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Background: The extent to which dairy products and their fat content influence cardiovascular health remains uncertain., Objective: This study aimed to assess how consumption of low-fat milk and regular-fat cheese enriched in γ-aminobutyric acid (GABA) influences daytime ambulatory blood pressure (BP) and other cardiometabolic risk factors., Methods: In this crossover controlled feeding study, 55 healthy men and women with high-normal daytime BP were randomly assigned to sequences of three 6-wk isoenergetic diets, each comprising 1) no dairy (control diet), 2) 3 daily servings of 1% fat milk, and 3) 1 daily serving of 31% fat cheddar cheese naturally enriched in GABA. Total proteins, carbohydrates, and fats were matched across all 3 diets. The additional 2% of energy from SFAs in the cheese diet was replaced by n-6 PUFAs in the other diets., Results: Comparison of postdiet ambulatory systolic BP revealed no difference (P = 0.34), which was also the case for ambulatory diastolic BP (P = 0.45). The cheese diet increased serum LDL-cholesterol concentrations compared with the control and milk diets (+5.8%, P = 0.006 and +7.0%, P = 0.0008, respectively) and increased LDL particle size compared with the milk diet (P = 0.02). HDL-cholesterol concentrations after the milk diet were lower than after the control diet (-4.1%; P = 0.009). The milk and cheese diets increased triglycerides compared with the control diet (+9.9%, P = 0.01 and +10.5%, P = 0.007, respectively). There was no significant difference between all diets for C-reactive protein concentrations and markers of glucose/insulin homeostasis., Conclusions: These results suggest that short-term consumption of dairy products, whether low or regular in fat, has no overall effect on daytime ambulatory BP compared with a dairy-free diet. Other cardiometabolic risk factors may be differently modified according to the fat content of the dairy product. This trial was registered at clinicaltrials.gov as NCT02763930., (Copyright © Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food, 2019.)

The availability of alternative food products fortified with vitamin D could help decrease the percentage of the population with vitamin D deficiency. The objective of this study was to fortify cheese with vitamin D. Cottage cheese was selected because its manufacture allows for the addition of vitamin D after the draining step without any loss of the vitamin in whey. Cream containing vitamin D (145 IU/g of cream) was mixed with the fresh cheese curds, resulting in a final concentration of 51 IU/g of cheese. Unfortified cottage cheese was used as a control. As expected, the cottage cheese was fortified without any loss of vitamin D in the cheese whey. The vitamin D added to cream was not affected by homogenization or pasteurization treatments. In cottage cheese, the vitamin D concentration remained stable during 3 weeks of storage at 4°C. Compared with the control cheese, the cheese fortified with vitamin D showed no effects of fortification on cheese characteristics or sensory properties. Cottage cheese could be a new source of vitamin D or an alternative to fortified drinking milk., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The technological challenge related to cheese fortification with vitamin D is the loss of a large proportion of vitamin D during the wheying-off step. The use of ultrafiltration (UF) to concentrate the milk before vitamin D enrichment and cheese manufacturing could be a way to reduce the volume of whey and consequently the vitamin D losses in cheese whey. Control (1.0×) and concentrated milks (1.4× and 1.8×) were fortified with vitamin D at a concentration of 450 IU per gram of milk. The 1.8× cheese milk concentration reduced slightly the vitamin D loss during the draining step (19.8%) compared with the control cheese (25.5%) and vitamin D remained stable during Cheddar cheese processing and ripening., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Lactones are important contributors to the flavour and aroma of milk and dairy products. This study was conducted to evaluate the effects of dietary linseed oil (LO) and forage to concentrate ratio on milk lactone profile. Twenty four Holstein cows were used during a 4-week feeding trial in a randomised complete block design. Cows were fed diets containing 30% (LC) or 70% (HC) concentrate, and 0% (NLO) or 3% LO in a 2×2 factorial arrangement of treatments. Milk lactone profile was evaluated using the solid phase microextraction technique. The highest levels of δ-lactones (δ-6:0, δ-8:0, δ-10:0, and δ-12:0) were found with the LC/NLO diet. These concentrations were then decreased when cows received either a high level of concentrate or supplemental LO, but these effects were not additive (interaction of LO by concentrate, P<0·01). An interaction of LO by concentrate (P<0·01) was also noted on milk γ-12:0 for which the highest concentration was observed when supplementing LO in HC diet, while no effect was apparent when LO was added in LC diet. Moreover, feeding HC increased the level of γ-12:1 in milk as compared with LC, while LO had no effect on this γ-lactone. Finally, γ-12:2 was not detected in any of the milk samples studied. Organoleptic properties of milk were evaluated in a triangle test showing that a significant number of assessors perceived a difference between milk from cows fed LC/NLO as compared with milk from cows fed HC/LO. The sensory evaluation was completed by a ranking test where the intensities of fresh lactic, foreign and global flavours were not different between treatments. In conclusion, feeding LO in HC diet modified milk lactone profile with a shift toward more γ- and less δ-lactones as compared with LC diet not supplemented with LO. A difference was perceived in a triangle test between milk from these two treatments, but the sensory attributes responsible for this difference have not been identified in the current trial.

