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.     

Effect of Added Lactobacilli on Composition and Texture of Cheddar Cheese During Accelerated Maturation

The evolution of cheese composition and texture was studied in maturing Cheddar cheese supplemented with live cells and cell homogenates of Lactobacillus casei-casei L2A in order to accelerate maturation. The pH was significantly modified by the lactic acid of the bacterial additives. The Theological properties showed the same general pattern of evolution in experimental as in control cheeses. The process we developed has led to a good-quality matured cheese with 40% increase in flavor intensity compared to control cheeses.     

Heat-Shocked Lactobacilli for Acceleration of Cheddar Cheese Ripening

The aim of this study was to establish adequate conditions for heat-shocking cells of lactobacilli, to sufficiently suppress lactic acid production without damaging the proteolytic enzyme system important for cheese maturation. Three temperatures, 65, 67 and 70°C were tested, for 22 sec. The best combination for maximum retardation of lactic acid production and minimum damage to the proteolytic system was obtained by treating cells at 67°C for 22 sec. Following such treatment, lactic acid production was retarded by 24 hr, while the proteolytic enzyme system remained scarcely unchanged.     

Accelerated Maturation of Cheddar Cheese: Influence of Added Lactobacilli and Commercial Protease on Composition and Texture

The addition of live and heat-shocked Lactobacillus casei-casei L2A and Neutrase© was tested for its ability to accelerate the maturation of Cheddar cheese. An evaluation of physicochemical and rheological properties showed that cheese pH was decreased by bacterial and enzymatic additives, while fracturability and cohesiveness were influenced principally by Neutrase. The integrated process recommended is composed of three parts: first, the addition of live L. casei-casei L2A to control the undesirable microflora, second, heat-shocked cells of the same species at a concentration of 1.0%, and third, Neutrase at a concentration not higher than 1.0 × 10^-5 AU/g of cheese. This process led to a good-quality sharp Cheddar cheese with 60% increase in flavor intensity compared to control cheese.     

Accelerated Cheddar Cheese Ripening by Added Microbial Enzymes

Good quality medium sharp Cheddar cheeses with 3-mo curing at 10 C were produced when the following enzyme combinations and concentrations were used: fungal protease 31000 (Miles), .005% + fungal lipase-MY (Meito) .00005 to .0002%; and fungal protease P-53 (Rohm & Haas), .0035% + fungal lipase-MY (Meito), .00005 to .0002%.Cheddar cheeses treated with microbial enzymes developed higher soluble protein and free volatile fatty acids and displayed better flavor and greater acceptability than control cheeses. Added microbial proteases contributed to the breakdown of casein, especially β-casein. Also, αs₁-I casein and free amino acids were high in cheeses treated with protease. Increased rate of proteolysis in enzyme-treated cheese had a direct relation to accelerated ripening.     

Influence of Homofermentative Lactobacilli on Physicochemical and Sensory Properties of Cheddar Cheese

Cheddar cheeses were produced under pilot plant conditions using a commercial Streptococcus culture amended with one of 10 homofermentative Lactobacillus strains. During the ripening period, pH, acidity, salt, moisture, fat, texture, fissure formation, gas development and sensory status were evaluated. Lactobacillus treated cheese did not differ much from the control in pH and acidity but acidity increased substantially after draining and cheddaring. Lactobacillus numbers increased at all stages as compared with the uninoculated control. High quality Cheddar cheese was produced by L. casei-subsp-casei (119-10/62) and L. casei-subsp-pseudoplantarum (137-10/62) from 7 to 12 vats aged for 2 months at 15°C and for a further 10 months at 7°C or 15°C. Fissure formation was observed in cheese made with L. casei-subsp-rhamnosus, one of the four cultures of L. casei-subsp-casei (LH13) and two of the three strains of L. casei-subsp-pseudoplantarum (83-4-12/62 and L3E). Certain Lactobacillus strains produced cheese with slight flavor defects. Other strains, in particular L. casei-subsp-rhamnosus, contributed to high acidity (72 - 0.89° domic) and low pH (5.2) at salting.     

Evaluation of Yield and Quality of Cheddar Cheese Manufactured from Milk with Added Whey Protein Concentrate

Cheddar cheese was produced from whole milk with blends of whey protein concentrates added. Two whey protein concentrate powders containing 35 or 55% protein were each reconstituted to a 15% (wt/wt) suspension and heat treated at 70°C for 15 min. Addition of the denatured whey protein concentrate suspension to the milk was at 5 or 10% by weight of the milk. Addition of reconstituted partially denatured whey protein concentrate increased cheese yields from 1.4 to 6.2% above those of the control on a 63% solids basis. The only significant (P<.05) increase in yield was from the 55% whey protein concentrate suspension at 10% replacement by weight of the milk. The correlation coefficient between percent denaturation in the whey protein concentrate and yield in this cheese was .62. Experimental cheese had decreased fat and total solids contents and increased total nitrogen, ash, and salt. Fat reduction varied from 4.3 to 18.2% below the control cheese, and total solids were from 1.7 to 8.9% below the control cheeses. Total nitrogen values of experimental cheese were from .73 to 5.64% above the control. Cheeses were evaluated organoleptically; more flavor defects were associated with increased whey protein concentrate in the experimental cheese. The most common criticism of the experimental cheese was an atypical (unclean) cheese flavor.     

