Quantification of volatile compounds in goat milk Jack cheese using static headspace gas chromatography

Goat milk Jack cheeses were manufactured with different levels of proteolytic endo- and exopeptidases from lysed bacterial cultures and aged for 30 wk. The aroma compounds that are potentially important in contributing the typical flavor of goat milk Jack cheese were quantified using static headspace gas chromatography. The concentrations of volatile compounds were evaluated every 6 wk throughout the aging period. Odor activity values of volatile compounds were calculated using the sensory threshold values reported in literature and their concentrations in Jack cheeses. Odor activity values of identified compounds were used to assess their potential contribution to the aroma of goat milk Jack cheeses. The odor activity values indicated that the ketones 2-hexanone, 2-heptanone, 2-nonanone, and 2,3-butanedione (diacetyl) were important odor-active compounds. The major odor-active acids found in this semi-hard goat milk cheese were butanoic, 2-methyl butanoic, pentanoic, hexanoic, and octanoic acids. Among the aldehydes, propanal and pentanal had high odor activity values and likely contributed to the aroma of this cheese. The concentrations of butanoic, pentanoic, hexanoic, heptanoic, octanoic, and nonanoic acids increased significantly in goat milk Jack cheese throughout aging. The extracted enzymes from lysed bacterial cultures that were added to the cheeses during manufacturing caused considerable increases in the concentrations of butanoic and hexanoic acids compared with the control. However, the lower concentration of peptidases resulted in an increased concentration of butanal, whereas more peptidases resulted in a lower concentration of 2-nonanone in goat milk Jack cheeses. © American Dairy Science Association, 2009

Effects of aging on rheological and proteolytic properties of goat milk Jack Cheese produced according to cow milk procedures

Pasteurized milk from French Alpine goats was processed into Jack Cheese according to modified processing conditions used for manufacturing Monterey Cheese from bovine milk. The effect of time on proteolytic and rheological changes that occurred on this cheese during aging was investigated. Commercial mesophilic culture, Lactococcus lactis subsp. lactis, was added to milk at the rate of 16 ml/100 l. The percentages of moisture, salt, protein, and fat in this cheese were 46.43, 1.19, 22.38, and 27.4, respectively. The salt to moisture ratio was 2.56. This cheese was vacuum-packed and stored at 4-5°C for 30 weeks and the rheological and proteolytic properties were determined. The force required to compress the cheese to 20% of its original height during the first cycle increased during aging. However, the force required to compress the cheese to 75% of its original height during the first cycle did not change during aging. Similar trends were found during the second compression cycle. Elasticity values at 20% compression increased during aging; however, at 75% compression they did not change. Electrophoretic analysis of the caseins in the goat milk Jack Cheese revealed that beta casein was the most abundant casein and was less susceptible to proteolysis than other caseins. The alpha and kappa caseins were the second and the third major caseins in goat Jack Cheese, respectively. Similar to bovine gamma caseins, as beta casein was hydrolyzed in this cheese it gave rise to gamma caseins. The modified manufacturing conditions and elucidation of the chemical and physical properties of this goat milk cheese are not only providing scientific information for further research but also furnishing valuable information for practical application in production of goat milk Jack Cheese. © 2004 Elsevier B.V. All rights reserved

Effects of aging on rheological and proteolytic properties of goat milk Jack Cheese produced according to cow milk procedures

Pasteurized milk from French Alpine goats was processed into Jack Cheese according to modified processing conditions used for manufacturing Monterey Cheese from bovine milk. The effect of time on proteolytic and rheological changes that occurred on this cheese during aging was investigated. Commercial mesophilic culture, Lactococcus lactis subsp. lactis, was added to milk at the rate of 16 ml/100 l. The percentages of moisture, salt, protein, and fat in this cheese were 46.43, 1.19, 22.38, and 27.4, respectively. The salt to moisture ratio was 2.56. This cheese was vacuum-packed and stored at 4-5°C for 30 weeks and the rheological and proteolytic properties were determined. The force required to compress the cheese to 20% of its original height during the first cycle increased during aging. However, the force required to compress the cheese to 75% of its original height during the first cycle did not change during aging. Similar trends were found during the second compression cycle. Elasticity values at 20% compression increased during aging; however, at 75% compression they did not change. Electrophoretic analysis of the caseins in the goat milk Jack Cheese revealed that beta casein was the most abundant casein and was less susceptible to proteolysis than other caseins. The alpha and kappa caseins were the second and the third major caseins in goat Jack Cheese, respectively. Similar to bovine gamma caseins, as beta casein was hydrolyzed in this cheese it gave rise to gamma caseins. The modified manufacturing conditions and elucidation of the chemical and physical properties of this goat milk cheese are not only providing scientific information for further research but also furnishing valuable information for practical application in production of goat milk Jack Cheese. © 2004 Elsevier B.V. All rights reserved

