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1.
Opportunities for the production of milk and dairy products enriched with cis-9, trans-11 conjugated linoleic acid (CLA) were investigated. Eighteen mid-lactation cows were used in a continuous-design for 7 weeks. During the first week, cows received grass silage ad libitum supplemented with 10 kg per day of a cereal-based concentrate (control) that was replaced with a concentrate containing 50 g kg−1 of rapeseed oil (RO). Changes in milk fatty acid composition were monitored on a weekly basis and milk produced was used to manufacture Edam cheese and butter. Inclusion of RO in the concentrate supplement increased the mean levels of trans-octadecanoic, monounsaturated, CLA and polyunsaturated fatty acid in the milk fat from 1.6, 25.7, 0.46 and 2.8 to 4.3, 35.3, 1.02 and 3.9 g 100 g−1 total fatty acids, respectively. In contrast, the mean level of saturated fatty acids decreased from 71.4 to 60.7 g  100 g−1 total fatty acids. Changes in milk fatty acid composition due to RO occurred within 7 days, with responses reaching a plateau after 21 days. Furthermore, the CLA concentrations in the milk fat from individual cows ranged between 0.37 and 0.65 and 0.43 and 2.06 g 100 g−1 total fatty acids for the control and RO diet, respectively. CLA enriched milk was used successfully to manufacture of Edam cheese and butter with softer textures but with acceptable organoleptic and storage properties. Processing milk into butter or cheese had no effect on the CLA concentrations indicating that enrichment of dairy products is dependent on the content in raw milk fat.  相似文献   

2.
Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).Industrial relevanceHigh-pressure sterilization is a valuable alternative to produce superior quality milk products in cases where traditional thermal treatments have failed. This study evaluated the impact of processing conditions on the conjugated linoleic acid content at conditions where commercial sterilization has been achieved (7-log reduction of B. amyloliquefaciens). The outcomes of this study are considered as a step further for the development of high-pressure sterilized milk.  相似文献   

3.
To evaluate the effect of supplementing the diet of Comisana sheep with by-products from industrial tomato manufacture on the fat composition and conjugated linoleic acid (CLA) content of milk fat, two groups of 50 ewes each were fed either total mixed ration standard (TMRS) or total mixed ration with added tomato by-products (TMRA). Milk fat composition was determined by high-resolution gas chromatography (HRGC). The milk fat content for the animals fed the TMRA diet increased by 6.41% (P < 0.01) after six weeks, compared with the animals fed the TMRS diet. The CLA content in the milk fat for the group of animals fed the TMRA diet was 19.8% (P < 0.05) higher than for those fed the TMRS diet, and reached 1.33 g 100 g?1 fat, while the polyunsaturated fatty acid (PUFA) content increased by a 6.43% (P < 0.05) and reached 7.12 g 100 g?1 fat. The fatty acid composition showed an increase in the amount of polyunsaturated fatty acids. The n ? 3:n ? 6 ratio increased by 13% in the milk from sheep fed with the TMRA diet. These observations were confirmed by triglyceride analysis, which showed a decrease in the amount of short-chain (C28–C32) and medium-chain (C34–C42) triglycerides after six weeks, while the opposite was observed for the long-chain triglycerides (C44–C54).  相似文献   

4.
《International Dairy Journal》2003,13(2-3):221-230
The physico-chemical characteristics, proteolysis (classical nitrogen fractions, caseins and their degradation products and free amino acids), and lipolysis (fat acidity and free fatty acids) were studied throughout the ripening of three batches of Babia-Laciana cheese, a Spanish traditional variety made from raw goats’ milk. The main compositional characteristics of this cheese at the end of the ripening are its high content of total solids (TS) (78.0±2.4 g 100 g−1 of cheese) and fat (61.1±1.2 g 100 g−1 of TS), the presence of residual lactose (1.6±0.8 g 100 g−1 of TS) and its low content of sodium chloride (1.1±0.7 g 100 g−1 of TS) and ash (2.8±0.5 g 100 g−1 of TS). Its pH values (4.44±0.72) are extraordinarily low. The evolution and final values of the different nitrogen fractions show that this cheese undergoes a very slight proteolysis, a fact which was corroborated when the caseins and their degradation products were quantified: β-casein did not undergo any modification throughout ripening, while only 21% of the αs-caseins were degraded. Free amino acids content increased by a factor of about 7 throughout ripening, resulting in a high content of γ-amino butyric acid and a low content of glutamic acid at the end of the process. Fat acidity increased very slightly, approximately 4.5 times, during ripening, reaching final values of 3.5±2.2 mg KOH g−1 of fat. The total free fatty acids content showed a similar evolution to fat acidity. At the end of the ripening process, the main free fatty acid was C18:1, followed by C16 and C10.  相似文献   

