The formation of calcium lactate crystals is responsible for concentrated acid whey thickening

The use of spray drying for dehydration of acid whey is generally limited by the appearance of uncontrolled thickening and solidifying of the whey mass during the lactose crystallization step. The origin of this physical change is still unknown and probably linked to complex interactions between physical properties and chemical composition of these products. To understand this phenomenon, we simulated the thickening of concentrated acid whey on a laboratory scale by measuring the flow resistance changes as a function of time and whey composition. The thickening process was characterized by an amplitude of torque and a lag time (induction time). Thickening of lactic acid whey concentrate occurred regardless of the presence of whey proteins or lactose crystals. Moreover, this work clearly demonstrated that the thickening process was due to the formation of filamentous structures corresponding to calcium lactate crystals and showed a large dependence on calcium and lactate contents, pH, and phosphate concentration.     

Increasing calcium solubility from whey mineral residues by combining gluconate and δ-gluconolactone

Insoluble milk mineral residues from whey processing, dominated by hydroxyapatite and calcium hydrogen phosphate, dissolved isothermally in aqueous gluconate/δ-gluconolactone, spontaneously forming solutions supersaturated in both calcium hydrogen phosphate and calcium gluconate. Calcium concentration of maximally supersaturated solutions was proportional to gluconate concentration, indicating gluconate assisted dissolution, while gluconolactone increased calcium available for dissolution and supersaturation. Precipitation of calcium gluconate, rather than of calcium hydrogen phosphate, was critical for supersaturation robustness. For calcium gluconate ionic product:solubility product of calcium gluconate ratios <12, the supersaturated solutions had a lag phase for precipitation of several weeks, which increased to several months by addition of solid calcium saccharate prior to dissolution of the mineral residues. Such supersaturated solutions with up to 7 g calcium L⁻¹, corresponding to a factor of supersaturation of >100 times compared with equilibrium calcium hydrogen phosphate solubility, may be exploited for increasing calcium availability of whey mineral based functional foods.     

FUNCTIONAL PROPERTIES OF HIGH HYDROSTATIC PRESSURE-TREATED WHEY PROTEIN

Surface hydrophobicity, solubility, gelation and emulsifying properties of high hydrostatic pressure (HHP)‐treated whey protein were evaluated. HHP treatment of whey protein buffer or salt solutions were performed at 690 MPa and initial ambient temperature for 5, 10, 20 or 30 min. Untreated whey protein was used as a control. The surface hydrophobicity of whey protein in 0.1 M phosphate buffers treated at pH 7.0 increased with an increase in HHP treatment time from 10 to 30 min. HHP treatments of whey protein in salt solutions at pH 7.0 for 5, 10, 20 or 30 min decreased the solubility of whey proteins. A significant correlation was observed between the surface hydrophobicity and solubility of untreated and HHP‐treated whey protein with r = ?0.946. Hardness of HHP‐induced 20, 25 or 30% whey protein gels increased with an increase in HHP treatment time from 5 to 30 min. An increase in the hardness of whey protein gels was observed as whey protein concentration increased. Whey proteins treated in phosphate buffer at pH 5.8 and 690 MPa for 5 min exhibited increased emulsifying activity. Whey proteins treated in phosphate buffer at pH 7.0 and 690 MPa for 10, 20 or 30 min exhibited decreased emulsifying activity. HHP‐treated whey proteins in phosphate buffer at pH 5.8 or 7.0 contributed to an increase in emulsion stability of model oil‐in‐water emulsions. This study demonstrates that HHP treatment of whey protein in phosphate buffer or salt solutions leads to whey protein unfolding observed as increased surface hydrophobicity. Whey proteins treated in phosphate buffers at pH 5.8 and 690 MPa for 5 min may potentially be used to enhance emulsion stability in foods such as salad dressings, sausage and processed cheese.     

Composition and calcium status of acid whey from pasteurized,UHT‐treated and in‐bottle sterilized milks

Whey extracts were obtained from pasteurized, UHT‐treated and in‐bottle sterilized milks. After acidic precipitation of casein the concentration of protein, NPN, lactose, lipid, calcium, magnesium and potassium was determined. Among the parameters examined, protein content was significantly reduced in the whey extracts from UHT‐treated and in‐bottle sterilized milks compared with that from pasteurized milk, while lactose content was increased. Calcium extracted in whey was at least 80% of total calcium of the milk. The total calcium to protein ratio of whey was increased as a function of the thermal treatment of milk, while ionic calcium was about 50% of total calcium in all whey extracts. In vitro protein digestibility was found to be significantly lower in whey from UHT‐treated and in‐bottle sterilized milks than in that from pasteurized milk. Parallel estimation of the percentage of ionic calcium and of the solubility of proteins in the pH range 2–10 indicated that calcium was not involved in the pH‐dependent solubility of proteins extracted in the whey, the extent of solubility being essentially a function of the thermal treatment of milk. The results suggest that calcium was not responsible for the formation of soluble protein macroaggregates with impaired digestibility that are present in whey from milk subjected to heat treatment of increasing intensity.     