Nutrient composition and organoleptic properties of milk can be influenced by cow diets. The objective of this study was to evaluate the forage type effects on volatile organic compounds, fatty acid (FA) profile, and organoleptic properties of milk. Timothy grass was fed as hay, pasture, or silage during a period of 27 d to a group of 21 cows in a complete block design based on days in milk. Each cow also received 7.2 kg/d of a concentrate mix to meet their nutrient requirements. Forage dry matter intake averaged 13.9 kg/d and was not different among treatments. Milk yield was higher for cows fed pasture, intermediate for cows fed silage, and lowest for cows fed hay. However, milk fat content was higher for cows fed hay and silage, compared with cows fed pasture. As a result, fat-corrected milk and fat yield were not different among treatments. Increasing the supply of dietary cis-9,cis-12 18:2 (linoleic acid) and cis-9,cis-12,cis-15 18:3 (α-linolenic acid) when feeding pasture enhanced the concentration of these 2 essential FA in milk fat compared with feeding hay or silage. Moreover, the ratio of 16:0 (palmitic acid) to cis-9 18:1 (oleic acid), which is closely related to the melting properties of milk fat, was lower in milk from cows on pasture than in milk from cows fed hay or silage. Cows fed hay produced milk with higher levels of several free FA and γ-lactones, but less pentanal and 1-pentanol. More dimethyl sulfone and toluene were found in milk of cows on pasture. Cows fed silage produced milk with higher levels of acetone, 2-butanone, and α-pinene. Results from a sensory evaluation showed that panelists could not detect a difference in flavor between milk from cows fed hay compared with silage. However, a significant number of assessors perceived a difference between milk from cows fed hay compared with milk from cows fed pasture. In a sensory ranking test, the percentage of assessors ranking for the intensity of total (raw milk, fresh milk, and farm milk), sweet (empyreumatic, vanilla, caramel, and sugar), and grassy (grass, leafy vegetable, and plant) flavors was higher for milk from cows fed pasture compared with hay and silage. Using timothy hay, pasture, or silage harvested at a similar stage of development, the current study shows that the taste of milk is affected by the forage type fed to cows. More research is, however, needed to establish a link between the sensory attributes of milk and the observed changes in volatile organic compounds and FA profile., (Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30 degrees C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of gamma-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. gamma-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects., (Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Cheddar cheese in curd form is very popular in eastern Canada. It is retailed immediately after cheese manufacturing and can be maintained at room temperature for 24 h to provide better texture and mouthfeel. Subsequently, the cheese curds must be stored at 4 degrees C. The shelf life is generally 3 d. In this study, Cheddar cheese curds were produced by adding a high diacetyl flavor-producing strain (Lactococcus diacetylactis) to a thermophilic-based starter. The objective was to achieve both postacidification stability to increase the shelf life and enhanced flavor. The addition of L. diacetylactis increased processing time but did not affect cheese composition or the evolution of proteolysis and texture. During cheese manufacturing, streptococci became the dominant microflora in all cheeses, whereas populations of Lactococcus cremoris and L. diacetylactis decreased. During cheese storage, viable counts of L. diacetylactis and Streptococcus thermophilus increased but the counts of L. cremoris decreased. During cheese manufacturing and storage, the concentrations of lactic acid and diacetyl increased rapidly in cheeses produced with L. diacetylactis. Citric acid and galactose contents remained high in cheese made without L. diacetylactis. Sensory evaluation indicated that cheeses containing the L. diacetylactis strain were more flavorful and also had less sourness and could be stored at 4 degrees C for up to 7 d.

