Application of a dry heat treatment to enhance the functionality of low-heat nonfat dry milk

Nonfat dry milk is a valuable food and ingredient because it contains proteins, fat, carbohydrates, minerals, and vitamins. When manufactured, this product is classified into high heat (HH) or low heat (LH) depending on the pre-heat treatment used in pasteurization. Radio frequency dielectric heating, if used alone or as part of a dry heat technology, may induce component interactions in milk powders, which could alter or improve functionality. To pursue this objective, LH was subjected to radio frequency dielectric heating to 80, 85, and 90°C with a subsequent hold period of 60 or 90 min in an oven, set at the designated temperature, 80, 85, or 90°C, assessed for functionality in liquid and gel systems, cooled, and subsequently compared with LH and HH. The functionality assessment included heat stability and foaming, emulsion, and gelling properties. For foaming, LH presented a statistically lower overrun and foam stability compared with all dry-heated LH. The LH dry-heated at ≥85°C exhibited significantly greater foaming capacity than did the LH. Emulsification properties were not significantly different as a function of dry heating compared with LH. As gels, water-holding capacity was greater and syneresis was significantly less for all gels made with the dry-heated LH at <85°C. Gel firmness and cohesiveness were not affected by dry heating. The heat coagulation time at native pH was significantly greater for LH that were dry-heated for 90 min compared with LH. At adjusted pH (6.4 to 7.2), the heat stability was improved if the LH was dry-heated. The dry-heated LH had significantly less foaming properties, but greater emulsion activity compared with the HH. Overall, the dry heat treatment conditions of this study did not result in acid-induced gels with equivalent properties as gels made with HH. Syneresis was similar for all gels except for those made from the dry-heated LH to 90°C and held for 60 min, as this gel had significantly more syneresis than did the gels made from HH. However, the heat stability of dry-heated LH at native, 6.8, 7.0, and 7.2 pH was greater compared with the heat stability of HH. The application of a dry heat treatment enhanced the functional properties of LH, opening the opportunity to develop food products that can use this modified nonfat dry milk such as ice cream, bakery, and meat products.     

Application of fluorescence spectroscopy for monitoring changes in nonfat dry milk during storage

The objective of this study was to determine if fluorescence spectroscopy could be used to characterize the biochemical characteristics of nonfat dry milk (NDM) caused by manufacturing and storage conditions. Nine low-heat NDM samples were collected from 3 manufacturers and stored at 4 temperatures (4, 22, 35, and 50°C) for 8 wk. The spectra of Maillard products, tryptophan, and riboflavin were recorded and analyzed with principal components analysis. Colorimetric indices L*, a*, and b* were also determined. The before-storage NDM samples collected from each manufacturer had different fluorescent characteristics. Inconsistency was observed for the NDM samples collected from 1 manufacturer, whereas the samples from the other 2 manufacturers displayed consistent fluorescence characteristics. Biochemical reactions, such as Maillard reaction, modification of the tryptophan environment, and degradation of riboflavin occurred during the manufacturing process. For each of the data collections, discrimination of the NDM samples stored at 50°C from the samples stored at 4, 22, and 35°C was observed in the similarity maps. The factor loadings of the first 2 principal components for the fluorescence spectra of the samples before storage were similar to the principal components analysis results of the samples during storage. It appears that similar factors are responsible for the variation in the samples before storage and their changes during storage. Additionally, storage of the samples at 50°C accelerated these reactions. The results demonstrate that front-face fluorescence spectroscopy, coupled with multivariate statistical methods, can be utilized as an analytical technique to monitor variation in NDM samples from different manufacturers and changes during storage.     

