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Authors: M.S. Carrasco, L.G. Moragues, C.I. Vignatti, H.E. Scarinci and A.C. Simonetta
A total of 116 yeast strains were isolated from raw milk, cheese whey, and soft and hard cheeses produced in Argentina. They were identified using the standard conventional identification methods indicated by Kreger van Rij (1984) and Barnett et al. (2000), as well as API tests. The maximum level of yeasts in the cheese was 4.5x105 cfu/g, while in milks and whey it was 5x103 and 2x104 cfu/mL, respectively. Candida and Geotrichum dominated in the milk (50%), Candida (42.2%), Cryptococcus (21%) and Trichosporon (36.8%) in the whey, and Candida was the predominant genus in the cheeses. Less frequently isolated genera were Brettanomyces and Schizosaccharomyces. The yeasts were able to grow at a range of temperatures and pH values, and in the presence of 10% (w/v) NaCl concentration, although the ability to grow in 15% and 20% (w/v) NaCl concentrations was variable. Some strains were psychrotrophic. On the basis of these results and with further technological characterisation, some of the yeast strains isolated could be used in cheese starter technologies.
Authors: C. Garrigues, B. Stuer-Lauridsen and E. Johansen
Determination of the complete genome sequence of a probiotic bacterium allows a number of new approaches to understanding the biology of the bacterium and provides new insight into the beneficial effects obtained through the use of probiotic products. Genomic information for B. animalis subsp. lactis strain BB-12 has been used to make microarrays and characterise the proteome of this important probiotic strain. These tools have been used to characterise other Bifidobacterium strains and to develop a better understanding of the stresses BB-12 is exposed to during industrial-scale production. In addition, changes in gene expression when cells are grown in the presence of bile salts or fructooligosaccharides have been determined. A comparison of information derived from the genome sequence of BB-12 to information derived from the published genome sequences of other probiotic bacteria is also provided.
Authors: Kevin G. Wilkinson, Jason G. Issa, Barry Meehan, Aravind Surapaneni, Melanie Carew and
Twenty-six waste samples from eight factories in the Goulburn Valley and south-west Victoria were characterised to determine their suitability for a range of potential uses. The waste streams were found to be diverse in nature and composition. They included sludges and product rejects, such as cheeses, powders and icecream solids. The nutrient quality of many dairy processing wastes make them ideal for direct land application, but little information is available about their public health, agronomic and environmental impacts when they are applied to land. The moisture content of the sludges ranged from 21-97% (w/w wet basis). On a dry basis, the total nitrogen, total phosphorus and total potassium of these wastes ranged from 0.7-8.9% (w/w), 913-21,349 mg/kg and 205-19,673 mg/kg, respectively. Waste streams from cheese and/or ice-cream production were commonly recycled as stock feed. The digestibility for the stock feeds ranged from (w/w d.m.) 76.6-94.1%, and there was wide variation in carbohydrate (1.4-92%), protein (4.5-82.1%) and fat (0.4-78.9%) contents between samples. Waste streams that were recycled as tallow had fat contents ranging from (w/w d.m.) 75.3% to more than 95%, but only two of these were close to meeting the specifications for technical tallow production. Three high-fat (>44% w/w d.m.) waste streams were also composted, including two grease trap wastes. High-fat waste streams could possibly be used as boiler fuel, or for bio-diesel production, but at current waste volumes, these applications are probably not yet economically viable. Variability in the composition of dairy processing waste streams is probably not a major concern for the continuing low-level utilisation of these waste streams, such as for land application, composting and stock feed. However, a better understanding of this variability is needed if higher value uses are to be considered for dairy-processing waste streams.
Authors: Louise E. Bennett, Sunanda Sudharmarajan and Geoffrey W. Smithers
The Rapid Visco Analyser (RVA) is a rotational viscometer with the ability to vary shear and temperature during testing and has been used to assess the pasting properties of starch in food ingredients such as corn, flour and extrusion premixes. The RVA represents a potentially useful technique for studying other food systems where the conformations and interactions of components are sensitive to heat and shear. We report here the use of an RVA-based method for characterising the reheat rheological properties of skimmed milk powders.
