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The reduction of oil uptake in vacuum-fried Pleurotus eryngii chips by ultrasound assisted pretreatment was investigated regarding the pore structure changes. Pore structure of P. eryngii chips with four pretreatments, such as blanching, blanching + osmosis, blanching + ultrasound and blanching + ultrasound assisted osmosis was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). In addition, the quality parameters of vacuum-fried P. eryngii chips such as hardness, rehydration ratio, reducing sugar, protein and oil content were also measured. The results showed that the oil absorption of vacuum fried P. eryngii chips was affected by the porous structure. The oil content of vacuum fried P. eryngii chips was significantly and positively correlated with the pores with diameters above 50, 5–50, and 0.5–5 μm in the samples both before and after vacuum frying, while negatively correlated with the pores with diameters below 0.5 μm. Ultrasound pretreatment changed the microporous structure of P. eryngii chips, effectively hindering the oil absorption of samples. In particular, ultrasound assisted osmosis pretreatment induced the formation of more micropores. It was concluded that blanching + ultrasound assisted osmosis pretreatment is a promising method to reduce oil absorption and improve the quality of vacuum fried foods.

The characteristics of fried edamame were investigated in a newly designed vacuum frying assisted by ultrasound and microwave (USMVF) equipment to get better frying efficiency, shorten the frying time and improve the quality of fried edamame at low frying temperature in this work. Three frying temperatures (80,90 and 100 C) were comparatively analyzed in USMVF, microwave-assisted vacuum frying (MVF) and vacuum frying (VF). The USMVF remarkably enhanced the moisture diffusivity and moisture loss than MVF and VF at each frying temperature (80, 90 and 100 °C). The values of moisture diffusivity and activation energy were in between 2.014-3.823 x 10-9 m²/s and 22.57-20.07 kj/mol, respectively. Ten distinct mathematical models were applied to explain the dehydration kinetics of fried edamame and the most suitable model found was Midilli model. The drying data (moisture ratio versus time) were successfully fitted to the Midilli model. The energy consumption in USMVF decreased, diminishing by 28-39% depending on the frying temperature used in this work. The oil content and water activity of fried edamame was also reduced in the USMVF compared to the samples treated with MVF and VF. The color and texture (crispness), chlorophyll and vitamin C of fried edamame were also significantly improved in the USMVF. [ABSTRACT FROM AUTHOR]

As an important research aspect in food industry, fried products possessing both low oil content and good appearance still poses a challenge. The processing parameters of vacuum fried shiitake mushroom slices were investigated using response surface methodology. Frying temperature, vacuum pressure and frying time were studied as independent variables due to their significant effects on the quality attributes. Temperature and vacuum pressure presented the opposite effects on the four responses, for instance, the enhancement of fracturability and sensory performance and the reduction of color difference and oil absorption were observed as the temperature decreasing and vacuum pressure increasing. However, frying time generally induced all the response values increased among the testing range but only fracturability decreased after 28 min. In the optimal vacuum frying condition of frying temperature 105 °C, vacuum pressure −0.085 MPa and frying time 27.3 min, the total oil content and sensory values were observed to be 33.54% higher and 18.78% lower than those in conventional frying condition. The reason was supposed to be stronger surface-related phenomenon due to faster moisture loss and the resistant structure formation as starch gelatinization in vacuum frying environment. It provided a feasible optimized vacuum frying process for low-oil content and comprehensive acceptability fried shiitake slices. • Independent variables showed significant effects on shiitake quality attributes. • Temperature and vacuum pressure presented opposite effects on the responses. • Mechanism of low oil in vacuum may relate with water loss and starch gelatinization. • Optimum frying conditions can produce a low-oil and more acceptable fried mushroom. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovative frying methods are nowadays used to reduce the oil absorption in fried snacks such as chips. • Frying is considered to be a primary method of cooking throughout many food chains and catering industries. • This study evaluates novel technologies to improve the organoleptic properties of fried foods while reducing oil uptake. • Innovative methods such as air frying, microwave frying, and vacuum frying is a cost-effective and efficient process. • The fast-food industry has been adopting novel frying methods to extend the shelf life of products andtheirs quality. Frying is one of the most popular and traditional processes used in the food industry and food services to manufacture products that are high in quality and with unique sensory characteristics. The most common method of frying is deep-fat frying, used worldwide due to its distinct flavor profile and sensory aspects, which leads to physio-chemical changes at both macro and micro levels. One of the major concerns with deep-fried foods is their high oil content, and a variety of metabolic disorders can be caused by overconsumption of these foods, including heart disease, obesity, and high cholesterol. Due to their enticing organoleptic properties with their delicious flavor, pleasing mouthfeel, and unique taste, making them irresistible, it is also responsible for undesirable and unacceptable characteristics for consumers. Oil absorption can be reduced by developing novel frying methods that limit the amount of oil in products, producing products with fewer calories and oil while maintaining similar quality, flavor, and edibility. In addition, different pretreatments and post-frying treatments are applied to achieve a synergistic effect. The transfer of mass and heat occurs simultaneously during frying, which helps to understand the mechanism of oil absorption in fried food. Researchers have discovered that prolonged heating of oils results in polar compounds such as polymers, dimers, free fatty acids, and acrylamide, which can alter metabolism and cause cancer. To reduce the oil content in fried food, innovative frying methods have been developed without compromising its quality which also has improved their effect on human health, product quality, and energy efficiency. The aim is to replace the conventional frying process with novel frying methods that offer fried food-like properties, higher nutritional value, and ease of use by replacing the conventional frying process. In the future, it might be possible to optimize frying technologies to substantially reduce fried foods' oil content. This review focuses on a detailed understanding of different frying techniques and attempts to focus on innovative frying techniques such as vacuum frying, microwave cooking, and hot-air frying that have shown a better potential to be used as an alternative to traditional frying. [ABSTRACT FROM AUTHOR]

