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.     

Accumulation of Some Flavor Compounds in Full- and Reduced-fat Cheddar Cheese Under Different Ripening Conditions

Reduced-fat cheese showed higher levels of ethanol and lower acetoin than full-fat samples throughout ripening regardless of conditions. Total headspace volatiles, as well as butanoic and hexanoic acids, increased with ripening time and temperature. Full- and reduced-fat cheeses developed distinctly different headspace volatile profiles throughout ripening. The effects of ripening conditions were more notable in full-fat samples. Ripening reduced-fat Cheddar cheese at an elevated temperature for a limited time may enhance development of some desirable volatiles such as butanoic acid.     

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.     

Reduced-fat cheddar cheese manufactured using a novel fat removal process

Normally, reduced-fat Cheddar cheese is made by removal of fat from milk prior to cheese making. Typical aged flavor may not develop when 50% reduced-fat Cheddar cheese is produced by this approach. Moreover, the texture of the reduced-fat cheeses produced by the current method may often be hard and rubbery. Previous researchers have demonstrated that aged Cheddar cheese flavor intensity resides in the water-soluble fraction. Therefore, we investigated the feasibility of fat removal after the aging of Cheddar cheese. We hypothesized the typical aged cheese flavor would remain with the cheese following fat removal. A physical process for the removal of fat from full-fat aged Cheddar cheese was developed. The efficiency of fat removal at various temperatures, gravitational forces, and for various durations of applied forces was determined. Temperature had the greatest effect on the removal of fat. Gravitational force and the duration of applied force were less important at higher temperatures. A positive linear relationship between temperature and fat removal was observed from 20 to 33 degrees C. Conditions of 30 degrees C and 23,500 x g for 5 min removed 50% of the fat. The removed fat had some aroma but little or no taste. The fatty acid composition, triglyceride molecular weight distribution, and melting profile of the fat retained in the reduced-fat cheeses were all consistent with a slight increase in the proportion of saturated fat relative to the full-fat cheeses. The process of fat removal decreased the grams of saturated fat per serving of cheese from 6.30 to 3.11 g. The flavor intensity of the reduced-fat cheeses were at least as intense as the full-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.     

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.     

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.     

Rheological and Sensory Properties of Reduced-Fat Processed Cheeses Containing Lecithin

Reduced fat processed cheeses were prepared with granular or hydrogenated soy lecithin. Trained sensory panelists (n = 11) determined that reduced-fat cheeses containing lecithin were more similar in texture attributes to full-fat control cheeses than reduced fat cheeses without lecithin (P<0.05). Consumer flavor and acceptance scores (n =60) for cheeses with lecithin were not different from control cheeses, but texture acceptance scores for cheeses with lecithin were higher than scores for reduced fat control cheeses (P.0.05). Cheeses containing lecithin were less elastic than reduced fat control cheeses as determined by sensory panels and instrumental percent creep recovery. Lecithin improved processed cheese texture without negatively affecting acceptance.     

Impact of Fat Replacers on the Rheological,Tribological, and Aroma Release Properties of Reduced-Fat Model Emulsion Systems and Processed Cheese

