Proteolysis, dielectric properties and sensory data were measured during ripening of Edam type cheese (30% and 45% FDM). Cheese of different age (1-25 weeks) was analysed. Dielectric properties were used as a method for assessing proteolysis. Permitivity had significantly similar continuance as pH 4.4 total soluble N, both in opposite to sweet milky taste, during ripening period. This paper offers dielectric properties as useful characteristics for assessing proteolysis in cheese.Keywords: Edam cheese; proteolysis; dielectric properties; permitivity; sensory analysis; ripening 86Vol. 18, Czech J. Food Sci.(FDM). The factory processes about 50 000 l of milk a day in a standard manufacturing schedule. Approximately ten lots of 210 Edam blocks are produced. Immediately after salting, six randomly chosen blocks from different batches were cut to thick (about 0.5 kg) slices, five slices each, and vacuum-packed in cryovac foil. Samples were stored at 10°C for future measurements. Immediately after unwrapping from the foil, a 70 by 70 mm sample, 6 mm thick, was taken from the centre of each slice. A continuous measurement of dielectric properties followed.Chemical Analysis: All cheeses were analysed for dry matter (DM, expressed in g/100 g of cheese, oven dried at 102°C for 4 hrs), fat (F, g/100g, acidobutyrimetric method according to VAN GULIK, ISO 3433 [1975 -Sýry. Stanovení obsahu tuku v sýrech. Metoda Van Gulik]), tyrosine, tryptophan and total soluble N according to the spectrophotometric method by VAKALERIS and PRICE (1959).Dielectric Measurements: Samples were analysed at storing temperature 10°C. Fig. 1 represents a schematic diagram of the measuring instrument.The generator produces standard microwave signal with frequency 10 GHz. The phase of the signal in the measuring section is changed when passing through cheese sample. The alternation of the phase is measured in the phase move and changes the phase to the original. The ampli- Sensory Evaluation: Four sensory panellists, familiar with Edam cheese properties, performed the appraisal of sensory characteristics. Middle of the sliced piece was taken for sensory assessment. Colour, sour and milk smells, texture characteristics elasticity and deformability and flavour descriptors salt, bitter, sour, sweet and nutty were graded. All characteristics were graded zero to seven (integers only). The scores presented are the means of grading by all panellists. RESULTS AND DISCUSSIONBasic parameters (dry matter and fat), which characterise the tested Edam cheese more closely, are summarised in Table 1. These parameters do not change during the ripening process because of the presence of foil on cheese surface, so they were not measured again.As can be seen from our results, the methods used offer sufficient distinguishing among given samples of different age (Table 2). Each value is a mean of six measurements. The results show an increase of soluble tyrosine, tryptophan and also of total soluble N with prolonged tude of the signal passing through the sample is lower...
The rheological properties of cheeses are significantly connected with their final quality (KFOURY et al. 1989). Like most of solid biological materials cheeses exhibit the viscoelastic behaviour. This means that their behaviour under some mechanical loading consists of solid (elastic) and fluid (viscous) behaviour. The viscoelastic materials are those in which the relationship between stress and strain depends on time. There are many models of the viscoelastic behaviour of materials, see e.g. LAKES (1999) for a review. The choice of a viscoelastic model and the evaluation of its parameters is based on the use of some phenomena which occur in viscoelastic materials. The main phenomena are: -Creep -if the stress is held constant, the strain increases with time; -Relaxation -the stress decreases with time at constant strain; -The effective stiffness depends on the rate of load application; -If cyclic loading is applied, hysteresis occurs; -Acoustic waves experience damping; -Rebound of an object following an impact is less than 100%; and many others (LAKES 1999).
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