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.

Ibáñez RA ，Govindasamy-Lucey S ，Jaeggi JJ ，Johnson ME ，McSweeney PLH ，Lucey JA ... -  《-》

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.

Ibáñez RA ，Govindasamy-Lucey S ，Jaeggi JJ ，Johnson ME ，McSweeney PLH ，Lucey JA ... -  《-》

Effect of standardizing the lactose content of cheesemilk on the properties of low-moisture, part-skim Mozzarella cheese.

The texture, functionality, and quality of Mozzarella cheese are affected by critical parameters such as pH and the rate of acidification. Acidification is typically controlled by the selection of starter culture and temperature used during cheesemaking, as well as techniques such as curd washing or whey dilution, to reduce the residual curd lactose content and decrease the potential for developed acidity. In this study, we explored an alternative approach: adjusting the initial lactose concentration in the milk before cheesemaking. We adjusted the concentration of substrate available to form lactic acid. We added water to decrease the lactose content of the milk, but this also decreased the protein content, so we used ultrafiltration to help maintain a constant protein concentration. We used 3 milks with different lactose-to-casein ratios: one at a high level, 1.8 (HLC, the normal level in milk); one at a medium level, 1.3 (MLC); and one at a low level, 1.0 (LLC). All milks had similar total casein (2.5%) and fat (2.5%) content. We investigated the composition, texture, and functional and sensory properties of low-moisture, part-skim Mozzarella manufactured from these milks when the cheeses were ripened at 4°C for 84d. All cheeses had similar pH values at draining and salting, resulting in cheeses with similar total calcium contents. Cheeses made with LLC milk had higher pH values than the other cheeses throughout ripening. Cheeses had similar moisture contents. The LLC and MLC cheeses had lower levels of lactose, galactose, lactic acid, and insoluble calcium compared with HLC cheese. The lactose-to-casein ratio had no effect on the levels of proteolysis. The LLC and MLC cheeses were harder than the HLC cheese during ripening. Maximum loss tangent (LT), an index of cheese meltability, was lower for the LLC cheese until 28d of ripening, but after 28d, all treatments exhibited similar maximum LT values. The temperature where LT=1 (crossover temperature), an index of softening point during heating, was higher for MLC and LLC cheese at 56 and 84d of ripening. The LLC cheese also had lower blister color and less stretch than MLC and HLC cheese. Adjusting the lactose content of milk while maintaining a constant casein level was a useful technique for controlling cheese pH, which affected the texture, functionality, and sensory properties of low-moisture, part-skim Mozzarella cheese.

Moynihan AC ，Govindasamy-Lucey S ，Molitor M ，Jaeggi JJ ，Johnson ME ，McSweeney PLH ，Lucey JA ... -  《-》

Slower proteolysis in Cheddar cheese made from high-protein cheese milk is due to an elevated whey protein content.

A growing number of companies within the cheese-making industry are now using high-protein (e.g., 4-5%) milks to increase cheese yield. Previous studies have suggested that cheeses made from high-protein (both casein and whey protein; WP) milks may ripen more slowly; one suggested explanation is inhibition of residual rennet activity due to elevated WP levels. We explored the use of microfiltration (MF) to concentrate milk for cheese-making, as that would allow us to concentrate the casein while varying the WP content. Our objective was to determine if reducing the level of WP in concentrated cheese milk had any impact on cheese characteristics, including ripening, texture, and nutritional profile. Three types of 5% casein standardized and pasteurized cheese milks were prepared that had various casein:true protein (CN:TP) ratios: (a) control with CN:TP 83:100, (b) 35% WP reduced, 89:100 CN:TP, and (c) 70% WP reduced, 95:100 CN:TP. Standardized milks were preacidified to pH 6.2 with dilute lactic acid during cheese-making. Composition, proteolysis, textural, rheological, and sensory properties of cheeses were monitored over a 9-mo ripening period. The lactose, total solids, total protein, and WP contents in the 5% casein concentrated milks were reduced with increasing levels of WP removal. All milks had similar casein and total calcium levels. Cheeses had similar compositions, but, as expected, lower WP levels were observed in the cheeses where WP depletion by MF was performed on the cheese milks. Cheese yield and nitrogen recoveries were highest in cheese made with the 95:100 CN:TP milk. These enhanced recoveries were due to the higher fraction of nitrogen being casein-based solids. Microfiltration depletion of WP did not affect pH, sensory attributes, or insoluble calcium content of cheese. Proteolysis (the amount of pH 4.6 soluble nitrogen) was lower in control cheeses compared with WP-reduced cheeses. During ripening, the hardness values and the temperature of the crossover point, an indicator of the melting point of the cheese, were higher in the control cheese. It was thus likely that the higher residual WP content in the control cheese inhibited proteolysis during ripening, and the lower breakdown rate resulted in its higher hardness and melting point. There were no major differences in the concentrations of key nutrients with this WP depletion method. Cheese milk concentration by MF provides the benefit of more typical ripening rates.

