Conjugated Linoleic Acid Content of Cheddar-type Cheeses as Affected by Processing

Samples were taken at 9 stages of processing, from raw milk to cheese aged for 6 mo. Fatty acid distributions, conjugated linoleic acid (CLA), moisture, protein, lipid contents, and titratable acidity were determined. CLA contents were highest after 3 mo, with one type of Cheddar (3.76 mg/g lipid) higher than the other two (3.44 and 3.47 mg/g lipid). Multiple linear regression showed all composition parameters were directly related to CLA content (mg/100 g sample). The content of oleic acid isomer C_18:1ω7 was also directly related to CLA content (mg/g lipid). Thus, content of CLA in Cheddar-type cheeses might be controlled by stage and conditions of processing. An understanding of the effects of processing on CLA formation in Cheddar-type cheeses will be beneficial in designing processing methods to enhance CLA contents.     

Seasonal variation in conjugated linoleic acid and vaccenic acid in milk fat of sheep and its transfer to cheese and ricotta

The seasonal variation in conjugated linoleic acid (CLA) and vaccenic acid (VA) concentrations in sheep dairy products and the extent of their transfer from milk fat to cheese and ricotta fat were investigated. Samples were collected from 2 sheep milk processing plants in North Sardinia (Italy) every 2 wk from March through June. Concentrations of fatty acids (FA) in fresh cheese and ricotta fat were primarily dependent on the fatty acid content of the unprocessed raw milk. The content of c9,t11-CLA averaged 1.73, 1.69, and 1.75 mg/100 mg of FA methyl esters (FAME), respectively, for milk, cheese, and ricotta, and differed significantly between cheese and ricotta. The content of VA averaged 3.40, 3.33, and 3.43 mg/100 mg of FAME, respectively for milk, cheese, and ricotta. The FA composition of dairy products was markedly affected by period of sampling: the mean c9,t11-CLA and VA concentration decreased from March (2.20 and 4.52 mg/100 mg of FAME) to June (1.14 and 1.76 mg/100 mg of FAME) in all dairy products. No differences in c9,t11-CLA and VA concentration of dairy products were observed between the 2 dairy companies obtaining milk from the same geographical origin. The seasonal changes in CLA and VA in milk fat were probably related to changes in pasture quality.     

气相色谱法测定乳制品中共轭亚油酸的含量

共轭亚油酸（CLA）作为一种新型的功能性脂肪酸，其主要存在于瘤胃动物的乳和肉的脂肪中。CLA在乳制品中的含量受加工方式、贮藏等多种因素的影响。本文采用毛细管气相色谱法分析不同加工方法的各种乳制品中共轭亚油酸的含量，结果发现经发酵加工的乳制品中共轭亚油酸的含量明显高于未加工的原料乳，被测乳制品中以9c，11t结构的CLA含量为主，加工后的乳制品其反式CLA的含量都有所增加。     

The effect of pasteurisation temperature on the CLA content and fatty acid composition of white pickled cheese

In this study, the effect of pasteurisation temperature on fatty acid composition of cheese was investigated. The fatty acid composition of raw and different heat‐treated milk, salt and salt‐free cheese were determined using cheese made from raw milk at temperatures varying between 70 and 90°C for 5 min. Generally, C 16:0 palmitic acid was the major fatty acid present in all milk and cheese samples. C 18:1 t11 vaccenic acid was the major trans fatty acid (TFA) in all samples. C 18:2 cis‐9, trans‐11 (Rumenic acid) was the major CLA isomer in these samples. Pasteurisation temperatures had no effect on TFA, CLA and fatty acid composition of the milk and cheese samples.     

