利用3种凝固剂制作新鲜软质大豆干酪的工艺研究

以豆乳为原料,分别以葡萄糖酸内酯、氯化镁和木瓜蛋白酶为凝固剂制作新鲜软质大豆干酪。用正交试验法对发酵剂、凝固剂及食盐的添加量等参数进行优化,并将3种大豆干酪的主要理化指标及感官与牛奶新鲜软质干酪进行比较。结果表明,以葡萄糖酸内酯为凝固剂制备新鲜软质大豆干酪的最适工艺参数为发酵剂添加量0.020%、葡萄糖酸内酯添加量0.20%、食盐添加量1.0%;氯化镁为凝固剂的最适工艺参数为发酵剂添加量0.020%、氯化镁添加量0.20%、食盐添加量1.0%;木瓜蛋白酶为凝固剂的最适工艺参数为发酵剂添加量0.010%、CaCl2添加量0.02%、木瓜蛋白酶添加量0.05%、食盐添加量1.0%。3种大豆干酪的水分含量相近,木瓜蛋白酶大豆干酪感官得分最高,氯化镁大豆干酪的蛋白含量最高,而葡萄糖酸内酯大豆干酪的产率最高。与相同工艺下制作出的牛乳新鲜软质干酪相比,新鲜软质大豆干酪蛋白质含量与之相近,脂肪含量只有牛乳干酪的1/3,水分含量和出品率高于牛乳干酪,而感官评分上大豆干酪略低。新鲜软质大豆干酪可作为一种牛乳新鲜软质干酪的低脂保健型替代品。     

奶油干酪生产关键工艺参数研究

为研究奶油干酪的关键工艺参数,通过奶油干酪制作工艺过程中氯化钙添加量、凝乳酶添加量、凝乳温度、脂肪添加量这些工艺参数的设计,以产率、蛋白质含量、脂肪含量、水分含量、感官品质为评价指标进行实验,通过正交优化分析试验得到最佳的工艺参数组合为凝乳酶添加量0.002g/mL、凝乳温度32℃、脂肪添加量12%、氯化钙添加量0.01g/mL。所得最佳工艺效果较好,可作为奶油干酪的实际生产工艺。     

白牦牛乳软质干酪的加工及其质构特性的研究

以甘肃天祝牧区白牦牛乳为原料制作软质干酪。优化了加工白牦牛乳软质干酪的工艺参数,并测定其保藏期前后的理化指标和质构。结果表明,牦牛乳软质干酪在发酵剂添加量2g/100mL,凝乳温度35℃,凝乳pH5.9,CaCl2添加量0.01g/100mL时,品质最佳,出品率为22.5g/100g;保藏30d后的软质干酪与新鲜干酪相比,其非脂物质水分含量(P0.01)、干物质脂肪含量(P0.01)、胶着性(P0.05)、硬度(P0.01)和咀嚼性(P0.01)均有显著变化。     

甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响

为了探究甲醇芽孢杆菌（Bacillus methanolicus）凝乳酶在马苏里拉干酪加工中的应用,分别以使用甲醇芽孢杆菌凝乳酶、混合酶制剂（含质量分数10%甲醇芽孢杆菌凝乳酶和90%商品凝乳酶）制作的马苏里拉干酪作为实验组,以商品凝乳酶干酪作为对照组,测定不同组别干酪成熟期间的蛋白水解特性、质构、风味和微观结构变化,研究甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响。结果表明,实验组干酪在成熟过程中pH值（4.6～5.3）、微生物数量（8.80～9.68（lg（CFU/g）））与对照组无显著差异（P＞0.05）;实验组干酪水分质量分数（混合酶干酪为（43.21±1.17）%、甲醇芽孢杆菌凝乳酶干酪为（46.15±0.94）%）均显著高于对照组（（41.08±1.04）%）,得率（混合酶干酪为（9.27±0.17）%、甲醇芽孢杆菌凝乳酶干酪为（9.46±0.16）%）也显著高于对照组（（8.98±0.13）%）（P＜0.05）;且实验组干酪的蛋白水解特性（pH 4.6时可溶性蛋白、酪蛋白水解程度和游离氨基酸质量分数）以及风味物质种类和相对含量等指标也优于对照组干酪。但是实验组中甲醇芽孢杆菌凝乳酶干酪保形性相对欠佳,感官评定得分偏低,混合酶干酪与对照组质构及感官基本得分一致,因此甲醇芽孢杆菌凝乳酶可以作为商品酶的部分代替品应用于干酪的生产中。     