Due to the increasing prevalence of overweight and obesity and their associated health problems, the demand for low-calorie and low-fat foods is growing worldwide, especially in the fast food and convenience sectors. However, fat- or calorie-reduced products are often accompanied by sensory deficiencies. Although fat reduction in foods has been addressed in literature, an ideal fat replacer has not been identified due to the variety of fats, their multifarious functions in foods, and the wide range of food products. The aim of this work was to investigate the influence of selected fat replacers on the properties of reduced-fat model emulsion systems and processed cheese. The use of dietary fibers as fat replacers was of particular interest due to their intrinsic health benefits. In addition, both new and established methods of measurement of sensory attributes were applied and compared to determine correlations of findings between different methods of measurement. Chapter 1 addresses the influence of fat replacers on attributes such as energy density, flowability, and firmness in a real food product, processed cheese. To this end, microparticulated whey protein (MWP), which has been widely used as a fat replacer, and three dietary fibers (corn dextrin (CD), inulin, and polydextrose), were used in reduced-fat processed cheese slices. A reduction in energy density of about 30 to 40% was achieved using a fat replacer compared to standard commercial full-fat processed cheese. Higher CD and inulin concentrations reduced the flowability of the cheese slices upon heating, but only had a minor impact on the firmness of the unheated cheese. The addition of MWP resulted in firmer cheese slices with higher flowability compared to the other fat replacers. However, changes in the MWP concentration had little effect on either property. The results demonstrated that different fat replacers with varying concentrations need to be applied to achieve desired attributes for specific conditions of use, e.g., unheated cheese in sandwiches or heated cheese in cheeseburgers. To evaluate newly developed reduced-fat foods, the impact of fat replacers on sensory properties and aroma release also needs to be investigated, which is addressed in chapters 2 to 4. Due to the complex composition of cheese, systematic investigation of the mode of action of fat replacers is difficult. Therefore, emulsion-based model foods were used to eliminate interfering factors and natural variations of ingredients. The second study (chapter 2) focused on developing and validating appropriate methods to investigate the effects of fat, fat reduction and the use of fat replacers on emulsion systems. Tribology, a comparatively new method in food research, was used to instrumentally analyze selected aspects of food mouthfeel. Reduced-fat salad mayonnaises were prepared as separate samples containing different CD concentrations, and characterized using textural, rheological and tribological analyses together with measures of spreadability and human-sensory analysis. The results showed a very high correlation between tribological measurements and the sensory evaluation of the attribute stickiness. In addition, it was shown that some correlations between instrumental and sensory data were best described by a non-linear correlation (Stevens’ power law), such as the relationship between Texture Analyzer measurements and sensory sensations of firmness. Furthermore, the Kokini oral shear stress correlated very well with the sensory attribute creaminess. Hence, the instrumental analytical methods used showed the potential to predict elements of the sensory analysis and reduce the overall analytical effort. While aroma release plays a key role in consumer acceptance, the influence of fat replacers on this attribute has rarely been studied. The third study (chapter 3) therefore investigated not only techno-functional properties but also the release of typical cheese aromas using a liquid emulsion as a model food. While both MWP and CD exhibited a retarding effect on the release of lipophilic aroma compounds, MWP also reduced the release of hydrophilic aroma compounds. It was also shown that aroma release is not only influenced by a change in viscosity, but also by interactions between aroma compounds and fat replacers. In this context, CD exhibited a similar ability to interact with aroma compounds as fat, which is desirable for the development of low-fat foods. In the final study (chapter 4), the findings and methods developed in chapters 1-3 of this work, supplemented with additional methods, were used to investigate the effect of fat reduction and CD concentration on a model processed cheese spread (PCS). By replacing 50% of fat completely with CD, the fat content of the PCS could be reduced without causing any significant changes in properties compared to the full-fat version, e.g. in firmness, flowability upon heating and aroma release. CD was determined to be a promising fat replacer, mimicking important properties of fat. Additional correlations, such as those between the parameters of Winter's critical gel theory (gel strength and interaction factor) and spreadability and lubrication properties were identified and can help to further reduce the analytical effort. In conclusion, CD has been confirmed as a promising fat replacer in both liquid and semi-solid food emulsion products. Furthermore, this work contributes to closing the research gap in the instrumental measurement of sensory attributes by outlining correlations, for example, between tribological methods and mouthfeel sensations. Thus, the evaluation tools of this work can help to assess the potential applications of new fat replacers without extensive application and sensory testing which significantly shortens the development time for food manufacturers. In addition, the results contribute to a better understanding of the interactions between fat, fat replacers and aroma compounds in food matrices. This facilitates the systematic development of reduced-fat processed cheese and other dairy- and emulsion-based products which meet consumer preferences and accelerate the trend towards healthy eating.     

MILK GEL STRUCTURE. X. TEXTURE AND MICROSTRUCTURE IN CHEDDAR CHEESE MADE FROM WHOLE MILK AND FROM HOMOGENIZED LOW-FAT MILK1

Reduced-fat cheese (17% fat, 44% moisture) was considerably firmer and more elastic than full-fat cheese (35% fat, 35% moisture), even though the moisture levels in the nonfat matter (MNFM) of the cheese were the same, at 54%. Electron microscopy and compositional analysis revealed about 30% more protein matrix in the reduced-fat cheese. Apparently more of this matrix must be cut or deformed in sensorial and texture assessments. A practical implication is that MNFM should be slightly higher in the reduced-fat cheese than in full-fat cheese to achieve more similar texture. Homogenization of milk tended to increase the moisture content and decrease firmness and elasticity, but not markedly. The smaller fat globules, per se, did not apparently affect texture as measured in these experiments. Curd granule junctions were prominent in nonhomogenized-milk cheese, because large fat globules were lost at the granule surfaces leaving protein-dense junctions; those in homogenized-milk cheese were less apparent because the protein-dense areas, which resulted from the loss of small fat globules, were narrower. Sensory and textural parameters for firmness and elasticity were inter-correlated. The Bite Test was more useful than Instron measurements of deformation (20%), apparently because the latter was markedly affected by a slight openness in the cheese.     

