Bioactive peptides in ovine and caprine cheeselike systems prepared with proteases from Cynara cardunculus

The potential angiotensin-converting enzyme (ACE)-inhibitory and antioxidant activities of peptides in water-soluble extracts, obtained from raw and sterilized ovine and caprine cheeselike systems coagulated with enzymes from the plant Cynara cardunculus, were assessed. Prior to the assay, the 3,000-Da permeate from 45-d-old cheeselike systems was fractionated by tandem chromatographic techniques. Several peaks were obtained in each chromatogram, but only some were associated with ACE-inhibitory or antioxidant activity or both. Peptides Tyr-Gln-Glu-Pro, Val-Pro-Lys-Val-Lys, and Tyr-Gln-Glu-Pro-Val-Leu-Gly-Pro-* from β-casein, as well as Arg-Pro-Lys and Arg-Pro-Lys-His-Pro-Ile-Lys-His-* from α_s1-casein exhibited ACE-inhibitory activity. Peptides released upon cleavage of the peptide bond Leu190-Tyr191 (either in ovine or caprine β-casein), and corresponding to the β-casein sequence Tyr-Gln-Glu-Pro-*, possessed antioxidant activity.     

Influence of the technological properties of vegetable rennet (Cynara cardunculus) on the physicochemical,sensory and rheological characteristics of ‘Torta del Casar’ cheese

The purpose of this work was to investigate the influence of technological properties of vegetable rennet (Cynara cardunculus) on the characteristics of ‘Torta del Casar’ cheese to establish the parameters that can be useful for quality control of this coagulant. The physicochemical, microbial, texture and sensory properties of the cheeses were evaluated and correlated to clotting and proteolytic activities of the vegetable rennets used for their manufacture. The level of in vitro degradation of α‐casein and κ‐casein/β‐casein degradation ratio was found to be good tools to predict the effect of vegetable rennet on the rheological properties of these cheeses.     

Evaluation of Milk Quality in Delivering Sterilized Milk with Soft Tank Transportation System

ABSTRACT:  A new transportation system is proposed recently to improve the defects of liquid transportation by tank trucks. This method is called "soft tank transportation system"; a driver installs a sac-like container (soft tank), which is made from a tarpaulin with high-pressure resistant-waterproof zippers, in a general cargo vehicle. To evaluate the quality of sterilized milk by using the soft tank transportation system, ground and marine transportation for a long distance which took about 36 h from the shipper's loading to the receiver's unloading in a high-temperature summer season (average outside temperature was 33.4 °C) were carried out. Although the difference of milk temperature before and after the delivery varied from −0.7 to +1.4 °C, there was no difference in milk quality (fat, nonfat solids, total dissolved solids, and pH) and no coliform bacteria were detected. It can be evaluated that sterilized milk was carried in keeping good conditions by soft tank transportation system.     

Proteolysis and texture changes of a Spanish soft cheese (‘Torta del Casar’) manufactured with raw ewe milk and vegetable rennet during ripening

Proteolysis and textural changes of the Spanish ewe raw milk soft cheese of the Protected Designation of Origin Torta del Casar were studied in four different stages of ripening, with 1, 30, 60 and 90 days. In general, proteolysis in Torta del Casar cheese was weak at 1 and 30 days and it was more intense between the 30–60 days of ripening. Soluble nitrogen non‐protein nitrogen, polypeptide N and free amino acids values significantly increased during cheese ripening. Protein and casein nitrogen decreased significantly after 60 days of ripening resulting in the increase of the other nitrogen fractions measured. Caseins changes determined by capillary zone electrophoresis showed that proteolysis of β‐casein occurred faster than αs1‐casein but the latter suffered higher proteolytic degradation at the end of ripening (day 90). This pattern of degradation of caseins is reversed in other cheeses made with animal rennet. Texture analysis showed that firmness and consistency decreased along ripening while adhesiveness increased. Highly significant correlations were found between textural parameters, residual caseins levels and nitrogen fractions during maturation, which shows the importance of proteolytic changes for an optimal texture formation.     

