The survival of foot-and-mouth disease virus in raw and pasteurized milk and milk products

The Foot-and-Mouth Disease virus (FMDV) is not a public health threat, but it is highly contagious to cloven-footed animals. The virus is shed into milk up to 33 h before there are apparent signs of the disease in dairy cows, and, in extreme cases, signs of disease may not appear for up to 14 d. During this time, raw milk can serve as a vector for spread of the disease both at the farm and during transport to the processing plant by milk tanker. Raw milk and milk products fed to animals have the potential to cause infection, but the potential for pasteurized milk products to cause infection is largely unknown. Current minimum pasteurization standards may not be adequate to eliminate FMDV in milk completely. The purpose of this paper is to assess the literature on the thermal resistance of FMDV in milk and milk products, to identify the risks associated with ingestion of pasteurized products by animals, and to lay a strategy to prevent the spread of FMDV from contaminated milk.     

Thermal inactivation of foot-and-mouth disease virus in milk using high-temperature, short-time pasteurization

Previous studies of laboratory simulation of high temperature, short time pasteurization (HTST) to eliminate foot-and-mouth disease virus (FMDV) in milk have shown that the virus is not completely inactivated at the legal pasteurization minimum (71.7°C/15 s) but is inactivated in a flow apparatus at 148°C with holding times of 2 to 3 s. It was the intent of this study to determine whether HTST pasteurization conducted in a continuous-flow pasteurizer that simulates commercial operation would enhance FMDV inactivation in milk. Cows were inoculated in the mammary gland with the field strain of FMDV (01/UK). Infected raw whole milk and 2% milk were then pasteurized using an Arm-field pilot-scale, continuous-flow HTST pasteurizer equipped with a plate-and-frame heat exchanger and a holding tube. The milk samples, containing FMDV at levels of up to 10⁴ plaque-forming units/mL, were pasteurized at temperatures ranging from 72 to 95°C at holding times of either 18.6 or 36 s. Pasteurization decreased virus infectivity by 4 log₁₀ to undetectable levels in tissue culture. However, residual infectivity was still detectable for selected pasteurized milk samples, as shown by intramuscular and intradermal inoculation of milk into naïve steers. Although HTST pasteurization did not completely inactivate viral infectivity in whole and 2% milk, possibly because a fraction of the virus was protected by the milk fat and the casein proteins, it greatly reduced the risk of natural transmission of FMDV by milk.     

Survival of foot-and-mouth disease virus in cheese.

Persistence of foot-and-mouth disease virus during the manufacture of Cheddar, Mozzarella, Camembert cheese prepared from milk of cows experimentally infected with the virus was studied. Cheese samples were made on a laboratory scale with commercial lactic acid starter cultures and the microbial protease MARZYME as a coagulant. Milk was heated at different temperatures for different intervals before it was made into cheese. Food-and-mouth disease virus survived the acidic conditions of Cheddar and Camembert cheese processing but not that of Mozzarella. Foot-and-mouth disease virus survived processing but not curing for 30 days in Cheddar cheese preparaed from heated milk. However, the virus survived curing for 60 days but not for 120 days in cheese (pH 5) prepared from unheated milk. Foot-and-mouth disease virus survived in Camembert cheese (pH 5) for 21 days at 2 C but not for 35 days.     

口蹄疫、水泡性口炎和猪水泡病多重荧光定量RT-PCR检测方法的建立

目的建立同时检测口蹄疫病毒、水泡性口炎病毒和猪水泡病病毒的多重荧光RT-PCR检测方法。方法根据口蹄疫病毒3D蛋白编码基因、水泡性口炎病毒N蛋白编码基因和猪水泡病病毒VP1蛋白编码基因的高保守区设计特异性引物和探针,对3种动物病毒进行多重荧光定量RT-PCR扩增。结果经过扩增,可以同时检测口蹄疫病毒、水泡性口炎病毒和猪水泡病病毒,而其他参试病原均无扩增信号,显示其良好的特异性。对口蹄疫病毒、水泡性口炎病毒、猪水泡病病毒的最低检测限分别达到101、102、102个质粒拷贝浓度。结论本方法灵敏度高,特异性良好,可实现多种病毒混合感染的同时检测。     