Quantification of volatile compounds in goat milk Jack cheese using static headspace gas chromatography

Goat milk Jack cheeses were manufactured with different levels of proteolytic endo- and exopeptidases from lysed bacterial cultures and aged for 30 wk. The aroma compounds that are potentially important in contributing the typical flavor of goat milk Jack cheese were quantified using static headspace gas chromatography. The concentrations of volatile compounds were evaluated every 6 wk throughout the aging period. Odor activity values of volatile compounds were calculated using the sensory threshold values reported in literature and their concentrations in Jack cheeses. Odor activity values of identified compounds were used to assess their potential contribution to the aroma of goat milk Jack cheeses. The odor activity values indicated that the ketones 2-hexanone, 2-heptanone, 2-nonanone, and 2,3-butanedione (diacetyl) were important odor-active compounds. The major odor-active acids found in this semi-hard goat milk cheese were butanoic, 2-methyl butanoic, pentanoic, hexanoic, and octanoic acids. Among the aldehydes, propanal and pentanal had high odor activity values and likely contributed to the aroma of this cheese. The concentrations of butanoic, pentanoic, hexanoic, heptanoic, octanoic, and nonanoic acids increased significantly in goat milk Jack cheese throughout aging. The extracted enzymes from lysed bacterial cultures that were added to the cheeses during manufacturing caused considerable increases in the concentrations of butanoic and hexanoic acids compared with the control. However, the lower concentration of peptidases resulted in an increased concentration of butanal, whereas more peptidases resulted in a lower concentration of 2-nonanone in goat milk Jack cheeses. © American Dairy Science Association, 2009

Size distribution of fat globules in goat milk

Milk from French-Alpine goats and Holstein cows was obtained from a bulk tank immediately prior to analyses. Fat globule size was determined by laser particle size analysis. Individual globules of fat in goat milk ranged from 0.73 to 8.58 μm in diameter. The average diameter of particles based on volume to surface area ratio (dVS) was 2.76 μm and was less than the mean (dVS) of 3.51 μm for bovine milk, in which fat globules ranged from 0.92 to 15.75 μm in diameter. The specific surface area of particles in caprine milk was 21,778 cm2/ml, whereas the specific surface area of particles in bovine milk was 17,117 cm2/ml. Ninety percent of the total particles found in goat milk were less than 5.21 μm in diameter, whereas 90% of the total particles in bovine milk were less than 6.42 μm based on the volume frequency distribution. Dissociation of casein micelles by urea in goat whole and skim milk caused larger dVS values due to the effect of fat particles and reduced the specific surface area in both milks because the total number of detectable particles in both whole and skim milk was reduced

Iron contents of muscle meat and liver in alpine and Nubian goats

Concentrations of nonheme, heme and total iron in livers and longissimus dorsi and biceps femoris muscles of meat from 13 Alpine and 12 Nubian goats were evaluated by chemical analysis and atomic absorption spectrophotometry, and differences in levels of the three forms of iron between breeds, sexes and types of muscle were investigated. The respective mean contents (μg/g wet weight) of nonheme, heme and total iron for the pooled data of Alpine and Nubian goats were 12.9 and 12.4; 30.7 and 24.1; and 45.8 and 37.4, indicating that Alpines had slightly higher levels of iron which were statistically not different from Nubians. Likewise, differences in iron levels between sexes were not significant, although doelings had slightly higher iron contents than bucks. Levels of the three forms of iron in livers, regardless of breeds or sexes, were significantly (P \u3c 0.01) greater than those in the two skeletal muscles. It was concluded from this study and other reports that the nutritional value of goat meat as a source of iron is the same as beef but higher than lamb or pork. © 1988

