Pressure Frying Research Articles

The Effects of Atmospheric and Pressure Frying Processes on the Quality Characteristics of Meatballs

In the study, it was aimed to determine the effect of atmospheric and pressure frying on some quality properties of meatballs. For this purpose, meatballs have been subjected to deep frying process using hazelnut oil in atmospheric and pressure conditions. Fried meatball samples were analyzed in terms of pH, % moisture, TBARS (thiobarbutyric acid reactive substance), and instrumental color (internal and external surface). The meatballs were also tested for their instrumental texture properties. The frying factor had a significant effect (p˂0.05) on the moisture value and a very significant effect (p˂0.01) on the TBARS value of meatballs. The % moisture values of the samples fried in atmospheric conditions were determined lower than the samples fried in pressurized conditions. The pressure frying process reduced the TBARS value and increased the L *, a *, and b * values of the internal surface. This method resulted in an increase in the L * value and a decrease in the b * value in the external surface (p˂0.05). The frying repeat factor generally caused a decrease in the internal and external surface colors. The pressure frying process increased the hardness, adhesiveness, resilience, and cohesiveness values of the meatball samples. However, the frying method did not have a significant effect on the springiness (p˃0.05). The frying number caused a decrease in all texture parameters except the gumminess value.

The Effects of Frying Method and Oil Type on the Quality Attributes of Turkey Nuggets and Frying Oils

AbstractThe aim of the study is to determine the effects of frying under standard atmospheric and pressure conditions on some quality characteristics of turkey nuggets. Turkey nuggets are fried under atmospheric and pressure conditions using sunflower or hazelnut oil. Pressure frying decreases the thiobarbituric acid reactive substances (TBARS) value of turkey nuggets while sunflower oil increases this value. Under atmospheric conditions, nuggets fried with hazelnut oils show higher moisture content than hazelnut oil. The pH is affected by the type of oil. The frying under pressure results in a decrease in the internal and external a* value of nuggets. Under pressure conditions, the use of hazelnut oil increases the external a* value. The application of pressure also causes an increase in the external L* value in the presence of sunflower oil. These treatments also show higher hardness, springiness, gumminess, and chewiness values compared to atmospheric condition. The use of sunflower oil causes a decrease in resilience, cohesiveness, springiness, and chewiness values. After frying, hazelnut oil shows lower peroxide and total polar material values than sunflower oil. However, peroxide value and total polar material are not affected by frying method.Practical applications: Color and texture are very important factors for the quality of nuggets. Pressure and atmospheric conditions show different effects on color parameters. Frying under pressure conditions decreases the external L*, which is an important quality parameter. Hazelnut oil shows lower TBARS value than sunflower oil. Moreover, pressure application causes a decrease in TBARS value. Frying process under pressure decreases the hardness and adhesiveness, while it increases the juiciness of product. On the other hand, the use of hazelnut oil as frying oil shows less changes in peroxide and total polar material during frying than sunflower oil, but the frying method and oil type interaction has no significant influence on these parameters.

A review and research trends in alternate frying technologies

Deep-fat frying is a century-old process which is still being used for preparation of various food products in our regular diet. Increase in the consumer health awareness has motivated more research in development of healthy and safe fried products. Recent strategies to attain this goal have been focused on reduction in oil uptake by fried products and increasing the stability of frying medium. Another approach includes development of alternative frying technologies such as pressure frying, microwave frying, vacuum frying and radiant frying or their combinations. Among all the alternative frying technologies, only vacuum frying have shown acceptance and commercial utilization by the food industries. Pressure frying and radiant frying have also shown some promising potential, but need further exploration.

Phenolic profile and antioxidant activity of thermally processed sponge gourd (Luffa cylindrica) as studied by using high performance thin layer chromatography (HPTLC)

ABSTRACTThe effect of different extracting solvents (methanol, ethanol and butanol) and cooking treatments such as pressure cooking, microwave cooking and frying was studied in regards to phenolic profile and antioxidant activity of Sponge gourd (L. cylindrica). The antioxidant activity was investigated using different assays, namely, ferric thiocyanate test (FTC), thiobarbituric acid test (TBA), ferric reducing antioxidant power (FRAP) and DPPH free radicals scavenging test. A densitometric HPTLC analysis was performed for the analysis of phenolic acids and flavonoids. The inconsistent effect of cooking treatments on antioxidant potential was observed. In general, frying was most potent cooking treatments to retain the maximum antioxidant capacity. Correlation studies indicated that the phenolic compounds including flavonoids were mainly responsible for ferric reducing power, free radical scavenging activity and percent inhibition activity.