The aim of this study was to investigate the effect of whey protein isolate (WPI) gel microentrapment on the viability of Lactobacillus rhamnosus R011 during the production and storage of biscuits, frozen cranberry juice, and vegetable juice. Viability of microentrapped (ME) cells was compared to free cells freeze-dried in a milk-based protective solution as well as in a WPI-based solution (ungelled). During the production of biscuits and their storage for 2 wk at 23 degrees C, the highest stability was obtained with the cells ME in WPI gel particles. However, free cells prepared in the milk-based matrix were those that maintained the highest viability during storage of vegetable juice as well as during freezing and storage of cranberry juice. The culture prepared in a WPI-based solution had the highest drops in viable counts following the heating process of biscuits as well as during storage of vegetable juice and freezing and storage of cranberry juice. Although the WPI-based solution was not efficient in protecting free cells, it is concluded that the process of microentrapment in WPI can help in protecting the freeze-dried cells against subsequent acidic and alkaline pH conditions as well as heating and freezing of food products.

Several modifications that occur in milk during its processing and storage are driven by different oxidation-reduction reactions. In this study, a smooth electrolytic process was used to modify the redox state of the active species of milk thereby creating a mean to control these reactions. Five electroreduction treatments (2, 4, 6, 8, and 10 V) were applied to pasteurized skim milk. Parameters such as redox potential, dissolved oxygen, pH, conductivity, and current intensity were monitored during the course of each treatment. The proposed technology allows modulation of the redox potential of milk. Significant decreases of redox potential (441-707 mV) and of dissolved oxygen (3.3-8.3 mg L(-1)) were obtained. However, the results suggest that only a short-term modulation is created and that natural "milk equilibrium" is reestablished after 4-5 days of storage depending on the voltage difference applied during the electrochemical treatment.

Entrapping probiotic bacteria in gels with ionic cross-linking is typically achieved with polysaccharides (alginate, pectin, carraghenan). In this study, whey proteins were used for this purpose by carrying out the Ca(2+)-induced gelation of pre-heated whey protein isolate (WPI). A Lactobacillus rhamnosus cell suspension was added in a denatured WPI solution in a 30 : 70 volume ratio. Gelation was carried out by extrusion of the cell suspension in a CaCl(2) solution. Beads of approximately 3 mm diameter were formed. The population in the beads was 8.0 x 10(8) cells g(-1). Entrapment efficiency in gel beads was 96%, with a survival level of 23%. Scanning electron microscopy of beads before freeze-drying showed a tight protein network containing encapsulated Lb. rhamnosus cells homogeneously distributed throughout the matrix. The survival to freeze-drying of the bead-entrapped cells was 41%. Viability of microentrapped cells in a dynamic gastro-intestinal (GI) model was studied and the results were compared to free cells freeze-dried in a milk-based cryoprotective solution, as well as in a pre-denatured WPI solution. Results showed that protein gelation provided protection against acidic conditions in the stomach after 90 min, as well as against bile after 30, 60 and 90 min in the duodenum. Moreover, the milk-based cryoprotective solution was equally effective after 90 min in the duodenum. It is concluded that the gelation of whey proteins induced by Ca(2+) ions can protect the cells against adverse conditions of the GI system. However, certain stages in the entrapment process, particularly extrusion in the solution of CaCl(2), still need to be optimized in order to reduce the mortality of the cells during gelation.

The effect of incorporating a highly autolytic strain (Lactobacillus delbrueckii subsp. bulgaricus UL12) a proteolytic strain (Lactobacillus casei subsp. casei L2A), or a nisin Z-producing strain (Lactococcus lactis, subsp. lactis biovar diacetylactis UL719) into Cheddar cheese starter culture (Lactococcus lactis KB and Lactococcus cremoris KB) on physicochemical and rheological properties of the resultant cheeses was examined. Cheeses were ripened at 7 degrees C and analyzed over a 6-mo period for viable lactococcal and lactobacilli counts, pH, titratable acidity (TA), lipolysis, proteolysis, and textural characteristics. The combination of the nisin-producing strain and autolytic adjuncts significantly increased the production of water-soluble nitrogen, free amino acids, and free fatty acids. The effect of Lc. diacetylactis UL719 alone or of Lb. casei L2A on water-soluble nitrogen and free amino acid contents were also significant, whereas their effect on free fatty acids was not. Viable counts of Lb. bulgaricus UL12 were significantly reduced in the presence of Lc. diacetylactis UL719. Lactobacilli-containing cheeses showed significantly lower values for hardness, fracturability, and springiness. It could be concluded that the addition of Lb. bulgaricus UL12 together with a nisin-producing strain produces a greater increase in cheese proteolysis and an improvement in Cheddar cheese texture.

