Food Technology and Biotechnology

Whey

Whey is a by-product of milk coagulation by acids and/or renneting enzymes during cheese or casein manufacturing. It is produced in volumes (80-90%) close to those of the processed milk used during cheese manufacture and therefore requires proper management (1). Depending on the processing technique used to separate casein from milk, there are two main types of whey, sweet whey with a pH=5.9–6.6 and acid whey with a pH=4.3–4.6. Whey has the total dry matter about 6-6.5%. It contains lactose (~70%), minerals (~12%), both depending on the acidity of the whey, whey proteins (~10%), vitamins and some fat (2). Whey also contains small quantities of components like organic acids, non-protein nitrogen compounds (urea and uric acid) and B group vitamins. Its composition and sensory characteristics mostly depend on the production process (acid or sweet), but also on the used milk (cow’s, sheep’s, goat’s, etc.), the season and the stage of lactation. The main differences are in the calcium, phosphate, lactic acid and lactate contents, which are higher in acid whey (3).

Whey has a very high polluting potential due to a high biochemical oxygen demand (BOD; 40-60 g/L) and high chemical oxygen demand (COD; 50-80 g/L), which are mostly conditioned by very high lactose contents in the dry matter (4-6). Thus, it has been estimated that the waste load of whey is 100-175 times higher than that of a similar volume of domestic waste water (7, 8). Accordingly, adequate whey management is one of the priorities of the modern dairy processing sector.

Throughout the late 20th century a large body of scientific evidence indicated biological and technological value of whey. Such data were somewhat shocking to dairy processors, who treated whey as waste and disposed of it for decades. Nowadays, it is rather recognised as a highly valuable raw material that can be exploited by the agri-food, biotechnology, pharmaceutical and similar industries (8, 9).

Whey proteins – most valuable bioactive components of whey

Whey proteins are for sure the unique component responsible for the high nutritional and technological value of whey. They are mainly composed of thermosensitive fractions β-lactoglobulin (β-Lg), α-lactalbumin (α-La), blood serum albumin (BSA) and immunoglobulins. Thermostable proteose peptones as well as lactoferrin and lactoperoxidase are present in lower amounts too. Additionally, sweet whey contains caseinomacropeptide (CMP), resulting from chymosin (or pepsin) cleavage of k-casein. It constitutes approx. 20% of the sweet whey protein fraction and is not found in acid whey unless enzymatic coagulation was included in the process of manufacturing fresh cheese (4, 10). Whey proteins are small globular proteins with amino acid profiles quite different from caseins due to high ratios of essential amino acids, smaller fraction of glutamic acid (Glu) and proline (Pro), but a greater fraction of sulfur-containing amino acid residues (i.e. cysteine and methionine) and higher contents of the branched chain amino acids (BCAA), which were recognized as important metabolic regulators in homeostasis of proteins, glucose and lipids (7, 8). The parameters defining protein quality such as the protein digestibility-corrected amino acid score (PDCAAS) or biological value (BV) of whey protein exceed that of egg protein (the former benchmark), meat, fish, wheat and nuts (9). Accordingly, whey proteins have a superior nutritional value compared to common dietary sources of proteins.

Enzymatic hydrolysis of whey proteins in the human digestive system, fermentation of milk by starter cultures and hydrolysis by plant or microbial proteases result in the release of bioactive peptides. Once released, bioactive peptides act as signalling molecules and exert various physiological effects on the immune, gastrointestinal, cardiovascular and nervous systems (11, 12). There is a growing body of scientific evidence confirming valuable influence of whey proteins on human well-being such as antimicrobial, antioxidant, antihypertensive, antidiabetic and immunomodulatory properties, and they may take part in mechanisms of reducing body mass and reduce or inhibit allergic reactions (12-14). The most abundant whey protein, β-Lg, is a source of multiple bioactive peptides like lactokinins possessing ACE-inhibitory ability, β-lactorphin acting as opioid agonist and ACE inhibitor; and β-lactotensin, which was proven to have an anti-stress effect, but also the binding ability to neuroreceptors responsible for satiety feeling regulation (7, 12, 14). α-La was demonstrated to be cytotoxic, to act protectively against mucosal injuries and oxidative stress, and have opioid, anti-inflammatory and anti-carcinogenic activity. Due to high tryptophane content, α-La can be used to improve sleep, mood and cognitive functions. More recently, a new genetic variant of α-La was isolated and identified, the so-called HAMLET (human alpha-La made lethal to tumour cells) that showed the ability to induce apoptosis of tumour cells while sparing healthy tissues at the same time (7, 15). Among other whey protein fractions, lactoferrine should be mentioned as a source of lactoferricine – a bioactive peptide with confirmed antimicrobial, antiviral and immunomodulatory activity. Also, lactoperoxidase was demonstrated to possess high antimicrobial activity, while products containing this protein are successfully implemented in oral healthcare to promote healing of bleeding gums, gingivitis and oral irritation (8, 9). In addition, whey proteins have excellent functional properties, such as good solubility, viscosity, gelling and emulsifying properties, and their concentrates are widely used in the food industry (7).

