Casein Degradation of Fynbo Cheese Salted with NaCl/KCl Brine and Ripened at Various Temperatures

ABSTRACT: Effect of temperature and salt substitution on casein degradation of Fynbo cheese was studied. Fynbo cheeses, salted in solutions of 190 g NaCl/L and of 100 g NaCl/L and 100 g KCl/L and ripened at 5, 12, and 16 °C, were sampled at 1, 5, 10, 20, 30, 60, and 90 d of ripening, at central and external zones. Samples were analyzed for moisture and chloride contents, maturation index, and casein degradation by urea‐polyacrylamide gel electrophoresis. NaCl replacement by KCl did not affect any of the parameters studied. Total salt concentration and ripening temperature affected proteolysis significantly. First‐order kinetics constants for α_s1‐casein degradation were in the range of 0.002 to 0.016 day^‐1 and the activation energy of the reaction was approximately 26 kcal/gmol.     

Fynbo Cheese NaCl and KCl Changes during Ripening

In a model study we assumed that the cheese is a homogeneous solid with nonuniform initial concentration distributions, cheese surfaces are rendered impermeable after brining, and the generalized Fick's law form is valid for expressing the diffusive fluxes of solutes. NaCl and KCl concentrations at selected positions during distribution in Fynbo cheese kept at 12°C, after salting 10 hr in a brine of 100 g NaCl/L and 100 g KCl/L at the same temperature, were determined experimentally and compared with predicted values with the model at different storage times up to 30 days. Homogeneous distribution of solutes was reached at 20 days ripening, as predicted by the model and verified experimentally.     

Kinetics of Proteolysis of β-Casein During Ripening of Fynbo Cheese Salted with NaCl or NaCl/KCl and Ripened at Different Temperatures

ABSTRACT: The proteolysis of β-casein during ripening of low-fat Fynbo cheese was studied using 1st-order kinetics to improve the knowledge of the p-casein hydrolysis in Fynbo cheeses salted with NaCl or NaCl/KCl and ripened at different temperatures. Effects of ripening temperature, partial replacement of NaCl by KCl during cheese salting, and total salt concentration were evaluated. Central and external zones from cheeses at 1, 5, 10, 20, 30, 60, and 90 ripening days were analyzed by polyacrylamide gel electrophoresis. No significant differences in the kinetic parameters were observed between cheeses salted with NaCl and those salted with a NaCl/KCl brine. Kinetic constants were significantly affected by region within cheese and ripening temperature. Kinetic constant values were in the range of 0.004/d to 0.018/d, and the activation energy of the reaction was approximately 19 kcal/gmol.     

Proteolysis of Fynbo Cheese Salted with NaCl/KCl and Ripened at Two Temperatures

Cheeses salted in solutions of 100g NaCl/L and 100g KCl/L and ripened for 90 days at 12°C and 16°C were compared with cheeses salted in brine of 190g NaCl/L and ripened at the same temperatures. Peptides of the water-soluble nitrogen (WSN) fraction were quantified by the Kjeldahl method and analyzed by reverse-phase HPLC. There were no differences (P>0.05) attributable to salt treatments; and the cheeses stored at 16°C showed higher levels of WSN/Total Nitrogen (TN) than cheeses ripened at 12°C. HPLC profiles of WSN extracts showed differences in the hydrophilic zone for cheeses ripened at different temperatures, but profiles were similar for cheeses salted with NaCl and with NaCl/KCl.     

Modeling NaCl and KCl Movement in Fynbo Cheese during Salting

A model considering a ternary diffusion in axial and radial directions of a finite cylindrical solid was developed for predicting NaCl and KCl concentrations in cheese during brining. The generalized Fick's law form, negligible external mass transfer resistance, and an equilibrium between cheese and brine solution were assumed. Cheese samples (12 × 6 cm) were salted in a KCl-NaCl) brine solution. NaCl and KCl concentrations were determined experimentally and theoretically at 5, 10 and 15 hr. The average relative error of the model was higher for KCl than for NaCl and increased with brining time. The model can be applied to systems of similar geometry and conditions provided diffusion constants are known.     