Bifidobacterium cells were encapsulated in a mixed gel composed of alginate, pectin, and whey proteins. Two kinds of capsules were obtained: gel beads without membranes and gel beads with two membranes formed by the transacylation reaction. In vitro studies were carried out to determine the effects of simulated gastric pH and bile salts on the survival of free and encapsulated Bifidobacterium bifidum. The protective effects of gel beads without membranes and gel beads coated with two membranes formed by the transacylation reaction were evaluated. After 1 h in an acidic solution (pH 2.5), the free-cell counts decreased by 4.75 log units, compared with a <1-log decrease for entrapped cells. The free cells did not survive after 2 h of incubation at pH 2.5, while immobilized-cell counts decreased by about 2 log units. After incubation (1 or 3 h) in 2 and 4% bile salt solutions, the bifidobacterium mortality level for membrane-free gel beads (4 to 7 log units) was higher than that for free cells (2 to 3 log units). However, counts of bifidobacteria immobilized in membrane-coated gel beads decreased by <2 log units. Cell encapsulation in membrane-coated protein-polysaccharide gel beads could be used to increase the survival of healthy probiotic bacteria during their transit through the gastrointestinal tract.

The aim of this study was to characterize the biological and rheological stability of continuous immobilized cell fermentation for the production of mixed-strain mesophilic starters. Three strains of Lactococcus were immobilized separately in kappa-carrageenan-locust bean gum gel beads. Continuous fermentation was carried out in a 1 L pH-controlled stirred tank reactor, operated at 30 degrees C, pH = 6.2, and D = 2 h(-)(1) in whey permeate medium supplemented with yeast extract (1.5%) and 0.1 M KCl and inoculated with 30% (v/v) bead inoculum (strain ratio 1:1:1). The continuous mixed-strain immobilized cell fermentation demonstrated a high biological stability, and no strain became dominant or was eliminated during the 52 day fermentation. The total and specific free cell populations showed high time stability. All immobilized populations, except MD, were unchanged, but a cross contamination of gel beads initially immobilizing a pure culture occurred, leading to a redistribution of immobilized population in individual beads. After initial modifications of bead rheological properties during colonization batches, the beads demonstrated a high mechanical stability, even with reduced KCl supplementation of the broth medium, in the range 0.1-0 M. This work emphasizes the potential of immobilized cell technology for producing mixed lactic starters in continuous fermentation.

Probiotic cheeses (Cheddar-like cheese) were produced with microfiltered milk standardized with cream enriched with native phosphocaseinate retentate and fermented by Bifidobacterium infantis. During the manufacture and storage of cheeses, viability of the bifidobacteria was determined. Biochemical changes such as proteolysis, sugar metabolism, and organic acids production were estimated. No bifidobacteria growth was observed during cheese-making steps. Bifidobacteria survived very well in cheeses packed in vacuum sealed bags kept at 4 degrees C for 84 d and remained above 3 x 10(6) cfu/g of cheese. No significant difference was observed between cheeses produced with or without bifidobacteria for fat, protein, moisture, salt, ash, or pH. After 12 wk of storage, more than 56% of the as1-CN was hydrolyzed in cheeses that were produced with bifidobacteria and inoculated at 10(8) cfu/g in the cream, and > 45% of hydrolysis was observed in the control cheese. However, no significant differences in the electrophoretic sodium dodecyl sulfate-PAGE patterns were observed in cheeses at any period of storage. At the first day after manufacture, lactose was completely hydrolyzed in cheeses made with bifidobacteria, which suggested high beta-galactosidase activity by B. infantis. Small quantities of acetic acid were detected in bifidus cheeses. The results indicated that B. infantis introduced into hard pressed cheese exhibited excellent viability during storage for 12 wk and could be metabolically active.

Changes in proteolysis and in residual enzymatic activity as a function of time were compared in model cheeses, made with either free enzymes or liposomes containing enzymes and in control model cheeses. Cheeses were ripened under different conditions of pH, fat content and temperature. The release of enzymes from liposomes was significantly stimulated by increasing the fat content from 0 to 20% and the pH from 4.9 to 5.5. Ripening temperature (6 degrees C or 13 degrees C) did not affect 2 months of ripening, proteolysis was 30% lower in liposome-than in free enzyme-treated cheeses, indicating a possible inhibition of released enzymes.

