Application of exopolysaccharide-producing cultures in reduced-fat Cheddar cheese: texture and melting properties

Textural, melting, and sensory characteristics of reduced-fat Cheddar cheeses made with exopolysaccharide (EPS)-producing and nonproducing cultures were monitored during ripening. Hardness, gumminess, springiness, and chewiness significantly increased in the cheeses as fat content decreased. Cheese made with EPS-producing cultures was the least affected by fat reduction. No differences in hardness, springiness, and chewiness were found between young reduced fat cheese made with a ropy Lactococcus lactis ssp. cremoris [JFR1; the culture that produced reduced-fat cheese with moisture in the nonfat substance (MNFS) similar to that in its full-fat counterpart] and its full-fat counterpart. Whereas hardness of full-fat cheese and reduced-fat cheese made with JFR1 increased during ripening, a significant decrease in its value was observed in all other cheeses. After 6 mo of ripening, reduced fat cheeses made with all EPS-producing cultures maintained lower values of all texture profile analysis parameters than did those made with no EPS. Fat reduction decreased cheese meltability. However, no differences in meltability were found between the young full-fat cheese and the reduced-fat cheese made with the ropy culture JFR1. Both the aged full- and reduced-fat cheeses made with JFR1 had similar melting patterns. When heated, they both became soft and creamy without losing shape, whereas reduced-fat cheese made with no EPS ran and separated into greasy solids and liquid. No differences were detected by panelists between the textures of the full-fat cheese and reduced-fat cheese made with JFR1, both of which were less rubbery or firm, curdy, and crumbly than all other reduced-fat cheeses.     

Ultrafiltered milk reduces bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide-producing culture

The objectives were to reduce bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide (EPS)-producing culture and study relationships among ultra-filtration (UF), residual chymosin activity (RCA), and cheese bitterness. In previous studies, EPS-producing cultures improved the textural, melting, and viscoelastic properties of reduced-fat Cheddar cheese. However, the EPS-positive cheese developed bitterness after 2 to 3 mo of ripening due to increased RCA. We hypothesized that the reduced amount of chymosin needed to coagulate UF milk might result in reduced RCA and bitterness in cheese. Reduced-fat Cheddar cheeses were manufactured with EPS-producing and nonproducing cultures using skim milk or UF milk (1.2×) adjusted to a casein:fat ratio of 1.35. The EPS-producing culture increased moisture and RCA in reduced-fat Cheddar cheese. Lower RCA was found in cheese made from UF milk compared with that in cheese made from control milk. Ultrafiltration at a low concentration rate (1.2×) produced EPS-positive, reduced-fat cheese with similar RCA to that in the EPS-negative cheese. Slower proteolysis was observed in UF cheeses compared with non-UF cheeses. Panelists reported that UF EPS-positive cheese was less bitter than EPS-positive cheese made from control milk. This study showed that UF at a low concentration factor (1.2×) could successfully reduce bitterness in cheese containing a high moisture level. Because this technology reduced the RCA level (per g of protein) to a level similar to that in the control cheeses, the contribution of chymosin to cheese proteolysis would be similar in both cheeses.     

Effects of exopolysaccharide-producing cultures on the viscoelastic properties of reduced-fat Cheddar cheese

The objective was to study the influence of different exopolysaccharide (EPS)-producing and nonproducing lactic cultures on the viscoelastic properties of reduced-fat Cheddar cheese. Changes in the viscoelastic properties were followed over a ripening period of 6 mo. Results showed that the elastic, viscous, and complex moduli were higher in reduced-fat cheeses made with EPS-nonproducing cultures than in full-fat cheese. No differences in the viscoelastic properties were found between young reduced-fat cheese made with a ropy strain of Lactococcus lactis ssp. cremoris (JFR1) and its full-fat counterpart. Interestingly, the changes in viscoelastic moduli in both full-fat cheese and reduced-fat cheese made with JFR1 during ripening followed the same pattern. Whereas the moduli increased during the first month of ripening in those 2 cheeses, a dramatic decrease was observed in all other cheeses. Slopes of the viscoelastic moduli as a function of frequency were lower in the full-fat than in reduced-fat cheeses. The creep test showed that fresh reduced-fat cheese made with JFR1 was less rigid and more deformable than that made with EPS-nonproducing cultures. The creep and recovery properties of young reduced-fat cheese made with JFR1 and the full-fat type were similar. No differences were found in the viscoelastic properties between reduced-fat cheese made with no EPS and those made with EPS-producing adjunct cultures of Streptococcus thermophilus. After 6 mo of ripening, cheeses made with EPS-producing cultures maintained lower elastic and viscous moduli than did those made with no EPS.     