5.
The aim of this research was to investigate the distribution of conjugated linoleic acid (CLA) in the neutral and polar milk lipid fractions of samples of bovine, ovine and caprine milk. Lipids were fractionated by thin-layer chromatography to obtain triglyceride, diglyceride and monoglyceride fractions. Phospholipids were separated by solid-phase extraction. The CLA content was quantitatively determined after transmethylation and addition of internal standard. As expected, 95–97% of the CLA was found in the triglyceride fraction. The main differences between the species were observed in CLA content of the diglyceride and phospholipid fraction, while the amount of CLA in the monoglycerides fraction was negligible. Cows' milk showed comparable contents of CLA in both diglyceride and phospholipid fractions (4.2 and 5.5 mg 100 g?1 of lipids, respectively). The level of CLA in phospholipids of ewes' (38 mg) and goats' (20 mg) milk lipids was four times higher than the level of CLA in diglycerides (7 and 5 mg, respectively). In terms of the phospholipid content, CLA accounted for 2–4% (calculated as a percentage of total fatty acids esterified in phospholipids) in caprine and ovine and less than 1% in bovine milk.  相似文献   

6.
Fresh low-fat milk was fermented with five mixed lactic acid bacteria for up to 30 h at 42 °C. A protease, prozyme 6, was added 5 h after the beginning of fermentation. The whey was separated from the fermented milk and freeze-dried. As the fermentation time extended to 30 h, soluble protein content increased from 30.9 to 195.9 mg g−1, free amino acid content increased from 2.8 to 192.8 mg g−1, peptide content increased from 6.4 to 402.8 mg g−1 and γ-aminobutyric acid (GABA) increased from 0 to 80.6 mg 100 g−1, while inhibition of angiotensin I-converting enzyme (ACE) increased as indicated by a decrease of IC50 from 1.18 to 0.24 mg mL−1, respectively. The amino acid sequences of two ACE inhibitory peptides were Gly–Thr–Trp and Gly–Val–Trp, of which the IC50 values were 464.4 and 240.0 μm, respectively. The systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rat (SHR) were reduced 22 and 21.5 mm Hg, respectively, after 8 weeks of oral administration of diluted whey (peptide concentration 5 mg mL−1) from the 30 h fermentation.  相似文献   

7.
Available lysine, in vitro protein digestibility and lactulose values were determined in 23 commercial infant formulas. The mean available lysine content of the formulas based on dairy proteins was 66.7±9.5 mg g−1 protein, similar to that of human milk, while that of soy based formulas was considerably lower (45.0±8.3 mg g−1 protein). In vitro protein digestibility values ranged 85.5–88.9% for soy-based formulas and 90.5–98.3% for formulas based on dairy proteins. Formulas based on milk enriched with whey had higher lactulose content than those based on cow's milk. However, all values were below the limit of 600 mg L−1 recommended for UHT milk.  相似文献   

8.
《Meat science》2013,93(4):519-524
The meat lipid fraction of psoas major muscle from 20 adult (10 males and 10 females) feral Iberian red deer (Cervus elaphus hispanicus) was characterized by quantification of total fat, total cholesterol, vitamin E and fatty acid (FA) composition, including detailed trans octadecenoate isomers and conjugated linoleic acid (CLA) isomeric profile.The total lipid content revealed a very lean meat (0.99 g/100 g of meat), with total cholesterol content averaging 55.6 mg/100 g of muscle. The FA profile displayed a very high PUFA level for ruminant meat (30.2 g/100 g FA). The 18:2 cis-9,trans-11 content was fairly low (0.26% of total FA) compared with other ruminant meats.The comparison of stags and hinds showed more similarities than differences. Nevertheless, hinds displayed superior contents of α-tocopherol and trans MUFA and a better n−6/n−3 ratio than stags.  相似文献   

9.
Commercial samples of fresh and mature Halloumi cheeses made from ovine or bovine milk were studied in order to establish their chemical, microbiological and sensory characteristics. Significant differences were observed between the two types of Halloumi cheese both when fresh and mature. The free volatile fatty acid (FVFA) content of the cheeses increased with maturation from 483 to 1356 mg kg−1 for the ovine product, but lower values (380–1248 mg kg−1) were found in the bovine cheese. During maturation for 40 days, Enterococcus faecium, which dominated the microflora of fresh ovine cheese, was replaced by lactobacilli, including a new species, Lactobacillus cypricasei, which was not found in the bovine samples. Fewer than 100 cfu g−1 lactic acid bacteria (LAB) were present in the fresh bovine cheeses, but a microflora dominated by lactobacilli developed with time. Yeast counts in the mature ovine and bovine cheeses reached 2.3–2.8×105 cfu g−1 and, as some of the yeasts were proteolytic and/or lipolytic, it was assumed that they were having a positive impact of the flavour of the cheeses. The sensory panel distinguished significant differences in texture and flavour between the fresh and mature samples of both ovine and bovine cheeses and, overall, there was a significant preference for the ovine brand.  相似文献   

