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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. 相似文献
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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. 相似文献
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《Journal of dairy science》2023,106(7):4502-4515
Consumers' growing interest in fermented dairy foods necessitates research on a wide array of lactic acid bacterial strains to be explored and used. This study aimed to investigate the differences in the proteolytic capacity of Lactobacillus helveticus strains B1929 and ATCC 15009 on the fermentation of commercial ultra-pasteurized (UHT) skim milk and reconstituted nonfat dried milk powder (at a comparable protein concentration, 4%). The antihypertensive properties of the fermented milk, measured by angiotensin-I-converting enzyme inhibitory (ACE-I) activity, were compared. The B1929 strain lowered the pH of the milk to 4.13 ± 0.09 at 37°C after 24 h, whereas ATCC 15009 needed 48 h to drop the pH to 4.70 ± 0.18 at 37°C. Two soluble protein fractions, one (CFS1) obtained after fermentation (acidic conditions) and the other (CFS2) after the neutralization (pH 6.70) of the pellet from CFS1 separation, were analyzed for d-/l-lactic acid production, protein concentration, the degree of protein hydrolysis, and ACE-I activity. The CFS1 fractions, dominated by whey proteins, demonstrated a greater degree of protein hydrolysis (7.9%) than CFS2. On the other hand, CFS2, mainly casein proteins, showed a higher level of ACE-I activity (33.8%) than CFS1. Significant differences were also found in the d- and l-lactic acid produced by the UHT milk between the 2 strains. These results attest that milk casein proteins possessed more detectable ACE-I activity than whey fractions, even without a measurable degree of hydrolysis. Findings from this study suggest that careful consideration must be given when selecting the bacterial strain and milk substrate for fermentation. 相似文献
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We determined the effects of standardization material, protein content, and pH on the heat stability of reconstituted milk made from low-heat (LH) and medium-heat (MH) nonfat dry milk (NDM). Low-heat and MH NDM were standardized downward from 35.5% to 34, 32, and 30% protein by adding either edible lactose powder (ELP) or permeate powder (PP) from skim milk ultrafiltration. These powders were called standardized skim milk powders (SSMP). The LH and MH NDM and SSMP were reconstituted to 9% total solids. Furthermore, subsamples of reconstituted NDM and SSMP samples were set aside to measure heat stability at native (unadjusted) pH, and the rest were adjusted to pH 6.3 to 7.0. Heat stability is defined as heat coagulation time at 140°C of the reconstituted LH or MH NDM and SSMP samples. The entire experiment was replicated 3 times at unadjusted pH values and 2 times at adjusted pH values. At an unadjusted pH, powder type, standardization material, and protein content influenced the heat stability of the samples. Heat stability for reconstituted LH NDM and SSMP was higher than reconstituted MH NDM and SSMP. Generally, decreased heat stability was observed in reconstituted LH or MH SSMP as protein content was decreased by standardization. However, adding ELP to MH SSMP did not significantly change its heat stability. When pH was adjusted to values between 6.3 and 7.0, powder type, standardization material, and pH had a significant effect on heat stability, whereas protein content did not. Maximum heat stability was noted at pH 6.7 for both reconstituted LH NDM and SSMP samples, and at pH 6.6 for both reconstituted MH NDM and SSMP samples. Furthermore, for samples with adjusted pH, higher heat stability was observed for reconstituted LH SSMP containing PP compared with reconstituted milk from LH SSMP containing ELP. However, no statistical difference was observed in the heat stability of reconstituted milk from MH NDM and MH SSMP samples. We conclude that powder type (LH or MH) and effect of standardization material (ELP or PP) can help explain differences in heat stability. The difference in the heat stability of powder type may be associated with the difference in the pH of maximum heat stability and compositional differences in the standardization material (ELP or PP). 相似文献
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Endospores of Bacillus licheniformis [American Type Culture Collection (ATCC) 6634], Bacillus coagulans (ATCC 12245), and Geobacillus stearothermophilus (ATCC 15952) were spiked in sterile nonfat milk, and subjected to high intensity batch ultrasonication treatment at different amplitudes (80 or 100%) and durations (1 to 10 min). Increasing the amplitude from 80 to 100% did not result in enhanced inactivation of G. stearothermophilus endospores. However, an increase in the duration of ultrasonication from 1 to 10 min significantly increased the inactivation of endospores of all 3 species. About 48.96% of the G. stearothermophilus endospores were inactivated by ultrasonication alone, whereas ultrasonication and pasteurization combined increased the inactivation to 65.74%. Inactivation of endospores could be further enhanced to 75.32% by ultrasonication and higher heat (80°C/1 min) combination. Endospores of B. licheniformis and B. coagulans were inactivated to a lesser extent compared with G. stearothermophilus spores. Ultrasonicated B. licheniformis endospores germinated in higher numbers when compared with untreated endospores resulting in their greater inactivation during the combined treatment. During microstructure imaging of ultrasonicated endospores, although no structural damage was noticed, they showed irregular shrinkage and wrinkles with surface coarseness. This may also have contributed to their reduced thermal resistance, in addition to sporulation. 相似文献
