TEXTURE ANALYSIS OF CHEDDAR CHEESE MADE FROM ULTRAFILTERED MILK

The textural properties of Cheddar cheese made from ultrafiltered milk were assessed. Cheddar cheeses were prepared from 1.5- and 2.0-fold concentrated milk and ripened for three months. Textural characteristics of the UF cheeses were compared to control and commercial Cheddar cheeses by sensory and instrumental measures. The texture of cheese made from UF milk differed from the control commercial Cheddar cheeses. According to the trained sensory panel, the UF cheeses were harder and more rubbery, crumbly, chewy and grainy than the control and commercial Cheddar cheeses (P <0.01). The texture profile analysis (TPA), conducted using the Instron, did not correspond to the sensory measurements nor was it successful in discriminating among the cheese samples. Lack of agreement between the sensory and instrumental tests was attributed to differences in the testing conditions and procedures of the two methods. Instrumental tests should be validated against sensory measures in order to be useful as measures of palatability. Consumer preferences for the commercial, control and UF Cheddar cheeses were significantly different (P < 0.01), the UF cheeses being less preferred in terms of flavor, texture and overall acceptability.     

UNIAXIAL COMPRESSION OF UF-FETA CHEESE RELATED TO SENSORY TEXTURE ANALYSIS

Rheological characteristics of seven Feta cheeses with different textures and produced from ultrafiltered milk (UF-Feta cheeses) were evaluated by uniaxial compression and sensory texture analysis. The effect of uniaxial deformation rate (50–2500 mm/min) on four rheological parameters: Stress at fracture s?_f), Hencky strain at fracture (?_f), deformability modulus (E) and work to fracture (W_f) was examined. Three Principal Components (PC) described 76, 16 and 4% respectively, of the variation in the uniaxial compression data set (4 parameters at 12 deformation rates). Statistically α_f, E and W_f described the same type of information in the data set. Six sensory texture attributes of the UF-Feta cheeses were evaluated by a sensory texture panel: nonoral firmness, nonoral brittleness, nonoral spreadability, oral crumbliness, oral firmness and oral stickiness. One PC described 93% of the variation in the sensory texture data and grouped the sensory variables into two negatively correlated groups: nonoral firmness nonoral brittleness, oral firmness and oral crumbliness versus nonoral spreadability and oral stickiness. Correlations and Partial Least Squares regression (PLS) between instrumental and sensory texture variables showed that nonoral and oral firmness were the nonoral and oral sensory variables best predicted from instrumental measurements. α_f, E and W_f were all able to predict nonoral and oral firmness. Of the instrumental parameters, α_f generally gave the best correlation to nonoral firmness at all deformation rates. Above a deformation rate of 50 mm/min correlations between α_f and nonoral firmness were almost independent of deformation rate, and at any deformation rate correlations between α_f and oral firmness     

Application of encapsulated enzymes to accelerate cheese ripening

The suitability of gellan, κ-carrageenan and a high-melting-fat-fraction of milk fat (HMFF) to encapsulate protease enzymes (Flavourzyme) and impact in accelerating Cheddar cheese ripening were studied. The rates of enzyme entrapment were 48.2%, 55.6%, and 38.9% for gellan, κ-carrageenan and HMFF, respectively. The enzyme capsules were incorporated into milk during cheese manufacture. The moisture content of cheeses with added gum capsules was higher than control cheeses. Casein (β) degradation was monitored by High-Performance Capillary Electrophoresis. All cheeses treated with encapsulated enzyme showed higher rates of proteolysis than the control cheese throughout the ripening period. The rate of proteolysis was greater with cheeses made incorporating κ-carrageenan capsules containing protease. Cheese texture and sensory quality were not significantly influenced by the type of encapsulating material (gum or milk fat). Differences in textural and sensory quality between treated and control cheeses were consistent with release of protease enzymes from capsules.     

Torsion gelometry of cheese

Torsion gelometry, a fundamental rheological test in which specimens are twisted until they fracture, was applied to several different cheese varieties to determine its suitability for measuring their textural properties. Fresh and aged Brick, Cheddar, Colby, Gouda, Havarti, Mozzarella, and Romano cheeses were subjected to torsion analysis, and the results were compared with those from small amplitude oscillatory shear (SAOS) tests and texture profile analysis (TPA). Strong relationships (correlation coefficients > 0.8) were found between torsion shear stress and TPA hardness, and between torsion shear strain and TPA cohesiveness. SAOS, which measures rheological properties of intact samples, did not correlate well with torsion or TPA. A map showing trends during aging toward brittle, mushy, rubbery, and tough texture was drawn using the torsion data. The findings show that torsion gelometry provides fundamental rheological data on cheese at the fracture point. The information can be used to compare textural qualities of cheese samples as they are being cut.     