Secondary proteolysis of Fynbo cheese salted with NaCl/KCl brine and ripened at various temperatures

Effects of temperature and salt substitution on secondary proteolysis of Fynbo cheese were studied and different peaks of the chromatographic profiles were examined. Cheeses, salted in solutions of NaCl (190 g l⁻¹) and NaCl/KCl (100 g l⁻¹/100 g l⁻¹) and ripened at 5, 12, and 16 °C, were sampled during 90 days at two different zones. Samples were analysed by RP-HPLC of the trichloroacetic acid-soluble fraction. The information was successfully summarized in 2 dimensions, accounting for 86.5% of data variation using principal component analysis. The source of variation explained by PC1 (77.1% VAR) was related to the ripening time. Two groups of chromatographic peaks were distinguished according to the sign of PC2 loading. Total salt concentration and ripening temperature affected secondary proteolysis significantly, while NaCl replacement by KCl had no affect. An important peptide produced during cheese ripening (α_s1-casein (f1-23)) was tentatively identified, taking into account the chromatographic profile and the amino acid composition of the peak isolated.     

成熟温度和时间对Cheddar干酪成熟特性的影响研究

通过对不同成熟参数下Cheddar干酪蛋白分解、质构、pH及感官评价的分析,探讨了成熟参数对Cheddar干酪的影响,并得出研究条件下的最优成熟温度和时间,分析了Cheddar干酪在成熟过程中的游离氨基酸变化情况。     

豆奶干酪成熟过程中蛋白水解的研究

本文主要研究了豆奶干酪成熟过程中蛋白水解的变化,并与纯牛乳干酪进行比较。结果表明:豆奶干酪中pH4.6 SN 和12%TCA SN随着时间的延长逐渐增高,而且pH4.6 SN的增长速度比12%TCA SN快,这与纯牛乳干酪是一致的,但豆奶干酪的可溶性氮低于同一时期的纯牛乳干酪。     

Monitoring Proteolysis During Cheddar Cheese Ripening Using Two-Dimensional Gel Electrophoresis

A 2-D gel electrophoretic method, consisting of isoelectric focusing and alkaline urea-PAGE was used to monitor proteolysis during ripening (180d, 5°C and 8°C) of full- and reduced-fat Cheddar cheese. The method enabled quantifying changes in levels of peptides in cheese with good spot-resolution. Results can complement those from other analyses, especially those for determining low MW peptides. Notable effects were found for cheese composition and ripening temperature on gel pattern and on relative levels of selected proteolysis products. In both cheese varieties, most peptides reached a maximum during the first 3 ripening months and gradually disappeared as ripening advanced.     

Ripening Profiles of Goat Cheese Produced from Milk Treated with High Pressure

Goat cheeses were made from pasteurized (72 °C, 15 s) and high-pressure (HP)-treated milk (500 MPa, 15 min, 20 °C). At 45 days of ripening, cheeses made from both types of milk were similar in moisture, quality, electrophoretic profiles, water-soluble nitrogen, and total free fatty acid contents. Cheeses made from HP-treated milk had higher pH and salt, matured more quickly, as determined by formation of total free amino acids, and developed strong flavors. Reverse-phase high-performance liquid chromatography showed differences between the peptide profiles of the cheeses. Differences in small peptides and free amino acids indicated a higher extent of proteolysis in cheeses made from HP-treated milk.     

High Hydrostatic Pressure for Accelerating Ripening of Goat's Milk Cheese: Proteolysis and Texture

High hydrostatic pressurization is proposed for cheese ripening acceleration. Several treatments were used for accelerating ripening of goat's milk cheese: 50 MPa / 72 h, 400 MPa / 5 min and 400 MPa / 5 min followed by 50 MPa / 72 h all at 14 °C. Moisture content and pH were higher in 400 MPa treatments compared to the others. By measuring proteolysis indexes, 400 MPa treatments were found to accelerate ripening (14 d in contrast to 28 d conventionally) due to enhanced enzyme activity from inoculated starter culture. Sensory analysis indicated bitter notes in the accelerated ripened cheese. Pressurized cheeses were less crumbly and more elastic than control.     