10.
NIR technology was used to analyze the fatty acid composition of fat tissue from conjugated linoleic acid fed pigs by direct application of a fibre optics probe on two different locations of subcutaneous fat. One hundred and fifty-three pigs were fed three different diets and the fatty acid profile of subcutaneous fat from Gluteus medius was analyzed using gas chromatography and FT-NIR in a longitudinal and transversal cut. Spectra were acquired using a Bruker Optics Matrix-F duplex spectrometer equipped with a fibre optics probe (IN-268-2). Total saturated, monounsaturated and polyunsaturated together as well as oleic and stearic fatty acids were predicted accurately (R2 > 0.70), myristic, and linoleic fatty acids were predicted with lower accuracy (0.60 < R2 < 0.70), while palmitic, asclepic and α-linolenic fatty acids were poorly predicted (R2 < 0.60). Results indicated that NIR technology has potential as a rapid tool to discriminate carcasses from animals fed diets with different fatty acid composition by a direct measurement on the fat from the ham.  相似文献   

11.
The contributions of the coagulant Cynara cardunculus and of the microflora of raw milk to the volatile-free fatty acid profile of Serra da Estrela cheese were evaluated. The experimental design included both a model system and, dual cheeses. The study in the model system showed that isovaleric acid was the predominant volatile compound after 7 d of ripening. The systems inoculated with Enterococcus faecium produced the highest amount of this volatile (ca. 135.8 mg kg−1 curd), while those inoculated with Lactobacillus plantarum produced the least (21.4 mg kg−1 curd); Lactococcus lactis produced moderate amounts (ca. 34.2 mg kg−1 curd) but a total amount of volatile-free fatty acids similar to those found in control samples. This is considered advantageous since this volatile fatty acid confers a harsh, piquant, mature flavour to cheese, coupled with the realisation that excess volatiles may result in off-flavours. The addition of cultures in experimental cheeses helped reduce ripening time to about one half. Inclusion of Lb. plantarum led to cheeses containing the highest amounts of volatiles, and exhibiting an aroma closest to that of typical Serra da Estrela cheese.  相似文献   

12.
《Food chemistry》2004,87(1):151-158
The study describes an improved version of the reverse-phase-HPLC method. To determine free resveratrol isomers, the method uses isocratic elution and electrochemical detection with the use of a glassy working electrode at a potential of 0.75 V. The effects of important factors – such as the isomerization of standard resveratrol solution in diffused daylight and its dependence on temperature or resveratrol isomerization in wine samples – were investigated. The equilibrium between trans- and cis-isomer was achieved after a 5-h exposure to the daily diffused light and it was not significantly influenced by the temperature (30–60 °C). Linearity was obtained in the concentration range from 0.01 to 10 mg l−1. The detection limit (S/N=3) was 3 μg l−1 for trans-resveratrol and 15 μg l−1 for cis-resveratrol. The trans- and cis-resveratrol were determined in selected Czech red and white wines and in the extract from Vitis vinifera plant. The concentration of trans-resveratrol ranged from 0.7 to 11 mg l−1, that of cis-resveratrol from 0.6 to 5.1 mg l−1.  相似文献   

13.
The effect of two commercially available adjunct cultures, LBC 80 (Lactobacillus casei subsp. rhamnosus) and CR-213 (containing Lactococcus lactis subsp. cremoris and Lc. lactis subsp. lactis) on the proteolysis in low-fat hard ewes’ milk cheese of Kefalograviera-type was investigated. Two controls, a full-fat cheese (306 g kg−1 fat, 378 g kg−1 moisture) and a low-fat cheese (97 g kg−1 fat, 486 g kg−1 moisture, made using a modified procedure), were also prepared. The effect of adjunct culture on proteolysis, as examined by polyacrylamide gel electrophoresis of cheese and water soluble cheese extracts, was marginal. The reverse-phase HPLC peptide profiles of the water soluble extracts from low-fat cheeses were similar although some quantitative differences were observed between low-fat control cheese and experimental cheeses. The fat content as reflected by the differences in peptide profiles affected the pattern of proteolysis. Proteolysis, as measured by the percentage of total nitrogen soluble in water or in 120 g L−1 trichloroacetic acid, was significantly (P<0.05) affected by the addition of adjunct cultures. Furthermore, the adjunct cultures enhanced the production of low molecular mass nitrogenous compounds; the levels of total nitrogen, soluble in 50 g L−1 phosphotungstic acid, and of free amino acids were significantly (P<0.05) higher in the low-fat experimental cheeses than in the low-fat control cheese.  相似文献   