Buttermilk

Buttermilk is the aqueous phase released during the churning of cream in butter production. In terms of ash and lactose content, buttermilk is similar to whey, but contains much higher amounts of proteins (16) (Table 1 (3, 17)). However, they largely differ in terms of lipid fractions. Buttermilk contains about 4.6–14.5% fat in the dry matter (18), whereby a specific component derived from milk fat globule disruption during churning is present – the milk fat globule membrane (MFGM). Since MFGM is rich in phospholipids, buttermilk contains up to seven times higher concentrations (about 0.89 mg/g) of phospholipids than whole milk (about 0.12 mg/g) (19). Annual production of buttermilk in EU28 countries in 2016 accounted for 0.5 million tonnes (20).

There are a few types of buttermilk that should be distinguished. Most of the studies have focused on investigating sweet buttermilk originating from churning of uncultured cream. There are also other types of buttermilk that can be produced such as sour buttermilk, obtained from churning of cultured cream, or whey buttermilk, originating from churning of whey cream during manufacture of whey butter. Whey buttermilk is produced in much smaller quantities than sweet buttermilk (21, 22), but the potential market for whey buttermilk is huge considering the large volumes of whey produced annually.

Sodini et al. (21) determined the gross composition of sweet and sour cream buttermilk as well as of whey buttermilk. According to their results, sweet cream buttermilk had the highest content of total nitrogen (31.5%) and the lowest content of fat (13.1%). Whey buttermilk had the highest content of phospholipids and lactose. The lowest amount of nitrogen in whey buttermilk might be explained by the lack of casein in whey cream (22).

Libudzisz and Stepaniak (19) discussed the ability of buttermilk to increase the heat stability of recombined milk, mainly due to phospholipid-protein interactions preventing protein coagulation during sterilization. Thanks to casein and considerable amounts of phospholipids, buttermilk is characterised by good emulsifying properties suitable for wide use in the food industry (22, 23).

In some countries like Russia, Poland, Czech Republic, Finland or Germany, naturally fermented buttermilk is merchandised as a beverage or is sometimes used for animal feed. Problems with increasing the consumption of traditional buttermilk is in the short shelf-life (about 1 week at 4–7 °C), in obtaining a uniform quality and in the lack of marketing promotion. Therefore, without putting a special effort to commercialize natural buttermilk, its consumption is destined to decrease (21).

Bioactive components of buttermilk

During butter manufacture, milk fat globules are destabilized and disrupted by churning, which results in exclusion of the membrane covering the lipid matrix and its recovery in buttermilk along with other milk/cream components contained in the aqueous phase. Thus, a component known as MFGM is particularly rich in various proteins and phospholipids that possess an outstanding potential for functional and nutraceutical applications. Some of those are related to the prevention or amelioration of widespread chronic diseases such as cancer, obesity, diabetes and cardiovascular disorders (24, 25). Buttermilk has received increased interest, as food science and nutrition research turn to develop products with not only increased nutritional value but also health-promoting properties. The MFGM has a complex composition and supramolecular structure (26). It is mostly constituted of protein fractions (average content about 1800 mg/100 g) followed by polar lipids (about 730 mg/100 g), although some other components like vitamin A, carotenoids, enzymes, adsorbed casein and whey proteins are present too (27). Major MFGM proteins are butyrophilin (BTN), xanthine oxidase/dehydrogenase (XO/XDH), mucin-like glycoproteins MUC1 and MUC15, adipophilin (ADPH), breast cancer type 1 and type 2 susceptibility proteins (BRCA1 and BRCA2). The most abundant polar lipids found in the MFGM isolated from buttermilk are phospholipids and sphingolipids, more exactly fractions of phosphatidylethanolamine, phosphatidylcholine, sphingomyelin, phosphatidylinositol and phosphatidylserine (20). Both of these have been proven to show numerous beneficial effects on the human health, some of which are presented in Table 2 (20, 27-29).