Effect of various high-pressure treatments on the properties of reduced-fat Cheddar cheese

A major problem with reduced-fat cheese is the difficulty in attaining the characteristic flavor and texture of typical full-fat versions. Some previous studies have suggested that high hydrostatic pressure (HHP) can accelerate the ripening of full-fat cheeses. Our objective was to investigate the effect of HHP on reduced-fat (~7.3% fat) Cheddar cheese, with the goal of improving its flavor and texture. We used a central composite rotatable design with response surface methodology to study the effect of pressure and holding time on the rheological, physical, chemical, and microbial characteristics of reduced-fat Cheddar cheese. A 2-level factorial experimental design was chosen to study the effects of the independent variables (pressure and holding time). Pressures were varied from around 50 to 400 MPa and holding times ranged from 2.5 to 19.5 min. High pressure was applied 1 wk after cheese manufacture, and analyses were performed at 2 wk, and 1, 3, and 6 mo. The insoluble calcium content as a percentage of total Ca in cheeses were not affected by pressure treatment. Pressure applications ≥225 MPa resulted in softer cheese texture during ripening. Pressures ≥225 MPa increased melt, and resulted in higher maximum loss tangent values at 2 wk. Pressure treatment had a greater effect on cheese microbial and textural properties than holding time. High-pressure-treated cheeses also had higher pH values than the control. We did not observe any significant difference in rates of proteolysis between treatments. In conclusion, holding times of around 5 min and pressures of ≥225 MPa could potentially be used to improve the excessively firm texture of reduced-fat cheese.     

Application of exopolysaccharide-producing cultures in reduced-fat Cheddar cheese: composition and proteolysis

Proteolysis during ripening of reduced fat Cheddar cheeses made with different exopolysaccharide (EPS)-producing and nonproducing cultures was studied. A ropy strain of Lactococcus lactis ssp. cremoris (JFR1) and capsule-forming nonropy and moderately ropy strains of Streptococcus thermophilus were used in making reduced-fat Cheddar cheese. Commercial Cheddar starter was used in making full-fat cheese. Results showed that the actual yield of cheese made with JFR1 was higher than that of all other reduced-fat cheeses. Cheese made with JFR1 contained higher moisture, moisture in the nonfat substance, and residual coagulant activity than all other reduced-fat cheeses. Proteolysis, as determined by PAGE and the level of water-soluble nitrogen, was also higher in cheese made with JFR1 than in all other cheeses. The HPLC analysis showed a significant increase in hydrophobic peptides (causing bitterness) during storage of cheese made with JFR1. Cheese made with the capsule-forming nonropy adjunct of S. thermophilus, which contained lower moisture and moisture in the nonfat substance levels and lower chymosin activity than did cheese made with JFR1, accumulated less hydrophobic peptides. In conclusion, some EPS-producing cultures produced reduced-fat Cheddar cheese with moisture in the nonfat substance similar to that in its full-fat counterpart without the need for modifying the standard cheese-making protocol. Such cultures might accumulate hydrophobic (bitter) peptides if they do not contain the system able to hydrolyze them. For making high quality reduced-fat Cheddar cheese, EPS-producing cultures should be used in conjunction with debittering strains.     

