A study on organic acid, sugar and ketone contents in typical Piedmont cheeses

The dairy industry is a very important sector for the Piedmont(Italy) economy with ten Protected Denomination of Origin (PDO) cheeses and fifty-five classified as ìTraditionalî. Among these ìTraditionalî cheeses, some are very interesting because of the quantity produced, cheese-making procedures used and sensory characteristics. Therefore, these cheeses might qualify for the PDO designation, but chemical information is lacking and only their gross composition is usually known. The aim of this study was to characterise some Piedmont cheeses by studying important compounds responsible for their flavour. Sugars (lactose, glucose and galactose), organic acids (citric, orotic, pyruvic, lactic, oxalic, hippuric, formic, acetic, propionic, butyric, isobutyric, valeric and isovaleric) and ketones (diacetyl and acetoin) were quantitatively determined in 460 samples from 17 cheese varieties using a simple isocratic HPLC method. Lactose concentrations varied from 0 to 73.9 mg/g of cheese and were inversely correlated to ripening time. Glucose concentrations ranged from 0 to 4.3 mg/g of cheese while galactose showed a maximum value of 9.4 mg/g of cheese. The range of diacetyl and acetoin were from 0 to 4.3 mg/g and from 0 to 0.2 mg/of cheese, respectively. Among the organic acids, lactic acid was the most abundant (0.3 to 39 mg/g). Citric acid was also very important with a maximum value of 4 mg/g. High variability characterised the carboxylic acids due to differences in raw material, cheesemaking technique and use of a starter. For all compounds high variability was observed due to home-made production, but nevertheless it was possibleto obtain a good characterisation of all these cheeses.