감압 튀김 방법이 산패 변화에 미치는 영향

Abstract This study investigated the oxidative stability of oils when dough was fried under a lower pressure than the ambient atmosphere. The pressure during the frying process was controlled at measures of 760, 560, 360 or 160 mmHg. The oil containing the dough was heated at 180℃ for 48 hours. Rancidity values, including acid value, peroxide value, fatty acid analysis, color changes, and browning of oil samples, were measured every 8 hours. As the frying process continued at all 4 pressure levels, the acid values (AV) increased. However, compared to the other pressure levels, the increase in AV was the least at 160 mmHg. In addition, the peroxide value at 160 mmHg was only 0.81 meq/㎏ compared to 1.52 meq/㎏ at 760 mmHg. For all pressure levels, stearic acid, oleic acid, ω-6 linolenic acid were increased, while linoleic acid and ω-3 linolenic acid were decreased. In terms of color, a-values representing redness were decreased, whereas b-values were increased as the frying proceeded. These results revealed that the oxidation of frying oil was decreased under reduced pressure condition. Thus, the usage of frying oil may be extended, owing to less oxidative concerns. This leads to a lower cost to the manufacturer, and furthermore, helps the environment by reducing industrial wastes.Key words: frying oils, reduced pressure frying, oxidation, acid values, peroxide value

Deep‐fat frying under moderate vacuum of potato cylinders

SummaryThis study evaluates parameters relating to the mass transfer during the frying of potato cylinders at different temperatures (100, 120 and 140 °C) and moderate vacuum (around 25 kPa). In all cases, there is a linear relation between water loss and fat uptake. The parameters relating to the textural and structural modifications show less marked changes in vacuum fried products compared to those fried under atmospheric pressure. The maximum penetration force reaches 30%–40% of the initial hardness in vacuum frying and 10% for atmospheric pressure frying; starch gelatinization and pectin methylesterase enzyme activity reduce more quickly under atmospheric pressure, although after 240 s both values are negligible. The scanning electron microscopy images verify that the surface of potato cylinders fried under vacuum or atmospheric pressure are completely different as a result of the steam being released at different temperatures.

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.

Determination of heat transfer coefficient during high pressure frying of potatoes

Besides traditional atmospheric frying, high pressure (super-atmospheric) frying might be an alternative approach to the frying of food products. In this study, convective heat transfer coefficient during atmospheric and high pressure frying was compared. For this purpose, a pressure cooker was modified to allow the immersion of a sample into frying oil under pressure and temperature measurement of sample and oil. Heat transfer coefficient versus frying time was determined on potato slabs using changes of total mass of the experimental set-up. At the pressure of 2 bar, the results showed an almost doubled heat transfer coefficient compared to the atmospheric pressure frying. The knowledge of heat transfer coefficient during pressure frying is expected to allow accurate determination of temperature distribution and hence the kinetic calculations to lead to development of an alternative frying process.

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.

The Effect of Edible Coatings and Pressure Frying Using Nitrogen Gas on the Quality of Breaded Fried Chicken Nuggets

: The effects of 2 edible coatings, methylcellulose (MC) and whey protein isolate (WPI), and 2 pressure sources (nitrogen gas and steam) on the quality attributes (crispness, moisture and fat content, juiciness, color, and texture) of breaded fried chicken nuggets were evaluated. MC or WPI was incorporated into either the pre-dust or the batter before frying. Chicken nuggets were fried in a modified restaurant-type pressure fryer under a constant pressure of 163 kPa at 175°C for 240 s. Samples were held under a heat lamp at 60°C for 0-, 10-, 20-, and 30-min time intervals. Crispness was evaluated using a nondestructive ultrasonic technique. Coating type and pressure source had a significant effect (P < 0.05) on all quality attributes. Chicken nuggets fried using nitrogen gas were crispier (P < 0.05) than those fried with steam. The treatment combination of MC incorporated into the pre-dust and frying with nitrogen gas was the most effective at maintaining product crispness.

Tocopherol losses in peanut oil during pressure frying of marinated chicken strips coated with edible films

Tocopherol losses were observed in peanut oil used for frying both marinated and non-marinated chicken products. The largest losses were seen for γ-tocopherol followed by α-tocopherol and then β- and δ-tocopherols. γ-Tocopherol losses were significantly reduced when hydroxypropylmethylcellulose was applied either as a film or as a breading mix ingredient to pre-fried chicken strips that had been marinated in pickle juice. It is conjectured that the edible film material served as a hydrophilic barrier to migration of the pro-oxidant, acetic acid, from the product to the oil.

Fiber Optic Spectrophotometry of Color Changes in Cooked Chicken Muscles

A fiber optic spectrophotometer with a continuously variable interference filter monochromator was used to measure the absorbance spectra of breast and leg meat from chickens. At less than 450 nm, absorbance was very high in both red and white muscles. In each spectrum, an absorbance peak at 560 nm due to myoglobin was detected. These peaks were of greater magnitude in red muscles than in white muscles. Thorough cooking by baking and pressure frying caused a marked drop in absorbance at all visible wavelengths above 500 nm. The absorbance peak of myoglobin was greatly reduced after cooking.