HRI Core projects completed 2005
Please click on the project title to review the project summary:
Developing science and technology platforms for the food and drink industries: Microbial metabolism and food biofermentation.
Developing science and technology platforms for the food and drink industries: Biotechnology and biogenesis of flavour in fermented food and cheese.
HRI/262/02 Developing science and technology platforms for the food and drink industries: Microbial metabolism and food biofermentation.
Final Costs: £683,980
The role of micro-organisms in flavour formation in fermented dairy, meat and other food products is well established. The use of microbial cultures to naturally transform the flavour and character of food is thus an attractive option given current consumer resistance to the use of chemical additives or approaches involving genetic manipulation. However, flavour development is a complex interactive process dependent on the microbial conversion of the protein, lipid and carbohydrate components initially present in the food. A detailed knowledge of the metabolic pathways leading to the generation of important flavour components and factors that regulate these catabolic activities is an essential pre-requisite for the inclusion of bacteria in food to generate and diversify basic and novel flavours. The research described here is intended to provide fundamental information on the intermediary metabolism and control of the conversion of amino acids to important flavour and aroma compounds in lactic acid bacteria and other food-grade micro-organisms. The investigations have the potential to indicate strains with biochemical attributes that could be exploited commercially to accelerate or diversify the aroma and flavour characteristics of fermented food products, especially cheddar cheese. Studies were also undertaken to identify cultures that possessed glutamate dehydrogenase activity. Such cultures have potential to generate a-ketoglutarate from naturally occurring glutamic acid, and thereby accelerate the catabolism of amino acids by keto acid-dependent aminotransferase enzymes present in the starter and non-starter populations. The proliferation of non-starter lactobacilli in cheese can be undesirable and studies were initiated to establish if these strains possessed the ability to degrade a-ketoglutarate. Other approaches to enhance amino acid turnover with bacterial cultures were also evaluated.
In addition, the effectiveness of differing heat treatment regimes to suppress the development of the adventitious non-starter bacterial population were examined as a means to allow the cheesemaker more precise control of the bacterial population that ultimately develops in the cheese during maturation.
Back to top
HRI/266/02 Developing science and technology platforms for the food and drink industries: Biotechnology and biogenesis of flavour in fermented food and cheese.
Final costs: £475,432
Development of characteristic flavours and textures in cheeses and other fermented products is a complex dynamic process which results from enzymic activity. Enzymes responsible for flavour and texture development in cheese include those which originate from the coagulant used in cheese manufacture, the lactic acid bacteria added in the starter culture, and adjunct bacteria which are employed to impart specific flavour attributes to a matured cheese. Enzymes responsible for flavour and texture development in cheeses include a diverse range of proteases, peptidases, amino peptidases, amino acid catabolising enzymes, lipases, esterases and glycosidases. A detailed knowledge of the texture is an essential pre-requisite for the production of novel and diverse flavours and textures in cheese and other foods. The research project focused on the interaction of proteolytic systems in the manipulation of texture and flavour in cheese. It was intended to provide fundamental information on the importance of primary proteolytic activity on texture development, and ultimate conversion of amino acids to important flavour and aroma compounds. The investigations explored and identified proteolytic activities which may be exploited to improve the textural characteristics of low-fat Cheddars while maximising potential for rapid flavour and aroma development using adjunct culture of lactobacilli and other microorganisms. We have previously shown that addition of the aminotransferase a-ketoglutarate to Cheddar results in enhancement of aroma intensity and manipulation of aroma profile. Studies with a-ketoglutarate were extended to explore the influence of altering the pool of amino acid substrates by manipulation of primary proteolysis. A model slurry system was developed to provide a more rapid means of assessing the potential effectiveness of adjunct cultures with diverse enzyme systems in manipulation of cheese flavour and aroma.
In addition, further enhancement of our sensory profiling protocol was carried out. Two aspects were investigated: 1) development of appropriate standard materials to allow enhanced data gathering during serial studies on food products that change over their natural ripening period e.g. spirits, wine and cheese, 2) methods for determining the rate of flavour release that will to allow a better understanding of the differences between low-fat and normal products.
Back to top