Influence of composition on the biochemical and sensory characteristics of commercial Cheddar cheese of variable quality and fat content

Ten commercial Cheddar cheeses of variable quality differing in fat content and age were subjected to compositional, proteolytic, lipolytic and sensory analyses. The compositional parameters of the full-fat cheeses were predominantly outside those typically associated with good-quality cheese. Sensory analysis discriminated the full-fat cheeses predominantly by age, with the longer ripened cheeses associated with more negative attributes, some which appeared to be due to excessive lipolysis and/or β-casein breakdown. Both proteolysis and lipolysis appear to be age dependent. The two reduced-fat cheeses were clearly discriminated from the eight full-fat cheeses by sensory analysis that appeared to be due to differences in composition and the extent of lipolysis.     

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.     

Impact of Using Exopolysaccharides (EPS)-Producing Strain on Qualities of Half-Fat Cheddar Cheese

Yield, textural, proteolysis, melting, and sensory properties of exopolysaccharide-producing Lactobacillus paracasei on properties of half-fat (about 16 g fat/100 g cheese) Cheddar cheese during ripening at 8℃ for up to six months were investigated. The results revealed that B-3 cheese, made with 2.0% (v/v) high yield exopolysaccharide-producing L. paracasei in combination with 0.011% (w/w) commercial Cheddar culture (B-3 cheese), had a 10.15, 7.71, and 10.04% separately increase in moisture content and had a 7.70, 5.05, and 6.76% separately increase in yield compared with B-2, B-4, and B-5 cheese, texture and melting characteristics were significantly improved (P < 0.05), sensory score surpassed B-4 and B-5 cheese and was similar to the full-fat one. Any differences of B-3 cheese detected among half-fat Cheddar cheeses were attributed to the presence of high yield exopolysaccharide-producing L. paracasei.     

Structural and textural characteristics of reduced-fat cheese-like products made from W1/O/W2 emulsions and skim milk

The chemical composition, yield, structural arrangement, instrumental textural characteristics, and preference sensory evaluation of reduced-fat cheese-like products manufactured from skim milk and different water-in-oil-in-water (W₁/O/W₂) emulsions were determined. A full-fat white fresh cheese (WFC) was prepared from milk containing 27 g of milk-fat L⁻¹, and five reduced-fat white fresh cheese-like products (EC) were made from skim milk added with 25 g of multiple emulsions L⁻¹ containing canola oil and stabilized/emulsified by amidated low-methoxyl pectin (LMP), carboxymethylcellulose (CMC), gum Arabic (GA), and blends of GA-CMC or GA-LMP. The chemical composition, yield, structural arrangement and texture of the cheese-like products were affected by the biopolymers used as emulsifying/stabilizing agents of the multiple emulsions. CMC produced an EC with similar textural behaviour than the WFC cheese. GA contributed to a higher yield and fat content in the EC cheese in comparison with CMC and LMP cheese. GA and LMP contributed to increased values of hardness and chewiness of the EC cheese. The cheese made with multiple emulsions incorporating GA and LMP emulated best the textural characteristics of the WFC cheese. All of the EC cheese showed marked differences in microstructure.     

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.     

Protein interactions in reduced-fat and full-fat Cheddar cheeses during melting

Changes in physicochemical properties of 12-wk-old, half-fat (50 g/100 g reduced-fat) and full-fat Cheddar cheeses on heating at 180 °C for 25 min were investigated. The loss of moisture and fat in both cheeses were proportional to their initial amounts present; both protein:fat ratio and protein:moisture ratio were higher in half-fat cheese than in full-fat cheese. Various types of protein interactions during melting were measured by dispersing cheeses in different dissociating agents (SDS, EDTA, mercaptoethanol, and urea). Protein interactions which were expressed by dissolving heated cheese in urea appeared to contribute the most; this was followed by those expressed by dissolving in SDS. In interaction with temperature, dissociating agents appeared to have the greatest effect on the undissociated proteins still present. The protein-protein interactions during melting of cheeses, which form the hard surface skin in reduced-fat cheeses, were shown to involve disulfide bonds and hydrophobic interactions and to some extent ionic bonds with calcium.