Consumers like fried snacks, and taste, color, and texture are key aspects in their preference. However, during frying of foods some toxic compounds, such as furan and acrylamide, are produced. The objective of this work was to mitigate furan and acrylamide formation in potato chips, without affecting their main quality attributes, by using vacuum frying. To accomplish this purpose, potato slices were fried at atmospheric ( P 29.92 inHg) and vacuum conditions ( P 3.00 inHg), using equivalent thermal driving forces ( T − T = 50, 60, or 70 °C). Furan and acrylamide concentration, oil content, and texture of both atmospheric and vacuum-fried samples were determined. Vacuum-fried potato chips showed reductions of about 81, 58, and 28% of furan, acrylamide, and oil content, respectively, when compared to their atmospheric counterparts. Additionally, the texture was not affected ( p > 0.05) by changes in the pressure during frying. Results clearly showed that vacuum frying is an effective technology for furan and acrylamide mitigation in potato chips, since it reduces the content of both contaminants and preserves the quality attributes of fried snacks. [ABSTRACT FROM AUTHOR]

Vacuum frying is a new technology that can be used to improve the quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper, the atmospheric and vacuum frying of Reshte-Khoshkar (a traditional Gilan-Iran sweet cookie) were compared. Four pressure levels (47.4, 57.83, 70.1 and 101.325 kPa), with three frying times (130, 160 and 190 s) and three thermal driving forces (ΔT=40, 60, and 80°C, constant difference between the oil temperature and the boiling point of water at the applied pressure) were used for frying. The effects of frying time, vacuum level and frying temperature on physical properties, such as moisture loss, oil absorption, and shrinkage were investigated. Moisture loss and oil absorption of fried Reshte-Khoshkar were significantly affected by frying pressure, frying time and frying temperature. The results showed that the moisture content decreased with increasing the frying pressure, frying time and frying temperature and fat content increased. Interestingly, a strong relationship between water loss and oil content was observed in both techniques. Vacuum frying was shown to be a promising technique that could be used to reduce oil content in the fried Reshte-Khoshkar. Shrinkage was not directly related to the frying condition of Reshte-Khoshkar.

The objective of this work was to sturdy the effect of different frying process as a novel technology (air and vacuum) compared with traditional frying process. The potato chips were fried in both air frying machines (Tefal Actifry) at 180°C ± 5°C for 40 min and vacuum frying at (120°C, 5.37 Kpa absolute pressure) for 40 min, 20 min/batch compared with traditional frying process at 180°C ± 5°C for 40 min, 20/ batch. After frying, the moisture content, oil uptake, acrylamide content and sensory characteristics were determined. Also, changes in some chemical properties of oil extracted from fried potato chips by different frying process were determined. Results indicated that the moisture content, oil uptake and acrylamide content in fried potato chips by (air and vacuum) frying process were significantly lower than fried potato chips by traditional frying process. Changes in some chemical properties (Acid value, peroxide value, polar, polymer and oxidized fatty acids contents) of oil extracted from fried potato were significantly higher in traditional frying process than (air and vacuum) frying process. Sensory characteristics of fried potato chips by new methods of frying (Air and vacuum) surprised on fried potato chips for traditional frying process. Air and vacuum frying can therefore be considered suitable methods of preparing potato chips for modern people who consume excessive oils and are interested in healthier and high quality products. [ABSTRACT FROM AUTHOR]

Frying generally leads to losses in nutritional value of foods, the production of foods with high-fat content, darkening in color prior to complete cooking process and rapid reduction of frying oil quality because of high temperatures (150-200°C) and the presence of oxygen. Vacuum frying process can be used to eliminate these undesirable changes in both food and oil quality. Vacuum frying, a frying process at low temperature and pressure, ensures to obtain fried foods with superior quality, and also increases the frying time of oil. Due to the positive effects of vacuum frying, many vacuum frying equipments of laboratory, pilot, and industry scales have been recently production. In this study, vacuum frying process is defined and vacuum frying equipments and the effect of vacuum frying on food and oil quality are reviewed. [ABSTRACT FROM AUTHOR]

