Browsing by Author "Alexandre, Elisabete M.C."
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- Assessment of the impact of hydrogen peroxide solutions on microbial loads and quality factors of red bell peppers, strawberries and watercressPublication . Alexandre, Elisabete M.C.; Brandão, Teresa R.S.; Silva, Cristina L.M.The impact of sodium hypochlorite and hydrogen peroxide (H2O2 at 1 and 5%) solutions on Listeria innocua in red bell peppers, total mesophiles in strawberries and total coliforms in watercress was studied. Quality attributes such as colour, firmness and pH were studied for all products; total anthocyanins content was determined for strawberries. Sensorial analyses were also carried out for all products. Results showed that H2O2 (5%) provided the highest reductions of microbial loads. Besides H2O2 (1%) had a lower impact, it was more effective than water-washings. Sodium hypochlorite solutions lead to microbial reductions comparable to water risings. In terms of quality, H2O2 (5%) was the solution with higher negative impact on products’ colour. For strawberries, such colour alterations were also detected by sensorial analyses. The anthocyanins content decreased significantly. Overall it was found that H2O2 (1%) was a good sanitizer solution, since microbial reduction was attained while quality factors did not suffer considerable alterations.
- Assessment of the impact of hydrogen peroxide soutions on microbial loads and quality factors of red bell peppers, strawberries and watercressPublication . Alexandre, Elisabete M.C.; Brandão, Teresa R.S.; Silva, Cristina L.M.The impact of sodium hypochlorite and hydrogen peroxide (H2O2 at 1 and 5%) solutions on Listeria innocua in red bell peppers, total mesophiles in strawberries and total coliforms in watercress was studied. Quality attributes such as colour, firmness and pH were studied for all products; total anthocyanins content was determined for strawberries. Sensorial analyses were also carried out for all products. Results showed that H2O2 (5%) provided the highest reductions of microbial loads. Besides H2O2 (1%) had a lower impact, it was more effective than water-washings. Sodium hypochlorite solutions lead to microbial reductions comparable to water risings. In terms of quality, H2O2 (5%) was the solution with higher negative impact on products’ colour. For strawberries, such colour alterations were also detected by sensorial analyses. The anthocyanins content decreased significantly. Overall it was found that H2O2 (1%) was a good sanitizer solution, since microbial reduction was attained while quality factors did not suffer considerable alterations.
- Efficacy of non-thermal technologies and sanitizer solutions on microbial load reduction and quality retention of strawberriesPublication . Alexandre, Elisabete M.C.; Brandão, Teresa R.S.; Silva, Cristina L.M.The effect of non-thermal technologies (ozone in aqueous solution, ultrasound and ultraviolet C radiation) and washings with chemical solutions (sodium hypochlorite and hydrogen peroxide) on safety and quality features of strawberries was studied. These treatments were applied before fruit storage at two different temperatures (4 and 15 C). The overall impact on microbial loads (total mesophiles, and yeasts and moulds) and selected quality attributes (colour, firmness, pH, total anthocyanins and ascorbic acid content) was assessed. During storage under refrigerated temperature, washing with hydrogen peroxide solutions resulted in strawberries with lower microbial loads, when compared to the other treatments. However, it produced significant key quality attributes losses, such as colour and total anthocyanins content. The results presented show that ozone and ultrasound are promising alternatives to thermal treatments. The application of such technologies, before refrigerated storage of strawberries, allowed a satisfactory retention of all quality characteristics analysed, while being efficient in controlling microbial contamination.
- Impact of high pressure on starch properties: a reviewPublication . Castro, Luís M.G.; Alexandre, Elisabete M.C.; Saraiva, Jorge A.; Pintado, ManuelaLarge amounts of different starches are produced worldwide since starch is widely used as a functional component in prepared foods and is one of the most important sources of energy for humans. However, in its native form starch does not have properties suitable for processing due to low thermal stability and high retrogradation. To promote and enhance these and other properties, starch is modified by chemical, physical, or enzymatic processes. Treatments such as high-pressure processing can be used to break/change non-covalent chemical linkages in and between starch molecules in order for starch to have the desired properties. The use of pressure can increase starch swelling and solubility depending on the temperature. Higher pressure levels can disrupt the starch granule morphology, induce the starch gelatinization and the granules birefringence can consequently decrease. Pressure can also alter significantly the thermal properties of starch, as well as its pasting properties, the dynamic oscillation and steady flow behavior of starch, and the amount of resistant/fast/slow digestible starch. The use of pressure can also delay/decrease starch retrogradation and change starch polymorphism from type A or C to type B. However, the change of these properties is always dependent on the pressure level, solvent type and treatment time used, but also from the starch type and origin. This paper revises the effect of high pressure on starch properties in order to improve their quality to obtain the desired properties that can promote human health.