Oon-Doo Baik

Kinetics of Quality Changes During Food Frying

This paper deals with kinetics of quality changes during food frying. The quality parameters of interests include color, texture, viscoelastic properties, volume/density, and nutraceuticals (Omega 3 fatty acids). The kinetic theory and determination methodology under isothermal/non-isothermal conditions are also reviewed. This paper presents the reported reaction rate constant, order of reaction, and activation energy for specific quality changes including phenomenological observations and important speculations. The changes of color, textural, and viscoelastic properties generally followed a first order reaction. In some studies, activation energy analysis could have been improved by applying corresponding system temperatures for the quality change reactions of interest. The kinetic information on volume/density changes and thermal degradation of nutraceutical is still limited to experimental observations of the changes.

Application of ultrasound as pretreatment for extraction of podophyllotoxin from rhizomes of Podophyllum peltatum.

The effect of high-power ultrasound pretreatment on the extraction of podophyllotoxin from Podophyllum peltatum was investigated. Direct sonication by an ultrasound probe horn was applied at 24 kHz and a number of factors were investigated: particle size (0.18-0.6 mm), type of solvent (0-100% aqueous ethanol), ultrasonic treatment time (2-40 min), and power of ultrasound (0-100% power intensity, maximum power: 78 W). The optimal condition of ultrasound was achieved with 0.425-0.6 mm particle size, 10 min sonication time, 35 W ultrasound power, and water as the medium. There was no obvious degradation of podophyllotoxin with ultrasound under the applied conditions, and an improvement in extractability was observed. The SEM microscopic structure change of treated samples disclosed the effect of ultrasound on the tissue cells. The increased pore volume and surface area after ultrasonic treatment also confirmed the positive effect of ultrasound pretreatment on the extraction yield of podophyllotoxin from the plant cells.

Pretreatments for the Efficient Extraction of Bioactive Compounds from Plant-Based Biomaterials

The extraction of medicinal or functional compounds from herbal plants is an important unit operation in food and bio-industries. The target compounds are generally present inter- or intra-cellularly in an intricate microstructure formed by cells, intercellular spaces, capillaries, and pores. The major resistance of molecular diffusion in materials of plant origin always comes from the intact cell walls and adhering membranes. Therefore, increasing the permeability of cell walls and membranes plays a very important role to increase extraction yield and/or extraction rate. Important pretreatment methods to modify the cellular structures and increase the permeability of cell walls or membranes are discussed in this paper. They include physical, biologic, and chemical treatments. In physical methods, mechanical disruption, high-pressure (HP) process, pulsed electric field (PEF) application, ultrasonic treatment, and freeze–thaw, and so on were applied. In biologic methods, different cell wall-degrading enzymes were applied to break-down cell walls or membranes and to diminish the overall internal resistance for transporting bioactive compounds from internal matrix to the external solution. In chemical methods, various chemicals for increasing the inner- or outer-membrane permeabilization were introduced. The principles of the technologies, examples of improvements, and advantages and disadvantages of the pretreatment methods are critically reviewed in this paper.

Thermal Properties of Sweet Potato with its Moisture Content and Temperature

Thermal properties of sweet potato were experimentally determined and modeled as a function of temperature and moisture content. The purpose is to develop empirical correlations that could predict thermal properties during sweet potato processing. Thermal conductivity from the study was 0.49 ± 0.038 Wm−1K−1 (mean ± s.d.), thermal diffusivity was 1.2 × 10−7 ± 9.05 × 10−9 m2s−1, specific heat was 3660 ± 477.4 Jkg−1K−1, and density was 1212 ± 73.5 kgm−3. All properties were determined within temperature range of 20 to 60°C and moisture content range of 0.45 to 0.75 w.b. Prediction models for the thermal properties of sweet potato were developed as a function of product temperature and moisture content with experimental data from this study. Mechanistic models were also developed for thermophysical properties of sweet potato using major food components of the product. Developed models were all presented and compared.

Deep Fat Frying Of Foods—Transport Phenomena

Many theoretical and experimental studies have been conducted to understand the mechanisms of heat and mass transfer during deep fat frying. This, in turn, has helped in understanding transport phenomena during frying and the relationships between thermal and physical properties of the products and the frying media. Most of the studies have focused on the determination of convective heat transfer coefficient and mechanisms of moisture and oil transfer. Mathematical models also have been developed to describe and predict the process. Many studies have adopted the assumptions used for the drying process for simplification. Recently, more realistic and sophisticated models have been introduced.

Determination and Modeling of Thermal Properties of Tofu

Abstract Thermal properties of tofu were determined in the temperature range of 5–80°C (10–105°C for specific heat) and the moisture content range of 0.3–0.7 (wb). Thermal conductivity (k: 0.24–0.43 W m−1 K−1) and thermal diffusivity (α: 7.6 × 10−8–1.15 × 10−7 m2 s−1) were measured simultaneously using dual probe method, and specific heat (C p : 2.52–3.69 kJ kg−1 K−1) with modulated differential scanning calorimetry. Good agreement was observed between perpendicular model and the thermal conductivity data, but not with parallel model. Simple empirical models were also developed as a function of the moisture content and temperature of the tofu.