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A comparison of the buttermilk solids functional properties to nonfat dried milk,soy protein isolate,dried egg white,and egg yolk powders 总被引:1,自引:0,他引:1
Physicochemical (i.e., sulfhydryl group, protein, and total solubility) as well as functional properties (i.e., water-holding and fat-absorption capacity, foaming and emulsification capacity, and stability) of commercial buttermilk solids (BMS) were compared to nonfat dried milk, soy protein isolate, and dried egg yolk and egg white powders on an equivalent protein basis. BMS showed limited functional properties in water-holding capacity (0.75 g water/g protein) and fat-absorption capacity (1.2 g of oil/g of protein), and foaming capacity (0.5 ml of foam/ml of solution) and stability. However, emulsifying capacity and stability of BMS was not significantly different from other dried protein powders. Results indicated that 0.9 g of protein (approximately 0.45%, wt/vol, concentration) from BMS was needed to emulsify a maximum oil concentration of 50% in water at temperatures up to 50 degrees C. Denaturation of protein, quantified by free sulfhydryl groups, was a critical factor affecting the functionality of BMS and all other protein powders tested. The milk fat globule membrane present in BMS did not enhance either emulsifying capacity or stability. 相似文献
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分别研究了各4种不同品种的全脂乳粉和脱脂乳粉在1kHz~10MHz波段的介电特性。结果发现:随着频率的增加,全脂乳粉和脱脂乳粉的ξ’和ξ″值呈单调递减趋势;全脂乳粉的ξ’和ξ″值都高于脱脂乳粉,相同类型乳粉各品种间的ξ’和ξ″差异不大;全脂乳粉的ξ″值在103~105Hz频率段减小趋势明显,且ξ″值的对数与频率的对数成线性反比关系,而脱脂乳粉无此规律;全脂乳粉和脱脂乳粉的穿透深度Dp随频率的提高而减小,两类乳粉的介电特性差异可能与它们各自的脂肪和乳糖含量有关。 相似文献
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M. Michael R.K. Phebus H. Thippareddi J. Subbiah S.L. Birla K.A. Schmidt 《Journal of dairy science》2014
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. 相似文献
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《Journal of dairy science》2021,104(9):9607-9616
Salmonella persistence in milk powders has caused several multistate foodborne disease outbreaks. Therefore, ways to deliver effective thermal treatment need to be identified and validated to ensure the microbial safety of milk powders. In this study, a process of hot air-assisted radio frequency (HARF) followed by holding at high temperatures in a convective oven was developed for pasteurization of milk powders. Heating times were compared between HARF and a convection oven for heating milk powders to a pasteurization temperature, and HARF has been shown to considerably reduce the come-up time. Whole milk powder (WMP) and nonfat dry milk (NFDM) were inoculated with a 5-serotype Salmonella cocktail and equilibrated to a water activity of 0.10 to simulate the worst case for the microbial challenge study. After heating the sample to 95°C using HARF, followed by 10 and 15 min of holding in the oven, more than 5 log reduction of Salmonella was achieved in WMP and NFDM. This study validated a HARF-assisted thermal process for pasteurization of milk powder based on previously collected microbial inactivation kinetics data and provides valuable insights to process developers to ensure microbial safety of milk powder. This HARF process may be implemented in the dairy industry to enhance the microbial safety of milk powders. 相似文献
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目的改进婴幼儿配方乳粉中三聚氰胺的检测方法。方法样品经高浓度三氯乙酸溶液-乙腈提取过滤,后经阳离子交换固相萃取柱净化,用高效液相色谱法测定,采用外标法定量。结果改进方法的检测时间缩短4 h,在0.5~10μg/m L范围内检测结果线性关系良好,方法检出限为0.5 mg/kg,定量限为1.5 mg/kg,回收率提高到99.3%~102%,精密度为0.47%,稳定性相对标准偏差为0.96%,能力验证结果表明可靠性好。结论改进方法能快速有效对婴幼儿配方乳粉产品进行检测,结果可靠,具有实践应用价值。 相似文献
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高效液相色谱法分析原料乳和奶粉中三聚氰胺 总被引:1,自引:0,他引:1
建立了二极管阵列检测器-高效液相色谱测定原料乳及奶粉中三聚氰胺的方法。奶粉样品经三氯乙酸超声提取,乙酸铅沉淀蛋白,三氯甲烷除去脂肪和非极性杂质,PROELUTPXCSPE阳离子交换固相萃取小柱进一步除去样品基质干扰,氨化甲醇洗脱。实验对色谱分离条件进行了优化,三聚氰胺的质量浓度在1.0~100.0μg/mL范围内与色谱峰面积呈良好的线性关系,回归方程为y=89.763x-113.72,相关系数为R2=0.9988。加标回收率为90.5%~105.0%,相对标准偏差(RSD)小于4.0%。该方法简单、快速,结果准确可靠。 相似文献
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Víctor Alonso García Londoño Martín Puñales Marcela Reynoso Silvia Resnik 《Food Additives and Contaminants: Part B: Surveillance Communications》2018,11(1):15-19
Forty samples of milk powder purchased in Uruguay were analysed to assess melamine (MEL) levels. Trichloroacetic acid and acetonitrile were used to extract and precipitate milk proteins previously to clean up of the samples by solid-phase extraction and then were determined by liquid chromatography coupled to ultraviolet detection. The limit of detection (LOD) and limit of quantification (LOQ)of MEL were 0.006 and 0.019 mg kg?1, respectively. Milk was fortified with MEL at three levels, producing average recoveries higher than 83.8%. The values for positive samples ranged from 0.017 to 0.082 mg kg?1. Nine samples were positive. Three of them had concentrations between LOD and LOQ. The mean MEL contamination was 0.028 mg kg?1. Consumption of milk powder containing these levels of MEL does not constitute a health risk for consumers. 相似文献
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目的 评定微生物法测定乳粉中叶酸的不确定度.方法 按照GB 5009.211—2014《食品安全国家标准食品中叶酸的测定》规定的微生物法对婴儿配方乳粉中叶酸含量进行测定,根据CNAS-CL01-G003:2019要求,依据GB/Z 22553—2010和JJF 1059.1—2012,分析测定过程中影响检验结果的因素主... 相似文献