Effect of combined treatments of high-pressure,citric acid and sodium chloride on quality parameters of tomato puree

Tomato puree was subjected to combined treatments of high hydrostatic pressure and natural additives citric acid and sodium chloride (NaCl)]. Their effects on the most important quality parameters of tomato puree as colour and viscosity, and biochemical parameters as enzymatic activities (polyphenoloxidase, peroxidase, and pectin methylesterase) and total protein content, and microorganisms (total microbial counts and yeasts and moulds) were studied. Response surface methodology was employed where the experiment was carried out according to a central composite face-centred design. The variables ranges used were: 50–400 MPa (pressure), 0–0.8% w/w (concentration of NaCl) and 0–2% w/w (concentration of citric acid) while temperature and holding time of high pressure treatments were constants at 25 °C and 15 min respectively. The results showed that enzymatic inactivation was significantly improved with these combined treatments at high values of pressure and concentration of additives. A very significant reduction of 4 logarithmic units was observed when pressure was increased to 400 MPa for total microbial counts. Thus, combined "hurdles" may be effective to produce minimally processed tomato products with optimal sensorial and microbiological characteristics.