Considering clinical trials, anticholesterolemic effect of sphingomyeline originating from MFGM has been examined since 1979, when Howard and Marks observed a significant decrease in serum cholesterol levels in patients who consumed cream in comparison to those who consumed butter (29). They concluded that such trends were most probably related to beneficial effects of MFGM, which is present in cream, but not detected in butter. Ito et al. (30) also conducted a clinical study and confirmed cholesterol-lowering effect in hypocholesterolemic mice fed with cream. Noh and Koo (31) found that hypercholesterolemic effect of sphingomyelin relies on its inhibitory action towards cholesterol absorption in the intestine. More recently, Baumgartner et al. (32) reported that a daily consumption of buttermilk during 12 weeks significantly lowered low density lipoprotein (LDL) cholesterol in individuals taking part in their clinical study. Conway et al. (24) reported that daily consumption of 45 g buttermilk significantly lowered LDL cholesterol levels in patients with hyperlipidemia. They also investigated the effects of buttermilk consumption on blood pressure and on the markers of the renin–angiotensin–aldosterone (RAS) system in humans (25). The obtained results were promising and confirmed that buttermilk consumption significantly reduced systolic blood pressure, the mean arterial blood pressure and plasma levels of the angiotensin I-converting enzyme compared to the placebo.

Thus, similarly to whey, buttermilk is also a nutritionally valuable coproduct with numerous potentially beneficial effects on human well-being. The production of buttermilk beverages should therefore be a key point when considering the future of milk-based beverages.

Whey beverages

Production of whey-based beverages appears to be the most economical and simplest solution for whey utilization in human nutrition. The need for development of whey-based beverages is closely related to nutritional and functional properties of whey proteins, as well as to fulfilling the expectations of modern consumers who demand innovative products with enhanced functionality (33). Up to now, numerous research studies have focused on optimising whey beverage production from native or processed whey (e.g. powdered, deproteinated, diluted) (34). Along with technological development, the application of alternative food processing methods such as membrane processes, high intensity ultrasound or supercritical carbon dioxide technology is being investigated too. By applying nonthermal processing methods, hurdles like the low shelf life due to microbiological deterioration, occurrence of undesired sediments or whey protein denaturation might be overcome, but also the existing products could be improved (9, 35-37). Over the past two decades, numerous whey-based beverages and similar products containing isolated whey components (mainly whey proteins) have been placed on the market as refreshing, value-added and/or functional foods (33).

Nonfermented whey beverages

Although the easiest solution for designing a functional whey beverage seems to be using native sweet or acid whey as a basis, recently it has been suggested to use deproteinised whey or whey permeate remaining after ultrafiltration (33) in order to avoid undesirable sediment formation and blurring. Among the most frequently examined combinations is for sure the addition of orange juice to whey, often together with CO₂. Chatterjee et al. (38) tested the production of a refreshing beverage consisting of concentrated whey and orange juice in various ratios. The mixture of orange juice and concentrated whey in ratio 3:2 appeared to be the optimal formulation with the best sensory properties. The shelf life at room temperature was determined to 11 days, while it lasted up to 3 months under cold storage conditions. Kumar and Bangaraiah (39) also tested the sensory properties, chemical composition and shelf life of multiple formulations of orange juice and whey. Thereby, two formulations (70% whey and 30% orange juice, and 65% whey and 35% orange juice) were evaluated with the highest sensory scores, while all of the produced beverages showed good microbiological stability and the potential to be stored for up to 2 months at room temperatures. Sady et al. (40) studied the production of whey beverage with orange juice and compared its properties to the same beverage produced without whey. The beverage containing whey was characterized by higher contents of proteins, ash, glucose, lactose and vitamin B, but contained less sucrose, fructose and vitamin C. Also, there were not any considerable differences in the polyphenolic content and the sensory score for colour desirability. Pareek et al. (41) investigated the production of refreshing carbonated beverage consisting of orange juice and whey in different ratios (70:30, 60:40 and 50:50). The mixture containing 70% orange juice and 30% whey was the most acceptable one and was characterised by a general increase in nutrients in comparison with the standard orange juice. The addition of tropical fruits or berries to whey has been investigated frequently. For instance, Jaworska et al. (42) added blackcurrant juice to acid whey and compared the characteristics between the pure blackcurrant juice and the one containing whey. The whey beverage with blackcurrant juice had higher amounts of ash, proteins and vitamin B₂, while pure blackcurrant juice showed slightly higher antioxidant activity and received higher scores at sensory evaluation. Baccouche et al. (43) investigated the addition of prickly pear juice to acid whey. According to the obtained results, the beverages were physically stabilized by adding sugar and pectin to the heat-treated whey. Singh et al. (44) studied the production of whey beverage with guava consisting of approx. 68% whey and 20% guava pulp. The beverages were processed by pasteurisation at several temperature/time regimes and were stored in a cool place up to 90 days. The best beverage appeared to be the one pasteurized at 65 °C for 25 min and stored in a cool place for 45 days. Chavan et al. (45) optimised the production of a whey beverage with mango by mixing whey powder, whey protein concentrate or fresh whey with mango pulp or mango powder. The chemical composition, sensory properties and microbiological parameters of the produced beverages were analysed. The obtained results showed that regardless of prior processing (drying, concentrating), whey could be successfully utilized for beverage production, although a significant increase in acidity was detected in all samples. The beverage made from whey protein concentrate and mango powder showed good overall acceptability after 30 days of storage at refrigeration temperature. Valadão et al. (46) examined the possibilities of using ricotta cheese whey in sports drink production and found that tangerine, passion fruit and strawberry-passionfruit flavours achieved the best sensory scores. Janiaski et al. (47) optimised the production of fermented and nonfermented strawberry-flavoured whey beverages. The nonfermented strawberry-flavoured whey beverages were recognized as not enough acidic and viscous, having a more intense artificial strawberry aroma.