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.     

INSTRUMENTAL AND SENSORY TEXTURE ASSESSMENT AND FRACTURE MECHANISMS OF CHEDDAR AND CHESHIRE CHEESES

Textural attributes of Cheddar and Cheshire cheeses, falling within narrow compositional ranges, were assessed by sensory panels, and from force-compression curves generated by compression between two plates, and, for Cheddar cheese only, by penetrometry. Individual sensory measurements did not relate well to any instrumental one, and were better at discriminating between cheeses. Samples of each cheese variety were fractured in different ways and the fracture surfaces were examined in a scanning electron microscope. Fracture surfaces were formed by cutting directly through the matrix, tearing of the matrix along planes high in fat or cracking at grain boundaries. It is suggested that consideration of fracture mechanism may aid the selection and development of useful instrumental methods for texture assessment of cheese.     

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.     

Identification of aroma-active compounds in Cheddar cheese imparted by wood smoke

Cheddar cheese is the most popular cheese in the United States, and the demand for specialty categories of cheese, such as smoked cheese, are rising. The objective of this study was to characterize the flavor differences among Cheddar cheeses smoked with hickory, cherry, or apple woods, and to identify important aroma-active compounds contributing to these differences. First, the aroma-active compound profiles of hickory, cherry, and apple wood smokes were analyzed by solid-phase microextraction (SPME) gas chromatography-olfactometry (GCO) and gas chromatography-mass spectrometry (GC-MS). Subsequently, commercial Cheddar cheeses smoked with hickory, cherry, or apple woods, as well as an unsmoked control, were evaluated by a trained sensory panel and by SPME GCO and GC-MS to identify aroma-active compounds. Selected compounds were quantified with external standard curves. Seventy-eight aroma-active compounds were identified in wood smokes. Compounds included phenolics, carbonyls, and furans. The trained panel identified distinct sensory attributes and intensities among the 3 cheeses exposed to different wood smokes (P < 0.05). Hickory smoked cheeses had the highest intensities of flavors associated with characteristic “smokiness” including smoke aroma, overall smoke flavor intensity, and meaty, smoky flavor. Cherry wood smoked cheeses were distinguished by the presence of a fruity flavor. Apple wood smoked cheeses were characterized by the presence of a waxy, green flavor. Ninety-nine aroma-active compounds were identified in smoked cheeses. Phenol, guaiacol, 4-methylguaiacol, and syringol were identified as the most important compounds contributing to characteristic “smokiness.” Benzyl alcohol contributed to the fruity flavor in cherry wood smoked cheeses, and 2-methyl-2-butenal and 2-ethylfuran were responsible for the waxy, green flavor identified in apple wood smoked cheeses. These smoke flavor compounds, in addition to diacetyl and acetoin, were deemed important to the flavor of cheeses in this study. Results from this study identified volatile aroma-active compounds contributing to differences in sensory perception among Cheddar cheeses smoked with different wood sources.     

EFFECT OF CALCIUM AND PHOSPHORUS, RESIDUAL LACTOSE AND SALT-TO-MOISTURE RATIO ON TEXTURAL PROPERTIES OF CHEDDAR CHEESE DURING RIPENING

The texture profile analysis (TPA) parameters and meltability of Cheddar cheeses with varying levels of calcium (Ca) and phosphorus (P) content, residual lactose content and salt‐to‐moisture (S/M) ratio were studied at 0, 1, 2, 4, 6 and 8 months of ripening. The TPA hardness had an inverse relationship with the meltability of Cheddar cheese and at any given ripening time, lower TPA hardness corresponded to higher meltability of Cheddar cheese. Higher Ca and P content (0.67% Ca and 0.53% P) in Cheddar cheese resulted in up to 22.8, 5.7, 14.6, 13.5 and 35.2% increase in hardness, springiness, cohesiveness, resilience and chewiness values, respectively, and up to 23.5 and 27.7% decrease in meltability and adhesiveness values during ripening compared to the Cheddar cheese prepared with lower Ca and P content (0.53% Ca and 0.39% P). Higher residual lactose content (1.4%) in Cheddar cheese resulted in up to 24.6, 8.8 and 20.0% increase in hardness, cohesiveness and chewiness values, respectively, and up to 12.7% decrease in meltability value in the Cheddar cheese during ripening compared to the lower lactose content (0.78%). High S/M ratio (6.4) resulted in up to 29.4, 30.3 and 29.4% increase in hardness, adhesiveness and chewiness values, respectively, and up to 7.3% decrease in meltability value in Cheddar cheese compared to low S/M ratio (4.8) during ripening.     

