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。     

非成熟Mozzarella干酪的品质研究

通过改进传统Mozzarella干酪的工艺,制备了非成熟Mozzarella干酪,使用质构测定仪、改良的Schreiber实验法、电子显微等方法分别测定了样品的TPA质构、融化性、油脂析出性、拉丝性和微观结构.结果表明,非成熟Mozzarella干酪的功能特性与传统Mozzarella干酪相比有所提高;微观结构显示成熟...     

NaCl含量对Mozzarella干酪品质的影响

Mozzarella干酪中NaCl的含量影响Mozzarella干酪的品质。本试验采用3×3拉丁方试验设计,三个奶酪槽中凝乳磨碎后分别加NaCl为1%、2%、3%。研究干酪中NaCl的浓度对Mozzarella干酪的品质的影响。结果表明随着干酪中NaCl的浓度的增加,油脂析出性显著降低(p<0.05),干酪的蛋白质水解显著降低(p<0.05),干酪中NaCl的浓度对Mozzarella干酪的融化性,硬度及弹性没有显著的影响。     

Effect of frozen storage on physical properties of pasta filata and nonpasta filata Mozzarella cheeses

The effects of 1) ripening 2, 7, and 14 d at 7 degrees C before freezing; 2) tempering 7, and 14 d at 7 degrees C after freezing; and 3) frozen storage for 1 and 4 wk at -20 degrees C, on the meltability, stretchability, and microstructure of pasta filata and nonpasta filata Mozzarella cheeses were investigated. Cheeses were cut into 5 x 10 x 7-cm blocks and vacuum-sealed 1 d after manufacture. The results were compared to the corresponding results obtained with unfrozen control samples, aged at 7 degrees C between 2 and 21 d. The changes in physical properties of frozen-stored pasta filata and nonpasta filata Mozzarella cheeses were consistent with critical damage to the cheese microstructure as compared to the unfrozen control samples. Generally, aging before and tempering after freezing resulted in increased meltability of both frozen-stored pasta filata and nonpasta filata Mozzarella cheeses. The stretchability of frozen-stored pasta filata Mozzarella cheese increased during tempering, but that of nonpasta filata Mozzarella cheese decreased during aging and tempering. In most cases, one-week frozen stored pasta filata Mozzarella cheese had higher meltability and stretchability than 4-wk frozen-stored sample. For 1-wk frozen-stored nonpasta filata Mozzarella cheese, the meltability increased but stretchability decreased when it was frozen-stored for 4 wk.     

不同工艺参数对Mozzarella干酪质构和功能特性的影响

采用三因素二次通用旋转组合设计,研究热缩温度、堆酿pH、拉伸温度等关键工艺参数对全脂Mozzarella干酪的质构特性(硬度、凝聚性、弹性)和功能特性(融化性和油脂析出性)的影响规律,结果表明提高热缩温度可增加干酪硬度及干酪的油脂析出性;提高拉伸温度也可增加干酪的油脂析出性;堆酿pH对干酪的弹性有较大影响,随着堆酿pH的降低,干酪的弹性增大,并与热烫拉伸温度之间有交互作用,即低的堆酿pH和高的拉伸温度时干酪的弹性大。     

Relationships between flavoring capabilities,bacterial composition,and geographical origin of natural whey cultures used for traditional water-buffalo mozzarella cheese manufacture

Natural whey cultures (NWC) (n = 29) used for traditional water-buffalo Mozzarella cheese manufacture and arising from different geographical areas of production were characterized and grouped on the basis of their capability to develop neutral volatile compounds and according to their microbial diversity as revealed by molecular analysis. The flavoring properties of NWC were studied in dairy microcosms resembling the specific technological procedure used in the traditional water-buffalo Mozzarella cheese-making. Neutral volatile compounds were identified by high-resolution gas chromatography (HRGC)-mass spectrometry analysis while information on the microbial diversity occurring in the NWC was retrieved by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rDNA after direct DNA extraction. Neoformation volatile substances (n = 27) were found; 23 were identified and some of them recognized as odor-conferring molecules. Eight different bands, referable to eight microbial species, were obtained by PCR-DGGE analysis of the NWC. Statistical analyses were applied to PCR-DGGE and HRGC data. Interestingly, the flavoring capabilities and the microbial diversity of the NWC proved to be closely linked and both related to the geographical origin of the NWC. These results suggested a possible use of the molecular characterization of the dairy products to support the traceability criteria of typical dairy products like water-buffalo Mozzarella cheese.     

