Conventional Frying Research Articles

Industrial Applications of Selected JFS Articles

Industrial Applications of Selected <i>JFS</i> Articles

Comparison of Microwave and Conventional Frying on Quality Attributes and Fat Content of Potatoes.

A comparative analysis of quality attributes (moisture, fat, color, and relaxation modulus) of French fries was performed between conventional and microwave frying. Experiments were performed in triplicate for both frying operations at temperatures of 177, 185, and 193 °C for frying times of 60, 90, and 120 s. The real-time pressure and temperature profiles at above conditions indicated that during microwave frying, gage pressure had greater magnitudes that lasted longer, and the temperature increased to boiling point of water faster in comparison to conventional frying. Lower magnitude of negative pressure during microwave frying is expected to have caused lower fat content in fries obtained using this method (0.08 g/g solids less at 185 °C and 0.07 g/g solids less at 193 °C) than conventional frying. The lightness parameter (L* ) decreased to a lesser extent in microwave frying than in conventional frying. The stress relaxation function of the French fries were significantly different between the 2 frying operations. Consumer test confirmed that reduced fat uptake during microwave frying did not compromise with desirable quality attributes of French fries. X-ray micro-computed tomography scanning provided complementary understanding about differences in microstructural properties of fries made using microwave and conventional frying.

Protective role of vacuum vs. atmospheric frying on PUFA balance and lipid oxidation

Abstract The effect of vacuum frying processing on proximate composition, fatty acid profile, oxidative status and sensorial properties of fish patties, was evaluated as compared with conventional (atmospheric) frying. Vacuum frying procedure was carried out at 80 mmHg (water boiling point: 42 °C) and oil temperature (107 °C) determined to obtain an equivalent thermal driving force (Δ65 °C) of that of the atmospheric frying conditions used (165 °C). Frying times of 2, 4, 6, 8 and 10 min were investigated. Vacuum frying significantly prevented degradation of EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid), reducing the polyene index and maintaining a lower ω6/ω3 fatty acid ratio in samples, while no significant differences with conventional frying in total oil content were observed. The use of vacuum also reduced formation of peroxides and carbonyl derivatives. Tocopherol levels decreased in all samples regardless of the frying conditions used, although vacuum-fried samples maintained higher tocopherol levels after processing. These samples also showed higher lightness and lower a* and b* values, which can be associated to lower non-enzymatic browning levels. These results support the applicability of vacuum frying technology for fish patties, since it prevents colour changes, improves juiciness and reduces oxidation when compared to conventionally (atmospheric) fried counterparts. Industrial relevance Consumers are increasingly aware of the link between food and health, maintaining a high demand for healthy products. In this regard, consumption of fatty fish, with healthy properties widely known, is lower than recommended by health authorities, especially in children. Novel processing technologies focused on increasing the appealing of products based on fatty fish can help in ameliorating this deficient consumption. Vacuum frying is a promising way of obtaining attractive products, due to some product modification after the deep-fat frying process, and yet retaining natural colour, juiciness and healthy properties to a high extent. Vacuum frying allows reducing ω3 fatty acids and tocopherol degradation, differentiating fish products so obtained, which can be launched into the market and benefit from this technology. Compared to conventional frying, the results are better nutritional and sensory properties in a final product.

Influence of Combined Hot Air Impingement and Infrared Drying on Drying Kinetics and Physical Properties of Potato Chips

Air jet impingement combined with infrared drying (IMIRD) was developed as an alternative processing method to produce health-friendly potato chips in place of conventional deep-fat frying. This article investigates the effects of IMIRD compared to air jet impingement drying alone (IMD) and conventional convective drying (CCVD) on potato being processed as potato chips in term of drying characteristics, quality attributes (shrinkage, color, and hardness), and specific energy consumption (SEC) of the dryer. The experiments were carried out at three different air velocities (5, 10, 15 m/s) and infrared intensities (0.16, 0.27, and 0.33 W/cm2) at a fixed air temperature of 85°C. The experimental results show that the drying air velocity and infrared intensity had a significant effect on the moisture removal from potato slices. IMIRD, compared to IMD and CCVD, provided a higher drying rate, less shrinkage, lower hardness, and less color deterioration. An increase in air velocity at each infrared intensity caused a decrease in the total SEC value.