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Cheddar cheese mixed starter cultures containing exopolysaccharide (EPS)-producing strains of Lactococcus lactis subsp. cremoris (Lac. cremoris) were characterized and used for the production of reduced-fat Cheddar cheese (15% fat). The effects of ropy and capsular strains and their combination on cheese production and physical characteristics as well as composition of the resultant whey samples were investigated and compared with the impact of adding 0.2% (w/v) of lecithin, as a thickening agent, to cheese milk. Control cheese was made using EPS-non-producing Lac. cremoris. Cheeses made with capsular or ropy strains or their combination retained 3.6–4.8% more moisture and resulted in 0.29–1.19 kg/100 kg higher yield than control cheese. Lecithin also increased the moisture retention and cheese yield by 1.4% and 0.37%, respectively, over the control cheese. Lecithin addition also substantially increased viscosity, total solid content and concentrating time by ultra-filtration (UF) of the whey produced. Compared with lecithin addition, the application of EPS-producing strains increased the viscosity of the resultant whey slightly, while decreasing whey total solids, and prolonging the time required to concentrate whey samples by UF. The amount of EPS expelled in whey ranged from 31 to 53 mg L⁻¹. Retention of EPS-producing strains in cheese curd was remarkably higher than that of non-producing strains. These results indicate the capacity of EPS-producing Lac. cremoris for enhanced moisture retention in reduced-fat Cheddar cheese; these strains would be a promising alternative to commercial stabilizers.     

Impact of fat reduction on flavor and flavor chemistry of Cheddar cheeses

A current industry goal is to produce a 75 to 80% fat-reduced Cheddar cheese that is tasty and appealing to consumers. Despite previous studies on reduced-fat cheese, information is critically lacking in understanding the flavor and flavor chemistry of reduced-fat and nonfat Cheddar cheeses and how it differs from its full-fat counterpart. The objective of this study was to document and compare flavor development in cheeses with different fat contents so as to quantitatively characterize how flavor and flavor development in Cheddar cheese are altered with fat reduction. Cheddar cheeses with 50% reduced-fat cheese (RFC) and low-fat cheese containing 6% fat (LFC) along with 2 full-fat cheeses (FFC) were manufactured in duplicate. Cheeses were ripened at 8°C and samples were taken following 2 wk and 3, 6, and 9 mo for sensory and instrumental volatile analyses. A trained sensory panel (n = 10 panelists) documented flavor attributes of cheeses. Volatile compounds were extracted by solid-phase microextraction or solvent-assisted flavor evaporation followed by separation and identification using gas chromatography-mass spectrometry and gas chromatography-olfactometry. Selected compounds were quantified using external standard curves. Sensory properties of cheeses were distinct initially but more differences were documented as cheeses aged. By 9 mo, LFC and RFC displayed distinct burnt/rosy flavors that were not present in FFC. Sulfur flavor was also lower in LFC compared with other cheeses. Forty aroma-active compounds were characterized in the cheeses by headspace or solvent extraction followed by gas chromatography-olfactometry. Compounds were largely not distinct between the cheeses at each time point, but concentration differences were evident. Higher concentrations of furanones (furaneol, homofuraneol, sotolon), phenylethanal, 1-octen-3-one, and free fatty acids, and lower concentrations of lactones were present in LFC compared with FFC after 9 mo of ripening. These results confirm that flavor differences documented between full-fat and reduced-fat cheeses are not due solely to differences in matrix and flavor release but also to distinct differences in ripening biochemistry, which leads to an imbalance of many flavor-contributing compounds.     

Chymosin-mediated proteolysis, calcium solubilization, and texture development during the ripening of cheddar cheese

Full fat, milled-curd Cheddar cheeses (2 kg) were manufactured with 0.0 (control), 0.1, 1.0, or 10.0 μmol of pepstatin (a potent competitive inhibitor of chymosin) added per liter of curds/whey mixture at the start of cooking to obtain residual chymosin levels that were 100, 89, 55, and 16% of the activity in the control cheese, respectively. The cheeses were ripened at 8°C for 180 d. There were no significant differences in the pH values of the cheeses; however, the moisture content of the cheeses decreased with increasing level of pepstatin addition. The levels of pH 4.6-soluble nitrogen in the 3 cheeses with added pepstatin were significantly lower than that of the control cheese at 1 d and throughout ripening. Densitometric analysis of urea-PAGE electro-phoretograms of the pH 4.6-insoluble fractions of the cheese made with 10.0 μmol/L of pepstatin showed complete inhibition of hydrolysis of α_S1-casein (CN) at Phe₂₃-Phe₂₄ at all stages of ripening. The level of insoluble calcium in each of 4 cheeses decreased significantly during the first 21 d of ripening, irrespective of the level of pepstatin addition. Concurrently, there was a significant reduction in hardness in each of the 4 cheeses during the first 21 d of ripening. The softening of texture was more highly correlated with the level of insoluble calcium than with the level of intact α_S1-CN in each of the 4 cheeses early in ripening. It is concluded that hydrolysis of α_S1-CN at Phe₂₃-Phe₂₄ is not a prerequisite for softening of Cheddar cheese during the early stages of ripening. We propose that this softening of texture is principally due to the partial solubilization of colloidal calcium phosphate associated with the para-CN matrix of the curd.     