Effect of Curd Washing Level on Proteolysis and Functionality of Low-Moisture Mozzarella Cheese Made with Galactose-Fermenting Culture

Abstract: The effect of curd washing on functional properties of low-moisture mozzarella cheese made with galactose-fermenting culture was investigated. A total of 4 curd washing levels (0%, 10%, 25%, 50% wt/wt) were used during low-moisture mozzarella cheese manufacture, and cheeses were stored for 63 d at 4 °C and the influence of curd washing on proteolysis and functionality of low-moisture mozzarella cheese were examined. Curd washing had a significant effect on moisture and ash contents. In general, moisture contents increased and ash contents decreased with increased curd washing levels. Low-moisture mozzarella cheese made with 10% curd washing levels showed higher proteolysis, meltability, and stretchability during storage than other experimental cheeses. In general, galactose contents decreased during storage; however, cheeses made with 25% and 50% curd washing levels had lower galactose contents than those with control or 10%. L*-values (browning) decreased and proteolysis increased in low-moisture mozzarella cheeses during storage.     

Inhibitory effect of Cynara cardunculus L. extract on aflatoxin B1 production by Aspergillus parasiticus in sesame (Sesamum indicum L.)

Aflatoxin B₁ has been considered as the most potent liver carcinogen for humans. One factor that stimulates the production of aflatoxins in oilseed products, such as sesame seeds and their products is the presence of high levels of fatty acids. This work presents further evidence that sesame is a favorable substrate for aflatoxin B₁ production by Aspergillus parasiticus. Moreover, the use of wild artichoke (Cynara cardunculus L.) extract was examined showing inhibition of aflatoxin B₁ production in both sesame and yeast extract sucrose medium, inoculated with A. parasiticus. More specifically, the inhibition of aflatoxin B₁ production by A. parasiticus in sesame seeds paste was 99.6% and in yeast extract sucrose medium it was 99.4%.     

发酵剂对牦牛乳硬质干酪蛋白降解和苦味关系的影响

用甘肃天祝新鲜牦牛乳为原料分别添加嗜温、嗜热和混合发酵剂制作硬质干酪,以pH 4.6-可溶性氮（soluble nitrogen,SN）、12%三氯乙酸氮（trichloroacrtic acid-N,TCA-N）、游离氨基酸（free amino acid,FAA）含量和疏水性肽/亲水性肽（S/Q）为蛋白水解度指标,研究3 种牦牛乳硬质干酪在6 个月内成熟过程中苦味和蛋白质降解之间的关系。结果表明：3 种干酪在成熟过程中pH 4.6-SN、12% TCA-N和FAA含量均呈上升趋势,苦味值与pH 4.6-SN、12% TCA-N和FAA含量成正相关,相关系数分别为0.400、0.412和0.458。3 种干酪成熟过程中S/Q的变化趋势和程度不同,嗜温发酵剂干酪中S/Q呈现降低趋势;嗜热和混合发酵剂干酪中S/Q均呈现先降低后增大的趋势,但在这两种干酪中S/Q的变化程度不同,嗜热发酵剂干酪在1～3 个月S/Q略有降低,在3～6 个月S/Q快速增大,而混合发酵剂干酪正好相反。S/Q与苦味值成极显著正相关（r=0.895）,S/Q可很好地反映干酪中苦味的强弱。而干酪中苦味强弱与蛋白质降解强弱密切相关,对蛋白降解程度越大的发酵剂制作的干酪越容易产生苦味,其中,嗜热发酵剂对干酪蛋白降解程度最大,混合发酵剂次之,嗜温发酵剂最小。     

Characterization of Crude Esterase Activity from Two Plants Used in Cheese Making: Cynara cardunculus L. and Ficus carica L.

For centuries, extracts of Cynara cardunculus and the latex of Ficus carica have been used in cheesemaking, thanks to their proteases that clot milk casein. Since esterase activity is important to release odorous compounds in cheese, in this study we characterized the esterase activity of an extract of Cynara cardunculus and the latex of Ficus carica. The results, obtained by titration, spectrophotometric techniques, zymograms, and tests on agar plates, show the presence of esterase activity in the samples tested, with affinity towards the esters of short chain fatty acids, such as acetic, propionic, and butyric acid. In conclusion, this study provides a background information on esterases of two plants used in cheesemaking and represents a starting point for further investigations of their applications, not only in dairying but also in other industries involved in the processing and transformation of lipids.     

