Volatile compounds in cheeses made with Micrococcus sp. INIA 528 milk culture or high enzymatic activity curd

Volatile compounds were investigated in a semihard cheese made with lactic culture, lactic culture + Micrococcus sp. INIA 528 culture, and two levels of high enzymatic activity (HEA) curd made with this strain. The levels of acetaldehyde, 2‐methyl propanal, 3‐methyl butanal, ethanol, 2‐methyl propanol and 3‐methyl butanol were higher, and those of diacetyl and acetoin lower, in cheese made from milk with added Micrococcus culture. Free fatty acids and ethyl, propyl and isobutyl esters were at higher levels in cheeses with added HEA curd. Total esters increased up to 37‐fold in cheeses with added HEA curd.     

Innovative Caciocavallo cheeses made from a mixture of cow milk with ewe or goat milk

This study assessed and compared the physicochemical, microbiological, and sensorial characteristics of Caciocavallo cheeses, made from cow milk and a mixture of cow with ewe or goat milk, during ripening. Different cheese-making trials were carried out on an industrial scale following the standard procedure of pasta filata cheeses, with some modifications. The percentage of the different added milk to cow milk influenced compositional and nutritional characteristics of the innovative products, leading to a satisfactory microbiological and sensorial quality.     

Changes in organic acids during ripening of cheeses made from raw, pasteurized or high-pressure-treated goats’ milk

Organic acids of cheeses made from raw (RA), pasteurized (PA; 72°C, 15 s) or pressure-treated (PR; 500 MPa, 15 min, 20°C) goats’ milk were qualitatively and quantitatively assessed during ripening. Nine organic acids (citric, pyruvic, malic, lactic, formic, acetic, uric, propionic and butyric) were analysed in each sample by HPLC.Milk treatment did not affect the total organic acids content of 1-day-old cheeses, which increased steadily from day 1 to day 60. At the end of ripening, RA and PR milk cheeses both exhibited higher concentration of organic acids than in those made from PA milk.Lactic acid was found in higher concentration in PR milk cheese from 30 days of ripening. The RA milk cheese, that showed the highest nonstarter lactic acid bacteria counts, were characterized by an elevated amount of propionic and acetic acids. These cheeses also were negatively correlated with both pyruvic and citric acid contents. The PA milk cheese showed a high level of malic acid, and was clearly differentiate from RA and PR milk cheeses by its low level of butyric acid.     

一株产高活性多酚氧化酶菌株筛选鉴定及其酶学性质

采用变色圈法从土壤样品中分离筛选产多酚氧化酶的菌株,对其进行形态学观察、分子生物学鉴定,并对其所产多酚氧化酶的酶学性质进行研究。结果表明,筛选得到1株产多酚氧化酶活性较高的菌株,命名为ZL-2,其被鉴定为竹黄菌属（Shiraia sp.）。菌株ZL-2发酵8 d产多酚氧化酶酶活最高,达到521 U/mL。菌株ZL-2产多酚氧化酶最适底物为邻苯二酚,其最适pH值为6、最适温度为30 ℃;酶活在温度20～40 ℃及pH 3～6范围内稳定。金属离子Cu2+、Mg2+、Mn2+、Fe3+、Zn2+对多酚氧化酶都有激活作用,其中Cu2+激活作用最强;Ca2+、Al3+对酶活有一定抑制作用;L-抗坏血酸和亚硫酸氢钠对该酶抑制作用较强。     

Bioaccessibility of fatty acids from conjugated linoleic acid-enriched milk and milk emulsions studied in a dynamic in vitro gastrointestinal model

The present study evaluated the in vitro bioaccessibility of milk fatty acids (FA) and cis-9, trans-11 18:2 using the TIM-1 gastrointestinal model from TNO, Zeist, The Netherlands. Milk naturally enriched with cis-9, trans-11 18:2 (46 mg g⁻¹ FA) was obtained from a lactating dairy cow fed safflower oil. The other treatments consisted of synthetic conjugated linoleic acids as triacylglycerols or free FA incorporated into milk containing a low level of cis-9, trans-11 18:2. Treatments were standardised at 3.25% fat and pasteurised. Chyme was analysed for FA composition and lipid classes. FA bioaccessibility was 81.8 ± 3.1% and was not different between treatments. The degree of absorption of saturated FA decreased with chain length. Bioaccessibility was higher for unsaturated FA than for their saturated counterparts. Bioaccessibility of cis-9, trans-11 18:2 was similar among treatments and averaged 87.0 ± 3.4%. Results suggest that regiospecific distribution of cis-9, trans-11 18:2 on triacylglycerol structure does not influence its accessibility for intestinal absorption.     

