Sara I. Roura

An artificial neural network model for prediction of quality characteristics of apples during convective dehydration

In this study, the effects of hot-air drying conditions on color, water holding capacity, and total phenolic content of dried apple were investigated using artificial neural network as an intelligent modeling system. After that, a genetic algorithm was used to optimize the drying conditions. Apples were dried at different temperatures (40, 60, and 80 °C) and at three air flow-rates (0.5, 1, and 1.5 m/s). Applying the leave-one-out cross validation methodology, simulated and experimental data were in good agreement presenting an error < 2.4 %. Quality index optimal values were found at 62.9 °C and 1.0 m/s using genetic algorithm.

Electron microscopical and biochemical studies of actomyosin from pre- and post-spawned hake

Abstract 1. 1. The ultrastructure of actomyosin obtained from pre- and post-spawned hake was investigated. 2. 2. A characteristic arrowhead structure was found on actomyosin filaments obtained from post-spawned hake. 3. 3. The protein obtained from pre-spawned fish showed a loss of the filamentous structure. 4. 4. The loss of the filamentous structure in actomyosin from pre-spawned hake was related to a decreased affinity between myosin and actin.

Action of Triton X-100 on the biochemical and functional properties of hake (Merluccius hubbsi) myofibrils

Abstract 1. 1. The effects of Triton X-100 on the kinetic of Mg2+-ATPase and the functional properties of hake myofibrils were investigated. 2. 2. Triton X-100 increased the Hill coefficient to 1.5 in an allosteric type of reaction for the myofibrillar Mg2+-ATPase. 3. 3. Triton X-100 reduced the viscosity and the ATP response of myosin B and changed the contractile response of myofibrils. 4. 4. These changes would be due to the action of Triton X-100 on actin-myosin interacting sites.

Assessment of lettuce quality during storage at low relative humidity using Global Stability Index methodology

Abstract During postharvest, lettuce is usually exposed to adverse conditions (e.g. low relative humidity) that reduce the vegetable quality. In order to evaluate its shelf life, a great number of quality attributes must be analyzed, which requires careful experimental design, and it is time consuming. In this study, the modified Global Stability Index method was applied to estimate the quality of butter lettuce at low relative humidity during storage discriminating three lettuce zones (internal, middle, and external). The results indicated that the most relevant attributes were: the external zone - relative water content, water content , ascorbic acid, and total mesophilic counts; middle zone - relative water content , water content, total chlorophyll , and ascorbic acid; internal zone - relative water content, bound water, water content, and total mesophilic counts. A mathematical model that takes into account the Global Stability Index and overall visual quality for each lettuce zone was proposed. Moreover, the Weibull distribution was applied to estimate the maximum vegetable storage time which was 5, 4, and 3 days for the internal, middle, and external zone, respectively. When analyzing the effect of storage time for each lettuce zone, all the indices evaluated in the external zone of lettuce presented significant differences (p < 0.05). For both, internal and middle zones, the attributes presented significant differences (p < 0.05), except for water content and total chlorophyll.

Effect of triton X-100 treatment on the lipid composition, biochemical and functional properties of hake (Merluccius hubbsi) myofibrils purified from pre- and post-spawned fish

Abstract 1. 1. The effects of Triton X-100 treatment on the lipid contents and functional properties of hake myofibrils from pre- and post-spawned fish were investigated. 2. 2. Differences in lipids, biochemical and functional properties of hake myofibrils related to the gonadal condition of fish were observed. 3. 3. Triton X-100 treatment removed 65% of polar lipids in myofibrils from pre-spawned fish and only 10% in myofibrils from post-spawned fish. 4. 4. Triton X-100 increased the Hill coefficient to 1.5 in an allosteric type of reaction for the myofibrillar Mg2+-ATPase from pre-spawned hake. 5. 5. The detergent effect observed on the contraction response was greater in myofibrils from prespawned fish than in post-spawned fish.

Evolution of quality indices of fresh bunched spinach stored using low density polyethylene and polypropylene bags

Packaging technology constitutes an available method for reducing postharvest deteriorative processes on fresh products. The purpose of this work was to evaluate leaf water status, weight loss and colour retention of bunched spinach leaves packaged in low density polyethylene (LDPE) and polypropylene (OPP) bags, stored at 2°C for 25 days. Water status was determined through relative water content (RWC), the free:total water ratio (FW/TW) and bound water (BW); colour was evaluated colorimetrically as hue angle. Gaseous concentrations reached in OPP bags (11% O 2 , 3%–5% CO 2 ) were within those considered beneficial for spinach. Weight loss was higher in LDPE than OPP bags. RWC was lower in LDPE than in OPP bags. RWC decreased after day 18. Increases occurred in BW and decreases occurred in the FW/TW, indicating possible water movement within the leaf. Hue angle diminished after seven days of storage, indicating loss of green colour. Better physical and physiological properties were observed in spinach packaged in OPP bags.