Recent advances in whey processing and valorisation: Technological and environmental perspectives

Whey has several environmental risks if disposed of as waste in watercourses. However, there are numerous valorisation techniques to convert it into valuable and highly nutritious products. Techniques such as membrane filtration may be utilised, but these are not applicable to all categories of whey. Novel methodologies that are agile enough to deal with whey variability can produce valorised products. This review assesses the capability of whey processing techniques, applications and methodologies, discussing pertinent research that can innovate product development further. It focuses on environmental impacts of whey as a waste and ways of minimising it.     

Surfactant cleaning of ultrafiltration membranes fouled by whey

A polyethersulphone ultrafiltration membrane was prepared for concentration of whey. The membrane was fouled by whey and the effect of different cleaning agents on flux recovery of the fouled membrane was studied. The optimum cleaning procedure for membrane regeneration was elucidated. The results showed that a combination of surfactants (anionic, cationic and nonionic) may be employed as the optimum cleaning agent for maximum flux recovery. The fluorescence studies revealed that the cationic surfactant interact with proteins by breaking the intra‐chain hydrophobic bonding and providing electrostatic repulsion. Changing the alkyl chain from dodecyl to hexadecyl increases the interaction of surfactant–protein. Dodecyltrimethylammonium bromide (DTAB) provided a weak interaction with whey proteins than to tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). All data obtained in this study support a surfactant–protein interaction in which hydrophobic forces play a dominant role. The nonionic surfactants poly(oxyethylene) isooctyl phenyl ether (TX‐100) and anionic surfactants SDS interact with amino acids in the inner protein structure thus denaturate tertiary protein structure and reduce hydrophobic interaction of proteins by membrane surface.     

Effect of whey protein concentration on the fouling and cleaning of a heat transfer surface

In the studies of fouling and cleaning of heat exchange surfaces in dairy plants, whey protein deposits and heat induced whey protein gels (HIWPG) are considered as suitable model material to simulate the proteinaceous based type “A” milk fouling. Protein concentration of the fouling solution may significantly influence the formation of milk deposits on heat exchange surfaces, hence affecting the cleaning efficiency. In this study, a laboratory produced heat induced whey protein gels (HIWPG) and a pilot plant heat exchanger fouling/cleaning were used to investigate the effect of protein concentration on formation and cleaning of dairy fouling. Here, HIWPGs made from different protein concentrations were formed in capsules and then dissolved in aqueous sodium hydroxide (0.5 wt%). The dissolution rate calculation based on the UV spectrophotometer analysis. In the pilot-scale plant study, whey protein fouling deposits were formed by recirculating whey protein solutions with different concentrations through the heat exchange section in different runs, respectively. The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt%) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were monitored as indications of cleaning completion. It was found that increasing the protein concentration of the HIWPG significantly increased the gel hardness and the dissolution time. In addition, increasing the protein concentration significantly increased both, the amount of the fouling on the pilot-scale plant and the time required to clean the fouling deposit.     

Influence of different content of cheese whey and oligofructose on the properties of fermented lactic beverages: Study using response surface methodology

Lactic beverages have been used as an important vehicle for probiotics, and the utilization of cheese whey and oligofructose would contribute even more to the functional properties of this product. However, because of the short lifespan of probiotics, studies have been carried out aiming at the evaluation of the contribution of the prebiotics in the improvement of the viability of these microorganisms. The technological properties (fermentation time, acidity and syneresis index) and the population of probiotic bacteria in fermented lactic beverages manufactured with different content of cheese whey and oligofructose were evaluated. The results showed that oligofructose, at the concentrations evaluated in this study, did not show any significant influence on the response variables, whereas the content of cheese whey only influenced the syneresis index of lactic beverages.     

Influence of the degree of hydrolysis on the bioactive properties of whey protein hydrolysates using Alcalase®

Whey protein concentrate was enzymatically hydrolysed at several time courses using the commercial preparation Alcalase^® 2.4 L, different hydrolysates were achieved, and the effect of degree of hydrolysis (DH) on both technological and biological properties was studied. Results have shown that solubility, antioxidant and ACE inhibition activities were increased as DH was also augmented from about 8 to 17%. RP‐HPLC studies also revealed a decrease in hydrophobicity when samples were hydrolysed in comparison with controls. When the enzyme hydrolytic action was augmented, it stimulated both the bioactivity of whey protein and relevant technological properties, allowing these hydrolysates to be employed as additives in the development of food formulations.     

