When used in commercial fermented dairy products, bifidobacteria may enhance immunity by stimulat... more When used in commercial fermented dairy products, bifidobacteria may enhance immunity by stimulating cytokine secretion by leukocytes. To assess whether interaction between bifidobacteria and leukocytes promote cytokine production, we cultured RAW 264.7 cells (macrophage model) and EL-4.IL-2 thymoma cells (helper T-cell model) in the presence of 14 representative strains of heat-killed bifidobacteria. In unstimulated RAW 264.7 cells, all bifidobacteria induced pronounced increases (up to several hundred-fold) in the production of tumor necrosis factor-alpha compared with that of controls. Interleukin-6 production by unstimulated cells also increased significantly, but less than did tumor necrosis factor-alpha. Upon concurrent stimulation of RAW 264.7 cells with lipopolysaccharide, production of tumor necrosis factor-alpha and interleukin-6 were both enhanced between 1.5- to 5.8-fold and 4.7- to 7.9-fold, respectively, when cultured with 10(8) bifidobacteria/ml. In unstimulated EL-4.IL-2 cells, bifidobacteria had no effect on the production of interleukin-2 or interleukin-5. Upon stimulation of EL-4.IL-2 with phorbol-12-myristate-13-acetate, there were variable increases in interleukin-2 secretion (up to 2.4-fold for 10(6) Bifidobacterium Bf-1/ml) and interleukin-5 secretion (up to 4.6-fold for 10(8) B. adolescentis M101-4). The results indicated that, even when variations among strains were considered, direct interaction of most bifidobacteria with macrophages enhanced cytokine production, but the effects on cytokine production by the T-cell model were less marked. Interestingly, the 4 bifidobacteria strains used commercially for diary foods showed the greatest capacity for cytokine stimulation. The in vitro approaches employed here should be useful in future characterization of the effects of bifidobacteria on gastrointestinal and systemic immunity.
Abstract Yield of stirred curd cheese from milk containing 0, .02, .03, and .05% added calcium ch... more Abstract Yield of stirred curd cheese from milk containing 0, .02, .03, and .05% added calcium chloride and coagulated with prolease from Endothia parasitica was compared with the yield of curd coagulated with calf rennet. Five treatments replicated five times in a randomized block design were manufactured to produce 25 vats of cheese. Milk was analyzed for fat, total solids, total N, and non-casein N. Cheese was analyzed for fat, total solids, and total N. Whey was analyzed for fat and total N. Dry matter cheese yield data adjusted for covariants of milk fat and casein were lower for cheese manufactured from E. parasitica protease than from calf rennet. Addition of calcium chloride to cheese milk clotted with E. parasitica protease increased cheese yield. Calcium needed to be higher than .02% to produce maximum yields when cheese was manufactured with Endothia parasitica protease.
Edible Films and Coatings for Food Applications, 2009
Edible films and coatings are defined as continuous matrices that can be prepared from proteins, ... more Edible films and coatings are defined as continuous matrices that can be prepared from proteins, polysaccharides and/or lipids to alter the surface characteristics of a food. Although the terms films and coatings are used interchangeably, films in general are preformed and are freestanding, whereas, coatings are formed directly on the food product. Proteins used in edible films include wheat gluten,
Cheddar cheese with six different fat levels (34.3, 31.5, 26.8, 20.5, 12.6 and Cl%) were manufact... more Cheddar cheese with six different fat levels (34.3, 31.5, 26.8, 20.5, 12.6 and Cl%) were manufactured and allowed to ripen 4 mo at 7°C. Melting characteristics of the cheeses were studied by the Arnott test and dynamic rheological testing. Meltability of Cheddar cheese was significantly influenced by its fat content as determined by the Arnott test. A significant correlation (r = -0.80) occurred between the minimum complex modulus G* and meltability of Cheddar cheese. Minimum complex modulus G* may be a useful predictor of cheese meltability.
Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increa... more Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increases in G' and G". Proteolysis during ripening led to softening of all cheeses and thus decreases in G' and G" for cheeses containing 34, 27, and 20% fat. Cheese with 13% fat showed a decrease in G' upon ripening, but no change in G". This lack of change in viscous behavior may be important to the texture of reduced-fat Cheddar cheese and overall acceptability. Dynamic rheological testing was helpful in understanding rheological behavior associated with fat reduction in cheese.