FATTY ACID COMPOSITION AND CONJUGATED LINOLEIC ACID CONTENT OF COW AND GOAT CHEESES FROM NORTHWEST ARGENTINA

ABSTRACT

In this study, we evaluated chemical characteristics, fatty acid composition and conjugated linoleic acid (CLA) content of cow and goat cheeses from Northwest Argentina. Similar chemical and fatty acid composition were determined in milk and cheese of both species. Palmitic, oleic and myristic acids were the most abundant fatty acids in dairy products. CLA level averaged 0.85 and 0.96 in milk and 0.76 and 1.04 g/100 g of fatty acids in cheese of cow and goat, respectively. Cis‐9,trans‐11 was the major isomer present in both species. Significant differences in CLA desaturase activity were observed, showing a value of 0.068 and 0.064 in milk, and 0.077 and 0.071 in cheese of cow and goats, respectively. Good nutritional properties were determined for cheeses of both species, which are fed on natural pasture during spring and summer seasons. Goat's cheese represents a higher source of CLA for human consumers than cow's cheese, offering from 156.6 to 222.6 mg/ 100 g of sample.

PRACTICAL APPLICATIONS

The present work shows the fatty acid composition and chemical characteristics of two fresh cheeses manufactured with cow and goat milk. Animals were fed on natural pasture during summer and spring seasons. It is known that pasture increases conjugated linoleic acid (CLA) concentration in milk fat, and the content in cheese is directly related to it. The CLA content of dairy products for the human consumers was analyzed, showing goat cheese with high polyunsaturated fatty acid content, including CLA. Cow and goat fresh cheese offer CLA as many ripening products of different countries, as cheddar or hard cheeses. Lipid composition of food is related to many illnesses, but some compounds are beneficial to human health. The main sources of CLA are milk and cheeses, and in Northwest of Argentina, no data are reported about it, where artisanal cheeses are consumed by the population. Therefore, the atherogenicity index was determined as well.     

Dose response of milk fat to intravenous administration of the trans-10, cis-12 isomer of conjugated linoleic acid

Intravenous infusion of conjugated linoleic acid (CLA) was evaluated as a simpler method than abomasal infusion and the feeding of calcium salts to examine milk fat depression. The objectives were to determine the dose-dependent response of milk fat and plasma metabolites to intravenous administration of the trans-10, cis-12 isomer of CLA, an isomer identified to possess an inhibitory effect on milk fat synthesis. Four multiparous Holstein cows averaging 123 +/- 30 d in milk were randomly assigned to treatments in a 4 x 4 Latin square design. Catheters were inserted into the jugular vein for infusions and blood sampling. Treatments consisted of intravenous infusions of 0, 2, 4, and 6 g/d CLA (> 95% trans-10, cis-12 CLA). Infusates contained 72 g/d of a parenteral solution, saline, and CLA to 90 ml. Periods were of 5 d duration with a 7 d wash out. Milk was sampled at each milking and analyzed for fat, protein, and fatty acids. Blood samples were obtained on the last day of each period. Dry matter intake (22.4 +/- 2.4 kg/d), milk yield (28.5 +/- 3.3 kg/d), and protein percent (3.26 +/- 0.08%) of cows were not affected by treatment. However, milk fat percentage was reduced linearly with increasing doses of CLA. Milk fat percentage was 4.17, 3.53, 3.29, and 2.92% on d 5 for treatments 0, 2, 4, and 6 g/d CLA, respectively. Concentrations (4.2 mg/g of fat) of cis-9, trans-11 CLA in milk fat were not affected by treatment. However, an increase in the trans-10, cis-12 CLA content of milk fat was observed. Milk fat contained 0.00, 0.02, 0.06, and 0.10 mg of trans-10, cis-12 CLA per g of fat (SEM = 0.065) for treatments 0, 2, 4, and 6 g/d CLA, respectively. Plasma NEFA concentration increased linearly with the dose of the trans-10, cis-12 CLA. Intravenous infusion of the trans-10, cis-12 isomer of CLA depressed milk fat in a linear manner over the range of infusion studied and, therefore, is an alternative to abomasal infusion.     

