Improvement in texture using calcium lactate and heat-shock treatments for stored ready-to-eat carrots

The use of calcium lactate solutions has been shown to be a healthy alternative to chlorine washing in order to maintain the shelf-life of fresh-cut products. The aim of this research was to analyse the effects of calcium lactate (15 g L^-1) treatment at 25 °C and 50 °C (heat-shock) on the textural properties of sliced carrots and to compare those with the chlorine treatment (120 mg L^-1) widely used in industry. Several direct and indirect markers of textural changes in carrots during storage were used: Instron textural analysis, Cryo-SEM and optical microscopic, sensory analysis, pectin methylesterase (PME) activity, calcium content and water activity. Samples treated with calcium lactate maintained texture significantly (p < 0.05) better than samples treated with chlorine throughout storage. Calcium lactate treatment produced a reduction in the water activity in sliced carrots and a higher firmness (Instron analysis) than chlorine treatment. In addition, combined use of heat-shock and calcium lactate treatment increased PME activity significantly when compared to the other treatments, results that were confirmed by sensory analysis. Cryo-SEM analyses showed that combined heat-shock and calcium lactate treatment was more effective in maintaining the turgor of cortex tissue cells and reduced the extent of lignification at cutting-edge areas. The use of calcium lactate combined with heat-shock is a promising washing method for fresh-cut carrots in order to preserve their texture and improve their nutritional value, avoiding the use of chlorine washing.