Qualitative and quantitative changes in carbohydrates during the manufacture of yogurt.

The average lactose content of yogurt mix was 8.50% and decreased during fermentation to 5.75%. The initial galactose content of the mix was a trace but increased to 1.20% during fermentation. Glucose content remained a trace throughout fermentation. Several brands of commercial yogurt were purchased from local supermarkets and analyzed for carbohydrate content. Lactose ranged from 3.31 to 4.74%, galactose varied from 1.48 to 2.50%, and glucose was only a trace in all samples. Several samples of buttermilk also exhibited the near absence of glucose.     

Industrial yogurt manufacture: monitoring of fermentation process and improvement of final product quality

Lactic acid fermentation during the production of skim milk and whole fat set-style yogurt was continuously monitored by measuring pH. The modified Gompertz model was successfully applied to describe the pH decline and viscosity development during the fermentation process. The viscosity and incubation time data were also fitted to linear models against ln(pH). The investigation of the yogurt quality improvement practices included 2 different heat treatments (80°C for 30 min and 95°C for 10 min), 3 milk protein fortifying agents (skim milk powder, whey powder, and milk protein concentrate) added at 2.0%, and 4 hydrocolloids (κ-carrageenan, xanthan, guar gum, and pectin) added at 0.01% to whole fat and skim yogurts. Heat treatment significantly affected viscosity and acetaldehyde development without influencing incubation time and acidity. The addition of whey powder shortened the incubation time but had a detrimental effect on consistency, firmness, and overall acceptance of yogurts. On the other hand, addition of skim milk powder improved the textural quality and decreased the vulnerability of yogurts to syneresis. Anionic stabilizers (κ-carrageenan and pectin) had a poor effect on the texture and palatability of yogurts. However, neutral gums (xanthan and guar gum) improved texture and prevented the wheying-off defect. Skim milk yogurts exhibited longer incubation times and higher viscosities, whereas they were rated higher during sensory evaluation than whole fat yogurts.     

Technical note: Development of a noninvasive respiration rate sensor for cattle

The measurement of the respiration rate (RR) in cattle is a valuable tool for monitoring health status. Thus, an RR sensor can be essential for stress detection, especially heat stress. Heat stress leads to a deviation of the normal RR and results in a decrease of milk production and fertility. Therefore, continuous monitoring of the RR can help early detection of heat stress and, thus, initiate timely counteractive actions to minimize physical stress. The most common method to measure the RR in cattle is to count the flank movement visually; however, this method is time-consuming and labor-intensive. In addition, the continuous measurement of the RR is difficult to implement and can be physically strenuous. Therefore, a device based on a differential pressure sensor that can record RR automatically has been developed to make continuous long-term studies possible. The aim of this study was to validate the data measured by the device with the help of a reference method. The reference method used was counting the flank movements of a total of 6 cows (Holstein-Friesian). The rear flank movements of each cow were recorded by a camera and counted independently of the device by an observer. Eight videos of 1 min each were recorded per cow. The data analysis was done with cows in 3 different body positions: dozing, lying, and standing. A total of 48 RR measurements of the device were compared with the counted RR frequencies of the video recording. The results were highly correlated during dozing [correlation coefficient (r) = 0.92, n = 13], lying (r = 0.98, n = 15), and standing (r = 0.99, n = 20). The evaluation showed that the device is suitable for automated RR counting. Further development of a marketable device is planned.     

Technical note: a rapid pulsed-field gel electrophoresis method for analysis of bifidobacteria

Pulsed-field gel electrophoresis (PFGE) is a widely used and highly discriminatory molecular typing method that has been applied to bifidobacteria. However, published PFGE protocols used with bifidobacteria require between 5 and 7 d to complete. A rapid PFGE method was developed that can be completed within 24 h.     

Technical note: Evaluation of a triaxial accelerometer for monitoring selected behaviors in dairy calves

