Freeze‐drying concentration of Rangpur lime juice

The use of freeze‐drying for concentrating lime Rangpur juice was investigated. This procedure allowed obtaining concentrated Rangpur lime juices between 23 and 51.3 °Brix, without affecting their organoleptic and nutritional characteristics. The efficiency of the procedure was inversely related to the film thickness of the matrix to be lyophilised. The sublimation speed per unit area diminished with the reduction in the residual moisture content of the juice. The mathematical model that fitted to the concentration procedure allowed to predict the time required for concentrating Rangpur lime by freeze‐drying starting from samples of different thickness. When compared with other citric juices evaluated, the Rangpur lime juice was the most suitable for freeze‐drying concentration. The results could be used to devise optimal industrial freeze‐drying cycles for processing Rangpur lime juices at different concentrations.     

Effect of different treatments on the microstructure and functional and pasting properties of pigeon pea (Cajanus cajan L.), dolichos bean (Dolichos lablab L.) and jack bean (Canavalia ensiformis) flours from the north‐east Argentina

The effect of germination (G; 5 days), soaking‐cooking (SC; 6 h–20 min, 6 h–40 min, 6 h–60 min) and microwave (M; 50%, 70%, 100%) treatments on pigeon pea (PP), dolichos bean (DB) and jack bean (JB) seeds was studied. Microstructure of seeds and functional (protein solubility, water‐holding capacity, oil‐holding capacity, emulsion stability) and pasting properties of flours were determined. Germination and microwave treatments modified the protein matrix of cotyledon cells preserving the shape of the starch granule, whereas the SC treatment (6 h–60 min) affected both. The soaking‐cooking is the most influential treatment on the functional properties of PP, DB and JB flours, as increased water absorption capacity (73–96%), decreased protein solubility (>80%) and the tendency to retrogradation of amylose (69–85%) also improved emulsion stability.     

Structural Characterization of Amaranth Protein Gels

ABSTRACT: Gelation capacity of a native amaranth protein isolate was studied. Structural properties of gels prepared at different protein concentration and heating conditions were analyzed. Proteins present in amaranth isolates obtained by water extraction at pH 9.0 and subsequent isoelectric precipitation are able to form gels of yellowish appearance. Gel color intensity increased while luminosity decreased with increasing protein concentrations. High protein concentration allowed the formation of matrices with high water-holding capacity. In addition, increasing the heating temperature resulted in gels of high luminosity and low water-holding capacity. The increase of protein concentration (10% to 20% w/v) as well as the increase of heating temperature (70°C to 95°C) and heating time (10 to 30 min) resulted in the formation of a more ordered matrix with smaller pores, mainly stabilized by disulfide bonds and, at a lower extent, by noncovalent interactions (specially hydrogen bonds and hydrophobic interactions). Both amaranth globulin (11S globulin and P globulin) participated in gel structure via high-molecular-weight aggregates (>100 kD). Gel structure was stabilized via noncovalent bonds by monomer species of 42 kD and those of molecular mass lower than 20 kD localized in the interstitial spaces of gel matrix.     

Effect of thermal treatment on the proteins of amaranth isolates

The effect of thermal treatment of proteins from Amaranthus hypochondriacus was studied. Two protein isolates were obtained from the defatted flour by water extraction at a pH of 9 (A9 isolate) and 11 (A11 isolate), followed by isoelectric precipitation at a pH of 5. Effect of thermal treatment (70 and 90 °C, during 3, 5, 10, 15 and 30 min) on A9 and A11 dispersions were analyzed by differential scanning calorimetry (DSC), polyacrylamide gel electrophoresis, UV spectrophotometry, superficial hydrophobicity and solubility in water. Thermal treatment induced the aggregate formation of high molecular mass stabilized by disulfide and non‐covalent bond. Thermal treatment at 70 °C produced a 30% denaturation in both, while at 90 °C A9 was more denatured than A11 (75% and 55% of denaturation, respectively). An increase in thermal stability was also detected by DSC in A9 treated at 90 °C. The denaturation process was accompanied at short heating times by an increase in UV absorbance and changes in superficial hydrophobicity. A decrease in water solubility (35–50%, depending on time–temperature conditions) was also observed for the A9 isolates. The results suggest that the A9 isolates, enriched in a globulin protein fraction, are more sensitive to thermal treatment than isolates A11 enriched in glutelin protein fraction. The changes shown by both isolates, indeed, could affect their functional properties and could definitely limit their use in food products. Copyright © 2007 Society of Chemical Industry     

