Vanillin as an Antimicrobial for Producing Shelf-stable Strawberry Puree

The utilization of vanillin was studied as a natural antimicrobial in a combined technology for producing a shelf-stable strawberry purée. Mild heat treatment (blanching) was combined with addition of 3,000 ppm vanillin and 500 ppm ascorbic acid and adjustment of water activity (a_w) to 0.95 and pH to 3.0. This prevented growth of both native and inoculated flora for ≥60 days storage at room temperature.     

GROWTH OF EUROTIUM CHEVALIERI IN MILK JAM: INFLUENCE OF PH, POTASSIUM SORBATE AND WATER ACTIVITY

Milk jam (dulce de leche) is a typical Argentine sweet spread prepared by milk evaporation to about 70% w/w total solids at atmospheric pressure with added sucrose, glucose and vanillin. Growth of xerophilic molds represents a severe problem in this type of intermediate moisture product. This study evaluated the growth response of Eurotium chevalieri in milk jam with different potassium sorbate (KS) concentrations (0, 500, 1,000, 1,500 and 2,000 ppm) at selected water activity (a_w) values (?0.80 and 0.85) and two pH levels (?5.5 and 6.0) stored at room temperature (25C) for 90 days. Growth curves were characterized by the modified Gompertz model, and the effect of the independent variables on the estimated parameters (maximum specific growth rate, v_m, and lag time, λ) was analyzed through polynomial equations. Growth of E. chevalieri was prevented for at least 90 days when the addition of 1,000 ppm KS was combined with a decrease in a_w to 0.80 and ph 5.5. The boundary between growth and nongrowth of E. chevalieri as a function of a_w, pH, KS and storage time was also predicted by means of the probabilistic model using logistic regression, which provided a wide range of formulation possibilities depending on the targeted shelf life.     

Technical note: Kinetics of sorbic acid loss during storage of peaches preserved by combined factors

It was found that the loss of sorbic acid in stored peaches preserved by combined factors (water activity, pH, additives) followed first order reaction kinetics. Rate constants and activation energy (14 kcal/mol) were almost identical to those previously reported for sorbic acid loss in concentrated glucose solutions of identical water activity and pH.     

Determination of Sorbic Acid in Raw Beef: An Improved Procedure

Various analytical methods for sorbic acid determination based on removal of the preservative by distillation or ether extraction, followed by UV or colorimetric analysis gave relatively poor recoveries (52–84%) when applied to raw beef. An improved procedure was developed based on disintegration and dispersion of beef with sand prior to steam distillation and colorimetric determination. This resulted in almost 100% recovery of sorbate, attributed to more efficient extraction because of increased surface area.     

A Multi-parameter Approach to Control the Growth of Saccharomyces cerevisiae in Laboratory Media

The effects of combinations of reduced water activity (a_w from 0.97 to 0.93), pH (3, 4, 5, and 6) and addition of potassium sorbate (0, 100, 500, and 1,000 ppm) on the growth of one strain of Saccharomyces cerevisiae in laboratory medium were studied. The minimal a_w for growth inhibition in the absence of sorbate and in the range of optimal pH was 0.89. Various combinations of a_w, pH and sorbate concentration prevented growth of the yeast at a_w values above 0.89. For example, at v = 0.93, addition of 100 ppm sorbate at pH = 4.0 resulted in inhibition; at a_w= 0.97 and same pH (4.0), 500 ppm of sorbate were necessary. The combined effects of the above parameters on generation time, maximum population, and lag time of the cells were also determined.     

Water Activity of Galactose Solutions

The water activities (a_w) of galactose and mannose solutions were determined using an electric hygrometer. The results followed the general behavior reported for most types of nonelectrolytes and very well fit the Norrish equation. The a_w lowering effects of galactose were almost identical to those of mannose, glucose, and fructose.