Application of a microbial sensor for determination of short-chain fatty acids in raw milk samples.

A microbial sensor system, based on the use of immobilized Arthrobacter nicotiana and an oxygen electrode, was applied to determine free short-chain fatty acids in raw milk samples and the result was compared with gas chromatography (GC) and a titrimetric method. The sensor response was linearly related to the concentration of short-chain fatty acids obtained by GC (n = 10, r = 0.92) and to the total concentration of free fatty acids obtained by titrimetric measurement (n = 10, r = 0.78). This result suggests that the present microbial sensor can selectively determine free short-chain fatty acids in raw milk samples and may be useful as a very fast detection method of rancidity in milk.     

Changes in the concentration of metabolites in milk from cows fed on diets supplemented with soyabean oil or fatty acids

Cows were fed on diets supplemented with soyabean oil or soyabean fatty acids which in some cases were protected from rumen hydrogenation. The fat-containing diets reduced the output of short- and medium-chain fatty acids in milk. Associated with this fall in short- and medium-chain fatty acids was a decrease in the concentration of 2-oxoglutarate and an increase in that of isocitrate and citrate. Protection of polyunsaturated fat from rumen hydrogenation had no significant effect. Milk yields were unaffected by diet, but the variation in milk yield among cows correlated positively with the concentration of glucose in milk.     

Proteolytic activity of some Lactobacillus paracasei strains in a model ovine-milk curd system: Determination of free amino acids by RP-HPLC

Curd slurries were prepared from ovine milk to study the proteolytic properties of various strains of Lactobacillus paracasei. A commercial industrial starter and the strains to be tested in this study, Lb. paracasei strains Pa1, Pa2, Pa3, were inoculated in separate slurries. Free amino acids were analysed on days 0, 2, 5, 7, and 10. As ripening progressed, total free amino acids increased significantly (P < 0.01); content ranged from 150 mg/100 g dry matter (DM) on day 0 to 600 mg/100 g DM on day 10. Generally speaking, CIT, GLN, LEU, ASN, PRO, and 4-HYPRO were the main free amino acids in all four slurries tested, accounting for 60–82% of the total free amino acids. The slurries made using strains Pa1 and Pa3 were similar to the control slurry, and these three slurries exhibited the highest proteolysis levels. Differences between the strains of the species tested were observed.     

Antifungal activity of fatty acids and their monoglycerides against Fusarium spp. in a laboratory medium

The antifungal activity of lauric, myristic and palmitic acids and their monoglycerides against fusaria was investigated. Data were modelled through a re-parameterized Gompertz equation and the Minimum Detection Time (MDT), i.e. the time (days) to attain 1 cm colony diameter, was evaluated. Lauric acid exerted a strong bioactivity against moulds; palmitic and myristic acids and their monoglycerides showed a moderate effectiveness and in a reversible manner. The results of this work could be considered quite promising; however, further investigations are proposed to validate these data in foods.     

一株具高木二糖和木三糖形成活力木聚糖酶链霉菌的鉴定

对1株具高木二糖和木三糖形成活力木聚糖酶的链霉菌菌株进行了分离与鉴定。从土壤中筛选得到1株产木聚糖酶的链霉菌Streptomyces sp.F0107。从形态学特征、培养特征和生理生化特征等方面对该菌株进行了鉴定。PCR扩增得到16SrDNA序列全长为1406bp,从Genbank数据库中BLAST对比,并运用Clustalx1.8和MEGA3.1软件绘制系统发育树。分析结果表明,菌株与Streptomyces tauricusEU841578同源性达99.36%。结合传统生理生化实验结果,初步鉴定为公牛链霉菌。Streptomyces sp.F0107所产木聚糖酶水解不同木聚糖主要产物为木二糖和木三糖,在低聚木糖生产中具有潜在的应用价值。      