Microwave Frying Compared with Conventional Frying via Numerical Simulation

Microwave heating can be combined with other means of heating to yield a unique heating profile. In the study, microwave frying, a combination of convective and microwave heating, was compared with conventional frying. Frying experiments were performed by inserting a single food sample (chicken breast meat) in the hot oil at 180 ± 1°C for both frying methods. Center temperature of the sample and the oil temperature were recorded during both frying methods. Simulations were performed to predict heat transfer coefficients. Processing time was shorter with microwave frying. Simulations revealed a varying convective heat transfer coefficient, which was in the range of 160–490 W/m2 K, during conventional frying. Higher convective heat transfer coefficient, 500 W/m2 K, compared to conventional frying was observed during microwave frying with the simulations. This is suggested to be due to higher turbulence in microwave frying.

Effect of conventional and pressure frying on lipids and fatty acid composition of fried chicken and oil

Lipid class and fatty acid profile of pressure fried (PF) and conventionally fried (CF) chicken and medium of frying were evaluated. Depending on the frying cycle, neutral lipid (NL) content of PF chicken varied from 75-86% as compared to that of CF (84-90%). Similarly, glycolipid (GL) content varied from 11-21% in PF and from 9-12% in case of CF. Phospholipid (PL) was the least among lipid classes in both the products. The fresh frying medium (oil before frying cycle started), NL, GL and PL were 89, 10 and 0.33%, respectively. After the frying cycles were over, NL content of oil used for CF decreased to 82% and GL content increased from 10 to 17%. There was no significant difference (p ≥ 0.05) between the contents of lipid classes of oil used for PF or CF. Fried chicken and frying medium had higher concentration of linoleic acid and oleic acid irrespective of the frying cycle or frying method. PF chicken had moisture content in the range of 56-58% and total fat was 14% whereas in case of CF chicken it ranged from 49-52% and 18% respectively. TBA and FFA values of CF chicken and oil on repeated frying were higher (p ≤ 0.05) than PF. In comparison to conventional frying, pressure frying resulted in relatively tender and juicier product presumably due to better retention of moisture (p ≤ 0.05) and low oil uptake.

Quality characteristics of battered and fried chicken: comparison of pressure frying and conventional frying

The marinated and battered chicken leg meat and breast meat were pressure fried and their physico-chemical qualities were compared to the conventional fried product (open pan deep fat frying). Shrinkage due to frying process was significantly lesser in case of pressure fried leg meat (PLM) and breast meat (PBM) as compared to products prepared by conventional frying leg meat (CLM) and breast meat (CBM). Also, juiciness of pressure fried chicken products was superior (p ≤ 0.05) than fried products obtained by the conventional method. PLM and PBM had lower fat content (p ≤ 0.05) compared to conventionally fried CLM and CBM. Lipid oxidation was higher (p ≤ 0.05) in conventional frying as compared to pressure frying. Irrespective of the type of chicken meat, conventionally fried meat required higher shear force as compared to pressure fried products. Salmonella, Staphylococcus aureus, Shigella and E. coli were not detected. The study indicates the usefulness and superiority of pressure frying in comparison to conventional deep fat frying.

Influence of the vacuum break conditions on oil uptake during potato post-frying cooling

Reduced pressure frying is an alternative to conventional frying that enables products to be obtained at lower processing temperatures with lower fat content. The oil uptake in frying mainly occurs during the subsequent cooling stage. With vacuum frying, this stage necessarily includes a period of vacuum break when the system recovers the initial pressure. The different conditions under which this pressurisation occurs can influence the final oil content of the product. To study this effect, potatoes of the “Monalisa” variety, with different geometries, were fried at 140 °C and moderate vacuum (24.9 kPa). Various combinations of draining times (30, 60, and 90 s) and vacuum break velocity, VBV (0.75, 2.21, 4.43 and 12.43 kPa s −1), were tested for this stage, and the final oil content of the product determined by comparison with the dry weight. The results showed that both parameters have a significant influence ( α < 0.05) on oil uptake. A short draining time and a low vacuum break velocity result in greater final fat content. There is a linear relationship between the oil uptake and the inverse of VBV, following the Washburn equation. The influence of VBV is such that differences of up to 70% in the final fat content can be obtained in the range tested.