Effect of exopolysaccharide produced by isogenic strains of Lactococcus lactis on half-fat Cheddar cheese

Fat-reduced cheeses often suffer from undesirable texture, flavor, and cooking properties. Exopolysaccharides (EPS) produced by starter strains have been proposed as a mechanism to increase yield and to improve the texture and cooking properties of reduced-fat cheeses. The objective of this work was to assess the influence of an exopolysaccharide on the yield, texture, cooking properties, and quality of half-fat Cheddar cheese. Two pilot-scale half-fat Cheddar cheeses were manufactured using single starters of an isogenic strain of Lactococcus lactis ssp. cremoris (DPC6532 and DPC6533) that differed in their ability to produce exopolysaccharide. Consequently, any differences detected between the cheeses were attributed to the presence of the exopolysaccharide. The results indicated that cheeses made with the exopolysaccharide-producing starter had an 8.17% increase in actual cheese yield (per 100 kg of milk), a 9.49% increase in moisture content, increase in water activity and water desorption rate at relative humidities ≤90%, significant differences in the cheeses microstructure, and a significant improvement in both textural and cooking properties, without negatively affecting the flavor profiles of the cheeses.     

Composition and Quality Attributes of Reduced-Fat Cheese as Affected by Lecithin Type

Cheddar cheeses with 33% reduced-fat content were prepared with granular soy lecithin, hydrogenated soy lecithin, or oat. Addition of lecithin increased the wet weight yields and moisture of cheeses (P≤0.05). Reflected color values (L* and h_ab) were increased in cheeses containing granular soy lecithin (P≤0.05). Acid values of cheeses with lecithin were higher than control cheeses (P≤0.05). Concentrations of lecithin at 0.2% (w/w) resulted in visible changes in micro-structure of the cheeses. Granular soy lecithin or oat lecithin added to reduced-fat cheeses resulted in a decrease in flavor quality (P≤0.05). Hydrogenated soy lecithin added to reduced-fat cheeses improved texture quality without negatively affecting flavor quality.     

Effect of zinc fortification on Cheddar cheese quality

Zinc-fortified Cheddar cheese containing 228 mg of zinc/kg of cheese was manufactured from milk that had 16 mg/kg food-grade zinc sulfate added. Cheeses were aged for 2 mo. Culture activity during cheese making and ripening, and compositional, chemical, texture, and sensory characteristics were compared with control cheese with no zinc sulfate added to the cheese milk. Compositional analysis included fat, protein, ash, moisture, zinc, and calcium determinations. The thiobarbituric acid (TBA) assay was conducted to determine lipid oxidation during aging. Texture was analyzed by a texture analyzer. An untrained consumer panel of 60 subjects evaluated the cheeses for hardness, off-flavors, appearance, and overall preference using a 9-point hedonic scale. Almost 100% of the zinc added to cheese milk was recovered in the zinc-fortified cheese. Zinc-fortified Cheddar cheese had 5 times more zinc compared with control cheese. Zinc-fortified cheese had higher protein and slightly higher fat and ash contents, whereas moisture was similar for both cheeses. Zinc fortification did not affect culture activity during cheese making or during the 2-mo aging period. The TBA value of control cheese was higher than that of zinc-fortified cheese at the end of ripening. Although zinc-fortified cheese was harder as determined by the texture analyzer, the untrained consumer panel did not detect differences in the sensory attributes and overall quality of the cheeses. Fortification of 16 mg/kg zinc sulfate in cheese milk is a suitable approach to fortifying Cheddar cheese without changing the quality of Cheddar cheese.     