Compositional Analysis of Commercial Whey Drinks

Seven different whey-based beverages, including six commerical products from Europe and an experimental laboratory prototype, were analyzed for protein, carbohydrate, and other main components and for selected micronutrients. The labelling information available and the various tests carried out illustrated several aspects of the current whey drink technologies, including the choice of sweet, acid, or deproteinated whey; the use of variable amounts of whey, water, and fruit juice components; and inclusion of various sweetening agents. The products analyzed included clear, carbonated beverages that showed no sedimentation tendency, as well as products manufactured from unmodified whey resulting in various degrees of sedimentation upon centrifugation. The calcium and riboflavin content in some of the products was comparable to fluid milk, thus indicating that these beverages could be recommended especially for consumers with limited milk consumption habits.     

Rheological properties of reduced lactose whey dispersions

The rheological behaviour of reduced lactose whey (RLW) dispersions of several different types of whey products was investigated with dynamic small amplitude oscillatory (SAOS) rheometry and rotational rheometry. The different aggregation states of the proteins were measured by using size-exclusion chromatography (SEC) with multiangle laser light scattering (MALLS). Differences in the mineral content (especially calcium and phosphate) of the RLW samples contributed to their different rheological properties. Calcium phosphate/whey protein aggregates were probably formed when the mineral content increased, resulting in an increase in the size of the aggregates and higher viscosity. These complexes were also more sensitive to heating.     

Milk sugars and minerals as ingredients

Lactose is the natural carbohydrate source and prebiotic compound found in the milk of mammals, but large variations in lactase activity in the small intestines of adult populations can cause problems with its use. The value of lactose can be increased by hydrolysis, but even more valuable products can be made by changing the structure of lactose and preventing its absorption in the gut. Some of these nonabsorbable lactose derivatives are already used in medical and functional food applications.
Calcium phosphate precipitation to the heat-transfer surfaces is one of the oldest problems of the dairy industry, but if precipitation is carried out in controlled conditions, the precipitate can be further processed to form milk calcium powder. Milk calcium can be used as a natural source of calcium in calcium-fortified dairy products.
The mineral and salty taste of whey has reduced its use as a food ingredient. The use of modern membrane technology offers a means of producing whey salt as a by-product of whey demineralization. These otherwise wasted minerals can then be used as a natural mineral salt. Especially interesting is the possibility of recycling the whey salt into cheese, improving its nutritional status.     

Chemical composition and sensory analysis of cheese whey‐based beverages using kefir grains as starter culture

The aim of the present work was to evaluate the use of the kefir grains as a starter culture for tradicional milk kefir beverage and for cheese whey‐based beverages production. Fermentation was performed by inoculating kefir grains in milk (ML), cheese whey (CW) and deproteinised cheese whey (DCW). Erlenmeyers containing kefir grains and different substrates were statically incubated for 72 h at 25 °C. Lactose, ethanol, lactic acid, acetic acid, acetaldehyde, ethyl acetate, isoamyl alcohol, isobutanol, 1‐propanol, isopentyl alcohol and 1‐hexanol were identified and quantified by high‐performance liquid chromatography and GC‐FID. The results showed that kefir grains were able to utilise lactose in 60 h from ML and 72 h from CW and DCW and produce similar amounts of ethanol (～12 g L^?1), lactic acid (～6 g L^?1) and acetic acid (～1.5 g L^?1) to those obtained during milk fermentation. Based on the chemical characteristics and acceptance in the sensory analysis, the kefir grains showed potential to be used for developing cheese whey‐based beverages.     

Milk Protein Coatings Prevent Oxidative Browning of Apples and Potatoes

ABSTRACT Color analysis on apple and potato slices coated with calcium caseinate or whey protein solutions showed that the 2 coatings efficiently delayed browning by acting as oxygen barriers. The antioxidant properties of the films were realized using a model allowing the release of oxidative species by electrolysis of saline buffer. Whey proteins were a better antioxidant capacity than calcium caseinate. Furthermore, addition of carboxymethyl cellulose (CMC) to the formulations significantly improved their antioxidative power. Best scavenging of oxygen free radicals and reactive oxygen species was found for films based on whey proteins and CMC which inhibited by 75% the formation of colored compounds produced by the reaction of the oxidative species with N,N‐diethyl‐p‐phenylenediamine.     