The objectives of this study were (1) to develop an algorithm for the acceleration sensor of the Smartbow Eartag (Smartbow GmbH, Weibern, Austria) to distinguish between postures (lying and standing or locomotion) and to detect 6 kinds of activities (milk intake, water intake, solid feed intake, ruminating, licking or sucking without milk intake, and other activities) in dairy calves and (2) to evaluate this sensor for identifying these behaviors in dairy calves compared with observations from video. Accelerometers were applied to the left ears of 15 preweaned Holstein dairy calves. Calves were kept in a group pen and received milk replacer from an automatic calf feeder. Based on 38 h of acceleration data and video observation, an algorithm was established to detect the predefined behaviors. Using cross-validation, video recordings were used to analyze whether a behavior was detected correctly by the developed algorithm. For posture, sensitivity (94.4%), specificity (94.3%), precision (95.8%), and accuracy (94.3%) were high. Cohen's kappa was calculated as 0.88. For the 6 defined activities, overall (i.e., aggregated for all activities) accuracy was 70.8% and kappa was calculated as 0.58. Some activities (e.g., ruminating, feed intake, other activities) were identified better than others. In conclusion, the developed algorithm based on the acceleration data of the Smartbow Eartag was successful in detecting lying behavior, rumination, feed intake, and other activities in calves, but further development of the underlying algorithm will be necessary to produce reliable results for milk and water intake.     

Technical note: High-throughput method for antifungal activity screening in a cheese-mimicking model

In this study, we developed a high-throughput antifungal activity screening method using a cheese-mimicking matrix distributed in 24-well plates. This method allowed rapid screening of a large variety of antifungal agent candidates: bacterial fermented ingredients, bacterial isolates, and preservatives. Using the proposed method, we characterized the antifungal activity of 44 lactic acid bacteria (LAB) fermented milk-based ingredients and 23 LAB isolates used as protective cultures against 4 fungal targets (Mucor racemosus, Penicillium commune, Galactomyces geotrichum, and Yarrowia lipolytica). We also used this method to determine the minimum inhibitory concentration of a preservative, natamycin, against 9 fungal targets. The results underlined the strain-dependency of LAB antifungal activity, the strong effect of fermentation substrate on this activity, and the effect of the screening medium on natamycin minimum inhibitory concentration. Our method could achieved a screening rate of 1,600 assays per week and can be implemented to evaluate antifungal activity of microorganisms, fermentation products, or purified compounds compatible with dairy technology.     

Stability of the intense sweetener neohesperidine DC during yogurt manufacture and storage

The stability of the intense sweetener neohesperidine dihydrochalcone (DC) has been assessed during yogurt manufacture and storage. No significant decomposition was detected during and after milk pasteurization, the fermentation process and storage for 6 weeks at 3 °C. In addition, the maximum authorized concentration of neohesperidine DC did not affect the rate of acidification by lactic acid bacteria during the fermentation process. Taken together, these results suggest that neohesperidine DC can be added to milk products and will remain stable throughout pasteurization and fermentation processes.     

Technical note: Evaluation of an ear-attached real-time location monitoring system

Position tracking of cows within the barn environment allows for determining behavioral patterns and activities. Such data might be used for detection of estrus and disease. A newly marketed real-time location monitoring system (Smartbow, Smartbow GmbH, Weibern, Austria) was tested in this study. Cow location was continuously monitored with the Smartbow tags mounted on the cow's ear, which sends low-frequency signals to receivers further transmitting the information to a server. Through incoming data, the server triangulates the location of the cow within the barn environment in real time. The validation of the system was carried out in 4 steps. The first 2 steps served as static testing steps (tags and 1 cow positioned at 30 reference points), and steps 3 and 4 were dynamic steps with cows moving in the barn environment. For 48 h, locations of 15 cows were confirmed each hour by laser measurements performed by a team (step 3) or 1 observer (step 4). Interobserver variability was 0.83 m (range: 0.05 to 2.87 m), and intraobserver variability had a range of 0.02 to 0.31 m. In the 4 validation steps, the mean distance between observer laser measurements and Smartbow was between 1.22 and 1.80 m. Step 4, with 334 observations, resulted in a mean distance difference of 1.22 m (standard error = 1.32 m). Data can be used for development of algorithms to detect sick cows with changed behavioral patterns. Data may also be used to monitor cow responses to physical environment, potentially improving facility design. Time budgets in proximity to important barn features (i.e., feed bunk and water trough) and distances traveled can be calculated and used to identify cows in need of caretaker's attention and identify the cow's exact location in the barn.     