Effect of dietary lipid source on conjugated linoleic acid concentrations in milk fat

Conjugated linoleic acids (CLA) found in ruminant milk fat are a byproduct of incomplete biohydrogenation of lipids by ruminal bacteria. We examined the effect of different dietary fat supplements and processing methods on CLA. In trial 1, dietary supplements of Ca salts of fatty acids from canola oil, soybean oil, and linseed oil increased CLA content of milk fat by three- to fivefold over the control diet. Trials 2 and 3 examined the effect of processing methods for heat treatment of full fat soybeans. In trial 2, extrusion, micronizing, and roasting resulted in two- to threefold greater concentrations of CLA in milk fat than the control diet (raw ground soybeans). In trial 3, different temperatures of extrusion (120, 130, and 140 degrees C) increased the CLA content of milk fat to a similar extent; CLA averaged 19.9 mg/g of fatty acids for the extrusion treatments compared with 4.2 mg/g of fatty acids for the control diet (raw ground soybeans). Fish oil (200 and 400 ml/d) was examined in trial 4 and both levels resulted in CLA concentrations in milk fat that were about threefold greater than the control diet. In trial 5, grain and silage from a high oil corn hybrid increased the CLA content of milk fat; however, responses were modest with the CLA concentration (mg/g of fatty acids) averaging 4.6 and 2.8 for diets with high oil hybrid and normal hybrid, respectively. Similarly, dietary supplements of animal fat byproducts (tallow plus yellow grease; trial 6) resulted in modest increases in the CLA content of milk fat. Overall, several dietary manipulations involving lipid sources and processing methods were identified that allow for a marked increase in the conjugated linoleic acid content of milk fat.     

Seasonal variation in cis-9, trans-11 conjugated linoleic acid content in milk fat from Nordic countries

We investigated the content of cis-9, trans-11 isomer of conjugated linoleic acid (CLA) and its seasonal variation in bovine milk fat from Denmark, Finland, Iceland, Norway, and Sweden. Milk samples were collected during winter and summer and analyzed using gas chromatography. The CLA content in milk samples from the Nordic countries ranged from 0.41 to 1.02 g/100 g total fatty acids. The CLA content was higher in Iceland (0.64 +/- 0.02) than in the other countries together (0.57 +/- 0.02), and the concentration in Icelandic and Danish milk (0.63 +/- 0.03) was higher than in Finnish milk (0.48 +/- 0.02) in a comparison of single countries. The CLA concentration during summer was on average 41.6% (11.9) higher than during winter (0.48 g/100 g (0.03) vs. 0.068 g/100 g (0.07)). Season exerted similar changes in all 5 countries. The concentration of CLA in milk fat from the Nordic countries seems lower than in milk from European countries reported previously in the literature, which may be due to shorter summers and longer winters in the Nordic countries. Health implications of varying concentrations of CLA need to be studied.     

Fatty acid composition and CLA content in goat milk and cheese samples from Umbrian market

Goat dairy products are considered as a suitable alternative to cow milk products for some special categories of consumers (infants, old, and convalescent people). In the present research, a study on the lipid fraction of commercial goat milk and cheese samples purchased from Umbrian market was carried out. Particular attention has been paid to evaluating conjugated linoleic acid (CLA) content and determining some interesting nutritional indexes. The results of goat milk samples showed that saturated, monounsaturated and polyunsaturated fatty acid contents were on average 71.2, 23.4, and 3.8 %, respectively. CLA content (cis-9, trans-11 isomer) was on average 11.5 mg/100 g in milk. Considerable variability was observed for n6/n3 ratio that varied from 2.7 to 10.6 in the considered goat milk samples. With regard to goat cheese samples CLA concentration was on average 118.8 mg/100 g in fresh cheese and 217.7 mg/100 g in semi-hard cheese, and the difference was not significant. Interestingly, α-linolenic acid content was higher and n6/n3 ratio was lower in semi-hard with respect to fresh cheese samples (p < 0.05).     