ABSTRACTWater solubility, hermal properties, tensile strength, percent elongation, oxygen permeab... more ABSTRACTWater solubility, hermal properties, tensile strength, percent elongation, oxygen permeability (OP), water‐vapor permeability (WVP) of cross‐linked glycerol plasticized whey protein isolate films were studied to determine the effect of cross‐linkers (glutaraldehyde, formaldehyde, dialdehyde starch, carbonyldiimidazole, and UV irradiation) on film properties. With the exception of UV treatment, solubility of the films decreased (P>0.05) upon treatment of the film‐forming solutions with chemical cross‐linkers. Tensile strength increased (P>0.05), whereas percent elongation was not affected by cross‐linking. Chemical cross‐linking increased (P>0.05) WVP and decreased (P>0.05) OP of the films. UV treatment had no effect on WVP and O P. With the exception of UV‐treated films, both onset temperature and degradation temperatures, as determined by differential scanning calorimetry, were increased upon cross‐linking.
Sage, alfalfa and sourwood honey, which vary in their oligosaccharide contents, were compared wit... more Sage, alfalfa and sourwood honey, which vary in their oligosaccharide contents, were compared with sucrose, high fructose corn syrup and inulin in their ability to support growth, activity and viability of lactic acid bacteria and bifidobacteria typically used in yoghurt manufacturing. Growth and the end products of fermentation (lactic and acetic acids) were determined. Growth and acid production by organisms studied in the presence of different sweeteners were dependent on the specific organism investigated; however, it was not influenced by sweetener type, oligosaccharide content or the floral source of the honeys. All the sweeteners studied supported the growth, activity and viability of the organisms studied.
Two commercial Bifidobacterium bifidum (Bf-1 and Bf-6) were cultured in 12% (wt/vol) reconstitute... more Two commercial Bifidobacterium bifidum (Bf-1 and Bf-6) were cultured in 12% (wt/vol) reconstituted nonfat dry milk (NDM) containing 5% (wt/wt) honey, sucrose, fructose, or glucose. Inoculated samples were incubated anaerobically at 37 degrees C for 48 h. Samples were collected at 12-h intervals and examined for (i) specific growth rate, (ii) pH, and (iii) levels of fermentation end products (lactic and acetic acids) as measured by high-performance liquid chromatography (HPLC). Viability of the organisms during 28 days of refrigerated storage at 4 degrees C was also assessed at 7-day intervals. Growth promotion and acid production were greatest when Bf-1 and Bf-6 were grown in the presence of honey. For both Bf-1 and Bf-6, retention of viability was greatest up to 14 days of refrigerated storageat 4 degrees C when they were grown and stored in the presence of honey compared to other sweeteners.
Whey protein isolate (WPI) films (pH 5.2) containing p-aminobenzoic acid (PABA) were heat-sealed ... more Whey protein isolate (WPI) films (pH 5.2) containing p-aminobenzoic acid (PABA) were heat-sealed to form casings. Hot dogs prepared with WPI, collagen, or natural casings were cooked, surface-inoculated to contain 10 3 Listeria monocytogenes CFU/g, and examined for numbers of L. monocytogenes, mesophilic aerobic bacteria (MAB), lactic acid bacteria (LAB), and yeast/mold during 42 d of storage at 4°C. Listeria populations on hot dogs prepared with WPI-1.0%-PABA casings remained relatively unchanged; however, numbers of Listeria on hot dogs prepared with WPI-0.0%-PABA, collagen, and natural casings increased about 2.5 logs during 42 d of refrigerated storage. Populations of MAB, LAB, and mold on WPI-1.0%-PABA casings were 1 to 3 logs lower compared to others casings.
ABSTRACTAn enzyme‐linked immunosorbent assay (ELISA) was developed to determine the susceptibilit... more ABSTRACTAn enzyme‐linked immunosorbent assay (ELISA) was developed to determine the susceptibility of Lactococcus cultures to bind bovine milk IgM, IgG and IgA. Agglutination susceptible (agg+) cultures bound high (P<0.05) concentrations of IgM, IgG and IgA, whereas agglutination resistant (agg−) strains bound less. The agglutination variable (aggv) cultures differed from the agglutination resistant (agg−) cultures only in their ability to bind IgG. The ELISA was a reliable indicator of agglutination susceptibility for mixed as well as single strain cultures. Laser Scanning Microscopy (LSM) was used to verify results of ELISA. The IgG ELISA described here may provide a rapid, sensitive and a reliable method for identification and selection of agg− cultures.
... A 0.177 N m torque sensor (Sensotec, Columbus, OH), connected to an xy recorder, was used to ... more ... A 0.177 N m torque sensor (Sensotec, Columbus, OH), connected to an xy recorder, was used to measure the torque applied to the vane during yield stress testing. ... Hanging weights, aligned with a pulley, were used periodically to calibrate the torque transducer. ...