稀奶油对农家干酪品质的影响

研究稀奶油对农家干酪品质的影响,确定农家干酪中稀奶油的最适添加量。采用短时发酵工艺的方法,设计5组实验,通过添加不同比例的稀奶油制作农家干酪,国标法分别测定五组实验中农家干酪的水分含量和蛋白质含量,质构仪和流变仪测定产品质构和相应流变学特性,同时对干酪产率和融化特性进行评估,最后从风味,质地及外观上对农家干酪进行感官学品评测试。结果表明:随着稀奶油添加量的增多,干酪的水分含量增加;产率增加;硬度下降;弹性模量降低;干酪风味和外观评分逐渐升高。确定农家干酪中的稀奶油最适添加量为5.2%。     

强化维生素C的涂抹型再制干酪的研制

使用2个月和7个月的天然契达干酪为原料制作涂抹型再制干酪,对其进行VC强化,测定VC含量及其在产品中的稳定性。同时研究水分、乳化盐添加量对再制干酪质构的影响。使用木糖醇、白砂糖、葡萄糖调整产品口味。结果表明:2个月成熟干酪与7个月成熟干酪以2:1的配比,50%水,2%的乳化盐焦磷酸钠与三聚磷酸钠(1:1),80℃,1 500 r/min搅拌10min,加入VC,2%木糖醇、3%白砂糖与2%葡萄糖搅拌3min,得到易于保存,风味良好的产品。VC含量在储存期间无较大改变。     

嗜酸乳杆菌发酵生产低脂干酪凝乳工艺的优化

以脱脂乳为原料,采用嗜酸乳杆菌发酵进行预酸化,对其生产的低脂干酪凝乳工艺条件进行了研究。实验选取凝乳pH、氯化钙添加量、凝乳酶添加量、凝乳温度4个影响因素,以干酪产率、乳清中非脂乳固体物质残留量、嗜酸乳杆菌活菌数为指标,采用L₉（3⁴）正交实验进行优化。结果表明,凝乳的最佳工艺参数为凝乳pH6.0,氯化钙添加量0.02%（w/w）,凝乳酶添加量0.01%（w/w,酶活20000u/g）,凝乳温度35℃,以此条件生产的低脂干酪脂肪含量小于5%,干酪产率29.41%,乳清中非脂乳固体物质残留量5.66%,嗜酸乳杆菌活菌数在10⁹cfu/mL以上。     

甘蔗渣制茶工艺优化

本研究利用甘蔗榨汁后的甘蔗渣制作甘蔗茶,通过二次回归正交旋转组合试验探讨了炒制温度、炒制时间和转速对甘蔗茶感官评分的影响,确定最优制作工艺条件,并测定最优制备工艺下甘蔗茶营养成分含量。结果表明,炒制温度为127 ℃,炒制时间33 min,转速为60 r/min时,在此条件下,甘蔗渣制茶工艺最优,感官评分为92.47分,感官评价良好,此时甘蔗茶营养成分含量分别为:脂肪0.25%±0.06%,蛋白质1.99%±0.39%,还原糖7.26%±0.38%,水分6.48%±0.27%,灰分1.89%±0.20%,该研究可为甘蔗渣利用提供参考。     

白牦牛乳硬质干酪加工工艺技术研究

以甘肃天祝牧区白牦牛乳为原料制作硬质干酪,优化加工白牦牛乳硬质干酪的工艺参数,并用扫描电镜(SEM)观察成熟期干酪的微观结构。结果表明,白牦牛乳硬质干酪在发酵剂添加量3%,凝乳酶添加量30μl/100ml,凝乳温度40℃,凝乳pH6.1,氯化钙添加量0.03% 时,品质较好,其成熟30d 时蛋白质含量为27.82%,脂肪含量为36.43%,出品率为15.5%;成熟30d 和90d 的白牦牛乳干酪微观结构变化明显。     