Validation of radio-frequency dielectric heating system for destruction of Cronobacter sakazakii and Salmonella species in nonfat dry milk

Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and Salmonella spp. can survive the spray-drying process if milk is contaminated after pasteurization, and the dried product can be contaminated from environmental sources. Compared with conventional heating, radio-frequency dielectric heating (RFDH) is a faster and more uniform process for heating low-moisture foods. The objective of this study was to design an RFDH process to achieve target destruction (log reductions) of C. sakazakii and Salmonella spp. The thermal destruction (decimal reduction time; D-value) of C. sakazakii and Salmonella spp. in NDM (high-heat, HH; and low-heat, LH) was determined at 75, 80, 85, or 90°C using a thermal-death-time (TDT) disk method, and the z-values (the temperature increase required to obtain a decimal reduction of the D-value) were calculated. Time and temperature requirements to achieve specific destruction of the pathogens were calculated from the thermal destruction parameters, and the efficacy of the RFDH process was validated by heating NDM using RFDH to achieve the target temperatures and holding the product in a convection oven for the required period. Linear regression was used to determine the D-values and z-values. The D-values of C. sakazakii in HH- and LH-NDM were 24.86 and 23.0 min at 75°C, 13.75 and 7.52 min at 80°C, 8.0 and 6.03 min at 85°C, and 5.57 and 5.37 min at 90°C, respectively. The D-values of Salmonella spp. in HH- and LH-NDM were 23.02 and 24.94 min at 75°C, 10.45 and 12.54 min at 80°C, 8.63 and 8.68 min at 85°C, and 5.82 and 4.55 min at 90°C, respectively. The predicted and observed destruction of C. sakazakii and Salmonella spp. were in agreement, indicating that the behavior of the organisms was similar regardless of the heating system (conventional vs. RFDH). Radio-frequency dielectric heating can be used as a faster and more uniform heating method for NDM to achieve target temperatures for a postprocess lethality treatment of NDM before packaging.     

Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella enterica in milk powders at different storage times and temperatures

While the increase in thermal resistance of microorganisms at reduced water activity is demonstrated for low-moisture food products, the effect of storage time on the thermal resistance of microorganisms in low-moisture foods is not well established. As low-moisture foods are stored for long periods and are used as ingredients, cross-contamination can occur at any time period before the lethality step. Therefore, this study was designed to investigate the effect of storage time (30, 60, and 90 d) on the thermal resistance of Salmonella and Enterococcus faecium NRRL B-2354 in milk powders at a low water activity of 0.10 (conservative level). In this study, 2 milk powders, whole milk powder (WMP) and nonfat dry milk (NFDM), were inoculated with a 5-serotype Salmonella cocktail or E. faecium and equilibrated to a water activity of 0.10. The thermal resistance of Salmonella and E. faecium in WMP and NFDM were determined at different storage times (30, 60, and 90 d) at 85°C. The storage time had no effect on the thermal inactivation kinetics of Salmonella within 90 d of storage at 85°C. In the second part of this study, isothermal treatments were also conducted at higher temperatures (90 and 95°C) to evaluate the suitability of E. faecium as a surrogate for Salmonella in milk powders. The D-values of Salmonella in WMP with 30 d of storage at 85, 90, and 95°C were 7.98, 3.35, and 1.68 min. The corresponding values for E. faecium were 16.96, 7.90, and 4.16 min. Higher D-values of E. faecium indicates that it is a conservative surrogate. Similar results were found for NFDM. In general, D-values of both microorganisms are slightly higher in NFDM than WMP. Two primary models (log-linear and Weibull) were compared for their goodness-of-fit. The Weibull model was found to be more appropriate than the log-linear model. This study provides valuable information for establishing process validation for the pasteurization of milk powders.     

Effect of partial substitution of caprine milk for ovine milk,dry salting and cured scalding on lipolysis in Urfa cheeses

The objectives of this study were to determine the effect of partial substitution of caprine for ovine milk, dry salting and curd scalding on the free fatty acid (FFA) level of Urfa cheeses. At the end of storage, lauric and linoleic acids were lower in cheese made from milk where up to the 30% partial substitution of caprine milk for ovine milk was made. Dry salted cheeses had higher butyric, lauric, linoleic and linolenic acid levels, and lower palmitic acid levels than their scalded counterpart. A relative increase in short‐chain FFAs occurred during ripening. Palmitic and oleic acids were the most abundant FFAs in fresh and ripened Urfa cheeses.     