How milk type,coagulant, salting procedure and ripening time affect the profile of free amino acids in Picante da Beira Baixa cheese

The concentration of total free amino acids (FAA) in Picante cheese increased with ripening time irrespective of the particular protocol used for manufacture (ie ratio of caprine to ovine milks, animal or plant rennet and number of salting steps). The experimental cheeses manufactured with 20% (v/v) caprine milk, coagulated with animal rennet and salted only once exhibited the highest content of total FAA by 120 days of ripening. All four manufacture parameters were statistically significant on the 0.5% level of significance in terms of total concentration of FAA. The dominating free amino acids present in the various experimental cheeses throughout the ripening period were valine, leucine and phenylalanine, each one representing more than 10% (w/w) of the total concentration of FAA. All four manufacture parameters were, in general, statistically significant with respect to the content of every single FAA, with particular emphasis on salting and ripening time. © 1999 Society of Chemical Industry     

Advantage of Eu3+‐Doped Polystyrene Microspheres Compared with Colloidal Gold Used in Immunochromatographic Assays for the Detection of Melamine in Milk

Colloidal gold and Eu³⁺‐doped fluorescent microspheres were applied as labels to develop the immunochromatographic strips for detecting melamine in milk. Under the optimized condition, the visual detection limit of colloidal gold‐immunochromatographic test strip (ICTS) was 150 μg/L of melamine in phosphate‐buffered saline (PBS), although the visual detection limit of fluorescent nanoparticles (FN)‐ICTS was 75 μg/L in PBS. As thermal acceleration test, FN‐ICTS could be stored at 37 °C for at least 11 d before sample testing, but the color of the lines on colloidal gold‐ICTS faded away after 7‐d storage. The visual result of FN‐ICTS was more stable than that of colloidal gold‐ICTS, and the fluorescence intensity of the line on FN‐ICTS could be maintained up to 30 d at 22 °C after sample testing. Once the immunochromatographic strips were used to detect melamine in milk, no negative effect of milk components on the performance of FN‐ICTS was identified, whereas the performance of colloidal gold‐ICTS was significantly influenced by milk matrix.     

Effect of the inclusion of artichoke silage in the ration of lactating ewes on the properties of milk and cheese characteristics during ripening

The effect of including artichoke silage in the rations of dairy ewes on milk characteristics and biochemical changes of ripened cheeses was evaluated. Four groups of lactating ewes were fed rations containing 0, 10, 20, or 30% artichoke silage on a dry matter basis. Bulk milk samples were collected 3 times during the feeding period, and semi-hard cheeses were manufactured and sampled during ripening. Milk composition and cheese yield were not affected by diet. Inclusion of 20 and 30% artichoke silage reduced the firmness of the curds at a level only detected by the Gelograph (Gelograph-NT, Gel-Instrumente, Thalwil, Switzerland) probe. Inclusion of artichoke silage in ewes’ diet decreased fat and total free fatty acids content of these cheeses and increased total free amino acids content. Despite the effect of diet on cheese ripening characteristics, the overall sensory scores for cheeses corresponding to artichoke silage diets were statistically higher than those for the control cheeses.     

Effect of the inclusion of whole citrus in the ration of lactating ewes on the properties of milk and cheese characteristics during ripening

The effect of including citrus fruits (CF) in the rations of dairy ewes on the milk characteristics and biochemical changes of cheeses during ripening was evaluated. For this purpose, 48 lactating ewes (Guirra breed) were divided into 4 homogeneous groups and fed with isoenergetic and isoprotein rations containing CF at 0, 10, 20, and 30% on a dry matter basis in substitution of dry barley and pelleted beet pulp. During the experimental period, 3 batches of bulk milk were collected from each group and semi-hard cheeses were manufactured. Cheeses were sampled at 15, 30, and 60 d of ripening. Milk coagulation parameters and cheese yield were not negatively affected by the inclusion of CF in the ration. Physicochemical composition of cheeses at 60 d showed statistical differences for lower total solids and fat content of 30% CF cheeses. Proteolysis of cheeses measured by water-soluble nitrogen and total free amino acids content was not influenced by the ration. Differences between rations with respect to free fatty acids were significant for medium- and long-chain free fatty acids, and therefore for total content, but differences did not show a trend related to the increase of CF in the diet. The inclusion of CF in the ration of lactating ewes up to levels of 30% did not negatively affect the properties of milk and the biochemical and sensory characteristics of cheeses.     