冷藏乳制作的牦牛乳硬质干酪成熟过程中生物胺含量的变化

目的:揭示冷藏原料乳制作的干酪成熟过程中生物胺含量变化规律,评价其质量安全性。方法:以冷藏24,48,72 h牦牛乳制作的硬质干酪为研究对象,利用高效液相色谱法对干酪成熟过程中生物胺含量进行测定。结果:在0～6个月成熟过程中,不同冷藏牦牛乳制作的硬质干酪中生物胺含量呈升高趋势。牦牛乳冷藏时间从24 h延长到72 h时,其干酪中总生物胺、2-苯乙胺、尸胺、酪胺和腐胺含量也依次增大。成熟4个月后,冷藏72 h牦牛乳制作的硬质干酪中各生物胺含量明显高于其余两组干酪。成熟6个月时,冷藏72 h原料乳制作的牦牛乳硬质干酪中生物胺总量和酪胺含量分别为(212.94±8.03),(81.04±3.92) mg/kg。结论:随着原料乳冷藏时间和干酪成熟时间的延长,干酪中生物胺含量增多,但是原料乳冷藏时间低于72 h时,其干酪中生物胺含量低于学者建议含量。     

Prediction of Inorganic Salt and Moisture Content of Process Cheese Using Dielectric Spectroscopy

The development of on-line sensors for compositional analysis during cheese manufacture is desirable for improved quality control. Dielectric properties of a food product are principally determined by its moisture and salt content. This indicates that dielectric spectroscopy may offer a rapid, on-line and non-destructive method for the determination of moisture and salt content of process cheese. However limited information is available in the literature on the dielectric properties of process cheese. Therefore the aims of this study are to investigate the dielectric properties of process cheese samples over a range of compositional parameters and to assess the potential of dielectric spectroscopy to improve process control during process cheese manufacture. Dielectric spectra of process cheese samples were measured using a coaxial line probe between 300 MHz and 3 GHz. A clear tend was observed between higher moisture content and increases in the dielectric constant. Inorganic salt content was found to have a major influence on the loss factor. The dielectric data obtained was used to develop chemometric models for the prediction of moisture and inorganic salt content of two experimental sets of process cheese samples (exp A and exp B). The root mean square error of prediction (RMSEP) for the models developed to predict moisture content were 0.524% (w/w) (exp A), and 0.423% (w/w) (exp B), while the RMSEP of the inorganic salt models were 0.220% (w/w) (exp A), and 0.263% (w/w) (exp B). It was concluded that dielectric spectroscopy has potential application for compositional analysis in process cheese manufacture.     

Prediction of moisture in cheese of commercial production using neural networks

Control of cheese moisture is paramount to maximizing yield and profitability of a cheesemaking operation. Modeling and prediction of cheese moisture prior to pressing from a large industrial database for stirred-curd Cheddar cheese made with non-standardized and standardized milk was carried out using neural networks (NN). The number of model input variables was reduced by removing or combining some of them, based on cheesemaking knowledge and on the results of two tests estimating the impact of each model input. Input removal was carried out until the validation mean absolute prediction error (MAPE) increased. An initial NN cheese moisture model with 38 input process variables, coded as 57 NN inputs, was reduced to one with 21 input process variables, coded as 34 NN inputs. For the latter, the validation MAPE was 0.53% cheese moisture in a range of cheese moisture of 13.2%, and 0.51% for the best 25% of models (out of 100). For the range of operating conditions of the process in this study, four main groups of variables were found to be the most influential on the prediction of cheese moisture: cutting and subsequent stirring of the curd, curd rinsing temperature, starter quantity, activity and strain, and seasonal variation of milk composition. The NN model with the selected input variables and optimized number of hidden neurons was then used to predict cheese moisture for ranges of these variables. This study showed that NN models can successfully extract input–output variable relationships from industrial production data in spite of the inherent error in these data. The resulting NN models can be used both for research to develop the base of knowledge on production variables and their complex interactions, as well as for the prediction of cheese moisture.     