Influence of Homofermentative Lactobacilli on the Microflora and Soluble Nitrogen Components in Cheddar Cheese

Cheddar cheese was manufactured by inoculation with and without cultures of homofermentative Lactobacillus strains (L. casei-subsp-casei, L. casei-subsp-pseudoptantarum, L. plantarum). Growth rate of microflora, the incidence of heterofermentative lactobacilli and the rate of proteolysis were then studied during aging. The total number of psychotrophs, mesophiles and lactic streptococci reached a maximum at 5 months but maximum numbers attained were dependent upon the curing temperature (7°C or 15°C). The acceleration of cheese ripening by Lactobacillus cultures was accompanied by a greater degree of protein hydrolysis which was detectable after 8 months aging as soluble nitrogen in TCA extracts (360 mg/100g at 15°C and 240 mg at 7°C, versus 170 mg and 75 mg, respectively, for the controls).     

Protein Quality of Cheddar Cheese Compared with Casein and Fabricated Cheese in the Rat

The protein quality of freeze-dried cheddar cheese, spray-dried cheddar cheese, freeze-dried fabricated cheddar cheese (with casein as the main protein source), and sodium caseinate was evaluated in rats using the protein efficiency ratio (PER) assay (AOAC procedures) in two feeding experiments with casein as the control. Biological evaluation of the products showed that PER values for freeze-dried cheddar cheese were significantly higher than casein (3.7 vs 2.5). Freeze-dried cheddar also had a PER value significantly higher than spray-dried cheddar cheese (3.7 vs 3.0). Freeze-dried fabricated cheddar cheese and sodium caseinate had PER values not significantly different from the casein control.     

Impact of Autolytic and Proteolytic Lactobacilli and Nisin-Producing Culture on Proteolysis and Sensory Characteristics in Cheddar Cheese

ABSTRACT: Cheddar cheeses were made using a nisin-tolerant starter culture with either Lactobacillus delbrueckii subsp. bulgaricus UL12 (autolytic strain), Lactobacillus casei subsp. casei L2A (proteolytic strain), Lactococcus lactis subsp. lactis biovar. diacetylactis UL719 (nisin producer), or of Lb. bulgaricus UL12 and Lc. diacetylactis UL719. Lb. bulgaricus UL12 produced more trichloroacetic acid-soluble nitrogen than did Lb. casei L2A, which produced more phosphotungstic acid-soluble nitrogen than did Lc. diacetylactis UL719. High-performance liquid chromatography analyses showed that either lactobacilli or Lc. diacetylactis UL719 increased the hydrophilic and hydrophobic peptide contents. Cheeses containing both Lb. bulgaricus UL12 and Lc. diacetylactis UL719 had the most intense old Cheddar cheese flavor after 6 mo of ripening.     

Milk Plasmin Activity Influence on Cheddar Cheese Quality during Ripening

Up to six-fold increase in plasmin activity in milk did not significantly (p<0.05) affect the composition (moisture, protein, NaCl) of cheese, although a slight increase in moisture and decrease in protein content of the cheese was noted. Proteolysis in cheese increased with plasmin activity, resulting in improved flavor and overall quality of the cheese after 3 and 6 months ripening. Consistently, increasing the plasmin activity in milk about three-fold resulted in cheese of superior sensory quality.     

不同发酵剂对切达干酪成熟期间品质的影响

应用乳酸乳球菌乳酸亚种LA、乳酸乳球菌乳脂亚种LC以及不同比例混合菌(LA∶LC=1∶1,LA∶LC=1∶2,LA∶LC=2∶1)制作切达干酪,研究这5种发酵剂在干酪成熟过程中对其质构、感官、风味物质形成及蛋白水解程度等方面的影响。结果表明:3种不同比例组合菌株发酵剂的蛋白水解能力适中,生产出的干酪口味清淡,其中按1∶1接种制作的干酪具有良好的成熟度、质地和风味,具有一定的商业应用价值,可将其用于切达干酪的生产。     

Salt Diffusion in Cheddar Cheese

Salt changes in Cheddar cheese made intentionally with poor salt distribution and in model systems have been determined. Salt equilibrium was not attained within blocks of Cheddar cheese during 24 wk ripening. Diffusion of salt from milled salted curd into unsalted curd in a model system likewise was very slow with a steep salt gradient still existing after 56 d.In contrast, salt diffusion in 2 × 2 × 6-cm pieces of Cheddar curd was rapid with equilibration in about 48 h. Also, salt diffusion into unsalted discs (7.4 diameter by 2 cm thick) of curd from salted discs of curd was rapid.Brine salting of Cheddar cheese showed that the diffusion coefficient was directly related to moisture content and was consistent with those obtained in other cheeses.Reasons for a slow rate of salt equilibration in nonbrine-salted Cheddar cheese are proposed.     

