveness. Standardization of milk to a specific L:CN ratio, while maintaining a constant casein level in the milk, would allow Cheddar cheese manufacturers to have tighter control of pH and acidity.

Lactose: Use, measurement, and expression of results

Lactose has different uses in the dairy, food, and pharmaceutical industries. Being aware of the different forms of lactose and their concentrations can be very helpful in managing dairy product quality, properties, and manufacturing efficiency. Correct measurement and reporting of lactose concentration in milk and other dairy products will be of increased importance in the future as more value-added uses of lactose are developed and as milk lactose data are used in farm management decision making. Lactose should be reported as anhydrous lactose because lactose data will be used to make increasingly important decisions in dairy processing, dairy product labeling, and milk production in the future. Lactose also plays an important role in milk synthesis within a cow. Milk production factors and dairy cattle breed selection influence the amount of high value fat and protein produced per unit of lactose. If the off-farm value of lactose remains low, more attention may be focused on using ultrafiltration to process milk and leave 50 to 60% of the lactose and water from milk at the farm to recover the energy value of the lactose as feed and reduce the hauling cost of the high value components of milk to a dairy product manufacturing factory. Many methods exist to determine lactose concentration, but the most important methods are enzymatic assays, HPLC, and mid-infrared analysis. New, value-added uses for lactose need to be developed. Consistent and accurate methods of lactose measurement and consistent expression of lactose results will support this development process. Starting in January 2017, the USDA Federal Milk Market Laboratories began reporting lactose content of milk as anhydrous lactose and discontinued the reporting of lactose by difference.

Effect of the incorporation of β-galactosidase in the GOS production during manufacture of soft cheese

Galactooligosaccharides (GOS) are non-digestible oligosaccharides with recognized prebiotic role. The present study aims to evaluate a β-galactosidase from K. lactis during soft cheese making and to analyse the impact on carbohydrates metabolism, proteolysis, and volatile compounds production, physicochemical and microbiological characteristics of the product. The enzyme was added to cheese milk (fluid milk plus whey powder) before (40 min.) or simultaneously of the starter addition (Ep and E treatments, respectively); cheese without enzyme addition was also made (C treatment). Also, we characterized fresh and soft commercial cheeses from the point of view of carbohydrate fraction, highlighting GOS, and organic acid profiles. The inclusion of the enzyme in soft cheese making produced a delay in reaching the target pH (~5.2). Carbohydrate fermentation profiles differed among treatments during cheese making and ripening. GOS were only detected in Ep and E cheeses (0.88 and 0.51 g/100 g, respectively). Lactose content was lower, and glucose and galactose levels were higher in E and Ep than C. No differences in physicochemical and microbial composition and organic acids profiles among samples were observed. Bioformation of volatile compounds belonging to the chemical families of aldehydes, ketones, alcohols, esters and acids, was not substantially affected by the modification in the carbohydrate profile. GOS were not detected in any of the commercial cheeses; great variations in the carbohydrate contents and organic acids were found. The results obtained demonstrate the feasibility of obtaining cheeses with GOS. Although the GOS values achieved are not adequate enough for the desired effect, the proposed technological approach turned out to be satisfying and original. Cheeses with prebiotic fiber are not still widespread in the market.

The Effect of Selected Factors on the Content of Fat-Soluble Vitamins and Macro-Elements in Raw Milk from Holstein-Friesian and Simmental Cows and Acid Curd Cheese (Tvarog)

Simple Summary

Depending on the region, specific methods of cheese production are used. Acid coagulation is applied in the production of the traditional acid curd cheese highly valued in Poland, called ‘tvarog’. It is important to maintain the traditional nature of production that guarantees cheese with a high nutritional value and health-promoting properties. By conducting an analysis of tvarog, taking into account the quality of the raw milk and the type of starter cultures used, we found that the content of fat-soluble vitamins (A, D₃, and E) mainly depended on the quality of the raw milk from which it was produced. A higher content of fat-soluble vitamins was found in milk obtained from Simmental cows kept in a traditional system in the spring/summer season and in the tvarog produced from it. Vitamin retention rates from raw milk to cheese were above 90%. In contrast, we noticed that the mineral composition of the cheese was not linked to the quality of the milk used. More Ca and Mg were lost with the whey, as indicated by the very low retention rates of these minerals from milk to tvarog (below 20%).

Abstract

The study was conducted to determine the content and retention of selected fat-soluble vitamins and minerals in curd cheese–tvarog made by a traditional method, taking into account the effect of the quality of the raw milk and the type of starter cultures used. The raw milk used to make the tvarog was obtained in various conditions, i.e., with and without the use of pasture forage (in a traditional and an intensive system), in two production seasons (spring/summer and autumn/winter), from two breeds raised in Poland (the Black-and-White variety of Polish Holstein-Friesian and Simmental). Two variants of starter cultures were used to make tvarog: Freeze-dried DVS starters (Flora Danica) and pure cultures of mesophilic lactic acid bacteria. The acidity and content of protein, fat, selected fat-soluble vitamins (A, D₃, and E), and selected macro-elements (Ca and Mg) were determined in samples of bulk milk and cheese. Retention rates of individual nutrients from the milk to the cheese were calculated. A higher content of fat-soluble vitamins was found in milk obtained from Simmental cows kept in a traditional system in the spring/summer season, as well as in the tvarog produced from it. Vitamin retention rates from the raw material to the tvarog were above 90%. The mineral composition of the cheese was not associated with the quality of the milk used. Very low retention rates from milk to cheese were obtained for Ca and Mg (below 20%). Higher retention rates were obtained in the spring/summer season when culture variant 1 was used. However, the starter culture was not found to significantly influence the concentration or retention of vitamins in the experimental cheese.