Probiotic Cheddar Cheese: Influence of Ripening Temperatures on Proteolysis and Sensory Characteristics of Cheddar Cheeses

ABSTRACT:  Bifidobacterium longum 1941, B. animalis subsp. lactis LAFTI^® B94, Lactobacillus casei 279, Lb. casei LAFTI L26, Lb. acidophilus 4962, or Lb. acidophilus LAFTI L10 were used as an adjunct in the production of Cheddar cheeses, which were ripened at 4 and 8 °C for 24 wk. Effects of ripening temperatures and probiotic adjuncts on proteolysis and sensory evaluation of the cheeses were examined. Higher ripening temperature increased the level of proteolysis in the cheeses. Product of proteolysis and organic acids released during ripening were shown to be important for the flavor of Cheddar cheeses. There were positive and significant correlations between the levels of soluble nitrogen, lactic, acetic, and butyric acids, percentage hydrolysis of α_s1-CN and β-CN to the scores of cheddary flavor ( P < 0.05). Scores for sour-acid and vinegary flavors were higher in cheeses with the addition of Bifidobacterium sp. or Lb. casei 279 ripened at 8 °C. The scores were positively and significantly correlated to the level of lactic, acetic, and free amino acids in the cheeses ( P < 0.05). The results show that both 4 and 8 °C have potential for use in the ripening of probiotic Cheddar cheeses.     

不同菌种大豆干酪后熟过程的研究

研究了3种不同大豆干酪后熟过程的变化情况。结果表明,L.rhamnosus+S.carnosus大豆干酪具有最低的pH和最高的酸度,同时具有最高的氨基氮含量和最高的活菌数。游离氨基酸分析表明,L.rhamnosus+S.carnosus大豆干酪中的游离氨基酸总量最高;L.rhamnosus大豆干酪降解产生的游离氨基酸以谷氨酸和精氨酸为主,S.carnosus大豆干酪和L.rhamnosus+S.carnosus大豆干酪降解产生的游离氨基酸则以色氨酸为主。脂肪酸分析表明,L.rhamnosus+S.carnosus大豆干酪C20以上的长链脂肪酸得到更加充分的降解。     

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.     

Cheddar Cheese Ripening and Flavor Characterization: A Review

Cheddar cheese is a biochemically dynamic product that undergoes significant changes during ripening. Freshly made curds of various cheese varieties have bland and largely similar flavors and aroma and, during ripening, flavoring compounds are produced that are characteristic of each variety. The biochemical changes occurring during ripening are grouped into primary events including glycolysis, lipolysis, and proteolysis followed by secondary biochemical changes such as metabolism of fatty acids and amino acids which are important for the production of secondary metabolites, including a number of compounds necessary for flavor development. A key feature of cheese manufacture is the metabolism of lactose to lactate by selected cultures of lactic acid bacteria. The rate and extent of acidification influence the initial texture of the curd by controlling the rate of demineralization. The degree of lipolysis in cheese depends on the variety of cheese and may vary from slight to extensive; however, proteolysis is the most complex of the primary events during cheese ripening, especially in Cheddar-type cheese.     

成熟温度对牦牛毛霉菌奶酪成熟过程中品质的影响

文章通过研究不同成熟温度对牦牛毛霉菌奶酪成熟过程的影响,找寻最适应的温度及成熟时间.选取实验材料牦牛毛霉菌奶酪,将其置于不同的成熟温度下(20,25,30℃),选取相应成熟时间节点,测定质构、色泽、蛋白质分解、pH值等.结果 表明,成熟温度为25℃时,牦牛毛霉菌奶酪在第6天时质构达到最佳值,此时感官评分也较高.3组牦牛...     

