Skim milk cryoconcentration as affected by the thawing mode: gravitational vs. microwave‐assisted

In the present study, skim milk was successfully cryoconcentrated up to 43.72 ± 0.69% (w/w) total dry matter after four cryoconcentration cycles. Total proteins were concentrated up to 22.49 ± 0.31% (w/w). It was found that the cryoconcentrated skim milk fraction was rich in potassium ions. The effect of the cryoconcentration cycle and thawing mode on process efficiency was studied. The obtained data showed that the cryoconcentration cycle effect was significant (P < 0.001). The thawing mode (gravitational and microwave assisted thawing) had no effect on process efficiency. However, the microwave assisted thawing mode was more efficient regarding to the time needed to obtain the desired thawed fraction. To achieve high process efficiency, three cryoconcentration cycles were sufficient since the process efficiency drastically decreased after this cycle. The concentration of the dry mater entrapped in the ice fraction was the highest at the fourth cryoconcentration cycle.     

Physical properties of yoghurt manufactured with milk whey and transglutaminase

The effect of milk protein polymerization prior to the yoghurt fermentation process was evaluated by enzymatic reaction with microbial transglutaminase (Streptoverticillium mobaraense). Yoghurt samples were manufactured with 100% milk or by substituting milk with 20 or 30% of liquid milk whey, aimed at determining the use of natural milk whey in dairy products. Transglutaminase was added at a protein ratio of 0.5 U g⁻¹ to all samples and evaluated regarding rheological behavior, syneresis index and texture profile. The addition of enzyme transglutaminase contributed to syneresis prevention and increased the consistency index in yoghurt samples manufactured with milk whey. Yoghurt manufactured from 70% milk plus 20% milk whey, followed by enzymatic treatment, presented similar characteristics to traditionally manufactured yoghurt (C 100), with no alteration in the syneresis of the samples (p > 0.05) and presented texture parameters similar to the control yoghurt (C 100).     

Astringency of bovine milk whey protein

Whey protein solutions at pH 3.5 elicited an astringent taste sensation. The astringency of whey protein isolate (WPI), the process whey protein (PWP) that was prepared by heating WPI at pH 7.0, and the process whey protein prepared at pH 3.5 (aPWP) were adjusted to pH 3.5 and evaluated by 2 sensory analyses (the threshold method and the scalar scoring method) and an instrumental analysis (taste sensor method). The taste-stimulating effects of bovine and porcine gelatin were also evaluated. The threshold value of astringency of WPI, PWP, and aPWP was 1.5, 1.0, and 0.7 mg/mL, respectively, whereas the gelatins did not give definite astringency. It was confirmed by the scalar scoring method that the astringency of these proteins increased with the increase in protein concentration, and these proteins elicited strong astringency at 10 mg/mL under acidic conditions. On the other hand, the astringency was not elicited at pH 3.5 by 2 types of gelatin. A taste sensor gave specific values for whey proteins at pH 3.5, which corresponded well to those obtained by the sensory analysis. Elicitation of astringency induced by whey protein under acidic conditions would be caused by aggregation and precipitation of protein molecules in the mouth.     

Production of concentrated cherry and apricot juices by cryoconcentration technology

In this study, apricot and cherry juices were successfully cryoconcentrated. Two freezing temperatures −10 ± 1 °C, −20 ± 1 °C, and three cryoconcentration stages were studied. Freezing temperature did not show any affect on total dry matter content of the concentrated juices, as well as on their physico-chemical properties. At the same time, the cryoconcentration stage effect was highly significant on total dry matter content and juice qualities. Total dry matter of the apricot juice increased from 14.50 ± 1.12 g/100 g up to 35.50 ± 2.09 g/100 g in three cryoconcentration stages. Cherry juice total dry matter increased from 15.50 ± 1.26 g/100 g up to 45.50 ± 2.47 g/100 g. Concentrated juices had high aroma numbers and high content of ascorbic acid compared to the same juices obtained by the conventional method. The present study demonstrated that cryoconcentration as an environmentally friendly technology is a promising and highly effective food processing technique in the juice industry. Aroma number increased from 3.55 up to 8.38 and from 5.23 up to 15.75 for apricot and cherry juices, respectively. The juices obtained by cryoconcentration technology were compared to the same juices obtained by the conventional method of evaporation.     

