Intraregional classification of wine via ICP-MS elemental fingerprinting.

The feasibility of elemental fingerprinting in the classification of wines according to their provenance vineyard soil was investigated in the relatively small geographical area of a single wine district. Results for the Stellenbosch wine district (Western Cape Wine Region, South Africa), comprising an area of less than 1,000 km(2), suggest that classification of wines from different estates (120 wines from 23 estates) is indeed possible using accurate elemental data and multivariate statistical analysis based on a combination of principal component analysis, cluster analysis, and discriminant analysis. This is the first study to demonstrate the successful classification of wines at estate level in a single wine district in South Africa. The elements B, Ba, Cs, Cu, Mg, Rb, Sr, Tl and Zn were identified as suitable indicators. White and red wines were grouped in separate data sets to allow successful classification of wines. Correlation between wine classification and soil type distributions in the area was observed.

Effect of Chemical and Physical Dry-curing Parameters on Cathepsins B, H and L from Ostrich Muscle.

The effects of curing agents (NaCl, nitrate, ascorbic acid and glucose) and processing parameters (pH, temperature and cooking temperatures) on cathepsins B, H and L activities were investigated. NaCl, nitrate, ascorbic acid and glucose exhibited different influences on ostrich cathepsin B, B+L and H activities. In the range 20-60gl(-1), NaCl inhibited cathepsin B+L and H activities. All three cysteine proteinase activities were inhibited by up to 8g ascorbic acid l(-1). With the exception of cathepsin B activity, which was inhibited by glucose, nitrate and glucose had very little effect on cathepsin B, B+L and H activities. Cathepsins B and D were active at 65 and 69°C and might play an important degradative role during the cooking of meat and meat products. Cathepsins B, B+L and H were optimally active at temperatures of 40-45°C and 50°C, and were still quite active at the low temperatures used in the dry-curing process; they showed maximum activity in the pH range 5·5-7. A simulation of the three stages of the dry-curing process of hams revealed that cathepsins B and B+L might play an important role throughout the complete process, whereas cathepsin H could only participate in the middle and at the end of the dry-curing process. Although ostrich cathepsins show many properties similar to those from other species, the present study also revealed some interesting distinguishing features.

The effects of Ca ions, EGTA and storage time on myofibrillar protein degradation, levels of Ca(2+)-dependent proteases and cathepsins B, H, L and D of ostrich skeletal muscle.

The effect of Ca ions and ethylene glycol-bis(ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) on myofibrillar protein degradation showed that when ostrich iliotibialis lateralis muscle was incubated with 10 mM EGTA at 2-4 °C for 24 hr, the activity of extracted cathepsin H was unchanged compared with a buffer-incubated sample. Ca(++) had no effect on extracted cathepsin H activity, while that of Ca(2+)-dependent protease (CDP) decreased significantly (p < 0.05). Ca(2+)-treatment enhanced post-mortem changes observed in myofibrillar protein patterns (production of fragments around 30 K) that were not observed in EGTA-incubated myofibrils. The effect of storage time on shear force, CDP activity, cathepsin B, D, H and L activities and the SDS-PAGE pattern of myofibrils showed a time-dependent reduction in CDP activity. Of the cathepsins studied only cathepsin H showed a reduction (40%) in activity. The most prominent component appearing on storage at 2-4 °C had a M(r) of 27 K. The incubation of myofibrils with CDP mimicked the post-mortem changes. CDP may be responsible for some of the post-mortem changes observed, although shear force measurements suggest these changes do not lead to significant tenderisation.

Optimisation of calcium-dependent protease and cathepsin D assays in ostrich muscle and the effect of chemical and physical dry-curing parameters.

The best conditions for the assay of cathepsin D and Ca(2+)-dependent pro tease (CDP) activity in ostrich muscle was established in order to have a simple, rapid and reliable method for its determination. Measurements of A(280nm) of TCA-soluble peptides and amino acid digests of casein and haemoglobin were used for measuring proteolytic activity in muscle extracts. The best conditions for the reliable determination of cathepsin D activity were found to be the incubation of an enzyme extract for 1 hr at 55 °C in a reaction mixture containing 0.9% (w v ) haemoglobin in 50 mM sodium formate buffer, pH 3.7. Characterization of the assay system for CDPs, obtained after phenyl-Sepharose chromatography, indicated that proteolytic degradation of casein by CDPs was linear with time up to 30 min at 30 °C and up to 0.1 units of activity. The effect of NaCl, KCl, nitrate, ascorbic acid, phosphate, glucose and sucrose on ostrich muscle CDP and cathepsin D activities has been studied. Salt (NaCl and KCl) acts as a strong inhibitor of proteolytic activity. Sodium and potassium nitrates (in the range 0-1000 mg l(-1)) affected activity to varying degrees. CDP activity was enhanced by sodium nitrate concentrations below 700 mg l(-1) and unchanged by potassium nitrate. Cathepsin D activity was inhibited to some extent by sodium nitrate above 200 mg l(-1) and completely by potassium nitrate. Results showed that phosphate is an inhibitor of both activities. High concentrations of ascorbic acid (above 6 g l(-1)) inhibited cathepsin D activity. Glucose (up to 2g l(-1)) activated cathepsin D activity and inhibited CDP activity (up to 1 g l(-1)). Sucrose activated enzyme activities at very low concentrations (1 × 10(-3) M) and inhibited activities above 1 × 10(-3) M.