Technical note: a computerized system for monitoring feeding behavior and individual feed intake of dairy cattle

The objective of this study was to develop and validate a computerized system to monitor feeding behavior and feed intake of loose-housed dairy cattle. The system consisted of 28 scales located in front of each self-locking place of a regular feedbunk. All cows had access to all scales indifferently. Each visit to the feedbunk was monitored by a transponder in the ear of each cow that was detected by a proximity reader located at the top right corner of each headlock. The data from the scales and the proximity readers were continuously recorded by a computer with an average scanning time of 3.5 s. The monitoring system was validated using all 28 feeding places and 51 lactating cows in a series of 4-h observations during 5 different d. During the observation periods, for each feeder, 2 observers recorded the cow number and the exact time of the visit. The observed data were then compared with the computer records. To validate the ability of the system to monitor feed consumption, on separate days, the amount of feed consumed by a cow during a visit was also measured manually with an external scale, and the feed that disappeared from each scale in 2 different 24-h periods was compared with the sum of feed consumed in each scale during these 2 periods. The average time spent in a given scale by each cow determined by direct observations was similar to that determined by the computer. The system was accurate and showed a high specificity (98.8%) and sensitivity (99.6%) for cow detections. Feed weights determined by the computer system were similar to those measured manually with an external scale, implying that the system was also accurate in measuring individual intake weights. In conclusion, the system provided a reasonable estimate of the number of visits per animal, length of each visit, amount of feed consumed per visit and animal, the total amount of feed consumed daily by each animal, and the rate at which animals consume feed.     

Technical note: a rapid lipid separation method for determining fatty acid composition of milk

A rapid method for milk lipid separation followed by transmethylation to produce fatty acid methyl esters from bovine milk samples is presented. Fat is separated by a nonsolvent method using centrifugation. The method was compared with the popular hexane:isopropanol solvent extraction method, and fatty acid proportions were statistically identical for both methods. In 108 replicates, variance accounted for by using the 2 methods was of a similar magnitude to variance due to repeat separations or repeat injections onto the gas chromatography column. It is concluded that the proposed method is accurate, simple, rapid, safe, economical, and especially suitable for large numbers of samples.     

Technical note: loss of nitrate from carrots during blanching

Loss of nitrate from carrots during blanching was studied using several parameters, such as temperature of water, thickness of carrot slices, and volume ratio of carrots and water. It was found that the kinetics of nitrate diffusion fitted well to the Fick's general diffusion equation. Surface mass transfer coefficient (K) was related to temperature by an Arrhenius type reaction. The values of activation energy ( E _a) and the constant K₀ were calculated as 74 kJ/mole and 2769 × 10³ kg/m²/sec. As expected the initial rates of diffusion were proportional to carrot surface and the efficiency of nitrate removal decreased with increasing blancher load. The proposed model may be used to determine the optimum blanching conditions of carrots in the baby food industry.     

TaqMan实时荧光聚合酶链式反应(PCR)技术定量检测婴幼儿配方食品中的金黄色葡萄球菌

靶向于耐热核酸酶基因nuc,研究建立了Taq Man实时荧光聚合酶链式反应(PCR)(qRT-PCR)法用于婴幼儿米粉及乳粉中金黄色葡萄球菌的快速定量检测。经优化的qRT-PCR体系特异性强,仅在金黄色葡萄球菌中产生典型扩增曲线;方法灵敏度高,对标准质粒、纯菌液、模拟染菌米粉及奶粉样液的检测限分别为17.94拷贝、1.2 CFU、0.42 CFU和0.74 CFU/PCR反应体系;10倍系列梯度稀释的标准质粒、纯菌及人工染菌样液的浓度对数与qRT-PCR的Ct值线性相关度良好,拟合方程的决定系数均≥0.99;平板计数法与qRT-PCR法对模拟米粉及乳粉盲样中金黄色葡萄球菌的定量检测结果间无统计学差异。文中所建立的qRT-PCR定量法特异性强、灵敏度高,简便快捷、可靠性佳,可为婴幼儿米粉及乳粉中金黄色葡萄球菌的快速、准确定量检测提供有效手段。     

Technical note: adaptation of an animal-model method for approximation of reliabilities to a sire-maternal grandsire model

A method used to approximate reliabilities for animal models was modified to estimate reliabilities for sire-maternal grandsire (MGS) models. Accuracy of the approximation was tested on a calving-ease data set for 2,968 bulls for which the inverse of the coefficient matrix could be obtained. Correlations between estimated and true reliabilities ranged from 0.984 to 0.998 for first- and later-parity calving ease for sire and MGS effects. With no modification of the animal-model procedure, MGS identification was treated as if it were dam identification, which resulted in overestimated reliability. When pedigree information was ignored, reliability was underestimated. Correlations with true values were lower for both of those cases when compared with correct processing of MGS information. The modification provided a slight improvement over assuming MGS to be unknown and will be used for routine USDA evaluation of calving traits.