Hot topic: Fatty acid and conjugated linoleic acid (CLA) isomer composition of commercial CLA-fortified dairy products: evaluation after processing and storage

Conjugated linoleic acid (CLA) exerts a strong positive influence on human health but intake of these fatty acids is typically too low, and increased consumption of CLA is recommended. A good way to raise the CLA content in the diet without a radical change in eating habits seems to be the enrichment of commonly consumed food products with CLA supplements. This study analyzed the total fatty acid content and the CLA isomer composition of 6 commercially available CLA-fortified dairy products during processing and 10 wk of refrigerated storage. Research was carried out by combining gas chromatography and silver-ion HPLC. The tested samples were a CLA oil supplement, and several skim milk dairy products fortified with the supplement (milk, milk powder, fermented milk, yogurt, fresh cheese, and milk-juice blend). The CLA oil supplement was added such that the consumer received 2.4 g/d of CLA by consuming 2 servings. The predominant isomers present, C18:2 cis-9, trans-11 CLA and C18:2 cis-10, trans-12 CLA, were in at a similar ratio, which ranged from 0.97 to 1.05. These major isomers were not significantly affected by processing but a decrease in total CLA in fresh cheese samples was detected after 10 wk of refrigerated storage. Refrigerated storage and thermal treatment resulted in significant decreases or disappearance of some of the minor CLA isomers and a significant increase of trans, trans isomers from both cis, trans, trans, cis, and cis, cis isomers especially in CLA-fortified milk powder but also in fermented milk, yogurt, and milk-juice blend.     

Cheese manufacture with milk with elevated conjugated linoleic acid levels caused by dietary manipulation

The objective of this study was to assess the effect of dietary supplementation of cows on pasture with sunflower oil for conjugated linoleic acid (cis-9, trans-11 CLA) enrichment of milk, for the production of CLA-enriched cheese. A group of 40 autumn-calving dairy cows were assigned to either a control group (indoor feeding on grass silage ad libitum and 6 kg/d of a typical indoor concentrate) or an experimental group (on pasture, being fed 6 kg of a supplement containing 100 g/kg of sunflower oil per d). These diets were fed for 16 d, during which time milk was collected for pilot-scale hard cheese manufacture. The pasture-based diet with sunflower oil resulted in a significant effect on the milk fatty acid CLA content. The concentration of cis-9, trans-11 CLA in the milk produced from cows on this diet increased to 2.22 g/100 g of fatty acid methyl esters (FAME) after 14 d, compared with 0.46 g/100 g of FAME in milk produced on the control indoor diet. The content of cis-9, trans-11 CLA in the cheese manufactured from the indoor control milk was 0.78 g/100 g of FAME and that from the pasture-based sunflower oil milk was 1.93 g/100 g of FAME. The cheese was assessed during the ripening period and CLA concentrations were stable throughout the 6 mo of ripening. Other cheese variables (microbiology, composition, flavor, free AA) were monitored during the ripening period, and the cheese with the elevated CLA concentrations compared favorably with the control cheese. Thus, a pasture-based diet supplemented with an oil source rich in linoleic acid resulted in an enhanced CLA content of bovine milk fat, compared with an indoor grass silage-based diet.     

Characteristics of traditional Croatian ewe's cheese from the island of Krk

Krk cheese is a hard, full-fat cheese made from raw sheep's milk, characterized by a delicate, full and strong flavour. The aim of this study was to determine farm influence on the chemical composition of sheep's milk for Krk cheese production, and the chemical characteristics of Krk cheese during ripening. Gross composition of the milk used complies with the average sheep's milk composition from the Croatian Adriatic region. During ripening, fat, protein, salt content and lactic acid concentration increased ( P <  0.01), as well as the water-soluble nitrogen fraction and the 12%-trichloroacetic-acid-soluble nitrogen fraction ( P <  0.05). Degradation of β-casein could be an indicator of the ripening quality of Krk cheese.     

trans-10, cis-12 conjugated linoleic acid decreases lipogenic rates and expression of genes involved in milk lipid synthesis in dairy cows