Lactose hydrolysis in acid whey with subsequent glucose isomerisation

The disposal of whey is a problem because of its high biological oxygen demand. Of the 1.8 × 10¹⁰ kg produced annually in the USA, only about half has any food or feed application (Jelen 1983). One possible approach to acid whey utilisation is the removal of the proteins either by ultrafiltration or by thermal precipitation, hydrolysis of lactose with soluble β-galactosidase (lactase, EC 3.2.1.23) and subsequent isomerisation of the glucose to fructose by the action of immobilised glucose isomerase (EC 5.3.1.5). The resulting syrup is composed of glucose, fructose and galactose plus small amounts of unhydrolysed lactose and other oligosaccharides. The syrup was found to have a predominantly sweet and slightly salty taste. Recently sucrose has been replaced in many foods by high fructose corn syrup produced by the action of glucose isomerase on glucose syrups from corn starch hydrolysates (Bucke 1981). The whey syrup also has potential as a sucrose substitute.     

Analysis of the preferential mechanisms of denaturation of whey protein variants as a function of temperature and pH for the development of an optical sensor

A pH‐ and temperature‐dependent study was conducted using reconstituted low‐heat skim milk at pH 6.3, 6.7 and 7.1 heated for 10 min at 80 and 90 °C to evaluate the relationship between bound and aggregate whey protein and optical light backscatter response. Significant correlations were found between casein micelle particle size and bound whey protein, and light backscatter correlations existed with both bound and aggregate whey protein, thus optical light backscatter may be useful to determine both whey protein attachment to the casein micelle and the formation of whey protein aggregates.     

Fouling behaviour of milk and whey protein isolate solution on doped diamond-like carbon modified surfaces

Doped diamond-like carbon (DLC) coated stainless steel surfaces were studied for their fouling behaviour with milk and whey protein isolate (WPI) solution at both laboratory and pilot-scale. Stainless steel (316 SS 2B) surfaces were modified with three different doped DLC coatings (DLC-1, DLC-2 and DLC-3) using plasma assisted chemical vapour deposition. At the laboratory-scale, the DLC-1 coated surface showed a statistically significant reduction in the mass of milk fouling deposits. However, at the pilot-scale, none of the modified surfaces offered significant benefit in fouling mitigation over the control stainless steel surface. Subsequently, in the laboratory-scale trials with a whey protein isolate (WPI) solution, the mass of fouling deposits for all doped DLC modified surfaces were about 35–40% lower in comparison to their controls when fouled for 120 min. However, these benefits were reduced to less than 15% with longer fouling duration. Thus, the results obtained in this study found no commercial benefit of modified surfaces in fouling mitigation when fouled for longer times with skim milk, whole milk or WPI solution.     

Bioutilisation of whey for lactic acid production

The disposal of whey, the liquid remaining after the separation of milk fat and casein from whole milk, is a major problem for the dairy industry, which demands simple and economical solutions. The bioconversion of lactose present in whey to valuable products has been actively explored. Since whey and whey permeates contain significant quantities of lactose, an interesting way to upgrade this effluent could be as a substrate for fermentation. Production of lactic acid through lactic acid bacteria could be a processing route for whey lactose and various attempts have been made in this direction. Immobilised cell technology has also been applied to whey fermentation processes, to improve the economics of the process. A fermentative means of lactic acid production has advantages over chemical synthesis, as desirable optically pure lactic acid could be produced, and the demand for optically pure lactic acid has increased considerably because of its use in the production of poly(lactic acid), a biodegradable polymer, and other industrial applications. This review focuses on the various biotechnological techniques that have used whey for the production of lactic acid.     

三槽隔膜式设备制取强酸性水的工艺特性

针对现行的二槽隔膜式强酸性水制取设备的结构和缺点提出了三槽隔膜式强酸性水制取设备的结构和方法,描述了三槽隔膜式强酸性水制取设备的结构及其工作原理,系统地讨论了三槽隔膜式强酸性水制取设备的单元材料和电解电压的选择.通过自制电解槽实验获得了该设备制取强酸性水的电极距离、电压、盐水浓度等影响因素的最佳工艺参数.三槽隔膜式强酸性水制取方法是一种有应用前景的制备强酸性水的方法.     

