Development of lytic Lactococcus lactis bacteriophages in a Cheddar cheese plant

The mixed TK5 starter culture was used in a Danish factory as the only starter for production of Cheddar cheese for more than 11 years before the factory experienced serious bacteriophage attacks with inhibition of the acid production in the curd. The cheese whey contained some phages from the beginning, and gradually new phages appeared able to infect an increasing number of isolates. Three bacteriophages jw30, jw31 and jw32 were isolated from the factory whey collected in 1989–94 and compared with lytic bacteriophages isolated in the period 1982–86 (Josephsen et al., 1994) DNA hybridisation showed that the type phage P008 had high homology to the new phages jw30, jw31 and jw32 as had the phages isolated in 1982–84. The new phages had broader host ranges and higher burst sizes than the previously isolated phages, showing that the lytic phages had become more virulent with time.     

Influence of selected lab cultures on the evolution of free amino acids, free fatty acids and Fiore Sardo cheese microflora during the ripening

Fiore Sardo Protected Denomination of Origin is a traditional Sardinian (Italy) hard cheese produced exclusively from whole raw ovine milk and coagulated with lamb rennet paste. Currently, Fiore Sardo is still produced by shepherds at the farmhouse level without the addition of any starter culture and the cheese-making process is characterized by significant waste. The first objective of the present work was to investigate the autochthonous microflora present in milk and Fiore Sardo cheese in order to select lactic acid bacterial (LAB) cultures with suitable cheese-making attributes and, possibly reduce the production waste. Secondly, the ability of selected cultures to guarantee cheese healthiness and quality was tested in experimental cheese-making trials. In this study, we show that the typical lactic microflora of raw ewe's milk and Fiore Sardo cheese is mostly composed of mesophilic LAB such as Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Lactobacillus casei subsp. casei. Moreover, strains belonging to the species were selected for cheese-making attributes and used in experimental cheese-making trials carried out in different farms producing Fiore Sardo. The evolution of the cheese microflora, free amino acids and free fatty acids during the ripening showed that the experimental cheeses were characterized by a balanced ratio of the chemical constituents, by a reduced number of spoilage microorganisms and, remarkably, by the absence of production waste that were significant for the control cheeses.     

Influence of starter cultures on the free fatty acids during ripening in Tea sausages

The influence of starter cultures on the free fatty acids content during ripening of Tea sausages, typical dry sausages produced in the south of Croatia, was studied. Three batches of Tea sausages were produced using different starter mixtures (Staphylococcus xylosus S81 and Lactobacillus sakei G20; Staphylococcus xylosus S142 and Lactobacillus sakei G20; Staphylococcus xylosus S206 and Lactobacillus sakei G20), while the control batch was produced without a starter. The amounts of free fatty acids present in the samples at the end of the ripening period were not significantly different, suggesting that the lipolytic enzymes naturally occurring in meat could play a predominant role in the free fatty acids release. Oleic and linoleic acids were present in the highest concentrations, while only small quantities of short-chain fatty acids were detected, with acetic acid being the most representative one.     

Seasonal variations in the free fatty acid composition of Manchego cheese and changes during ripening

 This paper examines the evolution of the free fatty acid concentration in Manchego cheese during ripening (up to 150 days) and in two different cheesemaking seasons (autumn and winter). Factorial analysis of the principal components showed that short-chain fatty acids were the variables that best correlated (81% of the total variance explained) with the samples when distributed according to ripening time. These fatty acids likewise differentiated autumn and winter samples. Received: 30 April 1999 / Revised version: 5 July 1999     

Lipolysis in probiotic and synbiotic cheese: The influence of probiotic bacteria, prebiotic compounds and ripening time on free fatty acid profiles

The influence of probiotic bacteria (Lactobacillus casei-01, Bifidobacterium lactis B94), prebiotic compounds (FOS and inulin) and ripening time (0-60 days) on the free fatty acid (FFA) profile of cheese, with special emphasis on the conjugated linoleic acid (CLA) content, was investigated. After 60 days of ripening, 10⁹-10¹⁰ cfu g⁻¹ cheese were recorded in both probiotic and synbiotic cheeses, despite harsh conditions of low pH values (4.1-5.1) and low moisture content (<30%, w/w). Increases in total FFA and CLA were observed throughout the ripening period, especially in synbiotic cheeses containing FOS and inulin (50:50) inoculated with B. lactis B94. The addition of FOS alone or combined with inulin did not significantly affect probiotic strain growth and viability during the ripening period; however, the advantage of the addition of prebiotic compounds in probiotic cheese manufacture is that it may allow the production of cheeses with improved performance as far as functional CLA compounds are concerned, as well as an improved nutritional quality reflected in a lower atherogenicity index.     