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.     

Effect of pasture versus indoor feeding systems on quality characteristics,nutritional composition,and sensory and volatile properties of full-fat Cheddar cheese

The purpose of this study was to investigate the effects of pasture-based versus indoor total mixed ration (TMR) feeding systems on the chemical composition, quality characteristics, and sensory properties of full-fat Cheddar cheeses. Fifty-four multiparous and primiparous Friesian cows were divided into 3 groups (n = 18) for an entire lactation. Group 1 was housed indoors and fed a TMR diet of grass silage, maize silage, and concentrates; group 2 was maintained outdoors on perennial ryegrass only pasture (GRS); and group 3 was maintained outdoors on perennial ryegrass/white clover pasture (CLV). Full-fat Cheddar cheeses were manufactured in triplicate at pilot scale from each feeding system in September 2015 and were examined over a 270-d ripening period at 8°C. Pasture-derived feeding systems were shown to produce Cheddar cheeses yellower in color than that of TMR, which was positively correlated with increased cheese β-carotene content. Feeding system had a significant effect on the fatty acid composition of the cheeses. The nutritional composition of Cheddar cheese was improved through pasture-based feeding systems, with significantly lower thrombogenicity index scores and a greater than 2-fold increase in the concentration of vaccenic acid and the bioactive conjugated linoleic acid C18:2 cis-9,trans-11, whereas TMR-derived cheeses had significantly higher palmitic acid content. Fatty acid profiling of cheeses coupled with multivariate analysis showed clear separation of Cheddar cheeses derived from pasture-based diets (GRS or CLV) from that of a TMR system. Such alterations in the fatty acid profile resulted in pasture-derived cheeses having reduced hardness scores at room temperature. Feeding system and ripening time had a significant effect on the volatile profile of the Cheddar cheeses. Pasture-derived Cheddar cheeses had significantly higher concentrations of the hydrocarbon toluene, whereas TMR-derived cheese had significantly higher concentration of 2,3-butanediol. Ripening period resulted in significant alterations to cheese volatile profiles, with increases in acid-, alcohol-, aldehyde-, ester-, and terpene-based volatile compounds. This study has demonstrated the benefits of pasture-derived feeding systems for production of Cheddar cheeses with enhanced nutritional and rheological quality compared with a TMR feeding system.     

Utilization of microfiltration or lactoperoxidase system or both for manufacture of Cheddar cheese from raw milk

The objective of the present study was to determine if application of microfiltration (MF) or raw milk lactoperoxidase system (LP) could reduce the risk of foodborne illness from Escherichia coli in raw milk cheeses, without adversely affecting the overall sensory acceptability of the cheeses. Escherichia coli K12 was added to raw milk to study its survival as a non-pathogenic surrogate organism for pathogenic E. coli. Five replications of 6 treatments of Cheddar cheese were manufactured. The 6 treatments included cheeses made from pasteurized milk (PM), raw milk (RM), raw milk inoculated with E. coli K12 (RME), raw milk inoculated with E. coli K12 + LP activation (RMELP), raw milk inoculated with E. coli K12 + MF (MFE), and raw milk inoculated with E. coli K12 + MF + LP activation (MFELP). The population of E. coli K12 was enumerated in the cheese milks, in whey/curds during cheese manufacture, and in final Cheddar cheeses during ripening. Application of LP, MF, and a combination of MF and LP led to an average percentage reduction of E. coli K12 counts in cheese milk by 72, 88, and 96%, respectively. However, E. coli K12 populations significantly increased during the manufacture of Cheddar cheese for the reasons not related to contamination. The number of E. coli K12, however, decreased by 1.5 to 2 log cycles during 120 d of ripening, irrespective of the treatments. The results suggest that MF with or without LP significantly lowers E. coli count in raw milk. Hence, if reactivation of E. coli during cheese making could be prevented, MF with or without LP would be an effective technique for reducing the counts of E. coli in raw milk cheeses. The cheeses were also analyzed for proteolysis, starter and nonstarter lactic acid bacteria (NSLAB), and sensory characteristics during ripening. The concentration of pH 4.6 soluble nitrogen at 120 d was greater in PM cheese compared with the other treatments. The level of 12% trichloroacetic acid-soluble nitrogen at 120 d was greater in RM, RME, and RMELP cheeses compared with PM, MFE, and MFELP cheeses. This could be related to the fact that cheeses made from raw milk with or without LP (RM, RME, and RMELP) had greater levels of NSLAB compared with PM, MFE, and MFELP cheeses. Cheeses at 60 d, as evaluated by 8 trained panelists, did not differ in bitterness, pastiness, or curdiness attributes. Cheeses at 120 d showed no differences in acid-taste, bitterness, or curdiness attributes. Sensory analysis at 60 d showed that PM and MFELP cheeses had greater overall sensory acceptability than RM and RME cheeses. The overall sensory acceptability of the cheeses at 120 d showed that PM, MFE, and MFELP cheeses were more acceptable than RM and RME cheeses.     

