Reprocessing effect on the quality of domestically cooked (boiled/stir-fried) frozen vegetables

This was a study of the effect on quality parameters of reprocessing (blanching at 97 °C for increasing times+freezing) prior to domestic cooking (boiling or stir-frying) of frozen green peas (cv. Mastim) and beans (cvs. Paloma and Moncayo). The results were compared with those of frozen control samples directly boiled or stir-fried. Kramer shear was the most suitable mechanical test for evaluating the effect of reprocessing on mechanical behaviour in both boiled and stir-fried frozen vegetables. Reprocessing significantly affected the mechanical behaviour of both green bean varieties with both cooking methods. Reprocessed products were softer than those supplied by the industry, and softening was significantly greater the longer the blanching time. The colour was more uniform and homogeneous in boiled than in stir-fried reprocessed vegetables; colour parameters showed that reprocessing affected the colour of stir-fried samples more significantly than that of boiled samples. In all the studied vegetables, less chlorophyll and more ascorbic acid were retained when samples were stir-fried than when they were boiled, although chlorophyll and ascorbic acid decreased with increasing reprocessing time in both cooking methods. In the two frozen green bean varieties in particular, SEM microphotographs confirmed the results of mechanical tests, indicating that with both cooking methods, the mechanical parameters were lower in the reprocessed samples than in the controls. The shortest reprocessing procedure (blanching at 97 °C for 2, 3 min+freezing), as a compromise among quality parameters, could shorten the time required for domestic stir-frying of frozen green peas and boiling or stir-frying of frozen green beans.     

Copper bioavailability in rats fed unused palm olein and palm olein used in frying

The influence of the consumption of unused and used (in repeated potato frying operations) palm olein on copper bioavailability was investigated. Three diets containing respectively 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying operation without turnover (PF), which nearly reached the limit of 25% polar compounds allowed by law, were given to rats for 28 days. No differences were found in food intake and body weight. The liver mass index was higher in PF than in P rats. No significant differences were observed in copper apparent absorption or in liver, skin, erythrocyte, serum and carcass copper contents. Therefore consumption of palm olein, whether unused or used in frying, does not alter copper bioavailability in growing rats. Copyright © 2004 Society of Chemical Industry     

Modeling the influence of water activity and ascospore age on the growth of Neosartorya fischeri in pineapple juice

The ascospores of resistant fungi, Neosartorya fischeri, can survive commercial pasteurization, diminishing the shelf life of these products. The time that the ascospores remain in the environment and the effect that they can cause on mold growth are still unknown. This study is aimed to evaluate the influence of water activity (a_w) from 0.90 to 0.99 and the ascospore age (I) from 30 to 90 days of vitro incubation on the growth of N. fischeri in pineapple juice by mathematical modeling. The growth parameters on pineapple juice: adaptation phase (λ), maximum specific growth rate (μ_max) and maximum diameter reached by the colony (A) were obtained by fitting Modified Gompertz and Logistic models to the experimental data. Both models were able to describe microbial growth in pineapple juice, but the Modified Gompertz model presented a slightly superior performance based on statistical indices (correlation coefficients (R²), mean square error (MSE), Bias Factor and Accuracy Factor). The minimum values of λ and A, calculated by the Modified Gompertz model, were 64.7 h and 6.3 mm, while the maximum values were 178.2 h and 20.8 mm, respectively. The result showed that ascospore age did not influence the growth but a_w was statistically significant to the growth parameters λ and A.     

Integrated approach for interpreting browning rate dependence with relative humidity in dehydrated fruits

Maillard reaction is relevant to define dehydrated food stability. The objective of this work was to evaluate the browning development in freeze-dried fruits as a function of relative humidity (RH) in relation to the physical properties of fruit materials. Intact tissue discs of melon and pear were freeze-dried and equilibrated in a broad RH range. The changes in reflectance were analyzed using a computer vision system, which was appropriate to determine the appearance changes during storage of dehydrated fruits. Time resolved ¹H NMR, thermal transitions, structural collapse and water sorption isotherms were evaluated. The browning rate versus RH curve presented a bell shape which could be related to the information provided by the determinations of the physical properties. The results allowed the integration of water sorption information, ¹H NMR relaxation times, T-T_g, and structural collapse to interpret the browning rate versus RH behavior of fruit systems.     