14.
Consumption of virgin olive oil (VOO) is highly recommended due to its human health benefits. Brazil is now beginning to experimentally produce VOO, and there are no data on its chemical profile. The aim of this work was to determine the phenolic compound, tocopherol and fatty acid contents of 17 monovarietal VOOs produced from olive varieties cultivated in the southeast region of Brazil during two crop years. The chemical composition of Brazilian VOO resembles that found in the literature for well-established VOOs. The analyzed compounds comprised palmitic acid (6–12%), stearic acid (1.6–2.2%), oleic acid (70–84%), linoleic acid (3.2–11.7%), α-linolenic acid (0.6–1.4%), tyrosol (NQ–155 mg kg 1), (+)-pinoresinol (2.9–23 mg kg 1), hydroxytyrosol (ND–38 mg kg 1), luteolin (ND–2.2 mg kg 1), α-tocopherol (29–233 mg kg 1), β-tocopherol (ND–9.6 mg kg 1), and γ-tocopherol (ND—19 mg kg 1). There was a significant difference in the contents of almost all of the analyzed compounds between the two crop years. Principal component analysis demonstrated that some varieties can be differentiated from one another by chemical composition. The results indicated that some Brazilian monovarietal VOOs are promising and that further studies will help to improve the quality of Brazilian VOO.  相似文献   

15.
The quality of plain stirred yoghurt produced from whole milk with somatic cell counts (SCC) at low (147,000 cells mL−1), intermediate (434,000 cells mL−1) and high (1,943,000 cells mL−1) levels was examined. Each milk treatment was obtained from selected cows, according to its SCC status and milk composition. Yoghurt samples were analysed on days 1, 10, 20 and 30 after production. Analyses included pH, acidity, fat, lipolysis (expressed as free fatty acids, FFA), proteolysis and apparent viscosity. Viscosity of high SCC yoghurt was higher (P<0.05) than the low SCC yoghurt on days 10, 20 and 30 of storage. High SCC yoghurt also had higher FFA content (P<0.05). SCC did not affect pH, acidity, fat content and proteolysis of the yoghurt (P>0.05). Results indicate that SCC in milk increases the lipolysis in the resulting yoghurt during storage for 30 d.  相似文献   

16.
Cheddar cheeses with the different fat contents were made in triplicate and ripened at 4°C for 30 d and at 7°C for the remainder of the 180-d investigation period. The cheeses were designated: full-fat (FFC), 300 g kg−1; reduced-fat (RFC), 219 g kg−1; half-fat (HFC), 172 g kg−1; and low-fat (LFC), 71.5 g kg−1. A decrease in the fat content from 300 to ≤172 g kg−1 resulted in significant (P<0.05) decreases in contents of moisture in non-fat substance and pH 4.6 soluble N (expressed as % total N), and increases in the contents of moisture, protein, intact casein and free amino acids. Reduction in fat content resulted in an increase in the volume fraction of the casein matrix and a decrease in the extent of fat globule clumping and coalescence. The mean values of fracture stress and firmness for the FFC were significantly lower than those of the RFC and HFC, which had similar values; the values for the LFC exceeded the limits of the test and were markedly higher than those of the other cheeses at all times. On baking the cheese, reduction in fat content resulted in significant increases in the mean melt time (time required for shred fusion) and apparent viscosity and a decrease in the mean flowability of the melted cheese. The stretchability of the FFC increased most rapidly and, at ∼15 and 30 d, attaining mean values which were significantly higher than those of the other cheeses. Thereafter the stretchability of the FFC decreased progressively to values that were significantly (i.e. at 150 d) or numerically (i.e., at 180 d) lower than those of the RFC and HFC. At ripening times ≥15 and ≤90 d, the stretchability of the LFC was significantly lower than that of the RFC, and significantly or numerically lower than the HFC.  相似文献   