Application of exopolysaccharide-producing cultures in reduced-fat Cheddar cheese: cryo-scanning electron microscopy observations

The microstructure of reduced- and full-fat Cheddar cheeses made with exopolysaccharide (EPS)-producing and nonproducing cultures was observed using cryo-scanning electron microscopy. Fully hydrated cheese samples were rapidly frozen in liquid nitrogen slush (−207°C) and observed in their frozen hydrated state without the need for fat extraction. Different EPS-producing cultures were used in making reduced-fat Cheddar cheese. Full-fat cheese was made with a commercial EPS-nonproducing starter culture. The cryo-scanning electron micrographs showed that fat globules in the fully hydrated cheese were surrounded by cavities. Serum channels and pores in the protein network were clearly observed. Young (1-wk-old) full-fat cheese contained wide and long fat serum channels, which were formed because of fat coalescence. Such channels were not observed in the reduced-fat cheese. Young reduced-fat cheese made with EPS-nonproducing cultures contained fewer and larger pores than did reduced-fat cheese made with a ropy strain of Lactococcus lactis ssp. cremoris (JFR1), which had higher moisture levels. A 3-dimensional network of EPS was observed in large pores in cheese made with JFR1. Major changes in the size and distribution of pores within the structure of the protein network were observed in all reduced-fat cheeses, except that made with JFR1, as they aged. Changes in porosity were less pronounced in both the full-fat and the reduced-fat cheeses made with JFR1.     

Assessing the yield,microstructure, and texture properties of miniature Chihuahua-type cheese manufactured with a phospholipase A1 and exopolysaccharide-producing bacteria

Chihuahua cheese or Mennonite cheese is one of the most popular and consumed cheeses in Mexico and by the Hispanic community in the United States. According to local producers the yield of Chihuahua cheese ranges from 9 to 9.5 kg of cheese from 100 kg of milk. Cheese yield is a crucial determinant of profitability in cheese-manufacturing plants; therefore, different methods have been developed to increase it. In this work, a miniature Chihuahua-type cheese model was used to assess the effect of a phospholipase A₁ (PL-A₁) and exopolysaccharide (EPS)-producing bacteria (separately and in combination) on the yield, microstructure, and texture of cheese. Four different cheeses were manufactured: cheese made with PL-A₁, cheese made with EPS-producing bacteria, cheese with both PL-A₁ and EPS-producing bacteria, and a cheese control without PL-A₁ or EPS-producing bacteria. The compositional analysis of cheese was carried out using methods of AOAC International (Washington, DC). The actual yield and moisture-adjusted yield were calculated for all cheese treatments. Texture profile analyses of cheeses were performed using a texture analyzer. Micrographs were obtained by electron scanning microscopy. Fifty panelists carried out sensorial analysis using ranking tests. Incorporation of EPS-producing bacteria in the manufacture of cheese increased the moisture content and water activity. In contrast, the addition of PL-A₁ did not increase fat retention or cheese yield. The use of EPS alone improved the cheese yield by increasing water and fat retention, but also caused a negative effect on the texture and flavor of Chihuahua cheese. The use of EPS-producing bacteria in combination with PL-A₁ improved the cheese yield and increased the moisture and fat content. The cheeses with the best flavor and texture were those manufactured with PL-A₁ and the cheeses manufactured with the combination of PL-A1 and EPS-producing culture.     

Rheological Properties of Cheddar Cheese as Influenced by Fat Reduction and Ripening Time

Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increases in G’and G”. Proteolysis during ripening led to softening of all cheeses and thus decreases in G’and G” for cheeses containing 34, 27, and 20% fat. Cheese with 13% fat showed a decrease in G’upon ripening, but no change in G”. This lack of change in viscous behavior may be important to the texture of reduced-fat Cheddar cheese and overall acceptability. Dynamic rheological testing was helpful in understanding rheological behavior associated with fat reduction in cheese.     

