Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Influence of low oxygen and high carbon dioxide on shredded Galega kale quality for development of modified atmosphere packagesPublication . Fonseca, Susana C.; Oliveira, Fernanda A. R.; Brecht, Jeffrey K.; Chau, Khe V.Respiration rate, sensory attributes, colour alterations, and water, chlorophyll and ascorbic acid contents were monitored during storage of shredded Galega kale (Brassica oleracea var. acephala DC.) at 20 ◦C to define an adequate range of O2 and CO2 partial pressures for product preservation. Different low O2 and high CO2 atmospheres were tested. First, tolerance to low O2 partial pressures (1, 2, 3 or 21 kPa O2 with balance N2) was tested. Quality retention was improved as O2 partial pressure was reduced and there was no induction of anaerobic respiration. Then, tolerance to high CO2 partial pressures (0, 10, 15 or 20 kPa CO2 plus 21 kPa O2 and balance N2) was tested. The high CO2 partial pressures extended the shelf life of the shredded kale and no symptoms of CO2 injury were detected. Finally, combinations of low O2 and high CO2 (1 or 2 kPa O2 plus 15 or 20 kPa CO2, with balance N2, and an air control) were analysed. No differences were observed among the different gas combinations. An atmosphere of 1–2 kPa O2 plus 15–20 kPa CO2 and balance N2 extends the shelf life of shredded Galega kale to 4–5 days at 20◦C, compared with 2–3 days in air storage. Predictive models of chlorophyll a and b degradation as a function of time and gas composition were developed.
- Effects of preharvest, harvest and postharvest factors on the quality of pear (cv. "Rocha") stored under controlled atmosphere conditionsPublication . Galvis-Sánchez, Andrea C.; Fonseca, Susana C.; Morais, Alcina M. M. B.; Malcata, F. XavierPears (cv. Rocha’) grown at two locations and picked up at various times during the harvest season were assessed for firmness and colour, following 9 mo of storage under air or under controlled atmosphere conditions. A second-order polynomial was able to accurately fit the effect of time of harvest on pear’s quality, in an essentially empirical modelling effort; the best estimates of the parameters therein depend on the growing location, as well as on the atmosphere gas composition prevailing during storage.
- Sensorial and physicochemical quality responses of pears (cv Rocha) to long-term storage under controlled atmospheresPublication . Galvis-Sánchez, Andrea C.; Fonseca, Susana C.; Morais, Alcina M. M. B.; Malcata, F. XavierPears (cv Rocha) kept under controlled atmospheres (CA) and air were evaluated after longterm storage in terms of sensory attributes and physicochemical parameters, namely colour, firmness, polyphenoloxidase (PPO) activity and concentration of hydroxycinnamic compounds. The CA conditions were all combinations of 2 and 4% (v/v) O2 with 0.5 and 1.5% (v/v) CO2. Storage under CA conditions produced a beneficial effect on ‘Rocha’ pears in maintaining their quality and, consequently, in extending their shelf life and acceptability. Clear differences in sensorial attributes, colour parameters and PPO activity were found between CA- and air-stored pears. The effect provided by the CA conditions persisted throughout the time of exposure to the open air. The 2%O2 concentration produced amore beneficial effect than its 4%counterpart on the sensorial and physical characteristics of the pears.The former concentration of O2 prevented yellowing and allowed regular softening, hence keeping a high flavour quality. No clear effects could be associated with CO2 levels. Empirical models were developed that describe the effects of O2 and CO2 concentrations, as well as time at room temperature on physicochemical parameters pertaining to ‘Rocha’ pears.
- Impact of thermal blanching and thermosonication treatments on watercress (Nasturtium officinale) quality: thermosonication process optimisation and microstructure evaluationPublication . Cruz, Rui M. S.; Vieira, Margarida C.; Fonseca, Susana C.; Silva, Cristina L. M.The objectives of the present work were to optimise watercress heat and thermosonication blanching conditions, in order to obtain a product with better quality for further freezing, and to evaluate the effects of thermosonication on the microstructure of watercress leaves. In a chart of optimal time-temperature conditions for a 90% peroxidase inactivation (imposed constraint), vitamin C (objective function) and a-value (improvement toward green) were mathematically predicted for both heat and thermosonication blanching treatments. Two optimal thermosonication combinations were selected: 92 A degrees C and 2 s, retaining 95% of vitamin C content and 5% a-value improvement, and a better condition in terms of practical feasibility, 86 A degrees C and 30 s, allowing a 75% vitamin C retention and 8% a-value improvement. The experimental values, for each thermosonication optimal time-temperature zone, were in good agreement with the models' predicted responses. In terms of microstructure, thermosonicated watercress at 86 and 92 A degrees C showed similar loss of turgor and release of chloroplasts. The proposed optimal thermosonication blanching conditions allow the improvement of the blanched watercress quality and consequently contribute for the development of a high-quality new frozen product. However, a suitable scale-up is mandatory for industrial implementation.
- Effect of CA-storage on the physical and sensorial quality of ‘Rocha’ pearPublication . Galvis-Sánchez, A. C.; Fonseca, S. C.; Morais, A. M. M. B.; Malcata, F. X.