Linear Viscoelastic Properties of Regular- and Reduced-Fat Pasteurized Process Cheese During Heating and Cooling

The rheology of process cheese during heating and cooling was examined by measuring the transient and dynamic linear viscoelastic properties of regular fat, lower moisture and an 80% reduced-fat, higher moisture pasteurized process cheese from 10 to 50°C. The dynamic (stress and frequency sweep) and transient (creep and recovery) rheological properties of the reduced-fat process cheese were found to be higher than that of regular-fat process cheese, indicating that fat content changed rheological properties more than moisture content. The temperature-dependent frequency dispersions of storage and loss moduli (dynamic mechanical spectra) were fitted with a power-law model, and master curves (at a reference temperature of 30°C) and shift factors were obtained by shifting the temperature-dependent frequency dispersion of dynamic mechanical spectra. The relaxation spectra (moduli, viscosities and relaxation times) of both cheeses were obtained from the master curves using the generalized Maxwell model and nonlinear regression. The viscosity distribution of corresponding Maxwell model elements were higher for the reduced-fat cheese by a factor of 1.6–4.7 compared to the regular-fat cheese, indicating that the higher moisture content in the reduced-fat process cheese did not loosen the protein matrix or soften the cheese even though higher moisture is recommended to cheese manufacturers in order to compensate for some textural defects in reduced-fat cheeses.     

Composition of Ragusano cheese during aging

Ragusano cheese is a brine-salted pasta filata cheese. Composition changes during 12 mo of aging were determined. Historically, Ragusano cheese has been aged in caves at 14 to 16 degrees C with about 80 to 90% relative humidity. Cheeses (n = 132) included in our study of block-to-block variation were produced by 20 farmhouse cheese makers in the Hyblean plain region of the Province of Ragusa in Sicily. Mean initial cheese block weight was about 14 kg. The freshly formed blocks of cheese before brine salting contained about 45.35% moisture, 25.3% protein, and 25.4% fat, with a pH of 5.25. As result of the brining and aging process, a natural rind forms. After 12 mo of aging, the cheese contained about 33.6% moisture, 29.2% protein, 30.0% fat, and 4.4% salt with a pH of 5.54, but block-to-block variation was large. Both soluble nitrogen content and free fatty acid (FFA) content increased with age. The pH 4.6 acetate buffer and 12% TCA-soluble nitrogen as a percentage of total nitrogen were 16 and 10.7%, respectively, whereas the FFA content was about 643 mg/100 g of cheese at 180 d. Five blocks of cheese were selected at 180 d for a study of variation within block. Composition variation within block was large; the center had higher moisture and lower salt in moisture content than did the outside. Composition variation within blocks favored more proteolysis and softer texture in the center.     

Soluble Hydrocolloids Enable Fat Reduction in Process Cheese Spreads

Aqueous dispersions of soluble hydrocolloids replaced lipids in process cheese spreads. About 40% and 50% fat reduction was obtained relative to a control cheese spread containing 25% fat by increasing moisture to 62% and 68%, respectively, and eliminating a portion of fat from the formulation. Xanthan, λ-carrageenan, three types of high-methoxyl pectin, propylene glycol alginate, low-viscosity guar and Zooglan 115 gums were added to process cheese spreads at 0.18% to 4.1% wet basis. Spreads with 2.2%λ -carrageenan, 1.7% to 2.2% pectin or 1.7% low-viscosity guar had textures consistent with a high-fat cheese control. Above these gum levels, cheese spread firmness (by Instron measure) increased while melt decreased. A 15% fat, 62% moisture cheese spread with 1.7% pectin was most like the control. In sensory studies it was less preferred than a control spread (25% fat, 48% moisture) due partially to less flavor.     

Effect of natural cheese characteristics on process cheese properties

Natural cheese is the major ingredient utilized to manufacture process cheese. The objective of the present study was to evaluate the effect of natural cheese characteristics on the chemical and functional properties of process cheese. Three replicates of 8 natural (Cheddar) cheeses with 2 levels of calcium and phosphorus, residual lactose, and salt-to-moisture ratio (S/M) were manufactured. After 2 mo of ripening, each of the 8 natural cheeses was converted to 8 process cheese foods that were balanced for their composition, including moisture, fat, salt, and total protein. In addition to the standard compositional analysis (moisture, fat, salt, and total protein), the chemical properties (pH, total Ca, total P, and intact casein) and the functional properties [texture profile analysis (TPA), modified Schreiber melt test, dynamic stress rheometry, and rapid visco analysis] of the process cheese foods were determined. Natural cheese Ca and P, as well as S/M, significantly increased total Ca and P, pH, and intact casein in the process cheese food. Natural cheese Ca and P and S/M also significantly affected the final functional properties of the process cheese food. With the increase in natural cheese Ca and P and S/M, there was a significant increase in the TPA-hardness and the viscous properties of process cheese food, whereas the meltability of the process cheese food significantly decreased. Consequently, natural cheese characteristics such as Ca and P and S/M have a significant influence on the chemical and the final functional properties of process cheese.     