Effect of sodium,potassium, magnesium,and calcium salt cations on pH,proteolysis, organic acids,and microbial populations during storage of full-fat Cheddar cheese

Sodium reduction in cheese can assist in reducing overall dietary Na intake, yet saltiness is an important aspect of cheese flavor. Our objective was to evaluate the effect of partial substitution of Na with K on survival of lactic acid bacteria (LAB) and nonstarter LAB (NSLAB), pH, organic acid production, and extent of proteolysis as water-soluble nitrogen (WSN) and protein profiles using urea-PAGE, in Cheddar cheese during 9 mo of storage. Seven Cheddar cheeses with molar salt contents equivalent to 1.7% salt but with different ratios of Na, K, Ca, and Mg cations were manufactured as well as a low-salt cheese with 0.7% salt. The 1.7% salt cheeses had a mean composition of 352 g of moisture/kg, 259 g of protein/kg and 50% fat-on-dry-basis, and 17.5 g of salt/kg (measured as Cl⁻). After salting, a faster initial decrease in cheese pH occurred with low salt or K substitution and it remained lower throughout storage. No difference in intact casein levels or percentage WSN levels between the various cheeses was observed, with the percentage WSN increasing from 5% at d 1 to 25% at 9 mo. A greater decrease in intact α_s1-casein than β-casein was detected, and the ratio of α_s1-casein (f121–199) to α_s1-casein could be used as an index of ripening. Typical changes in bacteria microflora occurred during storage, with lactococci decreasing gradually and NSLAB increasing. Lowering the Na content, even with K replacement, extended the crossover time when NSLAB became dominant. The crossover time was 4.5 mo for the control cheese and was delayed to 5.2, 6.0, 6.1, and 6.2 mo for cheeses with 10, 25, 50, and 75% K substitution. Including 10% Mg or Ca, along with 40% K, further increased crossover time, whereas the longest crossover time (7.3 mo) was for low-salt cheese. By 9 mo, NSLAB levels in all cheeses had increased from initial levels of ≤10² to approximately 10⁶ cfu/g. Lactococci remained at 10⁶ cfu/g in the low-salt cheese even after 9 mo of storage. The propionic acid concentration in the cheese increased when NSLAB numbers were high. Few other trends in organic acid concentration were observed as a function of Na content.     

Key aroma compounds identified in Cheddar cheese with different ripening times by aroma extract dilution analysis,odor activity value,aroma recombination,and omission

To determine the odor-active compounds in Cheddar cheeses with different ripening times (6, 10, and 14 mo), 39 potent odorants of Cheddar cheeses were identified with a flavor dilution factor range between 1 and 512 by aroma extract dilution analysis. To further determine their contribution to the overall aroma profile of Cheddar cheeses, odor activity values of 38 odorants with flavor dilution factors ≥1 were calculated. A Cheddar cheese matrix was developed to determine the concentrations and the odor thresholds of these key aroma compounds. The result of the aroma recombinant experiment prepared by mixing the key aroma compounds in the concentrations in which they occurred in Cheddar cheeses showed that the overall aroma profile of the recombinant sample was very similar to that of Cheddar cheese. The main different compounds in Cheddar cheese with different ripening time were acetic acid, butanoic acid, dimethyl trisulfide, methional, hexanal, (E)-2-nonenal, acetoin, 1-octen-3-one, δ-dodecalactone, furaneol, hexanoic acid, heptanal, and ethyl caproate. This study could provide important information for researching and developing Cheddar cheese–related products.     

Evolution of Free Amino Acids during the Ripening of Cheddar Cheese Containing Added Lactobacilli Strains

Cheddar cheese was produced with different lactobacilli strains added to accelerate ripening. The concentration of proteolytic products was determined as free amino acids in the water-soluble fraction at two, four, seven and nine months of aging and at two different maturation temperatures (6°C, 15°C). All amino acids increased during ripening and were higher in the Lactobacillus- added cheeses than in the control cheese, and higher in cheeses ripened at 15°C than at 6°C. Glutamic acid, leucine, phenylalanine, valine and lysine were generally in higher proportion in all cheeses. The cheeses with added L. casei-casei L2A were classified as having a “strong Cheddar cheese” flavor after only seven months of ripening at 6°C.