Phospho- and sphingolipid distribution during processing of milk, butter and whey

Phospho‐ and sphingolipids (SPHs) were monitored upon processing of raw milk into skimmed milk, cream, butter, buttermilk, fresh cheese, acid whey, anhydrous milk fat and butterserum (=the aqueous phase of butter). These products were analysed on polar lipids, fat and dry matter and corresponding balances were calculated. It was found that polar lipids were preferentially enriched in aqueous phases like skimmed milk, buttermilk and butterserum. Significant differences in relative SPH content were observed. Tangential filtration and thermocalcic aggregation of the acid whey successfully recovered the polar lipids. With 11.5% of polar lipids on a dry matter base, representing 28.4% of the milk polar lipids and only 0.9% of the milk mass, butterserum was found to be most suitable for further purification. This could result in a food (ingredient) with enhanced technological and nutritional properties, as recent studies reveal health‐improving capacities of phospho‐ and SPHs.     

近红外快速检测奶粉乳清粉成分研究

采用Perten8620近红外奶粉分析仪检测奶粉的近红外光谱特性，建立了奶粉近红外检测的校准模型。结果表明，近红外检测技术无需称重和化学试剂，可在1min以内快速检测奶粉和乳清粉的蛋白、脂肪、水分等指标，其准确性和精度可以达到在国际允许的误差范围内。根据近红外技术可能在短时间内收集大量样品的光谱图，开发了新检测项目的校准曲线。     

Physicochemical and functional properties of goat milk whey protein and casein obtained during different lactation stages

During lactation, goat milk contains colostrum, transitional milk, mature milk, and end milk. The protein present in goat milk during different lactation periods has different characteristics. This study aimed to characterize the protein profile of goat milk samples obtained at different lactation stages and to identify changes in the physicochemical and functional properties of whey protein and casein from goat milk collected at 1, 3, 15, 100, and 200 d after calving. The results demonstrated that the lactation period had a great influence on the physicochemical and functional properties of goat milk whey protein and casein, especially the protein properties of colostrum on the first day after delivery. The denaturation temperature, hydrophobicity, and turbidity of whey protein were significantly higher on the first day postpartum than at other lactation periods. Correspondingly, the colostrum whey protein also had better functional properties, such as emulsification, oil holding capacity, and foaming properties on the first day postpartum than at other lactation periods. For casein, the turbidity, particle size, water holding capacity, and foaming properties on the first day after delivery were significantly higher than those at other lactation periods, whereas the denaturation temperature, oil holding capacity, and emulsification followed the opposite trend. For both whey protein and casein, the 2 indicators of emulsifying properties, namely, emulsifying activity index and the emulsion stability, also followed an opposite trend relative to lactation stage, whereas the changes in foaming capacity with the lactation period were completely consistent with the change of foaming stability. These findings could provide useful information for the use of goat milk whey protein and casein obtained during different lactation stages in the dairy industry.     

Comparative study of the biochemical changes and volatile compound formations during the production of novel whey-based kefir beverages and traditional milk kefir

Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8–8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir.     

Invited review: Microfiltration-derived casein and whey proteins from milk

Milk, a rich source of nutrients, can be fractionated into a wide range of components for use in foods and beverages. With advancements in filtration technologies, micellar caseins and milk-derived whey proteins are now produced from skim milk using microfiltration. Microfiltered ingredients offer unique functional and nutritional benefits that can be exploited in new product development. Microfiltration offers promise in cheesemaking, where microfiltered milk can be used for protein standardization to improve the yield and consistency of cheese and help with operation throughputs. Micellar casein concentrates and milk whey proteins could offer unique functional and flavor properties in various food applications. Consumer desires for safe, nutritious, and clean-label foods could be potential growth opportunities for these new ingredients. The application of micellar casein concentrates in protein standardization could offer a window of opportunity to US cheese makers by improving yields and throughputs in manufacturing plants.     

Moisture adsorption by milk whey protein films

Edible films, using whey protein as the structural matrix, were tested for water vapour diffusion properties. Whey protein films were prepared by dispersing 6.5% whey protein concentrate (WPC) in distilled water with pH kept at 7.0. Glycerol was the plasticizer agent. Film slabs (13.5 × 3.5 cm) were put in a chamber at 25 °C and 75% relative humidity, being held in vertical planes for different periods of time. The mass gain was determined throughout the experiment. We show that moisture adsorption by milk whey protein films is well described by a linear diffusion equation model. After an adsorption experiment was performed the solution of the diffusion equation was fitted to the data to determine the diffusion coefficient of the material.     