Magnetic Resonance Temperature Mapping of Microwave‐Fried Chicken Fingers

The main objective of this study was to compare the heating patterns of chicken fingers deep-fried conventionally and using a microwave. Two dimensional internal temperature maps of fried chicken fingers with rectangular geometry were measured post frying using magnetic resonance imaging (MRI). Frying was performed in a microwave oven at 365 W power level for 0.5 and 1.5 min after bringing the oil temperature to 180 +/- 1 degrees C. Samples were also fried in a conventional fryer at 180 degrees C for 2 and 5 min for comparison. Variations in internal temperature distribution increased proportionally to frying time in both microwave and conventional frying. Internal thermal equilibrium is reached in all samples after 13 min of holding time. Internal structural changes, void formation, were also visualized in the images. Void formation did not significantly impact cooling rates.

Effect of osmotic pretreatment and microwave frying on acrylamide formation in potato strips

AbstractBACKGROUND: The presence of acrylamide, a probable carcinogen, is currently a major concern relating to the consumption of fried products. Therefore, recent frying studies have focused on ways of reducing the acrylamide content. The main objective of the present study was to determine the effects of microwave frying and osmotic treatment prior to frying on acrylamide formation in potato strips.RESULTS: Potatoes fried using 400 W microwave power for 1.0 min had an 87.85% lower acrylamide content than potatoes fried conventionally for 4.5 min (i.e. an 81.82% reduction in frying time) but a comparable moisture content. The acrylamide content of fried potatoes treated osmotically prior to both microwave and conventional frying was found to be lower than that of fried potatoes not pretreated osmotically. However, the reduction in acrylamide content was lower when osmotic treatment was applied before microwave frying.CONCLUSION: As a result of this study, it was concluded that microwave frying can be an alternative to conventional frying. Copyright © 2007 Society of Chemical Industry

Evaluation of soybean oil quality during conventional frying by FTIR and some chemical indexes

Conventional deep fat frying is a common food preparation technique in Mauritius. The deterioration of soybean oil, commonly used in conventional frying, has been studied during frying of potato chips. The oil was subjected to continuous frying at 180°C for a total of 600 min. The quality changes in soybean oil were evaluated at 90 min interval by Fourier transform infrared (FTIR) spectroscopy and some routine chemical parameters, namely peroxide value, iodine value and free fatty acid. An increase in hydroperoxide and free fatty acid concentration has been observed during the frying process by FTIR technique and the chemical parameters, peroxide value and free fatty acid respectively. A significant decrease in tryglyceride ester linkage was observed by FTIR. The linear decrease noted for iodine value (P < 0.01) indicated a general loss of unsaturation. Furthermore, FTIR studies showed a loss of cis double bonds along with an increase in trans unsaturation. The formation of unsaturated aldehyde has also been observed during the frying process by FTIR technique.

Studies in the application of infra-red for the production of French fries

1. Exposure of the cut potatoes at a distance of 4 inches from infrared quartz lamps resulted in faster heat penetration than exposure to quartz tube or infra-red calrod units; the rated wattages per linear inch of these radiators were 100, 53 and 41 watts, respectively. 2. Oil-blanching of French fries with infra-red quartz lamps resulted in approximately 8 to 12 per cent higher product yield after the first stage preparation and a 4 to 8 per cent higher product yield after the second stage preparation, as compared with conventional deep fat frying. 3. A 2 to 4 per cent lower fat content in the stage one and stage two product was obtained by use of the infra-red treatment. 4. Storage of french fries at 0° F. between stage one and stage two produced a finished product of only “fair” quality, regardless of the technique used to prepare the first stage product. 5. French fries, prepared by infra-red and deep fat frying, resulted in a finished product of “good” quality when stored up to 9 days at 38° F. between the first and second stage.