Authors: T.P. Guinee, M.A.E. Auty, D. Harrington, M.O. Corcoran, C. Mullins and E.O. Mulholland
Commercial cheddar (CC), low moisture mozzarella (LMMC) and analogue pizza cheeses (APC) were procured from local supermarkets or local companies. The cheeses (n=8 per category) were compared for gross composition, proteolysis as indicated by nitrogen levels soluble at pH 4.6 and 5% PTA, levels of expressible serum and oil on hydraulic pressing at 2.3 MPa, serum composition, microstructure using confocal laser scanning microscopy, functionality (melt time, flow, stretchability, apparent viscosity) and viscoelastic properties during heating from 20 to 82°C using low amplitude oscillation rheometry.
Authors: M.J. Auldist, S. Coats, G.L. Rogers and G.H. McDowell
Changes in the composition of mammary secretion from Friesian and Jersey cattle were monitored during the first two weeks after commencement of milking. Measurements were made on naturally-calving cows and heifers and on cows induced to calve prematurely. Irrespective of breed or age of animal or whether calving was natural or prematurely induced, the patterns of change were similar relative to the time of commencement of milking, not parturition. Although the characteristics of secretion continued to change during the first 10 or so days after milking commenced, by 5 days secretion resembled normal milk. It was apparent that measurements based on somatic cell count and concentration of immunoglobulin G1 could be used as the bases for a quality payment scheme to encourage supply of milk suitable for the manufacture of quality dairy products.
Authors: J.A. Reinheimer, M.R. Demkow and L.A. Calabrese
Samples of (223) of bulk-collected raw milk from the area of Santa Fe, were examined. Counts, isolation and identification of the psychrotrophic microflora were carried out. Caseinolytic and lipolytic activities, and protease thermoresistance of the strains were studied, as was the effect of pre-culturing milk with these strains on milk acidification by lactic cultures. High levels of psychotrophic contamination were found to exist (x > 106cfu/mL), with a high incidence of Pseudomonas spp (51.1% of the strains isolated). A significant proportion of the psychrotrophic bacteria was found to be proteolytic and lipolytic at 5°C and 25°C. The α-casein fraction was the most susceptible to attack by proteases. These proteases were highly stable at 40, 63, 100 and 140°C, but their activity was partially lost when heated at 55°C. When milk was pre-cultured with some psychrotropic strains, the acidification rate of lactic cultures was, in most cases, stimulated; this was related to the degree of proteolysis by the psychotrophic bateria.
Authors: Damian Frank, Patrick O'Riordan, Dimitrios Zabaras and Peter Varelis
The volatile profiles of five commercially available Australian cheddar cheeses of different maturities (mild, tasty and vintage) were investigated using a simultaneous gas chromatographymass spectrometry olfactometry (GC/MS-O) approach. Volatiles were concentrated by dynamic headspace onto Tenax-TA® and trained assessors (n=7) monitored the GC effluent at an olfactory port, simultaneously with mass spectrometric detection. The relative intensity of odour-active peaks was measured by each assessor and the 'average' odour-active profiles were represented as 'principal aromagrams' or unique odour-active volatile profiles for each cheese. More than 70 volatile compounds were detected by GC/MS, of which at least 29 were found to be odouractive. A further 13 odour-active compounds were perceived at the olfactory port, but not detected by the mass spectrometer. Principal component analysis indicated that the five cheddars could be successfully discriminated (mild, tasty vs. vintage) on the basis of: (1) integrated areas of all peaks detected by the mass spectrometer, i.e. instrumental data; and (2) aromagram peak intensities of odour-active compounds, i.e. 'sensory data' only. Discrimination of the cheddars was mainly on the basis of differences in absolute concentration and perceived odour intensity of a number of common cheddar volatile components, e.g. 3-methylbutanal (malty), 2,3-butanedione (diacetyl - sweet, dairy), ethyl butanoate (fruity, sweet), dimethyl trisulphide (garlic, savoury), methional (potato, savoury), 1-octen-3-one (fungus, mushroom), acetic acid (vinegar, sharp), butanoic acid (cheesy, sharp). In addition to these 'core' impact cheddar flavour compounds, a number of other odour-active compounds were responsible for more subtle differences in the cheddar cheese aroma signatures.