一种新型酚化木质素胺乳化剂的合成及其性能

以苯酚改性硫酸盐木质素得到了酚化木质素,再将其与脱氢枞酸单乙二酰胺、甲醛进行Mannich反应以引入脱氢枞酸单乙二酰胺甲基亲油基团,然后将反应产物进一步与二乙烯三胺、甲醛反应引入了二乙烯三胺甲基亲水基团,合成了一种新型酚化木质素阳离子乳a化剂。实验表明,在碱性条件下,当 n(苯酚)∶n(木质素)=1∶1、反应温度100℃、反应时间1.5 h时,所得产物酚化木质素的酚羟基含量较木质素增加了30.3%,相当于每个C9单元接枝了0~30个苯酚分子,质均分子质量增大7%,多分散性由1.49降至1.29;与木质素相比,酚化木质素中引入的脱氢枞酸单乙二酰胺甲基数量增加了1.1倍,引入的二乙烯三胺甲基数量增加了0.42倍;在pH值为2的稀盐酸溶液中,所合成的脱氢枞酸单乙二酰胺/二乙烯三胺/甲醛改性酚化木质素阳离子乳化剂的最大Zeta电位为38.0 mV,质量浓度为10 g/L时,表面张力为35.0 mN/m,甲苯乳液油水分层时间为70 min,均优于用未经酚化改性的木质素合成的产物。     

Influence of cleansers on a polysulphone membrane used for milk ultrafiltration

Membrane stress and apparent water flux were measured as a function of time, pressure and milk concentration during unstirred ultrafiltration of milk with a polysulphone membrane. Membrane properties changed considerably after exposure to six common membrane cleanser's with notable changes in the rate of declines in milk flux (Q), increase (inorganic and organic cleansers) and decrease (surfactants) in relative hydraulic resistance (RHR) values.     

Effect of a short dry period on milk yield and content,colostrum quality,fertility, and metabolic status of Holstein cows

We evaluated the effect of shortening the dry period (DP) on milk and energy-corrected milk (ECM) yields, milk components, colostrum quality, metabolic status, and reproductive parameters. Primiparous (n = 372) and multiparous (n = 400) Israeli Holstein cows from 5 commercial dairy herds were subjected to a 60-d or 40-d DP. Cows within each herd were paired according to milk production, age, days in milk, and expected calving. Analysis of the data from all cows, irrespective of age, revealed significant differences in milk and ECM yields that favored the 60-d DP, with a prominent effect in 2 of 5 examined herds. In primiparous cows, milk and ECM yields were similar between groups in 4 of 5 farms. In multiparous cows undergoing a 60-d (vs. 40-d) DP, milk and ECM yields were higher in 3 herds. These differences could not be explained by milk and ECM yields in cows diagnosed with metritis, ketosis, and mastitis (defined by a somatic cell count threshold of 250,000 cell/mL), distribution of infected and noninfected cows, or new infections during DP and after calving. Including the milk and ECM yields from an average of 19.55 d from the previous lactation revealed higher milk and ECM yields for 40-d (vs. 60-d) DP cows in all herds. Analyzing 2 consecutive lactations revealed similar milk and ECM yields between groups in 4 out of 5 herds. In 1 herd, yields were higher in the 40-d compared with the 60-d DP group. One week after calving, the nonesterified fatty acid concentrations of 40-d DP cows were significantly lower than those of 60-d DP cows, indicating better postpartum energy balance. Colostrum quality, measured as IgG concentration, did not differ between the 2 DP groups. Cows assigned to 40-d DP had better reproductive performance, as reflected by fewer days to first insemination, a lower proportion with >90 d to first insemination, and fewer days to pregnancy. With respect to primiparous cows, a short DP increased conception rate after first artificial insemination and decreased the proportion of nonpregnant cows after 150 d in milk. In light of these findings, we suggest that a short DP be applied for its economic and physiological benefits. This is highly relevant to dairy herds located in regions such as Israel, Spain, and Florida that suffer from reduced milk production during the hot season.     