Effect of starter cultures on the physico‐chemical and biochemical features in ewe cheese made with extracts from flowers of Cynara cardunculus L

The effect of starter cultures on the physico‐chemical and biochemical features of Los Pedroches cheese made by using Cynara Cardunculus L extracts as vegetable coagulant was assessed. Specimens of cheese containing no starter (vats A and C) and others to which a lactic acid starter was added (vats B and D) were stored either under typical farmhouse ripening conditions (vats A and B) or in a controlled chamber at 14°C and 80% relative humidity (vats C and D) for 90 days. The addition of starter cultures and the ripening conditions where found to have no appreciable effect on the moisture, fat, protein, ash, NaCl, Ca and P contents of the cheese, nor on its water activity; however, it resulted in increased lactic acid contents and lower pH values relative to control specimens throughout ripening. The protein breakdown of the cheeses was assessed in terms of soluble nitrogen, non‐protein nitrogen, aminoacid nitrogen, ammonia nitrogen, soluble tyrosine and tryptophan, and urea‐PAGE. Proteolysis was generally more marked and rapid in cheese containing the lactic starter, the NPN, NH₃ ‐N and soluble Tyr and Trp contents of which were significantly higher than those of the cheese obtained with no starter. The PAGE technique revealed no appreciable differences between the four cheese batches studied; however, it showed the cheese to be more resistant to β‐CN hydrolysis than to α_s‐CN hydrolysis. In general, the flavour and aroma scores were higher in batches obtained with starter cultures and ripened under controlled conditions. © 1999 Society of Chemical Industry     

Effects of Size and Stability of Native Fat Globules on the Formation of Milk Gel Induced by Rennet

Rennet‐induced gelation crucially impacts cheese structure. In this study, effects of the size and stability of native fat globules on the kinetics of rennet‐induced coagulation were revealed by determining the caseinomacropeptide release rate and rheological properties of milk. Moreover, the mobility and stability of fat globules during renneting was revealed using diffusing wave spectroscopy and confocal laser scanning microscopy. By use of a 2‐stage gravity separation combined centrifugation scheme, native fat globules were selectively separated into small (SFG, D_4,3 = 1.87 ± 0.02 μm) and large fat globules (LFG, D_4,3 = 5.65 ± 0.03 μm). The protein and fat content of SFG and LFG milk were then standardized to 3.2 g/100 mL and 1.2 g/100 mL, respectively. The milk containing different sized globules were then subjected to renneting experiments in the laboratory. Reduction of globule size accelerated the aggregation of casein micelles during renneting, giving a shorter gelation time and earlier 1/l^* change. The gel produced from LFG milk was broken due to coalescent fat globules and generated coarser gel strands compared to the finer strands formed with SFG milk. Structural differences were also confirmed with a higher final storage modulus of the curd made from SFG milk than that from the LFG. In conclusion, the size of fat globules affects the aggregation of casein micelles. Moreover, fat globule coalescence and creaming during renneting, also affects the structure of the rennet gel. A better understanding of the size of globules effect on milk gelation could lead to the development of cheese with specific properties.     

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.     

中外乳及乳制品法规与主要检测指标的比较分析

乳制品质量与安全是一个全球性的重要问题。许多国家纷纷采取立法、行政、司法以及提高检验技术等多种措施,以提高乳及乳制品的质量与安全。近年来,我国进口乳及乳制品的种类和数量与日俱增,但由于国内外法规与标准检测指标差异,导致进口乳制品“安全风险难以发现”、出口乳制品“遭受贸易技术壁垒”事件频发。为维护我国进出口乳制品企业和消费者合法权益,保障乳制品质量安全,亟需明确国内外乳制品法规与标准在检测指标方面的差异,提升检测方法的针对性和准确度。本文对我国乳制品的标准现状、我国与主要贸易国在乳制品质量与安全方面主要检测指标的差异进行了比较分析,指出了中外乳制品法规、检测指标和限量值的不同,并对我国乳制品法规、检测指标及限量值等标准的改进给出了建议,以期为我国全面科学地优化进出口乳及乳制品法规提供参考。     

The Effect of Silage and Concentrate Type on Intake Behavior, Rumen Function, and Milk Production in Dairy Cows in Early and Late Lactation