Rheological Evaluation of Maturing Cheddar Cheese

A number of Cheddar cheese samples of different age, pH and moisture content have been examined rheologically and electrophoretically to determine whether the progressive changes in cheese texture were related to casein proteolysis. The force-compression curves obtained by crushing cubes of cheese between small flat plates at constant speed were different for the different cheese samples and were affected by the moisture content, pH and extent of α_sl-casein proteolysis that had taken place in the cheese. These results support a model of cheese micro structure in which an extensive network involving α_sl- casein molecules traverses the cheese and as the cheese ripens, chymosin cleavage of α_sl-casein weakens the protein network. Such a model explains the rapid decrease in Cheddar cheese yield-force that occurs during the early stages of ripening.     

Cheddar Cheese from Water Reconstituted Retentates

Reconstituted creamed retentates of ultrafiltration were converted to ripened cheese by Cheddar manufacturing principles. Initially, the fresh cheeses resembled normal Cheddar but during ripening were transformed into Gouda-Swiss types with pH rising rapidly from 5.2 to approximately 6.0.Cheese composition was affected by amount of full fat retentate in reconstituted mixtures. As total milk solids increased in reconstituted retentates, cheese moisture decreased and cheese volume rose to high yields. Cheese yield efficiency showed 1.21 to 1.32 kg cheese per kg total solids. Rennet curd of higher total solids retentates formed more rapidly than normal, and curds were harder. Whey from retentate reconstituted cheeses showed relatively low ash and fat even from cheeses made with high retentate. Soluble protein in 2-mo-old cheeses held at 10° C was lower in cheese from retentates of high solids.     

Calcium Bioavailability from Ripening Cheddar Cheese

Calcium bioavailability to rats was compared from CaCl₂ (28 mM), CaCO₃, fresh milk, milk adjusted to pH 5.35, and Cheddar cheese. The cheese was manufactured from pasteurized bovine milk and all doses were labeled extrinsically with ⁴⁵Ca and ⁴⁷Ca and administered orally to rats. One label (⁴⁵Ca) was added to milk before cheese manufacture and the other (⁴⁷Ca) was added to the cheese 24 h prior to dosing. Calcium bioavailability was determined by: 1) absorption measured by whole body counting, and 2) availability for bone metabolism assessed by bone radioactivity measurements. Calcium absorption averaged 76.8% and was not affected by length of ripening (p>0.05). Absorption from CaCl₂, CaCO₃, fresh milk, milk at pH 5.35, and the cheeses was similar. The two methods gave similar estimates of relative bioavailability. The ratio of ⁴⁷Ca absorption to ⁴⁵Ca absorption for any cheese sample was significantly greater than 1, indicating extrinsic labels added after processing may overestimate Ca absorption from cheese.     

氯化钠添加量对Cheddar干酪品质和介电特性的影响

以不同氯化钠(NaCl)添加量(0%、1%、2%、3%)的切达干酪(Cheddar cheese)为材料,对其90 d成熟期内的理化指标和成熟变化进行质构特性分析和介电特性测试,研究NaCl添加量对切达干酪成熟发育的影响。结果表明,NaCl添加量对干酪的理化指标有显著影响。NaCl添加量增加,干酪水分含量和水分活度下降、脂肪含量增加,并具有显著的相关性。低添加量NaCl对干酪成熟度的促进作用明显高于高添加量,NaCl添加量为1%、2%对干酪蛋白水解为指标的成熟度有显著加速作用;高NaCl添加量(3%)对干酪成熟过程的蛋白质水解有显著的抑制作用;切达干酪相对介电常数与NaCl的添加量无显著的相关性,而干酪介电损耗因子随NaCl添加量的增加而上升。并且,NaCl添加量对切达干酪成熟期内的硬度、咀嚼性有显著影响。     

Fat Mimetics in Low-Fat Cheddar Cheese

Cheeses with 60% reduced fat content were prepared with three commercial fat mimetics. Low-fat cheeses without added fat mimetics and full-fat cheeses were prepared as controls. Cheeses were aged 3 months prior to sensory and instrumental evaluation. A low-fat cheese containing one of the fat mimetics received the highest texture scores from dairy judges and consumer panelists (P≤0.05). The low-fat control and another cheese with a fat mimetic received higher flavor scores from the trained dairy judges and consumer panelists than the other cheeses containing fat mimetics (P≤0.05). Low-fat cheeses containing fat mimetics were less rubbery than the low-fat control cheese (P≤0.05).