Some authors have studied the addition of herbs or spices in order to design a novel functional whey beverage. Yadav et al. (48) studied the production of whey beverage enriched with banana juice and Mentha arvensis extract. The optimal addition of Mentha extract was estimated at max. 2%, while the shelf life was determined to be 15 days. Similarly, Kumar et al. (49) developed a beverage from the ripe pineapple juice, whey and Mentha arvensis extract in the amount up to 3%. Refrigerated storability and BOD at room temperature of the produced beverages were analysed, while the possible changes were determined at 15-day intervals for up to 2 months. The most acceptable beverages were the ones containing between 0 and 1% Mentha arvensis, while its higher mass fraction caused a decrease in overall sensory quality. Satpute et al. (50) also incorporated Mentha arvensis extract into whey, but with beetroot pulp. There were four different types of beverages produced, and their chemical, sensory and microbiological parameters were analysed. Among all of the prepared beverages, the one consisting of 80% whey, 20% beetroot and 6% Mentha arvensis extract was evaluated as the best one. Alane et al. (51) optimised the preparation of a whey-based mango herbal beverage with the addition of ginger extract in volume fraction 0.5-5%. Thereby, the sample containing 10 g mango, 8 g sugar, 82 mL whey, 0.5% ginger extract and 0.05% guar gum achieved the highest overall acceptability. However, the microbiological quality of none of the produced beverage samples was satisfying during the tested storage period.

Regardless of the components chosen to create a refreshing whey beverage, the occurrence of sediment, salty sour taste and odour of cooked milk are still not avoided. Adding sufficient quantities of fruit base is critical for reaching the desired sensory quality, but on the other hand certain components of the fruit dry matter tend to precipitate and adversely influence beverage appearance. Thus, other solutions such as fermentation or non-thermal processing methods need to be reconsidered for application in whey beverage processing.