Adjunct cultures increase the intensity, and change the balance of cheese flavour, mainly in hard and semi-hard varieties. They are purpose-made cultures added deliberately by the cheesemaker, over and above the normal culture usage, to achieve flavour enhancement and/or modification. Most flavour adjuncts are lactic acid bacteria (LAB) derived from existing cheese starter lactic acid bacteria (SLAB), or the natural adventitious secondary non-starter lactic acid bacteria (NSLAB). SLAB-based adjuncts, developed from good flavour-producing starters, are effective in flavour enhancement, but require attenuation of acid production and concentration to high biomass before inclusion in cheesemaking recipes. NSLAB-based adjuncts are easier to use, not requiring any modification before use in cheesemaking, but can produce flavour and texture defects. Cheese smear bacteria, yeasts and moulds might be adapted as flavour adjunct, but they remain essentially experimental at this stage. Exopolysaccharide-producing LAB are under active trial, particularly in low fat cheese technology, to compensate for their poor texture and water phase control. Probiotic health ‘functional’ adjuncts are also in the pipeline.
Cheddar, Cheedam, Gouda, Brie, Camembert, Cream cheeses, yoghurt, sour cream and processed Cheddar cheese were experimentally manufactured from milk derived from cows whose ration included protected-lipid feed supplement containing a high proportion of linoleic acid. At least 20% of the total fatty acids in the milk was accounted for as linoleic acid. After milking, the antioxidant BHA, emulsified with Tween 80, was added to the milk to counter oxidized flavour development. The Cheddar, Cheedam and Gouda cheeses were matured and graded at 3 and 6 months of age and the Brie, Camembert and Cream cheeses at 4 and 6 weeks of age by a taste panel. All these cheeses were judged as acceptable. Acceptable polyunsaturated processed Cheddar cheese was also made when 12% of matured normal Cheddar cheese was added to the blend.
The body of the hard or semi-hard polyunsaturated cheese varieties tended to be either somewhat mealy or rubbery but not in all batches. The flavour was blander and less full than that of the control cheeses made from normal cows milk. The colour of all products was pale because of their reduced B-carotene content. Chemical analyses of these varieties of cheese indicated very reduced levels of acetic acid, acetoin, pentanal and penanol in comparison with the control cheeses. The reasons for the differences in physical and flavour characteristics and the means of overcoming them are discussed.
The Brie, Camembert, Cream cheese, yoghurt and sour cream presented no difficulties in manufacture, were free from oxidized flavour and acceptable to a taste panel. It is concluded that satisfactory and attractive polyunsaturated cheese and cultured dairy products can be made from milk with a high linoleic acid content.
Cheddar-type cheese was made experimentally from milk containing at least 20% of linoleic acid in its fat phase. Three different levels of the lipase Capalase K were added to the milk and the resultant cheeses were compared with cheese made from the same poly-unsaturated milk to which no Capalase K was added. The cheeses from all vats were matured and graded at 4 and 7 months of age by professional graders and a taste panel. Gas chromatography and other chemical analyses of the cheese at 4 months of age were also made.
The Capalase K-containing (test) cheeses showed much higher levels of butyric and hexanoic acids and a lower level of acetic acid as compared with commercial Cheddar cheese.
The professional graders and the taste panel judged the flavour of the cheeses with Capalase K as more "cheesey" but resembling that of a Romano-type cheese. The graders preferred the cheese with the lowest quantity of Capalase K and the taste panel that with the intermediate amount of the added enzyme. Both agreed that the preferred cheese was fully acceptable. It is concluded that polyunsaturated hard cheese with an attractive cheesey flavour can be made by the addition of a lipolytic enzyme of this type.