High pressure-induced denaturation of alpha-lactalbumin and beta-lactoglobulin in bovine milk and whey: a possible mechanism

In this study, high pressure (HP)-induced denaturation of alpha-lactalbumin (alpha-la) and beta-lactoglobulin (beta-lg) in dairy systems was examined. In both milk and whey, beta-lg was less baroresistant than alpha-la; both proteins were considerably more resistant to HP-induced denaturation in whey than in milk. HP-induced denaturation of alpha-la and beta-lg increased with increasing proportion of milk in mixtures of milk and whey. Addition of a sulphydryl-oxidising agent, KlO3, to milk or whey increased HP-induced denaturation of beta-lg, but reduced the denaturation of alpha-la. Denaturation of both alpha-la and beta-lg was prevented by adding a sulphydryl-blocking agent, N-ethylmaleimide, to milk or whey prior to HP treatment, highlighting the crucial role of sulphydryl-disulphide interchange reactions in HP-induced denaturation of alpha-la and beta-lg. Removal of colloidal calcium phosphate from milk also reduced HP-induced denaturation of alpha-la and beta-lg significantly. The higher level of HP-induced denaturation of alpha-la and beta-lg in milk than in whey may be the result of the abscence of the casein micelles and colloidal calcium phosphate from whey, which facilitate HP-induced denaturation of alpha-la and beta-lg in milk.     

Plasmin levels in fresh milk whey and commercial whey protein products

Growth of psychrotrophic bacteria in nonfat dry milk at refrigeration temperatures was shown previously in our laboratory to cause a shift in plasmin (a native milk protease) from the casein to the whey fraction. The whey fraction from cheesemaking is commonly used to make whey protein concentrates and isolates, which then are used as functional ingredients in various food systems. Plasmin activity in whey protein products may cause breakdown of food proteins to have desirable or undesirable effects on food quality. This raised questions about the level of plasmin in commercial whey protein products and factors that affect this plasmin level. Therefore, the objectives of this study were to determine: 1) plasmin concentrations in sweet and acid whey protein products as influenced by Pseudomonas growth during storage of fresh milk, and 2) plasmin concentrations in commercial whey protein products. Whey type (sweet or acid) had a significantly (P < 0.05) greater effect on whey-associated plasmin activity than did Pseudomonas fluorescens M 3/6 growth. Acid whey protein products had significantly (P < 0.05) higher plasmin concentrations than sweet whey. Plasmin activities associated with acid and sweet whey protein products were both significantly (P < 0.0001) affected by the growth of Pseudomonas fluorescens M 3/6. The interaction effect between bacterial growth and whey type on plasmin activity was not significant (P = 0.2457). Plasmin activity in the reconstituted commercial whey protein concentrates (i.e., sweet and acid) varied considerably (16.3 to 330 micrograms/g of protein), but was significantly lower (2.1 to 4.4 micrograms/g of protein, P < 0.05) in whey isolates. These quantitative data were supported by plasmin activity visualized by casein SDS-PAGE.     

Addition of acid whey improves organic dry‐fermented sausage without nitrite production and its nutritional value

In this study, the effect of acid whey on the physicochemical properties and nutritional value of non‐nitrite organic fermented sausage made from beef and tallow was investigated. Fermented sausage was prepared in three formulations: C (cured), S (salted) and SAW (salted with liquid acid whey). Each sample was analysed during the ripening process: at 0, 7, 14 and 21 days of ripening in a temperature of 16 °C. The obtained results indicated that the addition of acid whey improves physicochemical properties of organic dry‐fermented sausage without nitrite and its nutritional value. The application of acid whey resulted in a significantly lower pH and a higher lactic acid bacteria content in organic fermented sausage without nitrite than in the sample with curing salt (respectively, by 0.12 units and 0.66 log CFU g^?1). Acid whey successfully protected against haem iron loss in salted sausage during ripening. The salted sample with acid whey addition was characterised by a higher PUFA content (6.41%) at the end of ripening as compared to the cured sample (4.91%) and salted sample (5.58%). The addition of acid whey improves organic dry‐fermented sausage without nitrite production and its nutritional value.     