Enhanced nutty flavor formation in cheddar cheese made with a malty Lactococcus lactis adjunct culture

Nutty flavor in Cheddar cheese is desirable, and recent research demonstrated that 2- and 3-methyl butanal and 2-methyl propanal were primary sources of nutty flavors in Cheddar. Because malty strains of Lac-tococcus lactis (formerly Streptococcus lactis var. malti-genes) are characterized by the efficient production of these and other Strecker aldehydes during growth, this study investigated the influence of a malty L. lactis adjunct culture on nutty flavor development in Cheddar cheese. Cheeses made with different adjunct levels (0, 10⁴ cfu/mL, and 10⁵ cfu/mL) were ripened at 5 or 13°C and analyzed after 1 wk, 4 mo, and 8 mo by a combination of instrumental and sensory methods to characterize nutty flavor development. Cheeses ripened at 13°C developed aged flavors (brothy, sulfur, and nutty fla-vors) more rapidly than cheeses held at 5°C. Additionally, cheeses made with the adjunct culture showed more rapid and more intense nutty flavor development than control cheeses. Cheeses that had higher intensities of nutty flavors also had a higher concentration of 2/3-methyl butanal and 2-methyl propanal compared with control cheeses, which again confirmed that these compounds are a source of nutty flavor in Cheddar cheese. Results from this study provide a simple methodology for cheese manufacturers to obtain consistent nutty flavor in Cheddar cheese.     

Improvement of texture and structure of reduced-fat Cheddar cheese by exopolysaccharide-producing lactococci

The objective of this study was to evaluate the effect of capsular and ropy exopolysaccharide (EPS)-producing strains of Lactococcus lactis ssp. cremoris on textural and microstructural attributes during ripening of 50%-reduced-fat Cheddar cheese. Cheeses were manufactured with added capsule- or ropy-forming strains individually or in combination. For comparison, reduced-fat cheese with or without lecithin added at 0.2% (wt/vol) to cheese milk and full-fat cheeses were made using EPS-nonproducing starter, and all cheeses were ripened at 7°C for 6 mo. Exopolysaccharide-producing strains increased cheese moisture retention by 3.6 to 4.8% and cheese yield by 0.28 to 1.19 kg/100 kg compared with control cheese, whereas lecithin-containing cheese retained 1.4% higher moisture and had 0.37 kg/100 kg higher yield over the control cheese. Texture profile analyses for 0-d-old cheeses revealed that cheeses with EPS-producing strains had less firm, springy, and cohesive texture but were more brittle than control cheeses. However, these effects became less pronounced after 6 mo of ripening. Using transmission electron microscopy, fresh and aged cheeses with added EPS-producing strains showed a less compact protein matrix through which larger whey pockets were dispersed compared with control cheese. The numerical analysis of transmission electron microscopy images showed that the area in the cheese matrix occupied by protein was smaller in cheeses with added EPS-producing strains than in control cheese. On the other hand, lecithin had little impact on both cheese texture and microstructure; after 6 mo, cheese containing lecithin showed a texture profile very close to that of control reduced-fat cheese. The protein-occupied area in the cheese matrix did not appear to be significantly affected by lecithin addition. Exopolysaccharide-producing strains could contribute to the modification of cheese texture and microstructure and thus modify the functional properties of reduced-fat Cheddar cheese.     

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.