乳清多肽的制备及乳清多肽酒的研制

采用蛋白酶水解乳清粉，对乳清多肽进行酵母菌发酵，并对发酵所得乳清酒进行风味调配。乳清粉最佳的水解条件为：酶浓度与底物浓度之比为1％、温度60℃、pH9．0、时间120min，水解度21．22％。乳清多肽酒的最优发酵条件：接种量5％、起始pH7．5、温度22℃、发酵60h，酒精度可达到3．9％。多肽乳清酒的最佳基本调配是总酸（苹果酸：柠檬酸=1：1）为0．1％、蔗糖为7％、环状糊精为0．6％。     

Effect of microparticulated whey proteins on milk coagulation properties

The enhancement of milk coagulation properties (MCP) and the reuse of whey produced by the dairy industry are of great interest to improve the efficiency of the cheese-making process. Native whey proteins (WP) can be aggregated and denatured to obtain colloidal microparticulated WP (MWP). The objective of this study was to assess the effect of MWP on MCP; namely, rennet coagulation time (RCT), curd-firming time, and curd firmness 30 min after rennet addition. Six concentrations of MWP (vol/vol; 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0%) were added to 3 bulk milk samples (collected and analyzed during 3 d), and a sample without MWP was used as control. Within each day of analysis, 6 replicates of MCP for each treatment were obtained, changing the position of the treatment in the rack. For control samples, 2 replicates per day were performed. In addition to MCP, WP fractions were measured on each treatment during the 3 d of analysis. Milk coagulation properties were measured on 144 samples by using a Formagraph (Foss Electric, Hillerød, Denmark). Increasing the amount of MWP added to milk led to a longer RCT. In particular, significant differences were found between RCT of the control samples (13.5 min) and RCT of samples with 3.0% (14.6 min) or more MWP. A similar trend was observed for curd-firming time, which was shortest in the control samples and longest in samples with 9.0% MWP (21.4 min). No significant differences were detected for curd firmness at 30 min across concentrations of MWP. Adjustments in cheese processing should be made when recycling MWP, in particular during the coagulation process, by prolonging the time of rennet activity before cutting the curd.     

Skim acidic milk whey cryoconcentration and assessment of its functional properties: Impact of processing conditions

In the present research two objectives were studied. The first was aimed to optimize whey cryoconcentration process by minimizing the amount of the dry matter entrapped in the ice fraction. This was possible by recycling the ice fraction. It was possible to concentrate acidic whey from 5.71 ± 0.01% (w/w) up to 24.68 ±0.03% (w/w) total dry matter using three cryoconcentration cycles and one recycling ice cycle. The second objective was to study the emulsifying and foaming properties of the concentrated whey as function of the cryoconcentration cycle. Results showed that emulsion stability index (ESI) of the cryoconcentrated whey increased by increasing the cryoconcentration cycle whereas the emulsion activity index (EAI) decreased. Foaming ability expressed as nitrogen volume needed to get foam volume three times higher than the initial volume increased by increasing cryoconcentration cycle and foam stability decreased by increasing the cryoconcentration cycle.Industrial relevanceSeveral efforts and studies have been made to increase the use of milk whey, a valuable by-product of cheese processing, especially for human nutrition. In the present work, cryoconcentration technology was used for whey recovery and valorisation as promising ingredient in the food industry.     

以乳清为原料生产蒸馏型奶酒

介绍了以乳清为原料生产蒸馏型奶酒的工艺及蒸馏型奶酒各项指标和营养保健功能。     

Performance assessment of membrane distillation for skim milk and whey processing