羊毛脂的理化指标及主要成分分析

羊毛脂的理化指标和组成对其使用性能影响较大,因而采用国标等方法对原料羊毛脂的熔点、水分及挥发物含量、灰分含量、酸值、过氧化值、碘值、色度等基本理化指标进行分析,并通过薄层色谱及柱层析对其主要成分进行分析鉴定,采用气质联用色谱对羊毛醇和羊毛酸进行定性定量分析。结果表明：与精制羊毛脂（药典级）相比,原料羊毛脂色泽较深,水分及挥发物含量、灰分含量、碘值与酸值略高;羊毛脂的主要组成成分为脂肪酸酯、羟基酸酯、游离甾醇及多羟基物残留物,分别占羊毛脂总质量的55.14%、25.57%、4.04%和13.15%;原料羊毛脂中甘油三酯未检出;羊毛醇的主要组成为胆甾醇与羊毛甾醇,相对含量分别为44.31%与14.62%,羊毛脂中胆甾醇和羊毛甾醇含量分别为10.41%、3.43%（以全样原料羊毛脂计）;羊毛酸的主要组成为饱和脂肪酸,碳链长度为C13~C27,其中支链脂肪酸相对含量高达62.03%,异构支链脂肪酸相对含量为27.56%,反异构支链脂肪酸相对含量为34.47%。     

Survival of foot-and-mouth disease virus in sausage meat products (Italian salami)

Determination of the survival of foot- and-mouth disease virus (FMDV) in fresh meat from experimentally infected swine and in several types of sausage meat (Italian salami) produced according to the technology widely applied by the principal Italian producers has been carried out. The purpose of the experiment was to assess if typical Italian salami can be considered safe with regard to the spread of FMD through international trade. The results obtained showed: (a) high titers of FMDV were detected in both muscle and fat tissues from animals slaughtered at the peak of the experimental disease; and (b) FMDV was not detectable in the above tissues 72 h after slaughtering and the same applies to the different types of salami tested 7 days after production. The above results were obtained in tissue cultures and confirmed through piglet inoculation.     

Physicochemical properties of fermented Arabian mares' milk

Due to its numerous benefits, including health-promoting characteristics, there is increasing interest in finding product applications for mares' milk. In the present study, the physicochemical properties, turbidity and conductivity of Arabian mares' milk were studied during acidification by fermentation at 30 °C and compared with those of bovine milk. The data for the acidification rate were modelled using a logistic equation. Mares' milk showed a longer latency phase (284 min) and lower acidification rate (μ_max = 0.0052 dpH min^?1) compared with bovine milk (194 min and 0.0098 dpH min^?1 respectively). The general shape of the curves of the turbidity versus time and pH were similar in nature for the acidification of both milks. However, the characteristic points were different, due to the differences in casein micelle composition. Measurement of electrical conductivity during acidification showed that maximum demineralization of casein micelles started around pH 6.09 and 5.31, for mares' and bovine milk, respectively. In conclusion, the technological characteristics of mares' milk were very different from those of bovine milk, due to intrinsic physicochemical properties of both milks.     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

中国荷斯坦牛泌乳早期乳常规成分及乳蛋白组分变化规律的研究

对扬州大学实验农牧场7头中国荷斯坦牛泌乳早期乳常规营养成分、酸度及乳蛋白组分的相对含量进行研究。结果表明，产犊后1h的乳脂率、乳蛋白含量、总固形物含量、滴定酸度、密度最高，而pH值最低，随后乳脂率、乳蛋白率、总固形物含量、滴定酸度密度急剧下降，到60h时接近常乳水平，而pH值逐渐上升，到第7d时接近常乳水平。产犊后1h初乳中免疫球蛋白的相对含量最高，为20．6％，到第5d时接近常乳水平。研究表明，产犊后3d内所产的乳最具有开发价值。     

不同泌乳期羊乳的理化特性及其酶凝固特性

以不同泌乳期羊乳为原料,研究其基本理化特性(色泽、膻味、p H值、酸度、密度、乳化学成分)及酶凝固特性(硬度、内聚性、弹性)和持水力,以便为羊乳制品的开发提供更适宜的生产原料。结果表明,不同泌乳期羊乳的各理化特性和酶凝固特性差异较大。随着泌乳期的延长,羊乳由乳黄色逐渐变为乳白色,其膻味逐渐变淡,p H值缓慢上升,而酸度、密度、乳化学成分含量及酶凝固特性、持水力均呈下降趋势。经综合分析,建议将泌乳第120~150天的羊乳作为稀奶油生产的较优质原料;泌乳第4~150天的羊乳更适合用于凝固型酸奶和奶酪的加工;而泌乳第7~240天的羊乳均可用于生产液态羊乳或羊乳粉,但需要对其主要化学成分进行标准化处理。     

Inactivation and degradation of O Taiwan97 foot-and-mouth disease virus in pork sausage processing