The effect of using nonchlorine products for cleaning and sanitising milking equipment on bacterial numbers and residues in milk

Seven milking machine cleaning procedures which differed in the working solution content of sodium hydroxide, presence of chlorine, temperature of water, and inclusion of acid and four antimicrobial products used as sanitisers in the premilking rinse water were evaluated. The cleaning system, which incorporated a high working solution of sodium hydroxide (2525 ppm) used in cold water combined with a hot (70 °C) daily acid wash, had lower total bacterial counts (TBC) (1040 colony forming units (cfu)/mL) than the same detergent product without the addition of acid (1980 cfu/mL) (P < 0.05). Lower TBC were observed in milk and on equipment surfaces when a sanitiser was applied (P < 0.01). Trichloromethane levels in milk were higher when chlorine was used as a sanitiser (P < 0.01).     

Effects of bovine casein hydrolysate as a dry cow therapy on prevention and cure of bovine intramammary infection,milk production,and somatic cell count in the subsequent lactation

The primary objectives were to investigate the efficacy of bovine casein hydrolysate (bCNH) as a dry cow therapy at (1) preventing new intramammary infection (IMI) postpartum of all bacteria and coagulase-negative staphylococci (CNS), and (2) curing existing subclinical infections, mainly of CNS. The secondary objective was to measure the effects of bCNH on milk yield, composition, and somatic cell count (SCC) during the lactation postcalving. The trial was conducted as a randomized, blinded controlled experiment. Israeli Holstein dairy cows (n = 170) in first or higher lactations were recruited from 4 large commercial dairy herds. Cows were enrolled following clinical examination and bacteriological sampling of each quarter, which was the experimental unit. Random allocation was implemented at the cow level. All quarters of 100 cows were treated with 1 dose of bCNH (60 mg diluted in 20 mL of sterile solution) and those of 70 control cows were treated with saline solution. Clinical assessment of each cow's general appearance, teat-end leakage, and teat morphology was performed for 0, 1, 2, 3, 7, and 14 d after treatment, together with follow-up clinical observation and clinical examination of udder quarters. Quarter aseptic milk samples were obtained for bacteriological culture 48 h pretreatment, at time of treatment, and 3 and 5 d postcalving. Multivariable analyses were conducted to study the effects of bCNH on cure and prevention of IMI, adjusting for parity, farm, average of daily milk yield for 305 d, and average of monthly SCC values for 305 d of previous lactation. The odds of preventing IMI in cows treated with bCNH at dry-off were 2.15 times higher [95% confidence interval (CI): 1.15 to 4.00] than in cows treated with saline. Prevention was mostly of CNS. The odds of preventing CNS in cows treated with bCNH at dry-off were 2.20 times higher (95% CI: 1.58 to 3.07) than in control cows. The odds of curing IMI caused by CNS in cows treated with bCNH at dry-off were 4.80 times higher (95% CI: 0.75 to 30.75) than in saline-treated cows. Log SCC, adjusted to that of the previous lactation, was lower in the bCNH group compared with controls for 305 d in milk postcalving. The average milk yield per day for 305 d, adjusted to average daily milk yield of previous lactation, was higher by 2.1 kg in the bCNH group compared with controls (95% CI: 1.21 to 3.20). Clinical assessment of udders and cows posttreatment showed no negative effects of bCNH. Incidence of stillbirth, clinical mastitis, retained placenta, endometritis (5 to 12 d postcalving), ketosis, abortions, and reproduction did not differ between the 2 groups. Results suggest that a single intramammary administration of bCNH at dry-off effectively increases milk yield and lowers SCC, prevents new IMI during the dry period, and may be a beneficial alternative for curing existing IMI at dry-off, mainly by CNS.     

