Volatile profiles of healthy and aflatoxin contaminated pistachios.

The volatile profile of four different groups of dried pistachios namely: H: healthy, NC: naturally contaminated with aflatoxin, AC: artificially contaminated with aflatoxigenic strains of the fungi Aspergillus flavus and ANT: artificially contaminated with non-toxigenic strains of the fungi A. flavus, was determined. The volatiles were isolated by the HS-SPME method and determined by GC-FID and GC-MS, whereas aflatoxin by HPLC. Seventy two volatile compounds were identified almost equally distributed among the above four studied groups. The predominant chemical compounds were monoterpenes, alcohols, ketones, aldehydes, esters and hydrocarbons. The monoterpenes, mainly determined as α-pinene and α-terpinolene were detected in all samples. Even though the general volatile profile was similar among groups, some differences were detected between healthy and contaminated groups of samples. When some key volatiles such as eight-carbon and seven-carbon alcohols and aldehydes were used along with the species-specific sesquiterpenes and the other terpenes detected, a correct classification was obtained in H, NC, AC and ANT groups, as was demonstrated by cluster and discriminant analyses. This evidence provides a potential tool for distinguishing contaminated samples on the basis of characteristic volatile patterns.

Analysis of thermal processing of table olives using computational fluid dynamics.

In the present work, the thermal processing of table olives in brine in a stationary metal can was studied through computational fluid dynamics (CFD). The flow patterns of the brine and the temperature evolution in the olives and brine during the heating and the cooling cycles of the process were calculated using the CFD code. Experimental temperature measurements at 3 points (2 inside model olive particles and 1 at a point in the brine) in a can (with dimensions of 75 mm × 105 mm) filled with 48 olives in 4% (w/v) brine, initially held at 20 °C, heated in water at 100 °C for 10 min, and thereafter cooled in water at about 20 °C for 10 min, validated model predictions. The distribution of temperature and F-values and the location of the slowest heating zone and the critical point within the product, as far as microbial destruction is concerned, were assessed for several cases. For the cases studied, the critical point was located at the interior of the olives at the 2nd, or between the 1st and the 2nd olive row from the bottom of the container, the exact location being affected by olive size, olive arrangement, and geometry of the container.

Ultrasonic energy input influence οn the production of sub-micron o/w emulsions containing whey protein and common stabilizers.

Ultrasonication may be a cost-effective emulsion formation technique, but its impact on emulsion final structure and droplet size needs to be further investigated. Olive oil emulsions (20wt%) were formulated (pH∼7) using whey protein (3wt%), three kinds of hydrocolloids (0.1-0.5wt%) and two different emulsification energy inputs (single- and two-stage, methods A and B, respectively). Formula and energy input effects on emulsion performance are discussed. Emulsions stability was evaluated over a 10-day storage period at 5°C recording the turbidity profiles of the emulsions. Optical micrographs, droplet size and viscosity values were also obtained. A differential scanning calorimetric (DSC) multiple cool-heat cyclic method (40 to -40°C) was performed to examine stability via crystallization phenomena of the dispersed phase. Ultrasonication energy input duplication from 11kJ to 25kJ (method B) resulted in stable emulsions production (reduction of back scattering values, dBS∼1% after 10days of storage) at 0.5wt% concentration of any of the stabilizers used. At lower gum amount samples became unstable due to depletion flocculation phenomena, regardless of emulsification energy input used. High energy input during ultrasonic emulsification also resulted in sub-micron oil-droplets emulsions (D(50)=0.615µm compared to D(50)=1.3µm using method A) with narrower particle size distribution and in viscosity reduction. DSC experiments revealed no presence of bulk oil formation, suggesting stability for XG 0.5wt% emulsions prepared by both methods. Reduced enthalpy values found when method B was applied suggesting structural modifications produced by extensive ultrasonication. Change of ultrasonication conditions results in significant changes of oil droplet size and stability of the produced emulsions.

Numerical simulation of variable water diffusivity during drying of peeled and unpeeled tomato.

UNLABELLED: A mathematical model was formulated for the estimation, in conjunction with experimental measurements, of water diffusivity parameters during convective drying of peeled and unpeeled tomatoes. Fick's 2nd law of diffusion was solved numerically for a sphere, by explicit finite differences, considering shrinkage effect, variable diffusivity, and constant boundary conditions. Experiments were performed in a laboratory tunnel dryer. The equivalent radius of tomato decreased by 50% until the end of the process, which explains the necessity for shrinkage inclusion in the mass transfer model. The mean estimated diffusivities varied between 2.03 × 10(-10) and 15.1 × 10(-10) m(2)/s for peeled tomatoes and 0.59 × 10(-10) and 15.2 × 10(-10) m(2)/s for unpeeled tomatoes. The estimated water diffusivities and their variation with the tested drying temperatures (45, 55, and 65 °C) provide an insight of peeling effect during air-drying. Peeling was beneficial since yielded greater drying rates and shortened significantly drying times, thus saving energy during drying. In all the studied cases, good agreement was found between experimental and predicted drying curves (≥ 0.99, mean relative deviation [MRD]≤ 0.12, and root mean square error [RMSE]≤ 0.03). In overall, the proposed methodology provides a reliable and easy estimation of temperature and moisture-dependent mass transfer properties and drying simulation of shrinkable food products such as tomato. PRACTICAL APPLICATION: Water diffusivity is a food property, difficult in estimation but essential in drying processing optimization. This property was estimated as a function of moisture content and drying temperature employing a numerical simulation procedure. The peeling effect was also studied and found beneficial for lower temperature drying (<55 °C) which is useful in the energy optimization of the drying process as well as the retention of the end-product quality.