Membrane distillation is an emerging membrane process based on evaporation of a volatile solvent. One of its often stated advantages is the low flux sensitivity toward concentration of the processed fluid, in contrast to reverse osmosis. In the present paper, we looked at 2 high-solids applications of the dairy industry: skim milk and whey. Performance was assessed under various hydrodynamic conditions to investigate the feasibility of fouling mitigation by changing the operating parameters and to compare performance to widespread membrane filtration processes. Whereas filtration processes are hydraulic pressure driven, membrane distillation uses vapor pressure from heat to drive separation and, therefore, operating parameters have a different bearing on the process. Experimental and calculated results identified factors influencing heat and mass transfer under various operating conditions using polytetrafluoroethylene flat-sheet membranes. Linear velocity was found to influence performance during skim milk processing but not during whey processing. Lower feed and higher permeate temperature was found to reduce fouling in the processing of both dairy solutions. Concentration of skim milk and whey by membrane distillation has potential, as it showed high rejection (>99%) of all dairy components and can operate using low electrical energy and pressures (<10 kPa). At higher cross-flow velocities (around 0.141 m/s), fluxes were comparable to those found with reverse osmosis, achieving a sustainable flux of approximately 12 kg/h·m² for skim milk of 20% dry matter concentration and approximately 20 kg/h·m² after 18 h of operation with whey at 20% dry matter concentration.     

Technical note: Direct enzyme immunoassay of progesterone in bovine milk whey

A simple extraction-free or direct quantitative ELISA for progesterone in bovine milk whey was developed. Whey samples are easy to collect, transport, and store. This method also allows for monitoring progesterone levels in cattle, which is important in reproductive management. The assay was designed to cover the concentration range 0.05 to 2 ng/mL, and the sensitivity of the method was 1.5 pg/mL. The intra- and interassay coefficients of variation were 8 and 12%, respectively. A high correlation (r = 0.90) between ELISA and radioimmunoassay measurements of progesterone in the same milk whey samples was obtained. The method can be easily applied in practice because samples can be stored at room temperature (22 to 26°C) for 4 d. Moreover, because analysis requires milk coagulation, that process can be initiated during transport by standard mail services to the laboratory. Upon arrival at the laboratory, whey can be kept refrigerated for 1 wk before analysis. This tool is useful for monitoring luteal activity of dairy cows.     

Buttermilk as milk powder and whey substitute in compound milk chocolate: Comparative study and optimisation

The aim of this study was to investigate the optimal concentration of milk, whey and buttermilk powder by using mixture design for the formulation of compound milk chocolate. The influence of buttermilk as a milk and whey substitute on the main physicochemical parameters of compound milk chocolate was investigated. The optimisation of the variables indicated that using 35.660% milk powder, 27.957% whey powder and 36.383% buttermilk produced the optimum milk chocolate with the highest desirability without undesirable changes in the quality properties. Chocolates containing equal amounts of buttermilk and milk powder and also equal amounts of whey powder and buttermilk powder demonstrated high consumer acceptability.     

乳清多肽的制备及其发酵饮料的开发

研究了乳清多肽的制备、性质及其发酵饮料的开发,结果表明,碱性蛋白酶比中性蛋白酶水解乳清蛋白的能力强,且更经济,水解最佳条件为加酶量为7000(U/g蛋白)、底物添加量为5%、水解温度为60℃、水解初始pH值为8.5,最大乳清蛋白水解度可达到22.45%。最优酒精发酵条件为接种量5%、初始pH7.5、温度22℃、时间45h。乳清多肽发酵饮料的配方为酸量0.1%,蔗糖量为8%,-β环状糊精量为0.5%。     

Short communication: Composition of coproduct streams from dairy processing: Acid whey and milk permeate

This article provides composition information for 3 abundantly available but little characterized dairy coproduct streams: acid whey from Greek yogurt (GAW), acid whey from cottage cheese (CAW), and milk permeate (MP). Three replicate samples obtained on different dates from several dairy processors were analyzed. The main component in all streams was lactose, with up to 3.5, 2.1, and 11.9% in GAW, CAW, and MP, respectively. Crude protein content ranged from 1.71 to 3.71 mg/g in GAW, 1.65 to 5.05 mg/g in CAW, and 3.2 to 4.35 mg/g in MP, and pH ranged from 4.21 to 4.48, 4.35 to 4.51, and 5.4 to 6.37, respectively. Chemical oxygen demand varied from 52,400 to 62,400 mg/L for GAW, 31,900 to 40,000 mg/L for CAW, and 127000 to 142,000 mg/L for MP; biochemical oxygen demand ranged from 45,800 to 50,500 mg/L (GAW), 32,700 to 40,000 mg/L (CAW), and 110,000 to 182,000 mg/L (MP). The GAW had the lowest pH (4.21–4.48) and highest mineral content of all streams. These data will assist processors and researchers in developing value-added uses of these dairy coproducts.