Authors: Arthur C. Ouwehand, Fandi Ibrahim and Sofia D. Forssten
Probiotics have been used for about a century as natural components in supplements and functional foods, mainly in milk drinks and yogurts. Selected probiotic strains have also been included into cheese which has been shown to be an appropriate carrier for probiotics and can deliver them in sufficient numbers. The food matrix in which probiotics are ingested may affect the survival in the intestine. Since survival is considered as a precondition for the beneficial effects of probiotics, in a recent study the survival and amount of probiotics in cheese were investigated by using models simulating the human gastrointestinal tract, after which an intervention study was performed. Gouda cheese with and without probiotic strains (Lactobacillus rhamnosus HN001 and L. acidophilus NCF M®) was first analysed in vitro. The cheese was digested, before it was tested in a human colon simulator. The in vitro simulation showed that the probiotics in the cheese survived the simulated passage through the upper gastrointestinal tract, and that the amount of total lactobacilli, L. acidophilus, and L. rhamnosus increased significantly in the colonic fermentation simulations of the probiotic cheese, compared to the nonprobiotic control cheese. A subsequent human intervention study showed that consumption of probiotic cheese (15 g, 109 cfu/day) increased both natural killer cell activity and phagocytic activity. This confirms earlier observations with L. rhamnosus HN001 in reconstituted fat-free milk, indicating that cheese can be an appropriate carrier for probiotics.
Authors: M. Hayes, M. Coakley, L. O'Sullivan, C. Stanton, C. Hill, G.F. Fitzgerald, J.J. Murphy and R.P. Ross
Cheese offers an attractive food-based delivery vehicle for probiotic cultures and biogenic substances such as conjugated linoleic acid (CLA) and bioactive peptides. Compared to many other fermented foods it has a relatively high pH and fat content, a solid consistency and a higher buffering capacity. Together these features probably afford improved protection of biological activity during manufacture, storage and gastrointestinal transit. However, it is desirable that probiotics and biogenics are technologically compatible with the cheese manufacturing process. Therefore, some important characteristics of probiotic strains and biogenics need to be assessed when considering cheese as the delivery matrix. Additionally, it is important that the delivery and generation of bioactive materials in cheeses does not disturb the cheese ecosystem by interfering with cheese maturation and/or flavour development. To date, many probiotic cheeses have been made without changing the manufacturing process by using probiotics as adjuncts with the starter cultures. Additionally, spray-dried skim milk powders containing probiotic Lactobacillus cultures have been developed which can be added as direct vat inoculants for cheddar cheese manufacture. Moreover, cheese itself is recognised as a natural source of bioactive peptides which originate from the proteolytic action of lactic acid bacteria (LAB) on milk proteins during cheese manufacture and/or maturation.
Authors: R.P. Ross, G. Fitzgerald, K. Collins and C. Stanton
Growing public awareness of diet-related health issues has fuelled the demand for probiotic foods, which are currently restricted predominantly to fermented milk drinks and yogurt. Probiotics are bacteria, generally lactobacilli or bifidobacteria associated with a plethora of health benefits ranging from alleviation of symptoms of lactose intolerance, treatment of diarrhoea, cancer suppression to reduction of blood cholesterol (Naidu et al. 1999 for review). While cheese has long been associated with a high quality nutritional image, more recently, research efforts devoted to the development of probiotic cheese containing viable numbers of Lactobacillus and Bifidobacterium sp. with demonstrated health promoting properties, have been made to push cheese into the 'functional foods' category. Generally, incorporation of probiotic bacteria into milk-based food systems, including cheese provides challenges in terms of maintaining viability and probiotic functionality during manufacture and shelf-life. In contrast to yogurt and fermented milk products, many hard cheeses such as cheddar have long ripening times of up to two years. During this time, the added probiotic bacteria would need to grow and/or survive to sufficient numbers to deliver the probiotic effect in the gastrointestinal tract. Since cultures can vary considerably with regard to their performance in cheese and intestinal environments, strain selection is vital to the successful development of probiotic cheese, as is retention of probiotic activity in the ripened product. Nevertheless, studies have demonstrated that cheddar cheese is suitable as a potential probiotic 'functional food' for a number of bifidobacteria and lactobacilli, with demonstrated health benefits. Our studies and others have led to the development of various probiotic cheeses, containing strains of probiotic bifidobacteria, lactobacilli and enterococci. Indeed, we have demonstrated that cheese can be an excellent carrier of some health-promoting bacteria, and that it also has certain advantages over yogurt and fermented milk as a delivery system for some probiotic strains.