Journal of Food Process Engineering
0145-8876
1745-4530
Mỹ
Cơ quản chủ quản: WILEY , Wiley-Blackwell
Lĩnh vực:
Chemical Engineering (miscellaneous)Food Science
Các bài báo tiêu biểu
ELECTRICAL CONDUCTIVITIES of SELECTED SOLID FOODS DURING OHMIC HEATING<sup>1</sup> ABSTRACT Electrical conductivities of three vegetable and two meat samples were determined by subjecting them to a constant voltage power supply in a static ohmic heating device. Conductivities of vegetable samples were increased by soaking them in salt solutions, while soaking in water resulted in reduced conductivity due to leaching of electrolytes. Conductivities under ohmic heating conditions increased linearly with temperature. When field strengths were decreased, the conductivity‐temperature curve gradually became nonlinear, and under conventional heating conditions, a sharp transition was observed.
Tập 14 Số 3 - Trang 221-236 - 1991
ELECTRICAL CONDUCTIVITY of SELECTED JUICES: INFLUENCES of TEMPERATURE, SOLIDS CONTENT, APPLIED VOLTAGE, and PARTICLE SIZE<sup>1</sup> ABSTRACT A device was developed to determine the electrical conductivities of foods under ohmic or conventional heating conditions. Orange and tomato juices (serum and various solids contents) were tested in the device. the electrical conductivity of juices increased with temperature and decreased with solids content. the temperature dependence of conductivity was linear, both under conventional and ohmic heating. Experiments on suspensions of carrot juice solids, and polystyrene spheres in sodium phosphate solution showed an increase in electrical conductivity of the suspension with decreasing particle size.
Tập 14 Số 4 - Trang 247-260 - 1991
ELECTROLYZED WATER AND ITS CORROSIVENESS ON VARIOUS SURFACE MATERIALS COMMONLY FOUND IN FOOD PROCESSING FACILITIES ABSTRACT ASTM A‐36 medium carbon steel, 110 copper, 3003‐H14 aluminum, polyvinylchloride (PVC) type 1 and 304 stainless steel coupons were immersed in electrolyzed (EO) water, chlorine water, modified EO water and deionized water for a period of 8 days, and the properties of these types of water, weights and surface roughness of the coupons were monitored. EO water significantly increased ( P < 0.05) the surface roughness of carbon steel, aluminum and copper with time; however, chlorine water, modified EO water and deionized water produced minimal changes on these materials. Regardless of the treatment water used, the surface roughness of stainless steel and PVC essentially remained the same. Carbon steel, copper, aluminum and stainless steel had a fair, good, good and outstanding corrosion resistance in EO water, respectively. Chlorine and modified EO water had a much less corrosive effect than EO water on all the materials tested.
Tập 28 Số 3 - Trang 247-264 - 2005
ELECTRICAL CONDUCTIVITY of APPLE and SOURCHERRY JUICE CONCENTRATES DURING OHMIC HEATING ABSTRACT Ohmic heating is based on the passage of electrical current through a food product that serves as an electrical resistance. In this study, apple and sourcherry concentrates having 20–60% soluble solids were ohmically heated by applying five different voltage gradients (20–60 V/cm). the electrical conductivity relations depending on temperature, voltage gradient and concentration were obtained. It was observed that the electrical conductivities of apple and sourcherry juices were significantly affected by temperature and concentration (P < 0.05). the ohmic heating system performance coefficients (SPCs) were defined by using the energies given to the system and taken up by the juice samples. the SPCs were in the range of 0.47–0.92. the unsteady‐state heat conduction equation for negligible internal resistance was solved with an ohmic heating generation term by the finite difference technique. the mathematical model results considering system performance coefficients were compared with experimental ones. the predictions of the mathematical model using obtained electrical conductivity equations were found to be very accurate.
Tập 27 Số 3 - Trang 159-180 - 2004
FACTORS AFFECTING THE ULTRAVIOLET INACTIVATION OF <i>ESCHERICHIA COLI</i> K12 IN APPLE JUICE AND A MODEL SYSTEM* ABSTRACT Ultraviolet (UV) light has been used successfully for years to sterilize water and was recently approved as an acceptable irradiation treatment for the processing of juice. Although there is considerable information on the efficacy of UV processing in the treatment of water, limited data are available on its efficacy in fluid food systems. The objectives of this work were to determine the effects of apple‐juice properties on the UV inactivation of Escherichia coli K12 and the interdependence of intensity and time on the efficacy of UV light. Results showed that absorbance (A) and suspended solids (SS) affected UV inactivation, while pH and dissolved solids did not. Concerning the interdependence of intensity and time, intensity levels can only be changed without sacrificing effectiveness at a limited range of intensity and dose levels. This means that the range of the intensity level of the actual UV reactor must be considered in process‐parameter determination.