Low- and reduced-fat milled curd, direct-salted Gouda cheese: Comparison of lactose standardization of cheesemilk and whey dilution techniques

Control of acidity is critical for cheese quality, as high acidity can be associated with poor flavor and textural attributes. We investigated an alternative method to control cheese acidity, specifically in low-fat (LF) and reduced-fat (RF) milled curd, direct-salted Gouda cheese, which involved altering the initial lactose content of cheesemilk. In traditional Gouda cheese manufacture, a critical technique to control acidity is whey dilution (WD); that is, partial removal of whey and its replacement with water. Direct standardization of the lactose content of milk during the ultrafiltration process could be a simpler and more effective technique to control cheese acidity. This study compared the effect of traditional WD at 2 different levels, 15 and 30% (WD15 and WD30), with the alternative approach of adjustment of the lactose content of milk using low-concentration-factor ultrafiltration (LCF-UF). The composition, texture, functionality, and sensory properties of these LF and RF Gouda cheeses were evaluated. A milled curd, direct-salted cheese manufacturing protocol was used. Milks used for cheesemaking had a lactose-to-casein (L:CN) ratio of approximately 1.8, which is the typical ratio found in milk, whereas milks prepared with lactose standardization (LS) were made from UF concentrated milks with water added during filtration to achieve a L:CN ratio of approximately 1.1. Cheeses made with LS exhibited lower lactose and lactic acid contents than WD30 and WD15, leading to significantly higher pH values in the cheese. Dynamic small-amplitude oscillatory rheology indicated that use of LS led to cheeses with a lower crossover temperature (melting point) than the cheeses made with WD. Cheeses made with LS had lower insoluble Ca contents, likely caused by the addition of water required to achieve the lower L:CN ratio in these milks. Sensory analysis also indicated that LS cheeses had lower acidity and softer texture. These results suggest that standardization of the L:CN ratio of milk could be a useful alternative to WD (or a curd rinse step) to reduce acidity in cheeses. In addition, LS could be used to help soften texture and increase meltability, if desired in lower-fat cheese types.

Understanding the differences in cheese-making properties between reverse osmosis and ultrafiltration concentrates

Concentrating milk by reverse osmosis (RO) has the potential to increase cheese yield but is known to impair cheese-making properties. The main compositional differences between ultrafiltration (UF) and RO concentrates are the high lactose and mineral contents of the latter. The objective of this work was to determine the distinct effects of high lactose and high minerals on the cheese-making properties of RO concentrate, by supplementing UF concentrate with lactose. The soluble colloidal equilibria of concentrates were studied as well as several other properties: rennet gelation behavior, cheese mass balance, composition, and microstructure. Rennet coagulation time was longer and gel firming rate was lower for RO concentrate than for UF concentrate. Lactose was mainly responsible for these differences. Lactose in RO concentrate was also responsible for the 7% increase of moisture-adjusted cheese yield, relative to UF concentrate. Compared with cheese made from UF concentrate, cheese made from RO concentrate showed higher moisture content, which could not be attributed to lactose but to the high mineral concentration. This study showed the potential of using RO instead of UF concentrate to maximize cheese yield. The approach is, however, limited to applications where post-acidification can be controlled, and will require appropriate strategies to reduce the negative effects of high mineral content in RO concentrate.

A 100-Year Review: Cheese production and quality

In the beginning, cheese making in the United States was all art, but embracing science and technology was necessary to make progress in producing a higher quality cheese. Traditional cheese making could not keep up with the demand for cheese, and the development of the factory system was necessary. Cheese quality suffered because of poor-quality milk, but 3 major innovations changed that: refrigeration, commercial starters, and the use of pasteurized milk for cheese making. Although by all accounts cold storage improved cheese quality, it was the improvement of milk quality, pasteurization of milk, and the use of reliable cultures for fermentation that had the biggest effect. Together with use of purified commercial cultures, pasteurization enabled cheese production to be conducted on a fixed time schedule. Fundamental research on the genetics of starter bacteria greatly increased the reliability of fermentation, which in turn made automation feasible. Demand for functionality, machinability, application in baking, and more emphasis on nutritional aspects (low fat and low sodium) of cheese took us back to the fundamental principles of cheese making and resulted in renewed vigor for scientific investigations into the chemical, microbiological, and enzymatic changes that occur during cheese making and ripening. As milk production increased, cheese factories needed to become more efficient. Membrane concentration and separation of milk offered a solution and greatly enhanced plant capacity. Full implementation of membrane processing and use of its full potential have yet to be achieved. Implementation of new technologies, the science of cheese making, and the development of further advances will require highly trained personnel at both the academic and industrial levels. This will be a great challenge to address and overcome.