Improvement of low fat mozzarella cheese properties using denatured whey protein

Mozzarella cheese was made from buffalo milk (6% fat) or from partially skimmed buffalo milk (2 and 4% fat) with 0.5 and 1% denatured whey protein. Adding whey protein to buffalo milk decreased rennet coagulation time and curd tension whereas increased curd synaeresis. Addition of whey protein to cheese milk increased the acidity, total solids, ash, salt, salt in moisture, also some nitrogen fractions. The meltability and oiling‐off values increased but the calcium values of mozzarella cheese decreased. The sensory properties of low fat mozzarella cheese were improved by addition of whey protein to the cheese milk.     

Trypsin hydrolysis of whey protein concentrates: Characterization using multivariate data analysis

Hydrolysis of whey protein concentrates (WPCs) was performed using trypsin under different combinations of temperatures and pH values in a total of three experiments, namely experiment A at 37 °C and pH 8, experiment B at 37 °C and pH 9, and experiment C at 50 °C and pH 8. Monitorization of the degradation of native whey proteins and the peptide formation throughout hydrolysis was performed by reverse phase HPLC/UV. Seven main peptides were separated according to their polarity and numbered from T1 to T7. In general a difference was observed between rate of hydrolysis of α-lactalbumin and β-lactoglobulin; in the former case hydrolysis was complete by 15 min in experiments B and C and by 120 min in experiment A, whereas in the later case the rate of hydrolysis was much slower.     

微生物法测定乳清蛋白粉类样品中的叶酸含量

目的 建立微生物法测定乳清蛋白粉类样品中叶酸含量的分析方法。方法 利用叶酸标准品制作叶酸标准曲线。将样品进行超声处理得到样品溶液。向试管中加入等体积的培养基和不同体积的样液,稀释至10mL,得到样品待测液。样品待测液和叶酸标准曲线溶液灭菌后,加入鼠李糖乳杆菌(Lactobacillus casei spp.rhamnosus)CICC 6224菌悬液进行培养,将培养物混匀后测其吸光度值,根据标准曲线计算相应的叶酸含量,并进行方法的空白试验、检出限、精密度、重复性、稳定性及回收率试验。结果 在0.1010~1.0103ng/mL范围内,叶酸标准曲线呈现良好的线性,相关系数R_²=0.99373,符合GB/T27404-2008《实验室质量控制规范》的要求,该方法的相对标准偏差(relative standard deviation,RSD)为3.8%(n=6),平均回收率为102.5%(n=9)。结论 该方法稳定准确,适合用于测定乳清蛋白粉类样品中的叶酸含量。     

Optimization of modified atmosphere packaging with respect to physicochemical characteristics of Requeijão

The effects of modified atmosphere packaging on physicochemical and sensorial characteristics (contents of free fatty acids, lactose, lactic acid and moisture, as well as pH and rigidity) in Portuguese whey cheese (Requeijão) were studied following a response surface methodology using storage time, storage temperature and fraction of CO₂ in the flushing gas as manipulated variables. Inspection of the sensorial optima in terms of the different parameters indicated that it is convenient to set the storage temperature equal to 4°C because no significant lipolysis takes place, irrespective of overhead atmosphere. Plain CO₂ as flushing gas will in general ensure more constant composition until 15 days and will provide protection against extensive lipolysis. In terms of overall visual aspect, all packaged cheeses were preferred to their unpackaged counterparts; however, in terms of acidic smell, only whey cheeses stored at 4°C exhibited significant differences relative to those stored at higher temperatures.     

Use of whey and buttermilk based media to obtain biomass of thermophilic LAB

The growth of commercial strains of thermophilic lactic acid bacteria (LAB) was determined in reconstituted dried whey and buttermilk. Kinetic (μ, /h and g, h) and growth (N, cfu/mL; X, cell yield and I_V , percentual variation) parameters were determined using Elliker (streptococci) and MRS (lactobacilli) broths, and a commercial medium as controls. Cheese whey was the least effective substrate for growing streptococci and lactobacilli strains. However, whey and buttermilk with added yeast extract gave the best performance. These media could be efficient and easily available alternatives for producing industrial biomass of thermophilic LAB.     