Fermented whey beverages

Fermented beverages have been recognized by consumers all over the world for their therapeutic value. Considering the fact that whey contains almost 70% lactose from the milk, fermentation to yogurt-like drinks appears to be a meaningful way of whey utilization. Since fermentation process is accompanied by a decrease in pH due to transformation of lactose to lactic acid, sweet whey appears to be a better choice for fermented beverage production. Whey fermentation usually employs starter and/or probiotic cultures able to metabolise lactose such as Lactobacillus acidophilus, Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus, Lactobacillus reuteri, Bifidobacterium bifidum, Lactobacillus rhamnosus, Propionibacterium freudenreichii ssp. shermanii, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus helveticus, Enterococcus faecium, Bifidobacterium animalis ssp. lactis and Lactobacillus paracasei (33). Sohrabi et al. (52) studied the production of whey beverage fermented with a commercially available yoghurt culture DELVO^®-YOG TY-17A DSL (DSM Food Specialties, Delft, The Netherlands). Thereby, whey protein concentrate was reconstituted and enriched by adding vitamin E prior to pasteurization and fermentation. At the same time, identical beverage was produced but without fermentation. Chemical, microbiological and sensory parameters of both drinks were analysed. Although there was no considerable difference in the chemical composition, fermented beverage achieved significantly higher overall acceptability and sensory scores. Very often probiotic whey beverages are investigated and are generally considered as one of the target segments of developing whey utilization for minimally processed functional products with added value (53). Among the most important factors is the chosen probiotic strain since it determines the unique flavour and texture of the fermented beverage. Lactobacillus rhamnosus is frequently used, but since it lacks the enzyme β-galactosidase, it does not have the ability to metabolize lactose. Therefore, it is often necessary to hydrolyse lactose prior to the fermentation or to use an appropriate co-culture. Pescuma et al. (54) studied the fermentation of whey protein concentrate by the strains Lactobacillus acidophilus CRL 636, Lactobacillus delbrueckii ssp. bulgaricus CRL 656 and Streptococcus thermophilus CRL 804, as single or mixed cultures. Fermented whey was then mixed with peach juice and calcium lactate and stored for 28 days at 10 °C. According to the obtained results, mixed cultures and single Streptococcus thermophilus CRL 804 culture showed a good surviving potential during the tested storage period. Also, all of the tested strains degraded β-lactoglobulin (41–85% after 12-hour incubation), which is of a great importance since β-Lg B is one of the major milk allergens. Koç et al. (55) fermented whey with probiotic strains Lactobacillus plantarum or Lactobacillus brevis and their combination. Fermented whey was supplemented with different fruit concentrates (lemon, mango, pineapple, apple or grape) and sucrose in order to mask the bitter flavour and achieve acceptable sensory characteristics. According to the obtained results, a beverage inoculated with Lb. plantarum and enriched with pineapple concentrate was the most preferred one. Seyhan et al. (56) studied the production of fermented whey beverages from whey powder fortified with soy isoflavones or phytosterols and inoculated with probiotic strains Lactobacillus acidophillus La-5 or Lactobacillus casei LBC-81. The addition of nutraceuticals did not change the basic composition of the produced beverages, but the phytosterol-fortified beverages were significantly more acceptable in terms of sensory quality and would be suitable for industrial-scale production. Similarly, Schlabitz et al. (57) studied the shelf life of fermented probiotic products produced from different mixtures of whey and powdered milk. The beverages were produced by inoculation with probiotic strains Lactobacillus acidophilus LA-5, Bifidobacterium animalis ssp. lactis BB-12 and Streptococcus thermophilus. They were fortified by adding prebiotics, strawberry pulp and strawberry flavour. Eleven formulations were developed and their chemical, microbiological and sensory parameters were analysed. The obtained results confirmed the possibility of producing a fermented probiotic beverage containing up to 70% ricotta cheese whey. Yasmin et al. (58) found that fermented whey beverages supplemented with probiotics play an important role in lowering cholesterol levels in rats. Faisal et al. (59) investigated the production of fermented probiotic whey beverages enriched with orange powder. Beverages were produced using the fresh cheddar cheese whey supplemented with orange juice powder and orange flavour and fermented at 42 °C by a combined thermophillic probiotic culture consisting of strains Lactobacillus acidophillus La-5, Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and Bifidobacterium sp. BB-12. The best ranked beverage consisted of 1 L cheese whey, 0.70 g stabilizer, 8% sugar, 1% orange powder and 0.40 mL flavour. The authors concluded that the addition of orange flavour and sugar into whey fermented by probiotic strains might be a successful method for utilizing cheddar cheese whey for beverages with acceptable sensory characteristics. Skryplonek and Jasińska (60) and Skryplonek (61) studied the potential of acid whey in fermented drink production. Acid whey was inoculated with yoghurt culture and probiotic strains Lactobacillus acidophilus La-5 and Bifidobacterium animalis ssp. lactis BB-12. For further supplementation, buttermilk powder, sweet whey powder, condensed milk, UHT milk and skimmed milk powder were tested. The obtained results showed that acid whey could also be used as a raw material to manufacture fermented probiotic beverages and also provide sufficient levels of bacteria required to ensure health benefits to consumers.