反浮选-冷结晶氯化钾生产过程中硫酸钙旋流分离试验研究

为了有效地分离粗光卤石矿中的硫酸钙颗粒,在实验室筛分分级法的基础上,利用水力旋流法,对青海盐湖钾肥公司提供的试样进行了实验室分离试验及工业试验研究。实验室试验结果表明,通过水力旋流器旋流分离粗光卤石矿的CaSO4,在一定的进料浓度范围内,旋流器均有较好的分离性能,运用二级旋流分离,可以使二级旋流分离下出口物料CaSO4降低至0．3％。粒度分布表明,一次旋流分离大颗粒在上出口物料及小颗粒在下出口物料中夹带量不大,且经过二级分离可以提高分离精度。     

SPINNING DISC MEASUREMENT OF TWO-STAGE CLEANING OF HEAT TRANSFER FOULING DEPOSITS OF MILK

The efficient and effective cleaning of milk protein – based deposits from heat transfer equipment is essential in the dairy industry. The aim of this study was to evaluate the effectiveness of two‐stage cleaning using acid and caustic. Stainless steel discs were fouled during heat transfer by skimmed milk and whey protein. The discs were then cleaned with acid and sodium hydroxide solutions under controlled mass transfer conditions using spinning disc techniques. The use of 0.5% nitric acid, and a commercial acid known as Triplex, as a rinse before caustic cleaning increased the cleaning rate by 2.5 times. The foulant was found to swell about 40% and calcium was leached out within 5 min after exposure to acid. The acid treatment is believed to cause a reduction in the viscosity, and hence an increase in dissolution, of the gel layer formed when caustic cleaning takes place.     

Effects of proteose‐peptone fractions from yak milk on lipoprotein lipase lipolysis

The lipoprotein lipase (LPL) was purified almost 3800‐fold from yak skimmilk by Heparin‐Sepharose CL‐6B column chromatography; nonhydrophobic fraction of proteose‐peptone (NHFPP) and hydrophobic fraction of proteose‐peptone (HFPP) from yak milk whey were separated by Phenyl‐Sepharose‐6FF column chromatography. The HFPP was subjected to hydroxyapatite chromatography, and two fractions were collected: one fraction did not absorb onto the calcium phosphate matrix (HA1); the other fraction contained all the protein components of HFPP (HA2). The effects of the proteose‐peptone fractions on lipoprotein lipase lipolysis were studied. The results of experiments showed that NHFPP and HA1 enhanced the LPL lipolysis; in contrast, the HFPP and HA2 inhibited LPL lipolysis.     

Effects of the free and pre‐encapsulated calcium ions on the physical properties of whey protein edible film

Effects of the free and the pre‐encapsulated calcium ions on the physical properties of the whey protein isolate film were studied for improving calcium content in the edible films. At pH 8, the film‐forming process was hindered by serious protein aggregation and gelation caused by 0.5% (w/w) free calcium ions added in an 8% whey protein isolate solution. If the calcium ions were pre‐encapsulated in the protein microparticles (contained 17% Ca²⁺) using spray drying method, and then added in the film‐forming solution prepared using the same protein, the calcium content could be doubled (1%, w/w) without significant effects on the physical properties of the film. The calcium release ability (55% at pH 1.2, 32% at pH 7.4 and more than 75% with the enzymes) of the film was also investigated.     

钙盐和蛋白质配比对1,3-二油酸-2-棕榈酸甘油酯乳液体外消化的影响

利用体外模拟胃肠消化系统,考察酪蛋白和乳清蛋白的不同比例和矿物质含量及两者相互作用对1,3-二油酸-2-棕榈酸甘油酯（1,3-dioleoyl-2-palmitoylglycerol,OPO）消化的影响,并对体外消化后的脂肪酸释放率、粒度分布和脂肪酸组成进行测定。结果表明,胃消化阶段,相同乳化剂配比,OPO型乳液脂质生物利用率随CaCl2浓度增加而增加;且在20 mmol/L CaCl2浓度下,不同蛋白质配比（乳清蛋白-酪蛋白）,乳液体外消化过程中游离脂肪酸（free fatty acid,FFA）释放率大小顺序为：10∶0＞6∶4＞0∶10。体外模拟脂质消化前后平均粒径分析结果显示,在不同CaCl2浓度影响下,胃肠消化后乳液平均粒径大于新鲜乳液;随Ca2＋浓度增加,新鲜乳液d（0.1）、d（0.5）、d（0.9）值均增加,且在加胃肠消化液后,平均粒径显著增大。在肠消化阶段,3 组乳液在不同CaCl2浓度下,FFA释放速率及程度均随CaCl2浓度增加而增加。胃肠消化后的产物FFA和单甘酯组成分析表明：乳液消化后,FFA和单甘酯主要由棕榈酸和油酸组成。除此之外,本实验还考察了不同钙盐对OPO乳液脂质消化的影响,结果表明溶解度高的钙盐加速脂质水解,有利于脂肪酸的释放即在肠消化阶段FFA释放速率和程度次序为：柠檬酸钙＞氯化钙＞乳酸钙＞碳酸钙。     