Improvement and modification of whey protein gel texture using polysaccharides

Whey proteins (WP) and polysaccharides are two gelling biopolymers used in the food industry for their wide range of rheological and textural properties. Mixed gels containing more than one gelling agent are usually classified into three types: interpenetrating, coupled, and phase-separated networks. Large deformation behavior of whey protein gels mixed with polysaccharides is presented. pH, and the concentration and nature of the cations added in the system, affect both protein and polysaccharide gels. These factors will also modify the mixing behavior of protein-polysaccharide solutions. The effect of cations and pH are respectively explained using WP/κ-carrageenan and WP/pectin systems. Under the conditions studied, two types of mixed systems were obtained: one with two gelling biopolymers (WP/κ-carrageenan), and the other where protein is the only gelling biopolymer (WP/pectin). Conditions favoring incompatibility can lead to spherical inclusions of whey protein.     

响应面法优化电渗析乳清脱盐技术参数

试验探讨了利用电渗析技术应用于乳清脱盐技术的具体参数,采用4因素5水平二次回归正交旋转组合试验设计研究了乳清液脱盐的最佳优化工艺条件。选择电渗析工作电流、进料量、进料流速及进料温度进行单因素试验,并验证回归模型的显著性。结果表明,乳清液脱盐的最佳工艺条件为电渗析工作电流为45A、进料量26%、进料流速112mL/min、进料温度36℃,将含盐量为9%的乳清液降低到2.5%,脱盐率达到72%。     

Preparation of galacto-oligosaccharides using membrane reactor

Galacto-oligosaccharides (GOS) have many biological functions. They are produced from lactose by a glycosyl transfer of one or more d-galactosyl units onto the d-galactose moiety of lactose catalysed by β-galactosidase. This reaction can proceed in batch or in continuous system. Membrane reactor with ultrafiltration ceramic membrane (150 kDa) was used and batch system as well. Lactose in phosphate buffer (197.9 g L⁻¹), recombined whey (197 g L⁻¹) and evaporated ultrafiltration permeate (200.7 g L⁻¹) were used as substrates. The used concentration of enzyme Maxilact LX 5000 was 6 U mL⁻¹. The highest concentration of GOS in buffer was reached after 30 min of batch reaction and it was 25.5 g L⁻¹, for recombined whey it was 31.1 g L⁻¹ and for ultrafiltration permeate it was 32.9 g L⁻¹. For continuous process was obtained 8.8 g L⁻¹ of GOS for buffer and 21.0 g L⁻¹ for recombined whey and 16.7 g L⁻¹ of GOS for ultrafiltration permeate.     

The effects of biofilms formed on whey reverse osmosis membranes on the microbial quality of the concentrated product

The study investigated the development of bacterial biofilms on spiral wound reverse osmosis (RO) whey concentration membranes and their influence on the microbial quality and safety of concentrated whey (retentate). Used RO membranes, obtained from a commercial whey processing plant, were evaluated at intervals of 2 months for a total duration of 14 months using standard techniques. Results confirmed the presence of multi‐species bacterial biofilms on whey RO membranes. Considerable variations were noticed in the distribution pattern of biofilms constitutive microflora as the membranes aged. A greater increase in retentate counts as compared to feed suggested the possibilities of cross‐contamination from the membrane biofilms.     

Size classification of precipitated calcium phosphate using hydrocyclone technology for the recovery of minerals from deproteinised acid whey

Acid whey is generated during the manufacture of acidified dairy products, such as soft cheeses, acid casein ingredients and strained yoghurts. Examples of these whey‐based by‐products include Cottage cheese acid whey and Greek yoghurt acid whey. Alkalisation of acid whey at elevated temperatures (60 °C) precipitates calcium phosphate, which can be recovered and used as an ingredient. The novel application of a liquid–solid hydrocyclone in the size classification of calcium phosphate from heated and neutralised acid whey was investigated in this study. Factors influencing hydrocyclone performance were tested, and the technology was integrated into a membrane filtration‐based process for the production of milk mineral powders.