Reale E ，Govindasamy-Lucey S ，Lu Y ，Johnson ME ，Jaeggi JJ ，Molitor M ，Lucey JA ... -  《-》

Effects of the depletion of whey proteins from unconcentrated milk using microfiltration on the yield, functionality, and nutritional profile of Cheddar cheese.

Some European dairies use low concentration factor microfiltration (MF) in their cheese plants. Removal of whey protein (WP) from milk before cheesemaking using microfiltration without concentration provides the opportunity to produce a value-added by-product, milk-derived whey. However, few studies have focused on the effects on cheese properties caused by the depletion of WP from cheese milk. Most studies have concentrated cheese milk using MF in addition to depletion of WP. In our approach, cheese milk was not concentrated during WP depletion using MF. We wanted to quantify residual WP levels in cheese made from MF milk and to explore whether WP depletion from milk would influence functionality, nutritional profile, and cheese quality during ripening. Casein (CN) contents for all milks were kept at ∼2.5%, to eliminate the confounding factor of concentration of CN, which was observed in some previous MF studies. Cheese milks had similar ratios of CN to fat. Three standardized milks were produced with various CN:true protein (TP) ratios: (a) control with a CN:TP ratio of 83:100, (b) 35% WP depletion, 89:100 CN:TP, and (c) 70% WP depletion, 95:100 CN:TP. Cheddar cheeses were made from MF milk with various WP depletion levels and aged for 9 mo, and their functionality was evaluated during ripening. We found no major differences in cheese composition or pH values between samples. Cheese yield, solids recovery, and nitrogen recovery were slightly higher in the 95:100 CN:TP cheeses compared with the control. These enhanced recoveries reflect that MF-treated milk started with a higher fraction of CN-based protein solids, rather than WP solids. The standardized milk from the 95:100 CN:TP treatment also had a slightly higher fat content compared with the control, likely helping to increase cheese yield. Rheological properties of cheeses during heating were similar between treatments. Hardness initially decreased with age for all cheeses due to proteolysis or solubilization, or both, of calcium phosphate. Maximum loss tangent (LT), an index of cheese meltability, was slightly lower for the control cheese until 30 d of ripening, but after 30 d, all treatments exhibited similar maximum LT values. The temperature where LT = 1 (crossover temperature), an index of softening point during heating, was slightly lower for MF cheese compared with the control cheeses during ripening. Microfiltration treatment had no significant influence on proteolysis. Sensory properties were similar between the cheeses, except for bitterness. Bitterness intensity was slightly lower in the MF cheeses than in the control cheeses and increased in all cheeses during ripening. We detected no major differences in the concentrations of key nutrients or vitamins between the various cheeses. Depletion of WP in cheese milk by MF did not negatively affect cheese quality, or its nutritional profile, and resulted in similar cheesemaking yields.

Reale E ，Govindasamy-Lucey S ，Johnson ME ，Jaeggi JJ ，Molitor M ，Lu Y ，Lucey JA ... -  《-》