Scale-up of native beta-lactoglobulin affinity separation process

Affinity separation of beta-lactoglobulin in its native form with all-trans-retinal immobilized on calcium bio-silicate was scaled up and applied to separate it from industrial sweet whey. Three different methods of mixing the modified calcium bio-silicate and whey for the interaction between all-trans-retinal and beta-lactoglobulin were tried at pilot scale. The three methods used were 1) a column packed with calcium bio-silicate, 2) a stirred tank, and 3) a fluidized bed column of calcium bio-silicate particles. Adsorption and desorption of beta-lactoglobulin were carried out at pH 5.1 and 7.0, using 0.01 and 0.1 M phosphate buffers, respectively. The phosphate buffer containing desorbed beta-lactoglobulin was concentrated 20 times using ultrafiltration and then freeze-dried. The packed column, stirred tank, and fluidized bed column produced beta-lactoglobulin with purity of 80, >95, and >95%, and recovery of 0.65, 2.88, and 2.88 g per kilogram of calcium bio-silicate, respectively. The comparative poor purity and recovery of beta-lactoglobulin in the case of the packed column was attributed to insufficient contact between the passing fluids and the calcium bio-silicate during adsorption, desorption, and intermittent washing. The fluidized bed column method, with a gentle mixing action, was considered the best suited for further scale up to the industrial level.     

Isolation of caseins from whey proteins by microfiltration modifying the mineral balance in skim milk

The objective of this work was to study the effect of different salts and salt concentration on the isolation of casein micelles from bovine raw skim milk by tangential flow microfiltration. Tangential flow microfiltration (0.22 μm) was conducted in a continuous process adding a modified buffer to maintain a constant initial sample volume. This buffer contained calcium chloride (CaCl₂), sodium phosphate (Na₂HPO₄), or potassium citrate (K₃C₆H₅O₇) in concentrations ranging from 0 to 100 mM. The concentrations of caseins and whey proteins retained were determined by sodium dodecyl sulfate-PAGE and analyzed using the Scion Image software (Scion Corporation, Frederick, MD). A complete isolation of caseins from whey proteins was achieved using sodium phosphate in the range of 10 to 50 mM and 20 times the initial volume of buffer added. No whey proteins were detected at 50 mM but this was at the expense of low caseins being retained. When lower sodium phosphate concentrations were used, the amount of caseins retained was higher but a small amount of whey proteins were still detected by sodium dodecyl sulfate-PAGE. Among the salts tested, calcium chloride at 50 mM and all volumes of buffer showed the higher retention of casein proteins. The highest casein:whey protein ratio was found at 30 mM CaCl₂, but no complete casein micelle isolation was achieved. Potassium citrate was the most ineffective salt because a rapid loss of caseins and whey proteins was observed at all concentrations and with low quantities of buffer added during the filtration process. Our results show the potential of altering the mineral balance in milk for isolation of casein micelles from whey proteins in a continuous tangential flow microfiltration system.     

Studies of plasmin activity in whey

The presence of the indigenous milk alkaline proteinase, plasmin, in whey products may adversely affect the quality of food products that utilise such ingredients; factors promoting the release of plasmin into whey were therefore investigated. Acidification of pasteurised skim milk (PSM) with glucono-δ-lactone (GDL) or HCl resulted in acid whey with significantly higher (P<0.05) plasmin activity than PSM. Plasmin activity in such whey was inversely correlated with rate of acidification; thus, activity in the whey made with GDL was significantly higher (P<0.05) than in whey made with HCl. Negligible levels of plasminogen in acid whey suggested that activation of the zymogen, plasminogen, contributed to the elevated plasmin activity observed. Sweet whey, manufactured by addition of rennet to PSM, had plasmin and plasminogen-derived activities significantly lower (P<0.001) than those in PSM; the release of plasmin from renneted casein micelles into whey increased in a linear manner with cooking temperature in the range 45–65°C. However, dissociation of plasmin from casein micelles into acid whey reached a maximum at a cooking temperature of 50°C. Analysis of plasmin and plasminogen levels in ultracentrifugal supernatants of pH-adjusted milk indicated that plasmin was released from the micelles at pH>5.0, while plasminogen was released more gradually over the pH range 6.6–4.6. Overall, the technology of manufacture has significant implications for plasmin activity in whey and hence, inversely, for casein products and cheese.