Feeding milk supplemented with Ulva sp., Ascophyllum nodosum,or Saccharina latissima to preweaning dairy calves: Effects on growth,gut microbiota,gut histomorphology,and short-chain fatty acids in digesta

Emerging knowledge shows the importance of preweaning nutrition on programming the gastrointestinal microbiome and development of the gut barrier function. The aim of this study was to assess the effects of supplementing cow milk with either intact dried Ulva sp., Ascophyllum nodosum, or Saccharina latissima on growth performance and several gut health parameters of preweaning dairy calves. Forty male Holstein calves were selected based on birth weight (41 ± 4 kg) and plasma Brix percentage (≥8.7%) at d 2 of life. From d 2 to d 42 of life, the control calves (n = 10) were fed with cow milk (8 L/d) without seaweed supplementation, and the experimental calves were fed with cow milk (8 L/d) supplemented with either Ulva sp. (n = 10), A. nodosum (n = 10), or S. latissima (n = 10) at a concentration of 50 g/8 L of cow milk per day (i.e., 5% on a dry matter basis). Calves were weighed every week, and body weight gain and calf starter intake were monitored weekly. At d 42 ± 3 of life, calves were slaughtered. The organ weights and digesta pH from the reticulorumen, mid- and end small intestine, and mid-colon were recorded. A tissue sample (5 cm) collected from the mid-small intestine was analyzed for histomorphology. Digesta from the mid-small intestine and mid-colon were analyzed for lactobacilli, Escherichia coli, and Enterobacteriaceae, and short-chain fatty acid profile. Weight gain of the calves was not affected by seaweed supplementation. Proportional organ weights were not affected by seaweed supplementation except for reticulorumen weight, which was higher in calves fed Ulva sp. Both the mid-small intestinal and mid-colonic digesta populations of lactobacilli, Enterobacteriaceae, and E. coli, as well as the mid-small intestinal histomorphology in seaweed-supplemented calves were not different from control calves. However, acetic acid proportion in mid-colonic digesta was increased in calves fed Ulva sp. and A. nodosum, whereas butyric acid proportion was decreased compared with the control calves. Digesta pH in mid- and end small intestine and mid-colon were not affected, whereas ruminal pH was increased in calves fed Ulva sp. compared with the control calves. In conclusion, intact dried seaweed supplementation did not improve the growth or selected gut health parameters (i.e., histomorphology, digesta pH, bacteria, and short-chain fatty acids) in preweaning Holstein calves.     

Changes in milk fat in response to dietary supplementation with calcium salts of trans-18:1 or conjugated linoleic fatty acids in lactating dairy cows

Milk fat was investigated in lactating dairy cows fed diets supplemented with Ca salts of trans fatty acids (Ca-tFA) or Ca salts of conjugated linoleic acids (Ca-CLA). Forty-five Holstein cows (115 days in milk) were fed a control diet (51% forage; dry matter basis) supplemented with 400 g of EnerG II (Ca salts of palm oil fatty acids) for 2 wk; subsequently, 5 groups of 9 cows each were assigned for 4 wk to the control diet or diets containing 100 g of Ca-CLA or 100, 200, or 400 g of Ca-tFA in a randomized block design. Treatments had no effect on dry matter intake, milk production, protein, lactose, or somatic cell count. Milk fat percentage was reduced from 3.39% in controls to 3.30, 3.04, and 2.98%, respectively, by the Ca-tFA diets and to 2.54% by the Ca-CLA diet. Milk fat yield (1.24 kg/d in controls) was decreased by 60, 130, and 190 g/d with increasing dose of Ca-tFA and by 290 g/d with the Ca-CLA supplement. Consistent with increased endogenous synthesis of cis-9-containing CLA from precursors provided by the Ca-tFA diets, total CLA were similar in milk of cows fed Ca-CLA or Ca-tFA. Compared with controls, the Ca-CLA diet increased trans-10, cis-12-18:2 yield in milk, without altering levels of trans-18:1 isomers. In contrast, yields of most trans-18:1 isomers were elevated in milk of cows fed Ca-tFA diets, whereas yields of trans-10, cis-12-18:2 remained similar to control values. We conclude that milk fat depression can occur without an increase in trans-10, cis-12-18:2 in milk and that other components, perhaps the trans-10-18:1 isomer, may be involved.     