Tập 29 Số 1 - Trang 53-71 - 2006
Physical Stability and Antimicrobial Activity of Encapsulated Cinnamaldehyde by Self‐Emulsifying Nanoemulsion Abstract In the present study, natural cinnamaldehyde was encapsulated in self‐emulsifying emulsion systems. After optimization, the stability of encapsulated cinnamaldehyde was evaluated by dynamic light‐scattering and electronic nose. The antimicrobial activity of cinnamaldehyde was investigated by minimum inhibition concentration and time‐kill assay. The results showed that pure cinnamaldehyde as oil phase could not form stable emulsion under different oil‐to‐surfactant ratio. Stable cinnamaldehyde nanoemulsions were achieved with the addition of medium‐chain triglyceride. With the exception of temperature, the obtained nanoemulsions were stable against pH and NaCl . Phase separation was observed after 12 days of storage under 37C. Encapsulation efficiency of cinnamaldehyde in nanoemulsions was maintained around 80% within 1 week. Radar plots from electronic nose indicated that encapsulation could slow the release of cinnamaldehyde from nanoemulsion. Hence, the antimicrobial activity of cinnamaldehyde encapsulated in nanoemulsion could provide a long‐term inhibition on the bacterial growth of E scherichia coli compared with pure cinnamaldehyde. Practical Applications The applications of natural essential oils with their excellent antibacterial activities, such as cinnamon essential oils, as a food additive and green preservative are limited in the food systems, due to their highly instability against environmental conditions including temperature, light, air and others. The emulsification technique has been successfully utilized to overcome this drawback. However, it is known that emulsions with essential oils as oil phase will be highly unstable due to O stwald ripening. Although the evaluation of the stability and bioactivities of encapsulated essential oil is an important and critical issue during the practical application, hence, studies of the physical properties such as environmental stability, volatility and antibacterial activity can explore the ideal formulation and applications of natural essential oils.
Tập 39 Số 5 - Trang 462-471 - 2016
OPTIMIZATION OF BLANCHING PROCESS FOR CARROTS ABSTRACT Investigations were carried out to study the effects of selected blanching treatments on the quality of carrots over a temperature range of 80–100C. The blanching treatments selected were steam, water, 0.05 N acetic acid solution and 0.2% calcium chloride solution. These blanching treatments were evaluated with respect to the inactivation time of peroxidase (POD) and catalase, and the process was optimized on the basis of the maximum yield of carrot juice and minimum loss of vitamin C and β‐carotene. The most effective blanching treatment was 5 min in hot water at 95C. At this time–temperature combination, POD and catalase were completely inactivated and the yield of carrot juice and vitamin C and β‐carotene contents were found to be 55%, 8.192 mg/100 g and 3.18 mg/100 g, respectively. The kinetics of thermal inactivation of POD in carrot juice using various enzyme inactivation models available in the literature was critically evaluated. The Weibull distribution model provided a good description of the kinetics of the inactivation of POD in carrot juice over the temperature range of 80–100C. PRACTICAL APPLICATIONS Blanching is an important unit operation before processing fruits and vegetables for freezing, pureeing or dehydration. The findings of this study would be useful in determining the process parameters for blanching carrots with maximal retention of nutrients. The enzyme residual activity curve indicates the destructive effect of heat on the affected enzymes. A successful modeling will enable the processors to modulate their process according to different time–temperature combinations.
Tập 32 Số 4 - Trang 587-605 - 2009
DIELECTRIC PROPERTIES OF SHRIMP RELATED TO MICROWAVE FREQUENCIES: FROM FROZEN TO COOKED STAGES ABSTRACT Dielectric properties of shrimp (Penaeus sp.) were measured at frequencies between 0.3 and 3 GHz from ‐25 to 70C by using a network analyzer. The relationship between dielectric properties and temperature was determined at 915 MHz and 2450 MHz. Below the freezing point, the dielectric constant (ɛ′) and dielectric loss factor (ɛ″) increased rapidly with increasing temperature as ratio of frozen water in shrimp was decreasing. Above the freezing point, the dielectric constant (ɛ′) decreased as frequency and temperature increased at both frequencies. The dielectric loss factor (ɛ″) did not change significantly with temperature. The relationships between penetration depth and temperature at both frequencies were evaluated from the experimental data.
Tập 22 Số 6 - Trang 455-468 - 1999
THERMAL CONDUCTIVITY AND DIFFUSIVITY OF SHELLED CORN AND GRAIN ABSTRACT Increasing energy costs have stressed the importance of calculation of heat and mass transfer in a grain bulk in order to be able to optimize drying facilities. Therefore values for the thermal conductivity and diffusivity of grain and especially shelled corn were determined. The investigations were carried out for single kernels as well as for grain and corn in bulk. Thermal conductivity and diffusivity were found to be mainly dependent on moisture content. Regression analyses showed a good correlation between moisture content and thermal conductivity or diffusivity, respectively.
Tập 4 Số 3 - Trang 137-153 - 1981
CONTINUOUS PASTEURIZATION OF EGG YOLK: THERMOPHYSICAL PROPERTIES AND PROCESS SIMULATION ABSTRACT This article presents empirical correlations to predict the density, specific heat, thermal conductivity and rheological power–law parameters of liquid egg yolk over a temperature range compatible with its industrial thermal processing (0–61C). Moreover, a mathematical model for a pasteurizer that takes into account the spatial variation of the overall heat transfer coefficient throughout the plate heat exchanger is presented, as are two of its simplified forms. The obtained correlations of thermophysical properties are applied for the simulation of the egg yolk pasteurization, and the obtained temperature profiles are used for evaluating the extent of thermal inactivation. A detailed simulation example shows that there is a considerable deviation between the designed level of heat treatment and that this is predicted through process simulation. It is shown that a reliable mathematical model, combined with specialized thermophysical property correlations, provide a more accurate design of the pasteurization equipment that ensures effective inactivation, while preserving nutritional and sensorial characteristics.
Tập 28 Số 2 - Trang 181-203 - 2005