一种毛霉表面成熟干酪的蛋白质水解作用评价

从毛豆腐中分离出一株毛霉,并应用于表面成熟干酪,以研究干酪成熟过程中所发生的蛋白质水解作用。在90d 的成熟过程中,干酪的pH 值增加;蛋白质水解作用的评价指标,如干酪外层的水溶性氮- 总氮比、pH4.6水溶性氮- 总氮比、12g/100mL 三氯乙酸可溶性氮- 总氮比,在成熟90d 后分别增加至(23.68 ± 1.07)%、(19.38 ± 1.32)%和(8.61 ± 0.85)%,并且高于干酪的内部相应指标。SDS-PAGE 和毛细管电泳分析干酪的pH4.6 不溶性组分,结果表明酪蛋白在干酪成熟过程中被降解。对干酪成熟过程中分离出的水溶性组分进行RP-HPLC 分析,结果显示成熟过程中蛋白质被水解以及形成一些新肽分子。     

Reverse-Phase HPLC Analysis of Reference Cheddar Cheese Samples for Assessing Accelerated Cheese Ripening

Applying water extracts from Cheddar cheese to an octadecyl vinyl alcohol copolymer column using a reliable auto-sampling system provided highly repeatable HPLC patterns. Two batches of standard samples of mild, medium, sharp, and extra-sharp and one batch of abused samples (rapidly aged under abnormal conditions) were analyzed. Principal component similarity (PCS) analysis indicated similar shifts of plots due to aging of the standard batches, while the plot for the abused batch deviated from the pathway of normal aging. PCS may be useful for analysis of accelerated ripening effects as well as finding unusual samples during quality control.     

提高成熟温度对加速硬质干酪成熟的影响

本文通过对4 ℃、10 ℃、20 ℃条件下硬质干酪成熟90 d过程中干酪的成熟特性进行研究,通过测定干酪在成熟期间可溶性氮含量、微观结构改变情况、pH的值改变、游离脂肪酸含量的改变、风味物质种类和含量的变化、感官得分的变化分析表明：成熟温度的提高对干酪可溶性氮含量、游离脂肪酸含量、风味物质的种类和含量的增加都有显著的促进作用,其中10 ℃下经60 d成熟和20 ℃下经30 d成熟的干酪的可溶性氮含量、游离脂肪酸含量、风味物质种类已经等同于或者大于4 ℃下经90 d成熟的酪所具有的;而且提高成熟温度后,4 ℃成熟90 d的样品同10 ℃成熟60 d的样品以及20 ℃成熟30 d的样品微观结构相差不大。虽然20 ℃下也能在一定程度加速硬质干酪的成熟,但是会对风味和组织状态产生不良影响;所以可以将硬质干酪的成熟温度提高到10 ℃。     

地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响

利用地衣芽孢杆菌凝乳酶制作切达干酪和切达干酪类似物,分析干酪成熟过程中各蛋白水解指标的变化规律,以揭示地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响。结果表明,CDF组（添加地衣芽孢杆菌D3.11凝乳酶所制切达干酪）、CD3组（添加地衣芽孢杆菌D3.11凝乳酶但未添加发酵剂制成的干酪类似物）和CCF组（添加商品凝乳酶所制切达干酪）干酪蛋白含量、pH 4.6-可溶性氮、12%三氯乙酸-可溶性氮、5%磷钨酸-可溶性氮、总游离氨基酸含量均随着成熟时间延长呈显著增加趋势,并且成熟期间CDF组干酪均显著高于CCF组干酪（P＜0.05）;十二烷基硫酸钠-聚丙烯酰氨凝胶电泳分析表明,CDF组干酪α-酪蛋白水解程度较大;pH 4.6-可溶性肽段分析表明,随着干酪的成熟,总肽含量呈先增加后下降趋势,但疏水性肽与亲水性肽的比值呈持续下降趋势,在成熟第6个月时,CDF组、CD3组和CCF组干酪疏水性肽与亲水性肽比值分别为2.668、2.822、3.788。主成分分析表明,3 组干酪的蛋白水解程度与成熟度呈正相关,与疏水性肽和亲水性肽的比值呈负相关。以上结果表明,利用地衣芽孢杆菌凝乳酶制作的干酪蛋白水解度更高,但其疏水性肽比例较小,研究结果可为地衣芽孢杆菌凝乳酶在干酪生产中的应用提供理论依据。