Mycobacterium bovis: the importance of milk and dairy products as a cause of human tuberculosis in the UK. A review of taxonomy and culture methods,with particular reference to artisanal cheeses

Mycobacterium bovis is the cause of tuberculosis (TB) in cattle and other ruminants. It can also cause tuberculosis in humans, and consumption of unpasteurized milk or products made from infected and untreated animals is thought to be the primary vehicles of transmission. Although a control programme for cattle exists in the UK, the disease is becoming more prevalent in the cattle population. The increasing interest in artisan cheeses made from unpasteurized milk and recent cases of human TB in which cheese was the known cause has highlighted the need for empirical data on the survival kinetics of M. bovis during the manufacture and ripening of such cheeses.     

Effect of a bacteriocin-producing Lactococcus lactis strain and high-pressure treatment on the esterase activity and free fatty acids in Hispánico cheese

The effect of milk inoculation with a bacteriocin-producing (BP) culture and of high-pressure (HP) treatment of 15-day-old Hispánico cheeses (400 MPa, 5 min, 10 °C), separately or combined, on the release of intracellular esterases and cheese lipolysis was investigated. Esterase activity and free fatty acids (FFAs) content increased during ripening of Hispánico cheese and palmitic, oleic and stearic acids being the most abundant FFAs. On day 15, the highest esterase activity was recorded for HP-treated BP cheese. The activity for HP-untreated BP cheese was the next highest. No difference in the activities was found between HP-treated and untreated cheeses made without BP culture. Total FFAs on day 15 were at a lower concentration in BP cheeses than in cheeses made without BP culture, probably due to the lower pH values of the former. The rate of total FFA accumulation from day 15 to day 50 was higher in BP cheeses (31.1–32.1% increase) than in cheeses made without BP culture (19.3–21.7% increase). The highest total FFA concentration on day 50 (612 mg kg⁻¹) was found for HP-untreated cheese made without BP culture.     

Short communication: Diurnal profiles of conjugated linoleic acids and trans fatty acids in ruminal fluid from cows fed a high concentrate diet supplemented with fish oil, linseed oil, or sunflower oil

Trans-18:1 and 18:2 isomer composition in ruminal fluid during the daily feeding cycle was examined in 3 cows fed a high concentrate diet (35:65) with 5% (DM basis) sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) in a 3 x 3 Latin square with 3 4-wk periods. Grass hay and concentrate mixtures were fed at 0900, 1300, and 1700 h daily. Ruminal fluid was collected at 0900, 1100, 1300, 1500, 1700, 2000, and 0000 h. Feeding SO resulted in the greatest mean concentrations (% of total fatty acids) of trans10,cis12-18:2 and cis9,trans11-18:2. In particular, trans10,cis12-18:2 with SO was greater at 1500 (0.29%), 2000 (0.34%), and 0000 h (0.25%) relative to 0900 h (0.07%). Cis9,trans11-18:2 concentration increased from 0.47% at 0900 h to a peak of 2.06% at 1100 h; it remained greater than the percentage determined at 0900 h at 1300 (1.4%) through 0000 h (1.1%). Concentration of trans11,cis15-18:2 was greatest with LO, ranging from 3.3% (0900 h) to a peak of 11.4% at 2000 h. Mean trans10-18:1 concentration ranked by diet was SO > FO > LO. Peak trans10-18:1 with SO was observed at 1700 h (14.9%) compared with 0900 h (5.1%). Trans11-18:1 did not differ with diet or time. Stearic acid decreased over time with all diets reaching minimum concentrations at 1700 to 2000 h relative to 0900 h. Feeding FO, however, decreased mean 18:0 concentration 4-fold compared with LO or SO. The moderate effect on concentration of trans-18:1 coupled with accumulation of 18:2 intermediates and the decrease of 18:0 over time suggest that oils reduced the biohydrogenation of 18:2 isomers to trans-18:1.     

