Valérie Orsat

Microwave-Assisted Extraction of Flavonoids: A Review

Flavonoids are major bioactive compounds known to be beneficial against many chronic diseases such as cancer, cardiovascular disorders, and inflammation. Food products obtained from plants are key sources of flavonoids for humans. However, during different food-processing steps, flavonoids are lost in remarkable amounts. Supplementation of flavonoids as a food additive will help in retaining the required health-beneficial amount of flavonoids in the diet, and extraction is an important step in the preparation of food additives. Microwave extraction is one of the most advanced extraction methods, which has the potential of playing a major role in flavonoid extraction and analytical quantification. The present paper reviews the potential application of microwave extraction for flavonoids and the advantage of microwave-assisted process over the other extraction processes generally employed for extraction.

Spray Drying for the Production of Nutraceutical Ingredients—A Review

Contributions of spray drying to food processing applications are increasing as compared to other conventional drying methods. Spray drying has not only contributed in drying of fluids but also has played a vital role in encapsulation and microencapsulation of valuable foods and functional–nutraceutical ingredients. Microencapsulation by spray drying is a cost-effective one-step process as compared to other encapsulation methods. Encapsulation using spray drying is mainly used in the food sector to protect bioactive compounds or functional foods from light, temperature, oxidation, etc. This paper reviews the work done in past years in the functional food and nutraceutical sector using spray drying. The paper focuses on the role of spray drying in vitamins, minerals, flavouring substances, antioxidant compounds and fatty acids encapsulation.

Overview of new techniques for drying biological materials with emphasis on energy aspects

With increasing concern about environmental degradation, it is desirable to decrease energy consumption in all sectors. Drying has been reported to account for anywhere from 12 to 20% of the energy consumption in the industrial sector. Drying processes are one of the most energy intensive unit operations. There are a number of approaches to reduce energy consumption in dryers. This paper reviews some novel strategies used to decrease energy consumption in drying operations. Drying conditions can be modified or the drying equipments can be modified to increase overall efficiencies. Hybrid drying techniques can also be used, such as combining vacuum or convective drying with electro-technologies (microwave, radio frequency, infrared heating). There is much debate on how to define drying and energy efficiencies. Some techniques to determine these efficiencies can be misleading when the goal is to take a holistic approach to determining energy consumption.

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%.

A Comprehensive Review on Electrohydrodynamic Drying and High-Voltage Electric Field in the Context of Food and Bioprocessing

Increasing global energy demand and the application of more energy-consuming processes has forced food industries to investigate alternative processes. This article pertains to one such novel and promising alternative drying process called electrohydrodynamic (EHD) drying. EHD is a method of inducing electric wind that is generated by gaseous ions under the influence of a high-voltage electric field. This article evaluates the available literature and discusses the experimental investigations carried out to explain the effect of operating parameters on the drying rate and specific energy consumption (kJ/kg water) of the EHD process. Through the review it was established that the corona current increased linearly with an increase in applied voltage (kV) for both positive and negative polarities and a negative corona discharge produced a larger corona current compared to a positive corona discharge. It was also revealed that the specific energy consumption increased with an increase in applied voltage for both polarities but was lower compared to conventional drying processes such as fluidized bed drying; however, it was observed that the specific energy consumed by the EHD process was lower than that of latent heat of vaporization, indicating the removal of water from the surface of the sample by other means in addition to evaporation. Electrode configuration plays an important role in determining the efficiency of the EHD process; the multiple-needle electrode configurations had better efficiency than wire and single-electrode configurations. Recent and past studies on application of EHD both postharvest and in food processing were also reviewed and the benefit of using EHD for food and bioprocessing due to its unique properties supported the feasibility and applicability of EHD as a suitable alternative for processing thermally sensitive biological materials.

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.

Soybean Hydrophobic Protein Response to External Electric Field: A Molecular Modeling Approach

The molecular dynamic (MD) modeling approach was applied to evaluate the effect of an external electric field on soybean hydrophobic protein and surface properties. Nominal electric field strengths of 0.002 V/nm and 0.004 V/nm had no major effect on the structure and surface properties of the protein isolate but the higher electric field strength of 3 V/nm significantly affected the protein conformation and solvent accessible surface area. The response of protein isolate to various external field stresses demonstrated that it is necessary to gain insight into protein dynamics under electromagnetic fields in order to be able to develop the techniques utilizing them for food processing and other biological applications.

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.

Spray Drying of Elderberry (Sambucus nigra L.) Juice to Maintain Its Phenolic Content

Spray drying was studied with Elderberry (Sambucus nigra L.) juice using a Buchi B-290 spray dryer. Different inlet temperatures ranging from 70°C to 120°C and two feed flow rates of 180 ml/hr and 300 ml/hr were considered for the experiment. The operating parameters were optimized in terms of total phenolic content retention, color, and powder recovery. The inlet temperature of 80°C with feed flow rate of 180 ml/hr gave high phenolic content retention with good color but lower recovery of the dried powder, i.e., less than 50%. To increase the recovery percentage during the drying process, the elderberry juice was spray dried with five different wall materials, i.e., soya milk powder, soya protein powder, isolated soya protein, gum acacia, and maltodextrin. Wall materials were evaluated in terms of total phenolic content retention, color of the powder, and mass recovery percentage. The gum acacia and maltodextrin gave better results and high recovery percentage, i.e., more than 70%. The best three combinations were stored under three different storage conditions in three different packagings to monitor the stability of the phenolic content and color of the powder.