Low-fat strawberry yoghurts were prepared with each of five alternative sweeteners: sucrose, high... more Low-fat strawberry yoghurts were prepared with each of five alternative sweeteners: sucrose, high-fructose corn syrup and honey from three different floral sources. A ninety-nine-member consumer panel evaluated the yoghurts for flavour, aroma, sweetness and overall acceptance. Degree of liking was scored by the panellists on a nine-point hedonic scale. Panellists preferred sucrose-sweetened yoghurts over those sweetened with high-fructose corn syrup and honey (P < 0.05). Among the honey-sweetened yoghurts, sage honey was the most liked (P < 0.05), followed by alfalfa- and sourwood-sweetened yoghurts.
Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p-aminobenzoic acid (PABA) and/o... more Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p-aminobenzoic acid (PABA) and/or sorbic acid (SA) were assessed for antimicrobial and mechanical properties while in contact with sliced bologna and summer sausage that were inoculated with Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica subsp. enterica serovar Typhimurium DT104. WPI films containing SA or PABA decreased L. monocytogenes, E. coli, and S. Typhimurium populations by 3.4 to 4.1, 3.1 to 3.6, and 3.1 to 4.1 logs, respectively, on both products after 21 d at 4 °C. Background flora was inhibited compared with controls. Film tensile strength decreased while % elongation remained unchanged following 72 h of product contact.
Calcium alginate (CA) gels containing pork myofibrillar protein (MP) were prepared at pH 5.2-6.2,... more Calcium alginate (CA) gels containing pork myofibrillar protein (MP) were prepared at pH 5.2-6.2, at 25 and 92 "C. Molecular interactions in CA/MP composite gels were examined by determining the effects of 5 M urea, 0.5 M NaC1,0.5 M NaSCN, 10% propylene glycol, and 0.2 M 2-mercaptoethanol on gel strength. CA gel strength was increased by MP at pH 5.2-5.5 and destabilized above pH 5.5. Heating at 92 "C generally promoted CA gelation. CA/MP gels were markedly destabilized by NaCl and NaSCN and, to a lesser extent, by urea and propylene glycol but were slightly stabilized by 2mercaptoethanol at 92 "C. These results suggest that electrostatic interactions and hydrogen bonds were the major forces involved in the CA/MP gel systems.
When used in commercial fermented dairy products, bifidobacteria may enhance immunity by stimulat... more When used in commercial fermented dairy products, bifidobacteria may enhance immunity by stimulating cytokine secretion by leukocytes. To assess whether interaction between bifidobacteria and leukocytes promote cytokine production, we cultured RAW 264.7 cells (macrophage model) and EL-4.IL-2 thymoma cells (helper T-cell model) in the presence of 14 representative strains of heat-killed bifidobacteria. In unstimulated RAW 264.7 cells, all bifidobacteria induced pronounced increases (up to several hundred-fold) in the production of tumor necrosis factor-alpha compared with that of controls. Interleukin-6 production by unstimulated cells also increased significantly, but less than did tumor necrosis factor-alpha. Upon concurrent stimulation of RAW 264.7 cells with lipopolysaccharide, production of tumor necrosis factor-alpha and interleukin-6 were both enhanced between 1.5- to 5.8-fold and 4.7- to 7.9-fold, respectively, when cultured with 10(8) bifidobacteria/ml. In unstimulated EL-4.IL-2 cells, bifidobacteria had no effect on the production of interleukin-2 or interleukin-5. Upon stimulation of EL-4.IL-2 with phorbol-12-myristate-13-acetate, there were variable increases in interleukin-2 secretion (up to 2.4-fold for 10(6) Bifidobacterium Bf-1/ml) and interleukin-5 secretion (up to 4.6-fold for 10(8) B. adolescentis M101-4). The results indicated that, even when variations among strains were considered, direct interaction of most bifidobacteria with macrophages enhanced cytokine production, but the effects on cytokine production by the T-cell model were less marked. Interestingly, the 4 bifidobacteria strains used commercially for diary foods showed the greatest capacity for cytokine stimulation. The in vitro approaches employed here should be useful in future characterization of the effects of bifidobacteria on gastrointestinal and systemic immunity.