磁性微球表面光引发聚合制备金属配位印迹层及选择性富集奶样中氟喹诺酮类药物残留

目的发展一种金属配位印迹磁性微球的制备方法,并用于奶样中氟喹诺酮类药物残留的选择性富集。方法采用简便的溶剂热法合成磁性纳米粒子,再采用溶胶-凝胶法制备磁性硅胶微球,然后在磁性硅胶微球表面接枝光引发剂,在125 W紫外灯辐射下合成恩诺沙星-Co(Ⅱ)配位印迹层,并用于磁分散萃取奶样中恩诺沙星、环丙沙星和洛美沙星。结果该方法的加标回收率为89.6%~100.8%,相对标准偏差为1.4%~5.5%,其中环丙沙星的检出限和定量限分别为1.72μg/kg和5.74μg/kg,洛美沙星的检出限和定量限分别为2.05μg/kg和6.82μg/kg,恩诺沙星的检出限和定量限分别为1.18μg/kg和3.94μg/kg。结论该样品处理方法是一种选择性好、简单快速的分离检测奶样中氟喹诺酮类药物残留的方法。     

Effect of high-pressure homogenization, nonfat milk solids, and milkfat on the technological performance of a functional strain for the production of probiotic fermented milks

The aim of this research was the evaluation of the effects of milkfat content, nonfat milk solids content, and high-pressure homogenization on 1) fermentation rates of the probiotic strain Lactobacillus paracasei BFE 5264 inoculated in milk; 2) viability loss of this strain during refrigerated storage; and 3) texture parameters, volatile compounds, and sensorial properties of the coagula obtained. The data achieved suggested a very strong effect of the independent variables on the measured attributes of fermented milks. In fact, the coagulation times were significantly affected by pressure and added milkfat, and the rheological parameters of the fermented milk increased with the pressure applied to the milk for added nonfat milk solids concentrations lower than 3%. Moreover, the polynomial models and the relative response surfaces obtained permitted us to identify the levels of the 3 independent variables that minimized the viability loss of the probiotic strain used during refrigerated storage.     

真空气流细胞破壁技术对橄榄总黄酮提取的影响

以橄榄为原料,通过单因素及Box-Benhnken中心组合法研究橄榄切片厚度、质构保护液浓度及真空气流细胞破壁技术（VAPB）对橄榄总黄酮提取率及破果率的影响。结果表明,切片橄榄最适宜厚度为4⁵ mm;质构保护最佳处理工艺为:首先在浓度为0.20 g/100 m L的海藻酸钠溶液中浸泡20 min,接着在浓度为0.15 g/100 m L的氯化钙溶液中浸泡60 min;真空气流细胞破壁前处理最佳工艺为:泄压温度110℃、压力差122 k Pa、停滞时间16 min、泄压重复次数3次;最后采用亚临界水提取,其总黄酮提取率为64.93%,破果率20.60%,相比切片后直接进行亚临界水提取对照组,总黄酮提取率提高了21.23%,而破果率仅增加了3.89%。提取过总黄酮的橄榄切片79.40%结构保持完整,可以作为广式凉果原料。      

Short communication: Effect of a stable pen management strategy for precalving cows on dry matter intake, plasma nonesterified fatty acid levels, and milk production

During the close-up transition period, dairy cows are at risk for negative energy balance due to increasing energy demands and decreasing feed intake. This can result in postparturient health problems and decreased milk production after calving. Cows are frequently regrouped during this period, which can negatively affect feeding and resting behavior. The hypothesis was that housing in a stable pen during the close-up transition period should result in a more settled environment resulting in fewer displacements from the feed bunk, which would result in improved feed intake, energy balance [lower nonesterified fatty acid (NEFA) concentrations], and lactation performance. This study addresses precalving pen grouping strategies, which have the potential to affect feed intake and energy balance. A randomized complete block design with pen as the experimental unit was used to compare a stable (S) housing strategy (cows with similar calving dates added to a precalving pen at once) to the more traditional dynamic (D) housing strategy (cows added up to 2 times per week to a precalving pen). Twice-weekly blood samples were collected for NEFA analysis and cow interactions within the pen were observed. Dry matter intake (DMI), milk production, and postparturient health problems were recorded. Mean DMI for the duration of the 28 d of the study was not different (S: 25.5 ± 1.6 vs. D: 25.7 ± 1.0 kg/d), and when examined over time relative to calving, no treatment by time interaction was observed. Concentrations of NEFA were not different when cows initially entered the pens (S: 0.21 ± 0.10 vs. D: 0.18 ± 0.04 mEq/L) and remained not different for the time intervals closer to calving (d −9 to −14: S: 0.28 ± 0.09 vs. D: 0.21 ± 0.04; d −3 to −6: S 0.36 ± 0.10, D 0.32 ± 0.05 mEq/L). Pen grouping strategy did not affect DMI, plasma NEFA concentrations, or milk production.     