Comparison of two standard methods for determination of free fatty acids content in oils extracted from oilseeds and vegetable oils

Two standard titrimetric procedures for determination of free fatty acids in vegetable oils and in oils extracted from oilseeds were examined using rapeseed oil, illipe nuts and fat, and groundnuts and groundnut oil as test materials. Both procedures involve dissolution of the fat in an organic solvent and titration with standard alkali solution using phenolphthalein as indicator. Results obtained using each of the two methods agree closely in most cases and certainly for commercial contractual purposes the two methods are interchangeable. Suggestions are made for modification of these methods particularly in regard to solvents and allowed variation in analysis results.     

Free fatty acids and oxidative changes of a Spanish soft cheese (PDO 'Torta del Casar') during ripening

Free fatty acids (FFA) and lipid and protein oxidation changes during ripening were studied in Torta del Casar cheese. This cheese with protected designation of origin (PDO) is made from raw ewe milk and uses vegetable rennet. Cheeses were analysed at four different stages of ripening at 1, 30, 60 and 90 days. Most FFA significantly increased throughout maturation, except valeric and margaric acids. Acetic acid content increased during ripening and was the most abundant FFA in Torta del Casar cheese at the end of ripening. Short chain fatty acids (SCFA) showed an important increase throughout maturation, especially butyric, isovaleric and isobutyric acids. Lipid oxidation values significantly increased during the first month and decreased in the last 2 months of maturation; however, protein oxidation did not significantly change during ripening. Changes in FFA, especially SCFA, could have great importance in Torta del Casar cheese final characteristics; however, oxidative reactions did not play an important role.     

不同地域黄酒中酸类物质差异性研究

通过高效液相色谱、气相色谱法分别测定了全国不同地区的12种黄酒中的有机酸和游离脂肪酸含量,并以9种有机酸和5种游离脂肪酸为变量进行主成分分析。结果表明:黄酒有机酸中乳酸、乙酸和柠檬酸的含量最高,占总有机酸的80%以上;前4个主成分能代表12种样品中有机酸含量85.276%的信息,因子得分真实地反映了样品的产地、原料、工艺与有机酸的关联性。黄酒中游离脂肪酸种类丰富而且总量差异大,第一主成分、第二主成分累积贡献率达61.783%、83.822%,能够较好地代表原始数据所反映的信息,第一主成分包含C18∶0、C16∶0,第二主成分包含C14∶0、C18∶1,这4种物质对黄酒整体风味的作用可分为三种,即C18∶0和C16∶0、C14∶0、C18∶1。      

Effect of nitrate and nitrite curing salts on the generation and oxidation of fatty acids in non-fermented sausages

 The purpose of this work was to study the effect of nitrate and nitrite curing salts on FFA generation and oxidation during an industrial process of country-style dry sausages (35/40 mm casing diameter) to determine their role in flavour development. The pH values of the sausages are around 6.0 during the dry processing. FFA liberation is two or three times greater in the samples with nitrite than in those with nitrate. However, the intensity of the oxidative phenomena during the drying process does not depend on the quantity of FFA. In the samples with nitrate more intense oxidative phenomena take place, which lead to a stronger typical dry-cured flavour than in samples with nitrite. Received: 14 July 2000 / Revised version: 15 September 2000     

Effect of intensifying high-temperature ripening on lipolysis and lipid oxidation of Jinhua ham

The orthogonal experiment for fermenting-ripening process was carried out to effectively shorten the process time of Jinhua ham by intensifying high-temperature ripening. Lipolysis and lipid oxidation in the ham were affected by the process time, temperature and salt content during processing. Intensifying high-temperature ripening could accelerate the lipolysis and lipid oxidation. Both saturated and unsaturated free fatty acids (FFAs) were steadily increased with temperature rising (p < 0.01). The daily-increment of total FFAs in the muscle of modern process products was significantly higher than that in the traditional ones (p < 0.01) and kept at a high level through high-temperature ripening. TBARS in ripened hams was remarkably lower than that in traditional products (p < 0.01). These results explained that longtime high-temperature (35-37 °C) ripening could effectively promote lipolysis, decrease TBARS value and accelerate the development of flavor in Jinhua ham.     

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.     

Automated flow pH-method for the determination of total free fatty acids content in edible oils

An automated flow pH-method for the determination of titratable acidity (TA) in edible oil without titration is proposed, based on pH measurements on an oil sample emulsion in a suitable reagent. The developed flow pH system involves two constant rate flows: the flow of oils samples and the flow of reagent: triethanolamine + KNO₃ + H₂O + i-PrOH, in which oils is insoluble. The flows are mixed in the mixer forming the emulsion in which the free fatty acids (FFA) extraction is started. Then, the emulsion is passed to the coil for completion of FFA extraction and thermostation and then forwarded to pH-cell for pH measurement. Using pH values and linear dependence of pH vs. log (TA) allows the TA determination.The optimum parameters for the automated flow pH-system have been found, i.e., volumes of the mixer and the coils, the rate of sample and reagent, pH and TA ranges. The results of the TA determination in the edible oils were statistically compared with the standard titration method.     