Abstract Yield of stirred curd cheese from milk containing 0, .02, .03, and .05% added calcium ch... more Abstract Yield of stirred curd cheese from milk containing 0, .02, .03, and .05% added calcium chloride and coagulated with prolease from Endothia parasitica was compared with the yield of curd coagulated with calf rennet. Five treatments replicated five times in a randomized block design were manufactured to produce 25 vats of cheese. Milk was analyzed for fat, total solids, total N, and non-casein N. Cheese was analyzed for fat, total solids, and total N. Whey was analyzed for fat and total N. Dry matter cheese yield data adjusted for covariants of milk fat and casein were lower for cheese manufactured from E. parasitica protease than from calf rennet. Addition of calcium chloride to cheese milk clotted with E. parasitica protease increased cheese yield. Calcium needed to be higher than .02% to produce maximum yields when cheese was manufactured with Endothia parasitica protease.
Edible Films and Coatings for Food Applications, 2009
Edible films and coatings are defined as continuous matrices that can be prepared from proteins, ... more Edible films and coatings are defined as continuous matrices that can be prepared from proteins, polysaccharides and/or lipids to alter the surface characteristics of a food. Although the terms films and coatings are used interchangeably, films in general are preformed and are freestanding, whereas, coatings are formed directly on the food product. Proteins used in edible films include wheat gluten,
Cheddar cheese with six different fat levels (34.3, 31.5, 26.8, 20.5, 12.6 and Cl%) were manufact... more Cheddar cheese with six different fat levels (34.3, 31.5, 26.8, 20.5, 12.6 and Cl%) were manufactured and allowed to ripen 4 mo at 7°C. Melting characteristics of the cheeses were studied by the Arnott test and dynamic rheological testing. Meltability of Cheddar cheese was significantly influenced by its fat content as determined by the Arnott test. A significant correlation (r = -0.80) occurred between the minimum complex modulus G* and meltability of Cheddar cheese. Minimum complex modulus G* may be a useful predictor of cheese meltability.
Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increa... more Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increases in G' and G". Proteolysis during ripening led to softening of all cheeses and thus decreases in G' and G" for cheeses containing 34, 27, and 20% fat. Cheese with 13% fat showed a decrease in G' upon ripening, but no change in G". This lack of change in viscous behavior may be important to the texture of reduced-fat Cheddar cheese and overall acceptability. Dynamic rheological testing was helpful in understanding rheological behavior associated with fat reduction in cheese.
ABSTRACTWater solubility, hermal properties, tensile strength, percent elongation, oxygen permeab... more ABSTRACTWater solubility, hermal properties, tensile strength, percent elongation, oxygen permeability (OP), water‐vapor permeability (WVP) of cross‐linked glycerol plasticized whey protein isolate films were studied to determine the effect of cross‐linkers (glutaraldehyde, formaldehyde, dialdehyde starch, carbonyldiimidazole, and UV irradiation) on film properties. With the exception of UV treatment, solubility of the films decreased (P>0.05) upon treatment of the film‐forming solutions with chemical cross‐linkers. Tensile strength increased (P>0.05), whereas percent elongation was not affected by cross‐linking. Chemical cross‐linking increased (P>0.05) WVP and decreased (P>0.05) OP of the films. UV treatment had no effect on WVP and O P. With the exception of UV‐treated films, both onset temperature and degradation temperatures, as determined by differential scanning calorimetry, were increased upon cross‐linking.
Sage, alfalfa and sourwood honey, which vary in their oligosaccharide contents, were compared wit... more Sage, alfalfa and sourwood honey, which vary in their oligosaccharide contents, were compared with sucrose, high fructose corn syrup and inulin in their ability to support growth, activity and viability of lactic acid bacteria and bifidobacteria typically used in yoghurt manufacturing. Growth and the end products of fermentation (lactic and acetic acids) were determined. Growth and acid production by organisms studied in the presence of different sweeteners were dependent on the specific organism investigated; however, it was not influenced by sweetener type, oligosaccharide content or the floral source of the honeys. All the sweeteners studied supported the growth, activity and viability of the organisms studied.
Two commercial Bifidobacterium bifidum (Bf-1 and Bf-6) were cultured in 12% (wt/vol) reconstitute... more Two commercial Bifidobacterium bifidum (Bf-1 and Bf-6) were cultured in 12% (wt/vol) reconstituted nonfat dry milk (NDM) containing 5% (wt/wt) honey, sucrose, fructose, or glucose. Inoculated samples were incubated anaerobically at 37 degrees C for 48 h. Samples were collected at 12-h intervals and examined for (i) specific growth rate, (ii) pH, and (iii) levels of fermentation end products (lactic and acetic acids) as measured by high-performance liquid chromatography (HPLC). Viability of the organisms during 28 days of refrigerated storage at 4 degrees C was also assessed at 7-day intervals. Growth promotion and acid production were greatest when Bf-1 and Bf-6 were grown in the presence of honey. For both Bf-1 and Bf-6, retention of viability was greatest up to 14 days of refrigerated storageat 4 degrees C when they were grown and stored in the presence of honey compared to other sweeteners.