Effectiveness of a water-saving super-absorbent polymer in soil water conservation for corn (Zea mays L.) based on eco-physiological parameters

BACKGROUND: The objective was to study soil water conservation and physiological growth of corn (Zea mays L.) using water‐saving super‐absorbent polymer (SAP) at 30 kg ha^?1. The effectiveness of SAP was studied under three irrigation levels (adequate, moderate and deficit) using a new type of negative hydraulic pressure controlled auto‐irrigator in the years 2009 and 2010 in a greenhouse at Beijing, P.R. China. RESULTS: Eight weeks after sowing, plant height and leaf area increased significantly by 41.6 and 79.6% under deficit irrigation for SAP treatment. The SAP had little effect on shoot dry mass under adequate and moderate irrigation but increased it significantly by 133.5% under deficit irrigation. Similarly, the efficiency of water use also increased by 97.1%. Leaf water potential under adequate and moderate irrigation differs slightly for SAP application, whereas under deficit irrigation the values were exceeded significantly by 27.8%. The superior growth and water use efficiency of corn treated with SAP under deficit irrigation was ascribed to maintenance of higher relative water contents in leaves as well as intercellular carbon dioxide concentration, net photosynthesis and transpiration rate. CONCLUSIONS: Our results suggested that plant growth and different physiological activities are restricted by drought stress and the application of super‐absorbent polymer could conserve soil water, making same available to plants for increased growth and biomass accumulation especially under severe water stress. Thus, application of SAP is a suitable soil management practice for the locations characterised by severe water stress. Copyright © 2011 Society of Chemical Industry     

Progressive inclusion of pearl millet herbage as a supplement for dairy cows fed mixed rations: Effects on methane emissions,dry matter intake,and milk production

The inclusion of grazing in dairy feeding systems can improve animal welfare and reduce feed costs and labor for animal care and manure management. This work aimed to evaluate the effects of including pearl millet herbage (Pennisetum glaucum ‘Campeiro') as a supplement for dairy cows fed total mixed rations (TMR). The treatments included 100% TMR offered ad libitum (control, TMR₁₀₀), 75% TMR ad libitum intake + access to grazing of a pearl millet pasture between the morning and afternoon milkings (7 h/d; pTMR₇₅), and 50% TMR ad libitum intake + access to grazing of a pearl millet pasture between the morning and afternoon milkings (7 h/d; pTMR₅₀). Nine multiparous Holstein and F₁ Jersey × Holstein cows were distributed in a replicated 3 × 3 Latin square design with 3 periods of 21 d (a 16-d adaptation period and a 5-d measurement period). Cows in the TMR₇₅ and TMR₅₀ groups strip-grazed a pearl millet pasture with pre- and postgrazing sward height targets of 60 and 30 cm, respectively. The herbage dry matter intake (DMI) increased with decreasing mixed ration supplies, and the total DMI decreased linearly from 19.0 kg/d in the TMR₁₀₀ group to 18.0 kg/d in the pTMR₅₀ group. Milk production decreased linearly from 24.0 kg/d in the TMR₁₀₀ group to 22.4 kg/d in the pTMR₅₀ group, and energy-corrected milk (ECM) production decreased linearly from 26.0 kg/d to 23.6 kg/d. Enteric methane (CH₄) emissions decreased linearly from 540 g/d in the TMR₁₀₀ group to 436 g/d in the pTMR₅₀ group, and CH₄ yields (g/kg of DMI) tended to decrease linearly. The CH₄ intensity was similar between treatments, averaging 20 g of CH₄/kg of ECM. The inclusion of pearl millet herbage in the dairy cow diets decreased the total DMI and milk production to a small extent without affecting CH₄ intensity (g/kg of ECM).