17.
Low-fat Mozzarella cheeses containing 6% fat were made by pre-acidification of milk with citric acid to pH 6.1 and using encapsulated ropy or non-ropy exopolysaccharide (EPS) producing Streptococcus thermophilus. Moisture retention, changes in texture profile analysis (TPA), meltability and stretchability of cheese, and changes in colour, surface scorching and shred fusion were analysed after baking over 90 days (d). Control cheeses and those made from pre-acidified milk without EPS cultures had the lowest moisture content at 54.84% and 55.28%, respectively. Control cheeses were hardest and their meltability and stretchability were initially low. Hardness was reduced and the melt and stretch distances increased with time. When baked, control cheeses showed incomplete shred fusion. Pre-acidification reduced hardness and increased meltability. Capsular- and ropy-EPS were quantified at 30.42 and 30.55 mg g−1 of cheese, respectively, and increased moisture retention in pre-acidified cheese to 56.67% and 56.21%, respectively. These cheeses were softer and exhibited lower springiness. Greater meltability was observed initially but became similar to control cheeses after 90 d of storage. When baked after 45 d of storage, cheeses containing EPS producing cultures showed improved shred fusion, meltability and a reduction in surface scorching.  相似文献   

18.
《Food chemistry》1998,61(3):333-338
In-vitro binding of calcium (Ca) and magnesium (Mg) by total dietary fiber, hemicellulose A (HCL A), lignocellulose (LCL), cellulose (CL), and lignin (L) fractions isolated from rice bran (RB), wheat bran (WB), oat fiber (OF), apple fiber (AF) and tomato fiber (TF) was evaluated. At pH 6.8, significant amounts of Ca were bound by whole fibers, ranging from 800 μg g−1 for RB to 10 097 μg g−1 for TF. Mg bound by whole fibers varied from 496 μg g−1 for OF to 2177 μg g−1 for WB. Re-acid washing (pH<2.0) released 95–99% of the Ca and Mg bound to the fibers. Fibers with the highest endogenous Ca and Mg concentrations bound significantly (P<0.05) the highest amounts of the minerals studied. The Ca bound by HCL A varied from 9753 μg g−1 for RB to 11 337 mg g−1 for TF, whereas Mg bound varied from 1151 μg g−1 for OF to 5626  μg g−1 for TF hemicellulose fractions, respectively. Among the fiber components, Mg binding decreased in the order HCL A>LCL>L>CL, whereas Ca bound was in the order HCL A>LCL>CL>L. A relatively strong correlation was observed between the combined effects of protein content, hemicellulose, and lignin vs total Ca and Mg bound. 1998 Elsevier Science Ltd. All rights reserved  相似文献   

19.
A reliable and rapid capillary zone electrophoresis method for the determination of the major of cations in milk samples was developed. Sample preparation consisted of dilution, acidification to pH 4.0 with 1 mol L−1 acetic acid and filtration. The complete separation of K+, Ca2+, Na+ and Mg2+ could be achieved in 4 min with a simple electrolyte composed of 10 mmol L−1 imidazole and 1 mol L−1 acetic acid (pH 3.6). The running voltage was 25 kV at 25 °C. Indirect UV detection was achieved at 185 nm. Detection limits ranged from 0.06 to 0.57 mg L−1 and quantification limits ranged from 0.16 to 0.62 mg L−1. Precision data showed relative standard deviations (RSD%) lower than 4.1% for relative migration time and 2.4% for milk concentrations, respectively. Recoveries of cations in samples analysed ranged from 97.7% to 101.1%. Thirty samples of milk were analysed, obtaining mean values of 1.46, 1.19, 0.505 and 0.126 g L−1 for K+, Ca2+, Na+ and Mg2+, respectively.  相似文献   

20.
《Food chemistry》2005,90(3):409-415
Ganoderma tsugae Murrill are currently popular and used in the formulation of nutraceuticals and as functional foods. The non-volatile components in the form of mature and baby fruit bodies (Ling chih), mycelia and fermentation filtrate from submerged culture were studied. Mycelia and filtrate contained significantly higher moisture contents (10.3% and 19.8%) and higher contents of carbohydrates, reducing sugars, crude ash and crude protein. Four forms of G. tsugae contained from 7.65% to 10.1% dry weight of total soluble sugars and polyols. Total free amino acid contents ranged from 2.50 to 149 mg g−1 dry weight and in the descending order of filtrate, mycelia, baby Ling chih and Ling chih. Contents of monosodium glutamate-like components ranged from 0.16 to 26.0 mg g−1 whereas, contents of sweet components ranged from 0.50 to 24.6 mg g−1. The bitter components were predominant. Contents of total and flavour 5-nucleotides were high in filtrate (5.48 and 3.10 mg g−1, respectively). The umami intensities were expected to be in the descending order of filtrate, mycelia, baby Ling chih and Ling chih.  相似文献   

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