Effect of fat reduction on chemical composition, proteolysis, functionality, and yield of Mozzarella cheese

Mozzarella cheese was made from skim milk standardized with cream (unhomogenized, 40% milk fat) to achieve four different target fat percentages in the cheese (ca. 5, 10, 15, and 25%). No statistically significant differences were detected for cheese manufacturing time, stretching time, concentration of salt in the moisture phase, pH, or calcium as a percentage of the protein in the cheese between treatments. As the fat percentage was reduced, there was an increase in the moisture and protein content of the cheese. However, because the moisture did not replace the fat on an equal basis, there was a significant decrease in the moisture in the nonfat substance in the cheese as the fat percentage was reduced. This decrease in total filler volume (fat plus moisture) was associated with an increase in the hardness of the unmelted cheese. Whiteness and opacity of the unmelted cheese decreased as the fat content decreased. Pizza baking performance, meltability, and free oil release significantly decreased as the fat percentage decreased. The minimum amount of free oil release necessary to obtain proper functionality during pizza baking was between 0.22 and 2.52 g of fat/100 g of cheese. Actual cheese yield was about 30% lower for cheese containing 5% fat than for cheese with 25% fat. Maximizing fat recovery in the cheese becomes less important to maintain high cheese yield, and moisture control and the retention of solids in the water phase become more important as the fat content of the cheese is reduced.     

A multi-component approach to salt and water diffusion in cheese

A theoretically based model was developed using the Maxwell–Stefan equation to predict the salt gain and moisture loss of cheese during brine salting. The model was used to predict changes in the salt and moisture profile, and dimensions of the cheese. The best solutions were obtained when the diffusivities were made functions of porosity and salt concentration. For Gouda cheese the predicted moisture and salt/moisture profiles were within 0.6% moisture and 0.3% salt/moisture of published experimental data. The model predicted an overall gain in salt of 1.55% by weight, an overall reduction in moisture from 43.4 to 41.0%, a mass loss of 1.5% and a volume reduction of 2.6% after 8 days of brining.     

Application of salt whey in process cheese food made from Cheddar cheese containing exopolysaccharides

The objective of this work was to use salt whey in making process cheese food (PCF) from young (3-wk-old) Cheddar cheese. To maximize the level of salt whey in process cheese, low salt (0.6%) Cheddar cheese was used. Because salt reduction causes undesirable physiochemical changes during extended cheese ripening, young Cheddar cheese was used in making process cheese. An exopolysaccharide (EPS)-producing strain (JFR) and a non-EPS-producing culture (DVS) were applied in making Cheddar cheese. To obtain similar composition and pH in the EPS-positive and EPS-negative Cheddar cheeses, the cheese making protocol was modified in the latter cheese to increase its moisture content. No differences were seen in the proteolysis between EPS-positive and EPS-negative Cheddar cheeses. Cheddar cheese made with the EPS-producing strain was softer, and less gummy and chewy than that made with the EPS-negative culture. Three-week-old Cheddar cheese was shredded and stored frozen until used for PCF manufacture. Composition of Cheddar cheese was determined and used to formulate the corresponding PCF (EPS-positive PCF and EPS-negative PCF). The utilization of low salt Cheddar cheese allowed up to 13% of salt whey containing 9.1% salt to be used in process cheese making. The preblend was mixed in the rapid visco analyzer at 1,000 rpm and heated at 95°C for 3 min; then, the process cheese was transferred into copper cylinders, sealed, and kept at 4°C. Process cheese foods contained 43.28% moisture, 23.7% fat, 18.9% protein, and 2% salt. No difference in composition was seen between the EPS-positive and EPS-negative PCF. The texture profile analysis showed that EPS-positive PCF was softer, and less gummy and chewy than EPS-negative PCF. The end apparent viscosity and meltability were higher in EPS-positive PCF than in EPS-negative PCF, whereas emulsification time was shorter in the former cheese. Sensory evaluation indicated that salt whey at the level used in this study did not affect cheese flavor. In conclusion, process cheese, containing almost 13% salt whey, with improved textural and melting properties could be made from young EPS-positive Cheddar cheese.