Contribution of olive seed to the phenolic profile and related quality parameters of virgin olive oil

BACKGROUND: Conflicting results have been reported about the effect of fruit de‐stoning on the virgin olive oil (VOO) phenolic profile. The aim of the present study was to determine whether olive seed plays any role in the synthesis of this oil phenolic fraction. RESULTS: Increases of around 25% of total phenolic compounds were observed in oils obtained from de‐stoned olive fruits in three main Spanish cultivars. To investigate the involvement of olive seed in determining the phenolic profile of VOO, whole intact olive fruits were added with up to 400% olive stones. Excellent regression coefficients were found in general for the decrease of total phenolic compounds and, particularly, of o‐diphenolics in the resulting oils. On the other hand, it was found that olive seed contains a high level of peroxidase (POX) activity (72.4 U g^?1 FW), accounting for more than 98% of total POX activity in the whole fruit. This activity is able to modify VOO phenolics in vitro, similar to the effect of adding stones during VOO extraction. CONCLUSION: Olive seed plays an important role in determining VOO phenolic profile during the process to obtain an oil that seems to be associated with a high level of POX activity. Copyright © 2007 Society of Chemical Industry     

Quality, bioactive compounds, and antioxidant activity of new flat-type peach and nectarine cultivars: a comparative study

In this work, some organoleptic and nutritive parameters related to fruit quality (color, firmness, total soluble solids, and total acidity), the content of bioactive compounds (total phenolics and total carotenoids) as well as the total antioxidant activity (TAA) due to hydrophilic (H-TAA) and lipophilic (L-TAA) compounds have been determined in both skin and flesh of 10 flat peach and nectarine genotypes (7 peaches and 3 nectarines). Results showed that genotype plays an important role in determining the organoleptic and nutritive quality, as well as the concentration of bioactive compounds and the related TAA, since these parameters differed largely among cultivars. Overall data suggest that for commercial purposes and consumer's acceptability (based on color, firmness, acidity, and bioactive compounds), the flat nectarine "ASF-06-83" and the flat peaches "Sweet Cap" and "ASF-06-91" could be considered as the best cultivars. Additionally, it is suggested that the content of bioactive compounds should be included as an important factor in future breeding program to obtain new genotypes with enhanced bioactive compounds. PRACTICAL APPLICATION: Genotype of flat peaches and nectarines plays an important role in determining the organoleptic and nutritive quality, as well as the content of bioactive compounds. Given the differences on bioactive compounds concentration and antioxidant activity among peaches and nectarines flat cultivars, these parameters should be included as an important factor in future breeding program to obtain new genotypes with enhanced bioactive compounds.     

Infrared characterisation,monosaccharide profile and antioxidant activity of chemical fractionated polysaccharides from the edible seaweed sugar Kombu (Saccharina latissima)

The central goal of this study was to evaluate the antioxidant activities related to the nondigestible polysaccharides present in the brown alga Saccharina latissima. For this purpose, a chemical fractionation procedure based on the different solubilities of polysaccharides was achieved. FTIR spectra of freeze‐dried polysaccharide fractions were recorded to confirm the presence of sulphate. A significant correlation was found between sulphate content in the different fractions tested and antioxidant activities, either by reduction power (RP) or radical scavenging assay (RSA) (RP, P < 0.0001; and RSA‐ABTS P < 0.0001). The acidic fraction, with the highest sulphate content among soluble fractions and presumably containing sulphated fucans, showed the highest antioxidant activity either for reducing power or scavenging assays. Consistently, it is reported that the acid‐soluble fraction containing fucans shows higher antioxidant activity than those containing alginate and laminaran in Turbinaria conoides seaweed.     