Feeding conjugated linoleic acid (CLA) reduces milk fat synthesis in lactating dairy cows, and the effect has been shown to be specific for the trans-10, cis-12 CLA isomer. Our objectives were to examine potential mechanisms by which trans-10, cis-12 CLA inhibits milk fat synthesis. Multiparous Holstein cows (n = 4) in late lactation were used in a balanced 2 x 2 crossover design. Treatments consisted of a 5 d abomasal infusion of either skim milk (control) or purified trans-10, cis-12 CLA (13.6 g/d) emulsified in skim milk. On d 5 of infusion, mammary gland biopsies were performed and a portion of the tissue analyzed for mRNA expression of acetyl CoA carboxylase, fatty acid synthetase, delta 9-desaturase, lipoprotein lipase, fatty acid binding protein, glycerol phosphate acyltransferase and acylglycerol phosphate acyltransferase. Lipogenic capacity was evaluated with another portion of the tissue. Infusion of trans-10, cis-12 CLA decreased milk fat content and yield 42 and 48%, respectively and increased the trans-10, cis-12 CLA content in milk fat from < 0.1 to 4.9 mg/g. Reductions in milk fat content of C4 to C16 fatty acids contributed 63% to the total decrease in milk fat yield (molar basis). Analysis of the ratios of specific fatty acid pairs indicated trans-10, cis-12 CLA also shifted fatty acid composition in a manner consistent with a reduction in delta 9-desaturase. Mammary explant incubations with radiolabeled acetate established that lipogenic capacity was decreased 82% and acetate oxidation to CO2 was reduced 61% when cows received trans-10, cis-12 CLA. Infusing trans-10, cis-12 CLA also decreased the mRNA expression of all measured enzymes by 39 to 54%. Overall, data demonstrated the mechanism by which trans-10, cis-12 CLA inhibits milk fat synthesis includes decreasing expression of genes that encode for enzyme involved in circulating fatty acid uptake and transport, de novo fatty acid synthesis, desaturation of fatty acids and triglyceride synthesis.     

Conjugated linoleic acid and C18:1 isomers content in milk fat of sheep and their transfer to Pecorino Toscano cheese

The aim of the study was to evaluate the transfer of conjugated linoleic acid (CLA) and of C18:1 isomers from sheep milk to Pecorino Toscano protected denomination of origin cheese and to monitor the stability of these fatty acids during ripening. The total content of C18:1 fatty acids was not affected by milk treatment but there were changes in the isomers profile. In particular, the milk trans11 C18:1 decreased with pasteurization and after starter culture addition. In contrast, trans10 C18:1 and cis9, trans11 C18:2 were enhanced by the thermal treatment of milk. The fatty acid profile of cheese reflected that of milk used for cheese making with the exception of the C18:1 and CLA isomer profile. The cheese ripening affected the percentage of cis9, trans11 C18:2, which increased more than 10% on total content of CLA.     

新型豆汁牛乳混合型干酪的初步研制

采用驯化后的乳酪杆菌为菌种,以豆汁(以m大豆:V水=1:6的比例制成)、纯牛奶、V(豆汁):V(牛奶)=1:1、V(豆汁):V(牛奶)=1:5为原料制作干酪,比较研究不同原料和原料配比对干酪的化学成分、感官评价的影响。结果表明纯牛奶干酪的口感比豆汁干酪爽滑细腻,蛋白质和脂肪含量比纯豆汁的高;复配干酪的口感和脂肪含量介于纯牛奶干酪和豆汁干酪之间,并与牛奶的添加量成正比;复配干酪的蛋白质含量比纯牛奶干酪和豆汁干酪的都低。     

Conjugated Linoleic Acid Concentrations in Dairy Products as Affected by Processing and Storage

Total conjugated linoleic acid (CLA) concentrations increased 1.32 fold in salted and 1.27 in unsalted butter but did not alter the ratio of 9-cis 11-trans to total CLA. Nonfat yogurt showed an increase in CLA content with processing (5.25 mg total CLA/g fat) compared to unprocessed raw material (4.40 mg CLA/g fat). No changes in CLA content was observed in processed dairy products such as lowfat yogurt, regular yogurt, lowfat and regular ice cream, sour cream or cheeses such as Mozzarella, Gouda and Cheddar. Storage did not affect CLA concentration in any products suggesting that CLA is a stable component.     