Screening of a Bacillus subtilis strain producing both nattokinase and milk-clotting enzyme and its application in fermented milk with thrombolytic activity

Bacillus subtilis is a generally recognized as safe probiotic, which is used as a starter for natto fermentation. Natto is a functional food with antithrombus function due to nattokinase. Compared with natto, fermented milk is a more popular fermented food, which is commonly fermented by Lactobacillus bulgaricus and Streptococcus. However, there is no report on B. subtilis–fermented milk. In this study, to produce a functional fermented milk with antithrombus function, a B. subtilis strain (B. subtilis JNFE0126) that produced both nattokinase and milk-clotting enzyme was isolated from traditionally fermented natto and used as the starter for the functional fermented milk. In liquid fermentation culture, the peak values of thrombolytic activity and milk-clotting activity were 3,511 U/mL at 96 h and 874.5 Soxhlet unit/mL at 60 h, respectively. The optimal pH and temperature were pH 7.0 at 40°C for nattokinase and pH 6.5 and 55°C for milk-clotting enzyme, respectively. The thrombolytic activity in the fermented milk reached 215.1 U/mL after 8 h of fermentation. Sensory evaluation showed that the acceptance of the milk fermented by B. subtilis JNFE0126 was similar to the traditional milk fermented by L. bulgaricus and S. thermophilus. More importantly, oral intake of the fermented milk by the thrombosis-model mice prevented the development of thrombosis. Our results suggest that B. subtilis JNFE0126–fermented milk has potential as a novel, functional food in the prevention of thrombosis-related cardiovascular diseases.     

Effect of galactose metabolising and non-metabolising strains of Streptococcus thermophilus as a starter culture adjunct on the properties of Cheddar cheese made with low or high pH at whey drainage

Cheddar cheese was made using control culture (Lactococcus lactis subsp. lactis), or with control culture plus a galactose-metabolising (Gal⁺) or galactose-non-metabolising (Gal⁻) Streptococcus thermophilus adjunct; for each culture type, the pH at whey drainage was either low (pH 6.15) or high (pH 6.45). S. thermophilus affected the levels of residual lactose and galactose, and the volatile compound profile and sensory properties of the mature cheese (270 d) to an extent dependent on the drain pH and phenotype (Gal⁺ or Gal⁻). For all culture systems, reducing drain pH resulted in lower levels of moisture and lactic acid, a higher concentration of free amino acids, and higher firmness. The results indicate that S. thermophilus may be used to diversify the sensory properties of Cheddar cheese, for example from a fruity buttery odour and creamy flavour to a more acid taste, rancid odour, and a sweaty cheese flavour at high drain pH.     

The effect of a protective culture and exclusion of nitrate on the survival of enterohemorrhagic E. coli and Listeria in Edam cheese made from Finnish organic milk

This study compared the chemical composition and hygienic quality of Finnish organic and conventional milk. The composition and quality of milk from 126 Finnish organic and conventional farms from January 2000 to November 2001 were investigated. Finnish organic milk contained significantly less fat, and protein, and had a lower total bacterial count than conventional milk. Organic milk contained significantly more lactose and had a similar, or higher, somatic cell count and a similar, or lower, urea content than conventional milk. Although the differences between organic and conventional milk are rather small, they are of economical significance in large-scale cheese manufacture.This study also determined the effects of the exclusion of nitrate and the introduction of a protective culture on the microbiological safety and the counts of Listeria and non-pathogenic enterohemorrhagic Escherichia coli (EHEC) in organic Edam cheese. Nitrate failed to inhibit the growth of EHEC and Listeria. Thus, compared to Edam cheese from conventional milk, Edam cheese from organic milk without added KNO₃ poses no additional health risk with respect to Listeria and EHEC. The use of a protective culture containing Lactobacillus rhamnosus LC705, however, inhibited the growth of Listeria in Edam cheeses from organic milk.