Recently, some studies have focused on production of kefir-like whey beverages. Pereira et al. (62) studied the fermentation of ultrafiltered whey protein concentrates by kefir grains and/or selected probiotic strains. The fermented drinks were acceptable according to their physicochemical and sensorial properties, and contained satisfactory counts of microorganisms after 14 days of refrigerated storage. Magalhães et al. (63) compared kefir produced from milk with the one from whey by using kefir grains. Lactose hydrolysis, ethanol levels, formation of organic acids and volatile compounds determined during fermentation were compared among samples of milk kefir and whey kefir. The obtained results indicated that kefir grains utilized lactose from whey and deproteinised whey and produced similar amounts of ethanol, lactic acid and acetic acid to those obtained during milk fermentation. Thus, whey could be a valuable substrate for production of kefir-like beverages.

Application of non-thermal processing methods in whey beverage production

In recent years, lots of efforts have been put into optimizing the application of non-thermal processing methods into whey processing. In order to partially or entirely prevent the undesired advents such as sediment formation, poor mouthfeel, salty sour taste, etc., different attempts have been made including for example the application of membrane processes or whey treatment by high intensity ultrasound. Barukčić et al. (36, 64) examined the possibility of applying microfiltration and ultrafiltration in order to achieve adequate microbiological stability without whey protein denaturation and sediment formation. Promising results were obtained by combining microfiltration with a 0.5-µm membrane and a subsequent ultrafiltration with a 0.2-kDa membrane. Both membranes were ceramic and the process was performed at 20 °C. Optimal microbiological quality was obtained and the nutritional quality was almost entirely preserved, meaning that whey proteins were maintained in the native state. Such findings were better than those achieved by the usually applied pasteurization at 73 °C for 20 s, which opened new possibilities for producing minimally processed whey-based beverage of excellent nutritional quality. Ultrafiltration or reverse osmosis allow whey concentration and could solve the problem of the poor mouthfeel inherent to whey beverages (65). Accordingly, Dilipkumar and Yashi (66) investigated a production of refreshing fruit beverage using the native, prefiltered and ultrafiltered (UF) acid whey as basis. Thereby, the addition of mango, pineapple and orange juice in different amounts (18, 20, 22 and 24%) was tested. The best properties and overall acceptability among consumers were recorded for the carbonated beverage consisting of UF whey basis enriched with the addition of 22% pineapple juice. Since the implementation of membrane processes eludes great nominal financial expenses, they are mainly used for the production of more cost-effective products such as whey protein concentrates or isolates. In order to establish a production without waste products, many authors have proposed the utilization of the remaining UF permeate. Beucler et al. (67) investigated the application of whey permeate for the production of carbonated beverage enriched with addition of different flavours and vitamins. Amaral et al. (37) investigated the application of supercritical carbon dioxide for application as alternative technology to thermal processing during production of whey and grape juice. They found no differences in the characteristics (acidity, total solids, antioxidant activity) of the juice processed by conventional heat treatment and supercritical carbon dioxide technology. High intensity ultrasound was also investigated for purposes of preventing sediment formation or reducing its amount, for improving the fermentation or for partial substitution of pasteurization (35, 68). Barukčić et al. (68) investigated the influence of high intensity ultrasound on the quality and fermentation of reconstituted sweet whey. In the first stage of the study, whey was subjected to treatments with different power inputs (480 and 600 W) for 6.5, 8 and 10 min at constant temperature (45 and 55 °C). Microbiological quality, particle size distribution, protein content, acidity, electrical conductivity, viscosity and sensory properties of the treated whey samples were analysed. All of the parameters were compared to the control sample (pasteurized) and to fresh whey. Whey thermo-sonication by nominal power of 480 W for 10 min at 55 °C resulted in better microbiological quality and sensory properties than whey pasteurization. Influence of high intensity ultrasound on whey fermentation with yoghurt culture YC-380 and with monoculture Lactobacillus acidophilus La-5 (both Christian Hansen, Hørsholm, Denmark) was investigated. Different ultrasound treatments were applied for culture activation prior to or after the inoculation, and treatment with nominal input power of 84 W for 150 s resulted in the highest increase of the viable count during the activation process. Jeličić et al. (35) studied the application of a combination of high intensity ultrasound with nominal inlet power of 400 W with moderate heat (55 °C) in whey processing. The applied treatment resulted in a better reduction of the number of total bacteria, coliform bacteria, yeasts and moulds than conventional pasteurization. Also, sensory properties were improved regarding mouth feel, absence of sediment and unchanged colour in all of the ultrasound-treated whey samples.

Thus, along with the development of new processing technologies, whey utilization could be improved too. There are numerous scientific studies that have proven the feasibility as well as the importance of producing whey-based beverages and similar products, not only for resolving the question of environmental pollution, but also for its outstanding nutritional value.

Buttermilk beverages