Effects of high O2 levels on post-harvest quality and shelf life of table grapes during long-term storage

Freshly harvested Kyoho table grapes (Vitis vinifera × V. labrusca) were stored in controlled atmospheric chambers, either in air, 80% O₂, or 40% O₂ + 30% CO_2, for up to 60 days at 0 °C in 95% relative humidity followed by 5 days in air at 20 °C. Physical and chemical properties were recorded initially and at 15-day intervals during storage. Storage in 80% O₂ or 40% O₂ + 30% CO₂ improved berry hardness, springiness, chewiness, flavors and membrane integrity over control stored in air. In addition, these high O₂ storage conditions significantly reduced fruit decay, berry drop, rachis browning and weight loss, delayed the decrease of soluble solids, titratable acidity and ascorbic acid of table grapes, compared with storage in air. Treatment in 80% O₂ resulted in a significantly firmer berry, better texture, berry adherence strength, and sensory scores than those treated with 40% O₂ + 30% CO₂, but did not significantly affect cohesiveness, springiness, aroma and membrane integrity. Data obtained in this study suggest that high oxygen treatment improve the quality of table grapes and extend its shelf life.     

Provitamin A carotenoids in table olives according to processing styles, cultivars, and commercial presentations

The concentration of provitamin A carotenoids in table olives was determined. Only -carotene was found in all commercial presentations. -carotene was also present in final products containing carrots. Concentrations of -carotene, referring to 100 g edible portion, ranged from an average of 197 to 1,387 g in green olives, from 37 to 726 g in directly brined olives and from 39 to 333 in ripe (darkened by oxidation) olives. Thus, some commercial presentations of table olives can be considered reasonable sources of provitamin A. Several groups were formed within elaboration styles and cultivars, according to commercial presentations. Their averages and other statistical estimations are also given. These results may be used by the industry as a source of information for nutritional labelling or by nutritionists to estimate provitamin A intakes in diets that include table olives.     

Anti/pro-oxidative properties of selected standard chemicals and tea extracts investigated by DNA-based electrochemical biosensor

A DNA-modified screen-printed carbon electrode and the [Co(phen)₃]³⁺ complex as an electrochemical DNA marker were used for the evaluation of anti/pro-oxidative properties of -tocopherol, -carotene, quercetin, kaempferol and myricetin, as well as various tea extracts. Reactive oxygen species were generated using a model cleavage mixture composed of 5×10^–7 M [Cu(phen)₂]²⁺ as the catalyst, 1×10^–3 M ascorbic acid as the chemical reductant and air oxygen as the natural oxidant. The antioxidative activity of standard chemicals increases with their concentration, reaching a maximum where prooxidative behaviour becomes of importance. Antioxidative effects of tea exctracts varied with the temperature of their preparation. Similar results were obtained by the 2, 2-diphenyl-1-picrylhydrazyl free radical method.     

Effect of α- and δ-tocopherol on the oxidative stability of a mixed hydrogenated fat under frying conditions

Information on the antioxidative potential of -tocopherol is scanty, in particular for frying conditions. This study was aimed at assessing the antioxidative effects and degradation of - and -tocopherol between 0.01 and 0.1% on the oxidation of a commercial frying fat at 160 °C. Oxidation experiments were performed by assessing every 15 or 30 min the peroxide value and conjugated dienes as primary oxidation products, p-anisidine reactive products and hexanal as secondary oxidation products, as well as the stability of tocopherols. The fatty acid composition was determined after 6 h. The fat samples enriched with -tocopherol were considerably less resistant to oxidation compared to those with -tocopherol. Both primary and secondary oxidation parameters increased their speed of formation with -tocopherol but not with -tocopherol. The latter observation is confirmed for the total amount of oxidation and also for the first stage, showing a lag phase only for -tocopherol. These antioxidative effects can be due to the higher stability of -tocopherol compared to -tocopherol, which is oxidized faster into tocopheryl radicals, which can participate in side reactions that result in an acceleration of the oxidation speed. Neither -tocopherol nor -tocopherol influenced the fatty acid pattern. The investigation showed that during mild frying conditions the tocopherol homologues displayed various antioxidant activities. The less effective homologue, -tocopherol, underwent disintegration more quickly than -tocopherol.     

Modelling of drying and rehydration of carrots using Peleg’s model

The drying and rehydration process of conventionally and organically cultivated carrots was studied and the resulting data were fitted to the Pelegs model. Carrots were fluid-bed and halogen dried and after that soaked in water at room temperature. The Pelegs model gave a good prediction of water removal and water uptake in all experiments (R>0,994). During the drying process the Pelegs rate constant (K₁) was affected by temperature. K₁ values decreased with the increase of the drying temperature. This relation was linear for fluid-bed drying and exponential for halogen drying, which implied a higher impact of the drying temperature on the dehydration kinetics during halogen drying. The lower K₁ values for fluid-bed drying suggested higher initial drying rates in comparison with halogen drying at all drying temperatures. The temperature dependence of 1/K₁ followed an Arrhenius-type relationship. Both Pelegs rehydration constants (K₁ and K₂) increased with the increase of the drying temperature. This implied regular decrease of initial rehydration rate and water uptake with the increase of the drying temperature.     

Structural changes in the wheat dough and bread with the addition of alpha-amylases

The influence of fungal and bacterial -amylases on the texture and microstructure of dough and bread was investigated. Loaf specific volume, crumb porosity and texture properties were accepted as bread structure and texture characteristics. The microstructure analysis of dough and bread using light and scanning microscopy methods was performed.The changes in loaf specific volume, crumb porosity and texture properties showed different anti-staling activity of the enzymes used. The simultaneous action of enzyme addition and the fermentation process evoked significant changes in the microstructure of dough. The character of these changes depended on the kind of enzyme used. A substantial effect of both amylases on starch behaviour during bread baking and staling was also observed.     

Degradation of β-carotene with the effects of light and sulfur dioxide may be responsible for the formation of white spot in dried apricots

Light and sulfur-induced degradation of -carotene flushing out of cells with the effect of salivary pectolytic enzymes of bugs belonging to the family of Heteroptera have been shown to be responsible for the formation of white spot in dried apricots affecting the product quality adversely. The effects of light and sulfur dioxide on the degradation of -carotene were studied in the model systems. Light-induced degradation rate of -carotene was higher at shorter wavelengths. Sulfur-induced degradation reaction of -carotene followed a second-order rate law with a rate constant of 1687 M^–1 min^–1.At shorter wavelengths, light energy was mainly responsible for the degradation of -carotene while sulfur dioxide was more effective on -carotene degradation at higher wavelengths.     

The antigenic response of<Emphasis Type="Italic"> β</Emphasis>-lactoglobulin is modulated by thermally induced aggregation

The antigenic response of thermally denatured and aggregated -lactoglobulin was determined by an indirect competitive enzyme-linked immunosorbent assay using polyclonal antibodies from the egg yolk of chicken immunized with heat-denatured -lactoglobulin as a measure for the potential antigenicity/allergenicity. The heat denaturation and the aggregation of heated whey protein isolate solutions were followed by reversed-phase high-performance liquid chromatography and photon correlation spectroscopy. Thermally modified whey proteins showed a remarkable increase of antigenicity when heated to 90 °C, possibly as a consequence of the exposure or formerly hidden epitopes. Above 90 °C, the antigenic response decreased owing to the loss of conformational epitopes and masking of sequential epitopes in the course of aggregation to particles. When large and compact particles were formed, the antigenicity was reduced remarkably. Depending the heating conditions applied, the structure and the size of whey protein particles and thus the potential allergenicity may be modulated in a wide range.