Size distribution of fat globules in goat milk

Milk from French-Alpine goats and Holstein cows was obtained from a bulk tank immediately prior to analyses. Fat globule size was determined by laser particle size analysis. Individual globules of fat in goat milk ranged from 0.73 to 8.58 μm in diameter. The average diameter of particles based on volume to surface area ratio (dVS) was 2.76 μm and was less than the mean (dVS) of 3.51 μm for bovine milk, in which fat globules ranged from 0.92 to 15.75 μm in diameter. The specific surface area of particles in caprine milk was 21,778 cm2/ml, whereas the specific surface area of particles in bovine milk was 17,117 cm2/ml. Ninety percent of the total particles found in goat milk were less than 5.21 μm in diameter, whereas 90% of the total particles in bovine milk were less than 6.42 μm based on the volume frequency distribution. Dissociation of casein micelles by urea in goat whole and skim milk caused larger dVS values due to the effect of fat particles and reduced the specific surface area in both milks because the total number of detectable particles in both whole and skim milk was reduced

Iron contents of muscle meat and liver in alpine and Nubian goats

Concentrations of nonheme, heme and total iron in livers and longissimus dorsi and biceps femoris muscles of meat from 13 Alpine and 12 Nubian goats were evaluated by chemical analysis and atomic absorption spectrophotometry, and differences in levels of the three forms of iron between breeds, sexes and types of muscle were investigated. The respective mean contents (μg/g wet weight) of nonheme, heme and total iron for the pooled data of Alpine and Nubian goats were 12.9 and 12.4; 30.7 and 24.1; and 45.8 and 37.4, indicating that Alpines had slightly higher levels of iron which were statistically not different from Nubians. Likewise, differences in iron levels between sexes were not significant, although doelings had slightly higher iron contents than bucks. Levels of the three forms of iron in livers, regardless of breeds or sexes, were significantly (P \u3c 0.01) greater than those in the two skeletal muscles. It was concluded from this study and other reports that the nutritional value of goat meat as a source of iron is the same as beef but higher than lamb or pork. © 1988

Proteolysis in accelerated ripened goat milk Jack cheese

Pasteurized milk from Alpine goats was processed into control and accelerated ripened Jack cheeses. Mesophilic culture, Lactococcus lactis subsp lactis, was added to ferment cheese milk at the rate of 2% (v/v). The same culture was grown in 1 I batches of tryptic soy broth and bacterial cells were harvested by centrifugation. Harvested cells were washed with distilled water, disrupted, and the cellular extract was mixed with curd at 0.14 and 0.27 (g/100 g) to accelerate ripening of the treated cheeses. Control cheese did not contain any additional cellular extract. The treated cheeses had higher percentages of water soluble nitrogen when compared with the control. Similarly, the activity of endo- and exopeptidases was the lowest in the control during aging while the treatment with 0.14% extract had the second highest and the treatment with 0.27% extract had the highest level of enzymic activity. Electrophoretic analysis of the caseins in the cheese revealed that β-casein was the most abundant casein and was less susceptible to proteolysis while αs2 and κ-caseins were the second and the third major caseins in goat milk Jack cheese, respectively

Proteolysis in accelerated ripened goat milk Jack cheese

Pasteurized milk from Alpine goats was processed into control and accelerated ripened Jack cheeses. Mesophilic culture, Lactococcus lactis subsp lactis, was added to ferment cheese milk at the rate of 2% (v/v). The same culture was grown in 1 I batches of tryptic soy broth and bacterial cells were harvested by centrifugation. Harvested cells were washed with distilled water, disrupted, and the cellular extract was mixed with curd at 0.14 and 0.27 (g/100 g) to accelerate ripening of the treated cheeses. Control cheese did not contain any additional cellular extract. The treated cheeses had higher percentages of water soluble nitrogen when compared with the control. Similarly, the activity of endo- and exopeptidases was the lowest in the control during aging while the treatment with 0.14% extract had the second highest and the treatment with 0.27% extract had the highest level of enzymic activity. Electrophoretic analysis of the caseins in the cheese revealed that β-casein was the most abundant casein and was less susceptible to proteolysis while αs2 and κ-caseins were the second and the third major caseins in goat milk Jack cheese, respectively