• Application of Probiotic Bacteria to Functional Foods

      STANTON, CATHERINE; Ross, R Paul; Fitzgerald, Gerald F; Collins, K.; McBrearty, S.; Gardiner, Gillian E.; Desmond, C.; Kelly, J.; Bouchier, Paul J.; Lawless, Fergal; et al. (Teagasc, 2001-05-01)
      Probiotic cultures are described as live microbial feed supplements that improve intestinal microbial balance and are intended for maintenance of health or prevention, rather than the curing of disease. The demand for probiotic foods is increasing in Europe, Japan and the U.S. reflecting the heightened awareness among the public of the relationship between diet and health. Traditionally, the most popular food delivery systems for these cultures have been freshly fermented dairy foods, such as yogurts and fermented milks, as well as unfermented milks with cultures added. However, in the development of functional foods, the technological suitability of probiotic strains poses a serious challenge since their survival and viability may be adversely affected by processing conditions as well as by the product environment and storage conditions. This is a particular concern, given that high levels (at least 107 per gram or ml) of live micro-organisms are recommended for probiotic products. In previous studies (see DPRC No. 29) the successful manufacture of probiotic Cheddar cheese harbouring high levels (>108 cfu/g) of the probiotic Lactobacillus paracasei NFBC 338 strain was reported. Hence, the overall objective of these studies was to continue the development and evaluation of Functional Foods containing high levels of viable probiotic bacteria, with particular emphasis on overcoming the technological barriers and the identification of strains suited to particular applications, such as incorporation into Cheddar cheese and spray-dried powders.
    • Biochemical and Functional Relationships in Cheese.

      Guinee, Timothy P.; Fox, P.F.; Fenney, E.P; Mullins, C.; Corcoran, M.O.; Mulholland, E.; Auty, Mark (Teagasc, 2001-01-01)
      Cheese is used extensively in cooking applications, mainly because of its flavour and heat-induced functionality, which is a composite of different attributes such as softening, flow and stretch. The functional attributes of cooked cheese generally have a major impact on the quality of foods in which cheese is included as an ingredient, e.g. pizza pie. Owing to its importance in cookery applications, numerous studies have been undertaken on the effects of different factors on the age-related changes in the functionality of cooked cheese, especially Mozzarella, and to a lesser extent, Cheddar and processed cheese. These studies have shown that the functionality of natural cheese is dynamic, with the different functional attributes undergoing marked changes during ripening, and, for a given cheese variety, the desired functional attributes are optimum within a specific time frame during maturation. The time at which the cheese becomes functional and the width of the window - and hence the functional shelf-life, are affected by the extent of chemical changes, including the increase in proteolysis and the ratio of bound to free moisture. The main aims of this project were to investigate the effects of the following on the age-related changes in heat-related functional attributes (e.g. stretchability, fluidity) of cheese: * fat reduction, * the degree of fat emulsification, * the pH and calcium content and their interaction, * the correlation between proteolysis and functional attributes, especially attributes other than flowability, e.g. rheological properties of raw cheese, stretchability of heated cheese, and * the age-related changes in the functionality of cheeses other than Mozzarella, e.g. analogue pizza cheese and Emmental. At the outset of this project, comparatively little information was available on the effects of the above parameters on the age-related changes in heatinduced functional attributes (e.g. stretchability, fluidity) of cheese, especially for varieties other than Mozzarella.
    • The Effects of Processing and Ripening on the Quality of Pizza Cheese

      Guinee, Timothy P.; Mulholland, E.; Mullins, C.; Corcoran, M.O.; Auty, Mark (Teagasc, 1999-02-01)
      The main aims of this project were to quantify the changes in fuctionality during maturation of cheese and to develop an understanding of the factors which mediate the development of functionality. The approach to achieving these objectives involved the establishment of a suitable pilot plant production procedure for low moisture Mozzarella, developing and/or adapting existing methods for objective evaluation of the functional properties of pizza cheeses, and evaluating the effects of ripening and variations in cheesemaking conditions (e.g. pH at stretching) on the composition, yield and functionality of low moisture Mozzarella cheese. The main conclusions were as follows: The technology for developing low moisture Mozzarella cheeses, with different compositions and functionalities, via alteration of cheesemaking parameters, has been developed. A database has been established on the storage-related changes that occur in texture, proteolysis and functionality of low moisture Mozzarella cheeses of different compositions. In addition an extensive database on the compositional, biochemical, microstructural, rheological and/or functional properties of different commerical cheeses - low moisture Mozzarella, Cheddar and analogue pizza cheese, has been compiled. The functionality of low moisture Mozzarella changes markedly on storage/ripening at 4ºC. Initially, during the first 5-10 days of storage, the functionality of the baked cheese is poor but then improves on further storage as reflected by reductions in melt time and apparent viscosity (chewiness) and increases in stretchability and flowability. The changes in functionality are mediated by storage-related increases in pH, proteolysis, protein-bound water and free oil in the cheese. On prolonged storage (e.g. > 60 d at 4ºC), the cheese functionality becomes impaired as the shredded cheese develops an increased susceptibility to clumping/balling which makes it difficult to dispense the cheese onto the pizza pie and achieve a uniform surface distribution. Moreover, the baked cheese tends to exude excess free oil and loses its desired level of chewiness attaining a 'soupy' consistency. Novel methods were developed/adapted to objectively quantify functionality in the raw (susceptibility of shredded cheese to clump) and cooked (stretchability, chewiness, viscoelasticity) cheeses.
    • Identification of the key compounds responsible for Cheddar cheese flavour

      Beresford, Tom; Wallace, J.; Aherne, Seamus; Drinan, Finbarr; Eason, D.; Corcoran, M.O.; Mulholland, E.; Hannon, John A. (Teagasc, 2000-09-01)
      There is a poor understanding of the relationship between organoleptic assessment of cheese and quantitative analysis of flavour compounds. Further, the contribution of particular cheese-making parameters such as ripening temperature and starter culture has not been fully elucidated. During the ripening of most cheese varieties complex chemical conversions occur within the cheese matrix. In most cheese varieties breakdown of protein is the most important flavour development pathway. The primary cheese protein, casein, is degraded enzymatically to short peptides and free amino acids. The agents primarily responsible for these conversions are the residual rennet that is retained in the cheese curd at the end of the manufacturing phase and the proteinases and peptidases that are associated with the starter bacteria. While the rate and degree of proteolysis are of vital significance for desired flavour development, the direct products of proteolysis do not fully define cheese flavour. Much research is now demonstrating that the further biochemical and chemical conversions of the products of proteolysis, in particular the amino acids, are necessary for full flavour development. The products produced by these pathways are volatile at low boiling points and are thus released during mastication of the cheese in the mouth. Many of these volatile compounds contribute to the flavour sensation experienced by the consumer. A very wide spectrum of such compounds have been isolated from cheese, in excess of two hundred in some cheese varieties. It is now generally accepted that there is no individual compound which defines cheese flavour completely and that the flavour sensation is the result of numerous compounds present in the correct proportions. This has become known as the Component Balance Theory . The application of modern analytical techniques as proposed in this project would provide a greater understanding of the significant flavour compounds in Cheddar cheese and help to identify the impact of specific cheese-making parameters such as starter flora and ripening temperature on the production of volatile flavour compounds. This data would assist the general programme on flavour improvement of cheese which should ultimately benefit the cheese manufacturer. Hence this project set out to develop methods to identify the key flavour compounds in Cheddar cheese. These techniques would then be applied to experimental and commercial cheeses during ripening in an effort to identify key compounds and the influence of starter cultures and ripening temperature on their production.