Impact of free fatty acid concentration and structure on lipid oxidation in oil-in-water emulsions

Free fatty acids are strong prooxidants in both bulk and emulsified oils. Addition of oleic acid to an oil-in-water emulsions increased lipid hydroperoxide and hexanal formation at free fatty acid concentrations as low as 0.1% of the lipid. The prooxidant effect of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic < linoleic < oleic. There were no significant differences in lipid oxidation rates when free fatty acid isomers with cis or trans double bonds were compared. The prooxidant activity of the free fatty acids was postulated to be due to their ability to attract prooxidant metals as well as co-oxidise the triacylglycerol in the oil. Overall, these results show that the oxidative stability of oil-in-water emulsions is strongly linked to both the concentration and type of free fatty acids present.     

Simulation of the effect of sausage ingredients and technology on the functionality of the bacteriocin-producing Lactobacillus sakei CTC 494 strain

Bacteriocin-producing lactic acid bacteria may be applied as novel functional starter cultures for sausage fermentation. In this way, safer and more standardised end products may be obtained. However, it is not clear how such strains behave under sausage fermentation conditions. In this study, the combined effects of typical sausage ingredients and process technology on the functionality of Lactobacillus sakei CTC 494 were simulated by a modelling approach. Under simulated sausage fermentation conditions, the strain was able to produce a considerable amount of bacteriocin. Model simulations indicate that sausage fermentation conditions of temperature and pH favour bacteriocin production, whereas salting and curing with sodium nitrite decrease growth and bacteriocin production. Sodium nitrite inhibits cell growth under its undissociated nitrous acid form, and its inhibitory effect seems to parallel lactic acid production. Whereas oxygen and magnesium levels did not influence bacterial functionality, manganese limitations severely decreased cell growth. Moreover, the presence of large amounts of fat, which is typical for a sausage environment, leads to an apparent bacteriocin inactivation, probably due to adsorption of the bacteriocin molecules from the water phase to the fat particles.     

Study of organic acids, volatile fraction and caseins of a new Halloumi-type cheese during ripening in whey brine

Organic acids, fat hydrolysis, volatile compounds and sensory characteristics of a new brine cheese which combines characteristics of Halloumi and Feta cheeses during its ripening in whey brine (100g NaCl L⁻¹) were studied. Thermotolerant protease of Mucor miehei as a coagulant enzyme and a mixture of thermotolerant starter cultures Enterococcus faecium 0165 (0.5% w/w) and Lactobacillus casei 80 10D were used. Good quality new Halloumi-type cheese was produced with higher proteolysis than traditional Halloumi cheese kept in whey brine. The volatile compounds identified comprised alcohols, aldehydes, ketones, acids, esters, hydrocarbons and sulphur compounds. Ethanol was the dominant volatile compound determined. Lactic acid was the dominant acid produced; its concentration increased during ripening, reaching a maximum value of 9929 mg kg⁻¹ at day 30. Acetic acid was also found in high amounts, which increased during cheese ripening. Lipolysis of cheese was not intense. The most abundant acids of the mature cheese were palmitic, oleic and acetic acid. The Halloumi-type cheese scored higher in the sensory analysis when fresh than did the mature cheese.     

Effect of a bacteriocin‐producing strain of Lactobacillus paracasei on the nonstarter microflora of Cheddar cheese

In this study, the growth of chloramphenicol‐resistant bacteriocin‐sensitive indicator strain Lactobacillus casei DPC 2048^CM was evaluated in Cheddar cheese made with bacteriocin‐producing Lactobacillus paracasei DPC 4715. No suppression of growth of the indicator strain was observed in the cheese during ripening, and no bacteriocin production by L. paracasei DPC 4715 was detected by the well diffusion method in cheese and cheese extracts. The bacteriocin produced by L. paracasei DPC 4715 was sensitive to chymosin and cathepsin D, and it may have been hydrolysed by the rennet used for cheese manufacture or by indigenous milk proteases.     

Effect of dietary soybean oil addition on the odd-numbered and branched-chain fatty acids in rabbit meat

The effect of dietary soybean oil (SO) inclusion (20 g/kg) on the odd-numbered (ONFA) and branched-chain (BCFA) fatty acids (FA) of two muscles, differing in fatness (Longissimus lumborum and Biceps femoris), was studied in 24 New Zealand × Californian rabbits. The increased muscle fatness in Biceps femoris (P < 0.001) was related to higher saturated (P < 0.01) and monounsaturated (P < 0.01) fatty acids. Intramuscular ONFA and BCFA contents were not affected, but their proportions were reduced (P < 0.01 and P < 0.001) by SO addition, suggesting a dilution effect of the dietary polyunsaturates accumulated in both muscles, except for 17:0i which decreased only in Longissimus lumborum due to significant (P < 0.05) soybean oil × muscle interaction. The higher (P < 0.05) BCFA contents and the FA profile in Biceps femoris were not affected by fatness, indicating an association with other muscle properties. The present study supplies new information on ONFA and BCFA in rabbit meat.