Whey protein isolate (WPI) films (pH 5.2) containing p-aminobenzoic acid (PABA) were heat-sealed ... more Whey protein isolate (WPI) films (pH 5.2) containing p-aminobenzoic acid (PABA) were heat-sealed to form casings. Hot dogs prepared with WPI, collagen, or natural casings were cooked, surface-inoculated to contain 10 3 Listeria monocytogenes CFU/g, and examined for numbers of L. monocytogenes, mesophilic aerobic bacteria (MAB), lactic acid bacteria (LAB), and yeast/mold during 42 d of storage at 4°C. Listeria populations on hot dogs prepared with WPI-1.0%-PABA casings remained relatively unchanged; however, numbers of Listeria on hot dogs prepared with WPI-0.0%-PABA, collagen, and natural casings increased about 2.5 logs during 42 d of refrigerated storage. Populations of MAB, LAB, and mold on WPI-1.0%-PABA casings were 1 to 3 logs lower compared to others casings.
ABSTRACTAn enzyme‐linked immunosorbent assay (ELISA) was developed to determine the susceptibilit... more ABSTRACTAn enzyme‐linked immunosorbent assay (ELISA) was developed to determine the susceptibility of Lactococcus cultures to bind bovine milk IgM, IgG and IgA. Agglutination susceptible (agg+) cultures bound high (P<0.05) concentrations of IgM, IgG and IgA, whereas agglutination resistant (agg−) strains bound less. The agglutination variable (aggv) cultures differed from the agglutination resistant (agg−) cultures only in their ability to bind IgG. The ELISA was a reliable indicator of agglutination susceptibility for mixed as well as single strain cultures. Laser Scanning Microscopy (LSM) was used to verify results of ELISA. The IgG ELISA described here may provide a rapid, sensitive and a reliable method for identification and selection of agg− cultures.
... A 0.177 N m torque sensor (Sensotec, Columbus, OH), connected to an xy recorder, was used to ... more ... A 0.177 N m torque sensor (Sensotec, Columbus, OH), connected to an xy recorder, was used to measure the torque applied to the vane during yield stress testing. ... Hanging weights, aligned with a pulley, were used periodically to calibrate the torque transducer. ...
Low-fat strawberry yoghurts were prepared with each of five alternative sweeteners: sucrose, high... more Low-fat strawberry yoghurts were prepared with each of five alternative sweeteners: sucrose, high-fructose corn syrup and honey from three different floral sources. A ninety-nine-member consumer panel evaluated the yoghurts for flavour, aroma, sweetness and overall acceptance. Degree of liking was scored by the panellists on a nine-point hedonic scale. Panellists preferred sucrose-sweetened yoghurts over those sweetened with high-fructose corn syrup and honey (P < 0.05). Among the honey-sweetened yoghurts, sage honey was the most liked (P < 0.05), followed by alfalfa- and sourwood-sweetened yoghurts.
Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p-aminobenzoic acid (PABA) and/o... more Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p-aminobenzoic acid (PABA) and/or sorbic acid (SA) were assessed for antimicrobial and mechanical properties while in contact with sliced bologna and summer sausage that were inoculated with Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica subsp. enterica serovar Typhimurium DT104. WPI films containing SA or PABA decreased L. monocytogenes, E. coli, and S. Typhimurium populations by 3.4 to 4.1, 3.1 to 3.6, and 3.1 to 4.1 logs, respectively, on both products after 21 d at 4 °C. Background flora was inhibited compared with controls. Film tensile strength decreased while % elongation remained unchanged following 72 h of product contact.
Calcium alginate (CA) gels containing pork myofibrillar protein (MP) were prepared at pH 5.2-6.2,... more Calcium alginate (CA) gels containing pork myofibrillar protein (MP) were prepared at pH 5.2-6.2, at 25 and 92 "C. Molecular interactions in CA/MP composite gels were examined by determining the effects of 5 M urea, 0.5 M NaC1,0.5 M NaSCN, 10% propylene glycol, and 0.2 M 2-mercaptoethanol on gel strength. CA gel strength was increased by MP at pH 5.2-5.5 and destabilized above pH 5.5. Heating at 92 "C generally promoted CA gelation. CA/MP gels were markedly destabilized by NaCl and NaSCN and, to a lesser extent, by urea and propylene glycol but were slightly stabilized by 2mercaptoethanol at 92 "C. These results suggest that electrostatic interactions and hydrogen bonds were the major forces involved in the CA/MP gel systems.
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