Yvan Gariepy

Radio-frequency treatment for ready-to-eat fresh carrots

This study was conducted to determine the potential of an RF thermal treatment to improve and extend the storability of vacuum-packaged carrot sticks stored at 5–6C. The results have shown that it is possible to treat carrot sticks to 60C in less than 2 min in a parallel plate RF applicator, and thus reduce the initial total microbial load. The RF treatments were compared to chlorinated water dipping, and hot water dipping. All storage trials of 7–14 days at 6C, have indicated that the reduction of the initial microbial load alone does not maintain the quality of carrot sticks for 14 days, since at this point the microbial loads in all cases studied were higher than 310 6 . Nonetheless, the quality of the RF treated samples was greater than for either the control samples (chlorinated water) or hot-water-treated carrot samples. The RF-treatments maintained colour, taste and the vacuum of the packages, which was not the case for control and hot-water-treated carrots. # 2001 Elsevier Science Ltd. All rights reserved.

Microwave-Assisted Extraction of Phenolic Antioxidants from Potato Peels

A response surface method was used to optimize the microwave-assisted extraction parameters such as extraction time (t) (min), solvent (methanol) concentration (S) (v/v) and microwave power level (MP) for extraction of antioxidants from potato peels. Max. total phenolics content of 3.94 mg g−1 dry weight (dw) was obtained at S of 67.33%, t of 15 min and a MP of 14.67%. For ascorbic acid (1.44 mg g−1 dw), caffeic acid (1.33 mg g−1 dw), ferulic acid (0.50 mg g−1 dw) max contents were obtained at S of 100%, t of 15 min, and MP of 10%, while the max chlorogenic acid content (1.35 mg g−1 dw) was obtained at S of 100%, t of 5 min, and MP of 10%. The radical scavenging activity of the extract was evaluated by using the DPPH assay and optimum antioxidant activity was obtained at S of 100%, t of 5 min, and MP of 10%.

Respiration rate model and modified atmosphere packaging of fresh cauliflower

In the first part, the respiration rate of fresh cauliflower was measured in sealed containers at different temperatures. An enzymatic reaction was then used to model the respiration activity as a function of gas concentrations and temperature. An Arrhenius relationship was used in the model to account for the effects of temperature. Predictions derived from the model were in good agreement with the experimental data. In the second part, the ability of air-diffusion channels to maintain the desired modified atmosphere (MA) compositions (O2: 2.5–3.5%; CO2: 0%) in storage chambers was assessed. Fresh cauliflowers were stored at 2.5 °C for 21 days in laboratory chambers equipped with channels (D = 2e − 3 m) of 0, 0.3, 0.6 and 1 m in length, and for 33 days in chambers equipped with 0, 0.05, 0.15 and 0.25 m diffusion channels. The results have indicated that diffusion channels can be used to maintain MA conditions and that they could accommodate for some fluctuations in the air temperature.

Drying of Pineapple by Microwave-Vacuum with Osmotic Pretreatment

Drying of pineapple by microwave-vacuum (MW-V) with osmotic dehydration (OD) as a pretreatment was studied. Central composite design was used for the independent variables sugar concentration (40, 50, and 60 °Brix), immersion time (0, 3, and 6 hours) and product temperature in the microwave cavity (50, 60, and 70°C). The dependent variables were moisture content, shrinkage, rehydration coefficient, visual quality, color, and texture. The osmotic dehydration pretreatment was also evaluated with respect to weight reduction (WR), water loss (WL), and solid gain (SG). Maximizing moisture loss was the main objective of OD pretreatment for various combinations of sugar concentration and immersion time. OD preserved the color of the samples while drying. In the complete process composed by OD and MW-V, only the influence of temperature of the product on the drying rate was statistically significant (P < 0.05), whereas OD reduced shrinkage and improved rehydration capacity. The best visual quality was obtained when the independent variables were diminished. OD also significantly (P < 0.05) affected the texture of product producing softer, less surface-hardened product compared to untreated ones.

A Comparative Study on the Effect of Chemical, Microwave, and Pulsed Electric Pretreatments on Convective Drying and Quality of Raisins

In order to discourage the use of chemicals in raisin processing, the effect of microwave and pulsed electric field (PEF) pretreatments on the drying rate and other quality parameters like color, total soluble solids, bulk density, appearance, and market quality were compared with that of chemically pretreated raisins dried at 65°C. The untreated and pretreated samples had a statistically significant difference in drying rate (P < 0.05). The drying rate of chemically pretreated raisins was the highest when compared to others. The results showed that the PEF and microwave-treated samples had a significantly high Total Soluble Solids (TSS), along with good appearance and market quality.

Drying Kinetics of Tomato Slices in Vacuum Assisted Solar and Open Sun Drying Methods

A lab model vacuum-assisted solar dryer was developed to study the drying kinetics of tomato slices (4, 6, and 8 mm thicknesses) compared with open sun drying under the weather conditions of Montreal, Canada. The drying study showed that the time taken for drying of tomato slices of 4, 6, and 8 mm thicknesses from the initial moisture content of 94.0% to the final moisture content of around 11.5 ± 0.5% (w.b.) was 360, 480, and 600 min in vacuum-assisted solar dryer and 450, 600, and 750 min in open sun drying, respectively. During drying, it was observed that the temperature inside the vacuum chamber was increased to 48°C when the maximum ambient temperature was only 30°C. The quality of tomato slices dried under vacuum-assisted solar dryer was of superior quality in terms of color retention and rehydration ratio. The drying kinetics using thin-layer drying models and the influence of weather parameters such as ambient air temperature, relative humidity, solar insolation, and wind velocity on drying of tomato slices were evaluated.