VARIATION IN THE CONJUGATED LINOLEIC ACID CONTENT OF THREE TRADITIONAL GREEK CHEESES DURING A 1-YEAR PERIOD

The fat and fatty acid content of three traditional Greek cheeses were determined monthly for a period of 1 year. The analyzed cheeses, feta, graviera and manouri, are traditional Greek dairy products made exclusively or primarily from sheep milk. In all cheeses, the content of the fatty acids varies during several months, especially the conjugated linoleic acid (CLA) content of feta, graviera and manouri ranged between 0.5 and 0.9, 0.5 and 1.0 and 0.4 and 0.8 g/100 g total fatty acids, respectively. The average content of CLA in graviera and feta was similar (0.75 and 0.72 g/100 g fatty acids, respectively). On the other hand, the CLA content of manouri (0.54 g/100 g fatty acids) was less than that of the other two cheeses. In every case, the analyzed cheeses can be characterized as good or very good CLA sources.

PRACTICAL APPLICATIONS

No data exist about the variation in the fatty acid composition of standardized cheeses during the various months of the year. Several investigations were carried out in order to determine the fatty acid composition and especially the conjugated linoleic acid (CLA) content of various kinds of cheese. However, cheeses were produced from milk and it is suggested that the milk composition is affected by seasonal factors. In the present investigation, we tried to find out if the beneficial fatty acid content of cheeses, which were previously found as rich CLA sources, is season dependent. The results of this research are a potential tool for food technologist in order to provide CLA-enriched diets.     

Milk and cheese from cows fed calcium salts of palm and fish oil alone or in combination with soybean products

Twenty cows were used in a randomized block design experiment for 6 wk to determine the influence of feeding partial ruminally inert Ca salts of palm and fish oil (Ca-PFO), alone or in combination with extruded full-fat soybeans or soybean oil, on milk fatty acid (FA) methyl esters composition and consumer acceptability of milk and Cheddar cheese. Cows were fed either a diet containing 44% forage and 56% concentrate (control) or a diet supplemented with 2.7% Ca-PFO (FO), 5% extruded full-fat soybeans + 2.7% Ca-PFO (FOESM), or 0.75% soybean oil + 2.7% Ca-PFO (FOSO). Total dietary FA content in the control, FO, FOESM, and FOSO diets were 4.61, 6.28, 6.77, and 6.62 g/100 g, respectively. There was no difference in nutrient intake, milk yield, or milk composition among treatments. Conjugated linoleic acid (CLA) C_18:2cis-9, trans-11 isomer, C_18:1trans-11 (VA), and total n-3 FA in milk from cows on the control, FO, FOESM, and FOSO treatments were 0.56, 1.20, 1.36, and 1.74; 3.29, 4.66, 6.34, and 7.81; 0.62, 0.69, 0.69, and 0.67 g/100 g of FA, respectively. Concentrations of CLA, VA, and total n-3 FA in cheese were similar to milk. A trained sensory panel detected no difference in flavors of milk and cheese, except for acid flavor below a slightly perceptible level in cheese from all treatments. Results suggest that feeding Ca-PFO alone or in combination with extruded full-fat soybeans or soybean oil enhanced the CLA, VA, total unsaturated and n-3 FA in milk and cheese without negatively affecting cow performance and consumer acceptability characteristics of milk and cheese.     

