2006 IRISH SCIENTIST YEAR BOOK

Home Page

Table of contents

Index by Author

Index by topics

Search


Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co Cork
Kieran Kilcawley
Lipolysis in Cheddar cheese

Varian 3800 Gas Chromatograph with Flame Ionization Detection for quantification of individual free fatty acids.

The particular flavour and texture of any cheese arises from the biochemical degradation of protein, fat and carbohydrates, the extent of which governs the unique characteristics of each variety. Cheddar is a very popular cheese in English speaking countries and is extremely important in Ireland, as it consists of ~90% of all of cheese production (~120,000 tonnes per annum). It is therefore important that all biochemical factors influencing the quality of Irish Cheddar cheese are investigated.

Both protein and carbohydrate metabolism and degradation have been extensively studied, but very little research has been undertaken to investigate the role of lipolysis (fat degradation) in the flavour of Cheddar cheese. This was mainly due to the low levels of lipolysis in comparison to other varieties. Although intact dairy fat does not contribute directly to flavour or aroma, it can have a major influence through the production of free fatty acids (FFA) and their catabolic products as a result of lipolysis. These compounds can be perceived at low concentrations (parts per million) and thus have the ability to influence the sensory character of even a moderately lipolytic cheese, such as Cheddar.

Studies at MFRC have concentrated on determining the sources and factors influencing lipolysis in Cheddar cheese. Levels typically vary between 900 and 1800 mg FFA per kg of cheese, but often cause rancidity above ~2500 mg per kg. However, it also appears that the sensory perception of the products of lipolysis are influenced by the extent of proteolysis. The indigenous milk lipase, lipoprotein lipase appears completely inactivated by pasteurization (72�C � 15 sec). Starter lactic acid bacteria were found to be the prime lipolytic agents in Cheddar cheese. The levels of FFA in milk increase with stage of lactation and therefore are highest in cheeses made from late lactation milk. Moderate levels of lipolysis over ripening, do not appear to be due to a lack of enzyme activity, but rather a lack of availability and/or access to suitable fat substrates.

Contact: Dr Kieran Kilcawley,
Tel 025-42245
E-mail: [email protected]