Effects of Microwave-Assisted Hot Air Drying and Conventional Hot Air Drying on the Drying Kinetics, Color, Rehydration, and Volatiles of Moringa oleifera

In this study, the fresh Moringa oleifera pods (Drumsticks) were dehydrated by microwave-assisted hot air drying (MAHD) and conventional hot air drying methods. The samples were dried at three different temperatures, viz. 50, 60, and 70°C, with and without the application of microwaves. Microwave power density of 1 W/g was used for the MAHD. The final moisture content was targeted as 13% wb. The drying curves and drying rate curves were plotted and compared. The kinetics of drying obtained experimentally were correlated with the Page equation. The constants K and N of the Page equation were determined to predict the drying kinetics for varying conditions. The quality attributes, namely, color, rehydration ratio, and volatile compounds, were analyzed and compared with that of the fresh Moringa pods. The volatile compounds were analyzed using z-Nose (an electronic nose; Electronic Sensor Technology, Newbury Park, CA) and bioactive molecules were analyzed using gas chromatography–mass spectrometry. The results showed that the MAHD method had significantly (P < 0.05) reduced the loss of volatiles during drying. Also, MAHD preserved most of the bioactive molecules when compared to the conventional hot air drying method. The samples dried at 50°C using MAHD were the best in terms of all of the quality attributes tested in this study. Also, the results established that the z-Nose can be used as a quick and inexpensive means to assess the effect of different process parameters on the aromatic quality of the product and quantitatively classify quality based on aroma.

Microwave Drying of Corn (Zea mays L. ssp.) for the Seed Industry

Microwave drying of corn (Zea mays L. ssp.) was conducted in this study and its germination was tested after drying. The objective of the test was to determine an optimum microwave drying method for corn seeds to achieve maximum germination and minimum drying time, as well as to obtain the maximum temperature that can achieve the best results without reducing the viability. The different methods used for drying included constant temperature drying at 30, 40, and 50°C; intermittent power microwave drying; and fixed power microwave drying at 2, 3, 3.5, and 4 W/g. The drying was started with an initial moisture content of 33% (wb) and ended with a final moisture content of 16% (wb). In the constant temperature method, the microwave power was automatically controlled to keep the temperature constant throughout the drying period. A control cycle of 20 s was used for intermittent drying in which the microwave generator was on for 12 s and off for 8 s throughout the drying process. In fixed power microwave drying, the power was constant throughout the process. The germination tests were conducted on all samples with the rolled blotting paper method. The minimum drying time was reached with 4 W/g fixed power where 0% germination resulted. The optimum method for drying of corn seeds for maintaining a high germination rate was 4 W/g intermittent power microwave drying, which took 110 min to dry from 33% moisture content to 16% (wb). The germination percentage of 4 W/g intermittent power was 93.3%. The maximum permissible temperature of corn seeds when subjected to intermittent microwave power resulting in maximum germination was 67°C.

Electronic sensor for the determination of fruit and vegetable respiration

Abstract An instrument to measure the respiration rate of whole fruits and vegetables was designed and developed using a pressure variation method. The Motorola MPX-10-DP pressure transducer was used to monitor pressure changes due to respiratory activity. The operating procedures and calculations required to determine respiration rate (RR) in terms of CO2 produced, RR-CO2, and O2 consumed, RR-O2, with the respirometer were simple. The values of RR-CO2 and RR-O2 obtained by the pressure variation method were compared to changes in CO2 and O2 concentrations as determined by gas chromatography. The results showed no significant difference (0.05 level) between the two methods.

Controlled atmosphere storage of celery with the silicone membrane system

Abstract Laboratory experiments were performed to assess the potential of the silicone membrane system for long term storage of celery under controlled atmosphere (CA) conditions. Designed CO2 levels of 1.5, 3.5 and 5.5% were selected to calculate the silicone membrane areas to be installed on the chambers. Visual observations, mass losses and physiological analyses were the means selected to assess the quality of the product. Pascal celery, imported from California (USA), was stored at 1.5°C for 29 days under regular atmosphere (RA) with 80% relative humidity (RH), and 128 days under averaged carbon dioxide (CO2)+oxygen(O2) concentrations of 0.8+17.7, 2.0+12.6 and 4.0%+9.2% with RH close to saturation. The results showed that the first two CO2+O2 combinations were the most suitable CA compositions, among those tested, for long term storage of that cultivar, with total mass losses of less than 30 and 23% respectively. Clean cut celery, grown locally in Quebec on organic soil, was stored at 1.5°C under RA with 80% RH and under three CA compositions (1.1+ 14.8, 2.3+7.9 and 3.2% CO2+5.5% O2) with RH close to saturation for 62 and 71 days, respectively. The total mass loss averaged 25% and no significant difference was observed between the RA and CA stored celery. In the experiment with Clean cut celery, the losses were mainly attributed to bacterial infections. Both celery cultivars stored under CA with high RH showed better texture and crispness than those stored under RA. It was also noted that the total sugar content significantly increased with storage.