Modeling of the chemical-looping combustion of methane using a Cu-based oxygen-carrier

A mathematical model for a bubbling fluidized bed has been developed to simulate the performance of the fuel-reactor in chemical-looping combustion (CLC) systems. This model considers both the fluid dynamic of the fluidized bed and freeboard and the kinetics of reduction of the oxygen-carrier, here CuO impregnated on alumina. The main outputs of the model are the conversion of the carrier and the gas composition at the reactor exit, the axial profiles of gas concentrations and the fluid dynamical structure of the reactor. The model was validated using measurements when burning CH₄ in a 10 kW_th prototype using a Cu-based oxygen-carrier. The influence of the circulation rate of solids, the load of fuel gas, the reactor temperature and size of the oxygen-carrier particles were analyzed. Combustion efficiencies predicted by the model showed a good agreement with measurements. Having validated the model, the implications for designing and optimizing a fuel-reactor were as follows. The inventory of solids for a high conversion of the fuel was sensitive to the reactor’s temperature, the solids’ circulation rate and the extent to which the solids entering to the reactor had been regenerated. The optimal ratio of oxygen-carrier to fuel was found to be 1.7–4 for the Cu-based oxygen-carrier used here. In this range, the inventory of solids to obtain a combustion efficiency of 99.9% at 1073 K was less than 130 kg/MW_th. In addition, the model’s results were very sensitive to the resistance to gas diffusing between the emulsion and bubble phases in the bed, to the decay of solids’ concentration in the freeboard and to the efficiency contact between gas and solids in the freeboard. Thus, a simplified model, ignoring any restriction to gas and solids contacting each other, will under-predict the inventory of solids by a factor of 2–10.     

Decolorized porcine globin gels produced by heat-induced gelation. Physical and rheological characterization

Decolorized porcine globin gels have been developed due to their many potential applications in the area of food technology. In this study they are presented as possible foodstuffs, thickeners or films to cover food products. A precipitating agent and a bleaching agent were used to obtain decolorized globin from hemoglobin. To characterize these films, it was necessary to study their rheology and their resistance to external temperature. Rheological measurements were taken to characterize the gels in combination with the analysis of their microstructure, particle size, thermal behavior and water holding capacity. Results showed that G′ (the elastic modulus) was higher than G″ (the viscous modulus) and that the gelation point decreased with increasing pH for all the samples. Decolorized globin gels behaved dilatantly and presented a viscoelastic response, which was very suitable to form films to cover foodstuffs. DSC analysis corroborated the results obtained from rheological determinations and size distribution measurements presented unimodal curves for all the films. At basic pH, the globin gels were composed of tiny protein aggregates, forming a compact network without spaces between the particles in gels produced at pH 2. Gels produced at neutral pH were composed of a few large protein aggregates embedded in a matrix of smaller diameter particles. Furthermore, these gels presented an elevated moisture content and a very high WHC, which are desirable properties due to their potential applications.     

Colour evaluation of a phycobiliprotein‐rich extract obtained from Nostoc PCC9205 in acidic solutions and yogurt

BACKGROUND: Phycobiliproteins are coloured proteins produced by cyanobacteria, which have several applications because of their colour properties. However, there is no available information about the colour stability of phycobiliproteins from Nostoc sp. in food systems. The aim of this work was to study the colour stability of a purple‐coloured phycobiliprotein‐rich extract from the cyanobacterium Nostoc PCC9205 in acidic solutions and yogurt. RESULTS: Variations of pH for Nostoc PCC9205 extract have shown stability for the L* (lightness) and a* (redness) indexes in the range 1.0–7.0. The b* index (blueness), however, increased at pH values below 4.0, indicating loss of the blue colour. The Nostoc PCC9205 extract was used as colorant in yogurt (pH 4.17) stored for 60 days. Instrumental colour analysis showed no changes for the L* and a* indexes during storage, whereas the b* index changed after 20 days of storage. A multiple comparison test showed colour instability after 20 days of storage. A hedonic scale test performed on the 60th day of storage showed acceptability of the product. CONCLUSIONS: The red component of the phycobiliprotein‐rich extract from Nostoc PCC9205 presented an improved stability in acidic media and yogurt compared with the blue component of this extract. Copyright © 2011 Society of Chemical Industry