This study was to investigate the levels of inactivation and degradation of a field-isolated foot-and-mouth disease virus (FMDV)-strain O Taiwan97 in pork sausage processing. FMDV antibody-free pigs were inoculated with virus suspensions and slaughtered after developing observable symptoms. Lymph nodes (LN), blood clots (BC), and muscle were collected for the evaluation of inactivation during chilling, curing, drying and steaming processes. Viable virus was assessed by the TCID₅₀ technique and RT-PCR was used to detect viral genomes. Cell culture results revealed that viruses could be detected from LN and BC, but not from muscle. Ninety percent of FMDV was inactivated after each of the chilling, curing and steaming processes as compared to <80% inactivation after the drying process. The FMDV genome was detectable in 88% of the muscle, and was found in 100% of the serum, BC and LN. After processing, a majority of the genomes were not degraded more than 60%, with the exception of the thermal-steaming process. These findings indicated that the FMDV genome was detectable after each processing step, indicating a potential infectious risk. Thus, apart from regular surveillance in the field, monitoring of meat product pH and heat treatments are essential for FMDV inactivation.     

Physicochemical characteristics and rennet coagulation time of ultrafiltered goat milk

Goat skim milk was concentrated by ultrafiltration (UF) to volume concentration ratios (VCR) of 2, 3, 4 and 5. Gross composition, titratable acidity, pH, nitrogen distribution, percentage retention and recovery of components and rennet coagulation time (RCT) of skim milk during UF processing were studied. During UF of goat skim milk, all fat, CN, WPN, 19% of NPN, 78.1% of TS, 78.6% of ash and 3.5% of lactose were retained in 5-VCR retentate. Recovery of these components were 14.7, 53, 48, 17 for NPN, TS, ash, lactose and 100% for fat, WPN or CN, respectively. For TN, TS, ash, NPN and lactose, retention was increased by increasing the VCR. The titratable acidity was increased from an initial value of 0.14 to 0.38% in 5-VCR retentate, whereas pH decreased from 6.58 to 6.50. The RCT decreased as the protein concentration of the milk increased, but the precise influence of protein concentration decreased at higher levels of rennet.     

Physicochemical and kinetic properties of purified sheep's milk xanthine oxidoreductase

Xanthine oxidoreductase (XOR) was purified for the first time from sheep's milk. The ultraviolet-visible absorption spectrum was essentially identical to those of the corresponding bovine, human, and goats' milk enzymes and showed an A280/A450 ratio of 5.35 +/- 0.24, indicating a high degree of purity. Like milk XOR from other species, sheep's milk enzyme showed a single band on SDS-PAGE corresponding to a subunit with approximate Mr 150,000. Xanthine oxidase activity of purified sheep's milk XOR (0.69 +/- 0.04 micromole urate min(-1) mg(-1)) was low relative to that of the bovine milk enzyme (1.83 +/- 0.02 micromole urate min(-1) mg(-1)), but higher than those of human or goats' milk XOR. As in the latter 2 cases, the low activity of sheep's milk XOR can be attributed to its relatively low molybdenum content (0.18 atoms per subunit), compared with that of the bovine milk enzyme (0.56 atoms Mo per subunit). Consistent with this, NADH oxidase activity of sheep's milk XOR was similar to that of enzymes purified from bovine, human, or goats' milk. The presence of desulpho-enzyme in sheep's milk XOR was demonstrated by resulfuration experiments, whereby xanthine oxidase activity was increased by approximately 75%.     

Influence of milk components on properties and consumer acceptance of milk chocolate

The objective of the study was to assess the effects of various milk components on chocolate quality, defined by measurable properties and decisively by consumer liking.The choice of milk products considered different types, technologies and suppliers. Samples produced under standardised conditions were analysed for particle size, flow properties, colour and by a trained sensory panel. Consumer testing determined overall liking. Results revealed that milk ingredients influence consumer liking of milk chocolate through the quality driving parameters of particle size/sandiness, viscosity/melting mouthfeel and milk flavour. Chocolates made from milk products that contain high amounts of free fat - e.g. skim milk powder plus anhydrous milk fat - scored better than those using bound fat - e.g. whole milk powder. Milk fat status had more influence than differences between spray and roller-dried powders. High free fat cream powders were most suitable for cream chocolates. All milk components need to be free from off-notes that require sensory checks. Fillers like lactose could replace some sucrose, and whey protein concentrate can partially replace skim milk powder.     

Effect of local stimulation of one quarter on milk production and milk components

The existence of local udder regulatory mechanisms involved in the regulation of milk production was demonstrated. Because the four quarters of the udder are independent, yet share a common environment, the experiment was designed to give one quarter extra stimulation by hand-milking while the other quarters were machine-milked. A difference in milk production was found, proving the existence of local mechanisms. The largest differences were during evening milking with an increased production in the hand-milked quarter. The machine-milked quarters did not increase their production. The increased production was probably due to enhanced activity in the secretory cells, induced by some factor produced or activated locally in the udder.