Recovery of Astaxanthin from Paracoccus NBRC 101723 using Ultrasound-Assisted Three Phase Partitioning (UA-TPP)

Astaxanthin (AX) is a high valued ketocarotenoid having numerous applications in the food and pharmaceutical industry. The present study is a combined approach of using ultrasound extraction with three phase partitioning for an efficient recovery of Astaxanthin from Paracoccus NBRC 101723. The optimum conditions for the ultrasonic extraction of AX were: 100% amplitude for 20 s (wet biomass) and 60 s (dried biomass) using solid to solvent ratio (1:2) at a distance of 15 mm between the base of the extraction vessel and the tip of the probe. Pretreatment of the dried biomass (particle size 0.8 μm) with 70% acetone (70°C, 25 min) resulted in maximum ultrasonic extraction of 1035 μg/g of dried biomass. The astaxanthin content (μg/g) extracted using dried biomass, dried using different drying methods showed hot air oven drying at 35°C (946 ± 23) to be comparable to freeze drying (950 ± 19) and vacuum oven drying (945 ± 22). Astaxanthin from the disrupted cells recovered by three phase partitioning using (NH4)2SO4 and t-butanol (40°C, 30 min) resulted in 37% more recovery than conventional method.

Evaluation of radio-frequency heating in controlling Salmonella enterica in raw shelled almonds

This study was conducted to investigate the efficacy of radio-frequency (RF) heating to reduce Salmonella enterica serovars Enteritidis, Typhimurium, and Senftenberg in raw shelled almonds compared to conventional convective heating, and the effect of RF heating on quality by measuring changes in the color and degree of lipid oxidation. Agar-grown cells of three pathogens were inoculated onto the surface or inside of raw shelled almonds using surface inoculation or the vacuum perfusion method, respectively, and subjected to RF or conventional heating. RF heating for 40s achieved 3.7-, 6.0-, and 5.6-log reductions in surface-inoculated S. Enteritidis, S. Typhimurium, and S. Senftenberg, respectively, whereas the reduction of these pathogens following convective heating for 600s was 1.7, 2.5, and 3.7 log, respectively. RF heating reduced internally inoculated pathogens to below the detection limit (0.7 logCFU/g) after 30s. However, conventional convective heating did not attain comparable reductions even at the end of treatment (600s). Color values, peroxide values, and acid values of RF-treated (40-s treatment) almonds were not significantly (P>0.05) different from those of nontreated samples. These results suggest that RF heating can be applied to control internalized pathogens as well as surface-adhering pathogens in raw almonds without affecting product quality.

Dielectric Behaviour of Whole-Grain Wheat with Temperature at 27.12 MHZ: A Novel Use of a Liquid Dielectric Test Fixture for Grains

This paper is a step towards fulfilling the gap seen in temperature dependence of permittivity (ϵ) of grains at radio frequencies. A commercial device especially built for liquids was exploited for the first time in measuring ϵ of bulk wheat samples at various temperatures. The dielectric constant (ϵ′) of the wheat increased almost linearly with temperature, and varied between 3.82 and 5.95. The loss factor (ϵ″) increased non-linearly with temperature with values between 0.07 and 0.93. Regression models predicted ϵ′ and ϵ″ of the wheat with RMSE of 0.14 and 0.034, and R2 values of 0.97 and 0.99, respectively.

Thermal Conductivity, Specific Heat, and Thermal Diffusivity of Saponaria vaccaria Seed Particles

The seeds of Saponaria vaccaria (prairie carnation) are the major source of saponins, which are used for the treatment of cancers and various infections. The thermal conductivity, specific heat, and thermal diffusivity of Saponaria vaccaria seed particles were determined at temperatures ranging from 25°C to 55°C, moisture content from 15.35% to 80% dry basis, and effective density from 516.5 to 1328.05 kg m-3. The thermal conductivity was measured by the transient technique using a line heat source for the particles with and without air, and pores filled with ethanol-water solutions of 10%, 40%, 70%, and 100% volumetric ethanol concentrations. The values ranged from 0.057 to 0.625 W m-1 °C-1. Specific heat was measured by differential scanning calorimetry and ranged from 1118.57 to 3023.78 J kg-1 °C-1. Thermal diffusivity was calculated from thermal conductivity, specific heat, and density and ranged from 0.60 × 10-7 to 1.58 × 10-7 m2 s-1. Particle and bulk densities of the particles followed a parabolic relationship with moisture content. Thermal conductivity increased with moisture content. Specific heat increased linearly with temperature and exhibited ascending-descending trends with moisture content. Thermal diffusivity followed descending-ascending trends with moisture content. Regression models for all the properties were developed based on the experimental data.