The aim of this work was to study a new process for the continuous production of mixed-strain lactic acid bacteria starters using immobilized cells. Three strains of Lactococcus (two Lactococcus lactis subsp. lactis: KB and KBP, and one Lactococcus lactis subsp. lactis biovar diacetylactis: MD) were immobilized separately in kappa-carrageenan-locust bean gum gel beads. Continuous fermentations were carried out in a 1 L pH-controlled stirred tank reactor with a 30% (v/v) bead inoculum (strain ratio 1:1:1), continuously fed with a whey UF permeate medium, supplemented with 1.5% yeast extract and 0.1M KCl. The effects of three parameters-pH, temperature (T), dilution rate (D), and their interactions on the composition and activity of the culture in the effluent at pseudosteady state were studied according to a rotatable central composite design, during a 53-day fermentation. The process showed a high biological stability and no strain became dominant, or was eliminated from the bioreactor. The statistical analysis showed that the three strains were differently affected by the studied parameters, and that a large range of effluent starter composition can be achieved by varying D, pH, and T. However, the acidifying characteristics were not affected by the culture conditions. A cross-contamination from other strains of the mixed culture was observed in gel beads entrapping a pure culture at the fermentation onset, and led to a biomass redistribution within the beads. However, the strain ratio (KB:KBP:MD) observed after the 53-day experiment (1:2:2) was close to the initial bead ratio (1:1:1). The beads demonstrated a high mechanical stability throughout the 53-day continuous fermentation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 502-516, 1997.

This study investigated the influence of ionic strength, liposome net charge and enzyme concentration on the immobilization of chymotrypsin in liposomes obtained from proliposomes. Depending on ionic strength and chymotrypsin concentration, immobilization efficiencies (IE) as high as 96 and 68% were obtained for liposomes prepared with Pro-lipo 3045 S and Pro-lipo 3080 S respectively. Increasing ionic strength and enzyme concentration resulted in a decrease in IE for both types of liposomes, and this was more pronounced for ionic strength. Relatively high amounts of chymotrypsin were found to be immobilized on the surface of the liposomes. Hydrophobic interactions between chymotrypsin and the hydrophobic tails of the phospholipids during liposome formation were probably responsible for this phenomenon.

This review explores recent advances in the use of immobilized cells for the production of metabolites used in the food industry, such as enzymes, amino acids, organic acids, alcohols, aroma compounds, polysaccharides, and pigments. Some food bioconversions such as fermentation of soy sauce and various hydrolysis are also considered. Special emphasis was placed on existing or potential industrial processes. This article also reports the effects of the reactor (configuration and working conditions), the immobilized cell physiological status (growing, nongrowing, or permeabilized), and of the carrier type, configuration, and size on the performance of immobilized cell systems. Compared with free cell fermentation, the main advantage of using immobilized cells is an increase in productivity, particularly in the case of continuous fermentation. For monoenzymatic reactions, nongrowing immobilized cells are often reported to exhibit a higher stability than free or immobilized enzymes.

Microfluidization has been tested as a way to disperse phospholipids in aqueous hemoglobin solutions. Spherical and stable liposomes of 2 to 3 microns were obtained. Lipid incorporation (up to 85%) and hemoglobin encapsulation (up to 15%) in liposomes have been improved with respect to previous investigations. However, results show that a more efficient dispersion system using lower concentrations of lipid is required to obtain a high liposome hemoglobin concentration (limited actually to 150 g/l) and an economically and biologically suitable process for artificial blood production at large scale.

The development of a method for the continuous mass production of liposomes is vital for the industrial use of liposomes in food products. The method should be mild enough to prevent denaturation of the encapsulated material, and the materials used for the preparation of the liposomes should be safe and edible. Among the methods available, microfluidization seems to be the most promising. Microfluidization consists of processing emulsions under high pressure through an apparatus called a Microfluidizer. This apparatus also allows the production of another type of lipid vesicle: milkfat-coated microcapsules composed of milkfat and emulsifiers. The main advantages of microfluidization include the continuous production of large quantities of lipid vesicles without dissolving the phospholipids in organic solvents. These vesicles could be used in various food products for a variety of objectives. The addition of encapsulated material in liposomes or in milkfat-coated microcapsules to cheese milk resulted in a retention of 80-90% of the vesicles in the cheese, compared to only 2-4% if the material was added directly to the milk in the unencapsulated form. Liposomes and milkfat-coated microcapsules could be used as enzyme carriers to accelerate cheese ripening, or as carriers for flavouring systems to improve the organoleptic properties of low-fat cheeses or to impart distinctive flavours to new speciality cheeses. These microcapsules could also be used in food products to avoid undesirable side-reactions during food processing, or to supplement food products with nutritious additives.