Effects of trans-10, cis-12 conjugated linoleic acid on ovine milk fat synthesis and cheese properties

Trans-10, cis-12 conjugated linoleic acid (CLA) reduces milk fat synthesis in sheep in a manner similar to that seen in dairy cows, but its effects on cheese yield and flavor are unknown. Additionally, when dietary energy supply is restricted, CLA can increase milk and milk protein yield, which may alter cheese yield and eating quality. The objectives of the study were to examine the effects of supplementing ewe diets with a rumen-protected source of CLA at a high and low dietary energy intake on milk fat and protein synthesis and on cheese yield and eating quality. Sixteen multiparous ewes were randomly allocated to 1 of 4 dietary treatments: a high (6.7 Mcal of metabolizable energy/d) or low (5.0 Mcal of metabolizable energy/d) feeding level that was either unsupplemented or supplemented with 25 g/d of a lipid-encapsulated CLA (to provide 2.4 g/d of CLA) in each of 4 periods of 21 d duration in a 4 × 4 Latin square design. There was no effect of treatment on milk yield (g/d), but milk fat percentage and milk fat yield were reduced by 23 and 20%, respectively, in ewes supplemented with CLA. Milk fatty acid concentration (g/100 g) of chain length <C₁₆ was decreased and >C₁₆ was increased in milk and cheese following CLA supplementation, whereas decreasing the feeding level increased fatty acids ≥C₁₆. Milk fat contents of CLA were 0.01 and 0.12 g/100 g of fatty acids for the unsupplemented and CLA-supplemented treatments, respectively, whereas cis-9, trans-11 CLA was unaffected by CLA supplementation. There was no main effect of treatment on cheese yield, which was 0.11 ± 0.001 kg of cheese/kg of milk, but cheese yield was highest, at 0.12 ± 0.001 kg/kg, when made from milk of ewes fed the high feeding level + unsupplemented treatment. Cheese made from the milk of ewes supplemented with CLA, compared with the unsupplemented diet, was rated (scale 0 to 10) higher in the creaminess (2.1 vs. 1.4; SEM 0.15) and less oily (0.8 vs. 1.3; SEM 0.17) attributes, and was preferred overall (4.5 vs. 3.9; SEM 0.21). Cheese produced from sheep on the high vs. low feed level was rated less yellow (2.8 vs. 4.2; SEM 0.11), less salty (1.9 vs. 2.3; SEM 0.15), and more sour (1.5 vs. 1.1; SEM 0.13). We concluded that the effect of feeding level on animal performance and cheese characteristics was small, whereas supplementing the diets of ewes with a ruminally protected CLA source reduced milk fat yield, did not affect cheese yield, and beneficially altered the flavor characteristics of the cheese.     

Short communication: Effects of milk fat depression induced by a dietary supplement containing trans-10, cis-12 conjugated linoleic acid on properties of semi-hard goat cheese

Dietary supplements of conjugated linoleic acid (CLA) containing trans-10, cis-12 CLA reduce milk fat synthesis in lactating goats. This study investigated effects of milk fat depression induced by dietary CLA supplements on the properties of semi-hard goat cheese. Thirty Alpine does were randomly assigned to 1 of 3 groups and fed diets with lipid-encapsulated CLA that provided trans-10, cis-12 CLA at 0 (control), 3 (CLA-1), and 6 g/d (CLA-2). The experiment was a 3 × 3 Latin square design. Periods were 2 wk in length, each separated by 2-wk periods without CLA supplements. Bulk milk was collected on d 3 and 13 of each of 3 periods for cheese manufacture. The largest decrease (23.2%) in milk fat content, induced by the high dosage (6 g/d per doe) of trans-10, cis-12 CLA supplementation at d 13 of treatment, resulted in decreases of cheese yield and moisture of 10.2 and 10.0%, respectively. Although CLA supplementation increased the hardness, springiness, and chewiness, and decreased the cohesiveness and adhesiveness of cheeses, no obvious defects were detected and no significant differences were found in sensory scores among cheeses. In conclusion, milk fat depression induced by a dietary CLA supplement containing trans-10, cis-12 CLA resulted in changes of fat-to-protein ratio in cheese milk and consequently affected properties of semi-hard goat cheese.