Cutting edge: Moshe Rosenberg

The art of cheesemaking emerged from the need to preserve surplus milk. It has now evolved into a multidisciplinary, scientific and technological fermentation industry.

The quality and commercial value of cheese is determined not by the absence of defects but rather by a balanced profile of specific attributes such as flavour, texture and appearance, as well as other qualities such as nutritional value. In addition, it has become a functional ingredient in many food products. A given type of cheese, with a given composition, thus has to manifest different quality and functionality profiles in different foods prepared and consumed in different ways. Simply manufacturing defect-free cheeses that meet basic grading requirements, without introducing predetermined desired qualities, falls far short of what is needed for commercial success.

The consumer's definition of quality rests solely on describing the taste, aroma, texture and appearance of cheese in common language. Translating that into operable, quantitative data is a challenge industry has so far been unable to meet consistently.

While cheese is commonly marketed according to its age, we know that many other influences govern the development of its quality. Most varieties depend on the rate and extent of a plethora of biochemical events involving all major cheese constituents. Among the challenges that I have been attempting to address in my research programme is the development of industry-friendly tools to allow fast and relevant assessment of such biochemical activities and the development of quality attributes.

For example, proteolysis - the breakdown of proteins - critically determines the development of quality in most cheese varieties. Although numerous methodologies to assess proteolysis exist, most, if not all, are inapplicable to industry. Recently, my students and I demonstrated how a commercial assay kit to determine free L-Glutamic acid in medicine can also be used to assess and monitor the rate and extent of proteolysis in full and low-fat cheeses. The method can easily be used by industry to monitor the development of cheese quality and functional attributes.

We have also developed a new methodology to define, modulate and assess flavour and aroma. This consists of solid phase micro-extraction coupled with gas chromatography and principal component analysis. This allows us to produce variety-specific flavour "fingerprints". Such methods give cheesemakers the means to identify and control desired flavour profiles.

Mathematical modelling of the biochemical, microbiological and physicochemical events associated with cheesemaking has not yet been developed to the extent needed to automate cheesemaking.

Specific structural features are also of great importance to quality and commercial value. We have used magnetic resonance imaging to quantify eye development in Swiss cheese. This fast, safe, accurate and waste-free method allows online assessment of the cheese's structure, and we envisage it will become "a computerised, automated, cheese-grading expert system".

Moshe Rosenberg is a faculty member in the department of food science and technology, University of California, Davis, United States.