The objective of this experiment was to evaluate the effect of feeding total mixed rations (TMR) that differ in structural and nonstructural carbohydrates to dairy cows in early and late lactation on short-term feed intake, dry matter intake (DMI), rumen fermentation variables, and milk yield. A 5 × 5 Latin square experiment with 15 dairy cows was repeated during early and late lactation. The 5 treatments were a TMR with (all on dry matter basis) 55% roughage (a 50:50 mixture of corn silage and grass silage) and 45% concentrate (a 50:50 mixture of concentrate rich in structural carbohydrates and concentrate rich in nonstructural carbohydrates; treatment CON), a TMR with the concentrate mixture and 55% grass silage (RGS) or 55% corn silage (RCS), and a TMR with the roughage mixture and 45% of the concentrate rich in structural carbohydrates (CSC) or the concentrate rich in nonstructural carbohydrates (CNS). Meal criteria, determined using the Gaussian-Gaussian-Weibull method per animal per treatment, showed an interaction between lactation stage and treatment. Feed intake behavior variables were therefore calculated with meal criteria per treatment-lactation stage combination. Differences in feed intake behavior were more pronounced between treatments differing in roughage composition than between treatments differing in concentrate composition, probably related to larger differences in chemical composition and particle size between corn silage and grass silage than between the 2 concentrates. The number of meals was similar between treatments, but eating time was greater in RGS (227 min/d) and lesser in RCS (177 min/d) than the other treatments. Intake rate increased when the amount of grass silage decreased, whereas meal duration decreased simultaneously. These effects were in line with a decreased DMI of the RGS diet vs. the other treatments, probably related to the high neutral detergent fiber (NDF) content. However, this effect was not found in CSC, although NDF content of the TMR, fractional clearance rate of NDF, and fractional degradation rate of NDF was similar between CSC and RGS. Rumen fluid pH was lesser, and molar proportions of acetic acid and of propionic acid were lesser and greater, respectively, in RCS compared with all other diets. Milk production did not differ between treatments. There was no effect of type of concentrate on milk composition, but diet RCS resulted in a lesser milk fat content and greater milk protein content than diet RGS. Lactation stage did affect short-term feed intake behavior and DMI, although different grass silages were fed during early and late lactation. The results indicate that short-term feed intake behavior is related to DMI and therefore may be a helpful tool in optimizing DMI and milk production in high-production dairy cows.     

Short communication: Feed iodine concentrations on farms with contrasting levels of iodine in milk

In a previous study, milk iodine concentration from 501 farms across Canada was found to vary considerably and appeared to be influenced by feeding practices. Farms with contrasting levels of milk iodine from a subset of 200 participating farms were used to determine the relationship between milk iodine concentration and the concentration of this mineral in different feeds and complete diets given to lactating dairy cows. The 30 farms with the lowest levels of iodine in milk (low group) and the 30 farms with the highest levels (high group) were selected. Samples of bulk tank milk, all feed ingredients, and water were collected. Additionally, each farmer completed a questionnaire providing information on feeding management. The iodine offered on each of the farms was estimated from the amount of the feed in the diet recommended by the Ration’L software (Valacta, Ste-Anne-de-Bellevue, QC, Canada) and the iodine concentration in the feed sampled and analyzed using inductively coupled plasma mass spectrometry. The dietary concentration of iodine offered daily was 33% lower for the low group compared with the high group; that is, 1.20 ± 0.099 versus 1.81 ± 0.195 mg/kg of dry matter (DM), respectively. Milk iodine concentrations averaged 146 ± 13.9 μg/kg for the low group and 487 ± 44.6 μg/kg for the high group. A linear relationship was found between dietary iodine concentration and milk iodine level, as follows: milk iodine (μg/kg) = 145 (±66.9) + 113 (±39.4) dietary iodine concentration (mg/kg DM). However, the low R² value (0.15) indicates that other factors, such as milking management and the presence of goitrogens, may have affected the concentrations of iodine in milk. Forages supplied approximately 17% of iodine requirements in the average lactating cow diet. Therefore, variations in the iodine content of forages are unlikely to cause iodine overfeeding. In contrast, 27% of the mineral mix samples presented iodine concentrations >100,000 μg/kg of DM (and up to 322,000 μg/kg of DM). More than 85% of the farms tested were feeding iodine levels higher than the dietary iodine recommendations (0.5 mg of iodine/kg of DM). Iodine supplements should be used with caution in lactating cow diets.