Effect of pH and calcium concentration on proteolysis in mozzarella cheese

Low-moisture Mozzarella cheeses (LMMC), varying in calcium content and pH, were made using a starter culture (control; CL) or direct acidification (DA) with lactic acid or lactic acid and glucono-delta-lactone. The pH and calcium concentration significantly affected the type and extent of proteolysis in Mozzarella cheese during the 70-d storage period at 4 degrees C. For cheeses with a similar pH, reducing the calcium-to-casein ratio from -29 to 22 mg/g of protein resulted in marked increases in moisture content and in primary and secondary proteolysis, as indicated by polyacrylamide gel electrophoresis and higher levels of pH 4.6- and 5%-PTA-soluble N. Increasing the pH of DA cheeses of similar moisture content, from approximately 5.5 to 5.9, while maintaining the calcium-to-casein ratio almost constant at approximately 29 mg/g, resulted in a decrease in primary proteolysis but had no effect on secondary proteolysis. Comparison of CL and DA cheeses with a similar composition showed that the CL cheese had higher levels of alpha(s1)-CN degradation, pH 4.6- and 5%-PTA-soluble N. Analysis of pH 4.6-soluble N extracts by reverse-phase HPLC showed that the CL cheese had higher concentrations of compounds with low retention times, suggesting higher concentrations of low molecular mass peptides and free amino acids.     

H HRMAS-NMR metabolomic to assess quality and traceability of mozzarella cheese from Campania buffalo milk

The production of Mozzarella di Bufala Campana (MBC) is relevant for the agro-food economy of the Campania Region of Italy and the mark of Protected Designation of Origin (PDO) has been assigned to MBC in relation to its geographical origin. Advanced analytical methods must be then employed to assess authenticity, traceability, and quality of MBC. ¹H HRMAS-NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Resonance) spectroscopy was applied here to directly identify specific metabolites in MBC intact samples without time-consuming sample pre-treatments. Overcrowded conventional ¹H HRMAS-NMR spectra were selectively simplified with two NMR pulse sequences: eCPMG and eDiff, by modulating spin-spin relaxation times and diffusion of MBC molecular components, respectively. Signal elaboration of edited spectra was combined with multivariate analyses to enable significant metabolic differentiation between MBC samples from two different production sites in Campania. Principal Components Analysis (PCA) for eCPMG spectra explained 97.54% of total variance between the two MBC groups for four metabolites (β-galactose, β-lactose, acetic acid, and glycerol). Less efficient was groups distinction by PCA for eDiff spectra, although differences in polyunsaturated acids, such as linoleic and linolenic acids, were highlighted. Similarly, Discriminant Analysis (DA) provided MBC group classification with 100% success in validation tests for eCPMG spectra, while DA prediction ability was reduced to 94.12% for eDiff spectra. Hierarchical Cluster Analysis (HCA) gave a totally correct classification between the two MBC groups only for eCPMG spectra. eCPMG spectra were also used to identify metabolites during MBC aging. As compared to fresh samples, 2 days old MBC samples showed increasing signals for isobutylic alcohol, lactic acid, and acetic acid. This work shows that ¹H HRMAS-NMR spectroscopy can rapidly characterise the metabolic profile of intact MBC samples and statistically distinguish the geographical origin of buffalo milk mozzarella and its freshness.     

Use of milk protein concentrate to standardize milk composition in Italian citric Mozzarella cheese making

To better exploit manufacturing facilities and standardize cheese quality, milk composition could be standardized by fortifying its protein content with a milk protein concentrate (MPC) addition so avoiding partially skimming the milk. With this aim Mozzarella cheese was obtained adding citric acid into milk standardized at 4% protein and a fat to protein ratio of 1.0. Protein fortification was obtained adding MPC produced by ultrafiltration. Milk, whey, curd, cheese and stretching water were weighed and analysed for total solid, fat and protein content, to measure component recovery and yield. Yield increase (from 13.8% to 16.7%) was due to the higher recovery of the milk total solids and proteins in MPC cheese (48.2 and 78.3%, respectively) and to the slightly higher cheese moisture, obtained with a little modification of the cheese technology when adding MPC. Milk fat in cheese was lower than that reported in literature. Hot water stretching of the curd resulted in very low losses (1%) of protein and considerable losses (14%) of fat for both control and MPC cheeses. The likely reasons of this low recovery are discussed and it can be supposed that a further cheese yield increase is possible by changing the curd stretching procedures.     

Short communication: Identification and technological characterization of yeast strains isolated from samples of water buffalo Mozzarella cheese

Sixty yeast cultures were isolated from samples of water buffalo Mozzarella, a popular “pasta filata” cheese, originating on 16 farms located in the provinces of Salerno, Caserta, and Frosinone (Italy). Strains were identified by means of 5.8S internal transcribed spacer rDNA PCR-RFLP combined with 26S rRNA gene partial sequencing and characterized for their ability to exert biochemical properties of technological interest. The recorded dominance of fermenting yeasts such as the lactose-fermenting Kluyveromyces marxianus (38.3% of the total isolates) and the galactose-fermenting Saccharomyces cerevisiae (21.6% of the total isolates) suggests that these yeasts contribute to the organoleptic definition of the water buffalo Mozzarella. The speciographic analysis revealed the presence of 7 other species rarely or never reported in a dairy environment belonging to the genera Pichia and Candida, whose role in Mozzarella cheese organoleptic properties need to be further investigated.