Gelation,thermal and pasting properties of pigeon pea (Cajanus cajan L.), dolichos bean (Dolichos lablab L.) and jack bean (Canavalia ensiformis) flours

This study evaluated the rheological, thermal and pasting properties of pigeon pea (PP), dolichos bean (DB) and jack bean (JB) legume flours and gels. Starch and protein contents were also measured and its molecular weight distribution was determined by electrophoresis. PP and DB showed the highest viscosities while JB had the highest pasting temperature. The minimum flour concentrations for gel formation were estimated at 6–8% for DB and PP and 10% for JB. Above these concentrations all flour suspensions heated to 95 °C led to gels with a solid-like behavior. Differential scanning calorimetry showed two endothermic peaks in all flours at 80–89 °C and 96–100 °C. Avrami model was successfully fitted to the hardening kinetics of PP and DB gels stored at 4 °C. The half-life times were 22 and 6 h for PP and DB respectively. PP and DB flours were able to form self-supporting gels and could be applied in the formulation of gel-like foods.     

Functional properties and microstructure of cowpea cultivated in north-east Argentina

The goal of this work was to analyze the effect of different treatments on functional properties (Color parameters, water holding capacity, oil holding capacity, water imbibition capacity, protein solubility and apparent viscosity) and microstructure of three cowpea varieties. Proteins present in flours obtained from heat-treated seeds exhibited a significant increase in water and oil absorption values, water imbibition capacity, and apparent viscosity, whereas solubility decreased. Color determinations on flours showed a reduction in L* and H*, and an increment in C* with treatment intensity. Structural changes in seeds would explain the variations in the functionality of flours. This study shows that cooking and autoclaving affect significantly the functional properties of flours, while soaking had a lower impact. The knowledge about these changes will be very useful for developing and obtaining new preparations based on cowpea flour.     

Starch enzymatic hydrolysis,structural, thermal and rheological properties of pigeon pea (Cajanus cajan) and dolichos bean (Dolichos lab-lab) legume starches

Cajanus Cajans and Dolichos lab-lab legume starches from Argentine cultivars were investigated under a technological and nutritional point of view. Their physico-chemical, structural, thermal and the rheological properties of their gels were evaluated. Rice (RS) and potato (PS) starches were included as references. In vitro digestibility from Englyst method was also evaluated. Legume starches had the highest amylose content and the most stable chemical structure. Their rapidly digestible starch and starch digestibility rate index were very low, similar to PS, and fivefold lower than RS. They had a much higher slowly digestible starch content than PS. Legume starches showed the highest gel stability versus heating and stirring and an intermedium pasting temperature between RS and PS. They formed viscoelastic gels at 6% concentration with stronger elastic-like behaviour and higher yield stress than references. Our results indicate these legumes represent an efficient starch source to provide tailor-made properties to food/industrial applications.     

Indocyanine green angiography in the juvenile haemorrhagic choroidopathy

The effects of postmortem time, age and tissue storage time on synaptic density were investigated in the prefrontal cortex of human brains. Thirty normal cases and 10 patients with a variety of neurologic diseases were studied, using quantitative immunohistochemistry with a monoclonal antibody to synaptophysin. Synaptophysin immunoreactivity was stable during the first 36 h after death, showing no significant change at 1, 8, 12, 24 and 36 h postmortem in normals. However, at 48 and 72 h postmortem, synaptophysin immunoreactivity decreased significantly. A similar pattern of postmortem changes was found in the disease group. In 14 normal cases with a wide range of ages, a significant reduction in synaptic density with age was observed while the time of tissue storage as paraffin-embedded blocks had no significant effect on the synaptophysin immunoreactivity. These results support the validity of using synaptophysin immunohistochemistry as a measure of synaptic density in human brain autopsied within 36 h of death and stored as paraffin-embedded blocks for a long time.     

A DIFFUSIONAL MODEL FOR DRYING WITH VOLUME CHANGE

A diffusional model to study the drying process when volume change is significant is proposed. The effect of the foodstuff shape is taken into account. An empirical relation between moisture content and volume is presented. The resulting differential equations are numerically solved using a moving boundary finite differences technique. A good agreement between numerical results and experimental data is obtained.