Demand for safe and nutritionally rich fried products is gaining a momentum among consumers, leading to the increased consumption of vacuum fried products. The impact of vacuum frying (VF)(110 °C, 40 kPa) on chemical composition of food, fatty acid profile, microstructure, oxidative stability and sensory attributes was assessed and differentiated with that of atmospheric frying(AF) (180 °C). The potato slices were fried in mustard and soyabean oil used repetitively for 25 h. The oil content of VF potato chips was lower (15.18%) than AF chips (18.98%), however water loss in AF chips was higher than VF chips by 1.63-fold. VF significantly prevented the PUFA degradation, minimizes transfatty acid (TFA) formation and maintain a low C18:2/C16:0 ratio as compared to AF. VF Chips fried in soyabean oil show an increase in TFA content from 2.15 to 2.63% and a decrease in PUFA from 51.57 to 45.16% as compared to AF chips where TFA content increased from 2.15 to 3.72% and PUFA shows a higher reduction from 51.57 to 37.69% at the end of 25 h of frying. This indicate that in AF, oil is safe for use upto 10 cycles of frying, while as in VF, the same oil can be used for upto 40 cycles of frying without quality deteoriation. Sensorial analysis revealed that VF chips retain a better colour, taste and flavour but were less crispy than that of AF chips. These findings validate the application of vacuum frying technology for the production of high-quality foods with lesser degradation of frying oil. Food manufacturers are now impelled by the health-conscious consumer base for the production of healthy food products. The toxic effect of foods fried in degraded oils on human health is now widely known and thus the production of safe fried foods is the need of hour globally. In this context, vacuum frying is the most feasible approach for the production of quality fried products retaining the natural colour, flavour, sensory and nutritional properties better than that of atmospheric frying. Vacuum frying causes the least degradation of fatty acid of the frying oil and the fried potatoes, producing healthy potato chips. Therefore, the oil used for vacuum frying have a greater shelf life and oxidative stability than atmospheric frying. However, the higher installation cost of vacuum fryer still limits its use in the street fried food market, where degradation of oil is more likely. Thus, for its widespread commercialisation in developing countries, steps should be taken both by government and manufacturing companies to reduce the installation costs. • Vacuum frying minimizes the PUFA degradation and minimize TFA formation compared with atmospheric frying. • Vacuum fried chips retained better nutritional parameters. • Vacuum fried chips show low oil content than atmospheric fried chips. • Oxidative stability of frying oils was higher in vacuum frying compared to atmospheric frying. • Vacuum frying technology produces high-quality foods with lesser degradation of frying oil. [ABSTRACT FROM AUTHOR]

This paper explores the possibility of combining moderate vacuum frying followed by post-frying high vacuum application during the oil drainage stage, with the aim to reduce oil content in potato chips. Potato slices were initially vacuum fried under two operating conditions (140 °C, 20 kPa and 162 °C, 50.67 kPa) until the moisture content reached 10 and 15 % (wet basis), prior to holding the samples in the head space under high vacuum level (1.33 kPa). This two-stage process was found to lower significantly the amount of oil taken up by potato chips by an amount as high as 48 %, compared to drainage at the same pressure as the frying pressure. Reducing the pressure value to 1.33 kPa reduced the water saturation temperature (11 °C), causing the product to continuously lose moisture during the course of drainage. Continuous release of water vapour prevented the occluded surface oil from penetrating into the product structure and released it from the surface of the product. When frying and drainage occurred at the same pressure, the temperature of the product fell below the water saturation temperature soon after it was lifted out of the oil, which resulted in the oil getting sucked into the product. Thus, lowering the pressure after frying to a value well below the frying pressure is a promising method to lower oil uptake by the product. [ABSTRACT FROM AUTHOR]

Excess consumption of fat, a main component in fried food, is a key dietary contributor to coronary heart disease and perhaps some types of cancer. Although consumers are interested in healthier snacks, they are not willing to sacrifice organoleptic properties. Vacuum frying might be an alternative for the production of nutritious, healthy, palatable, and novel snacks. The objective of this review is to discuss the effect of atmospheric deep-fat frying on the main microstructural components and quality parameters of fried food, to understand how quality can be improved by lowering the operating pressure and, therefore, the processing temperature. [ABSTRACT FROM AUTHOR]

Vacuum frying is an alternative way to improve the quality of the fried food and could reduce the final oil uptake in the product. The product is heated at low pressure thus decreasing the boiling points of the frying oil and the water in the product. Moreover, the absence of air during vacuum frying may inhibit lipid oxidation and enzymatic browning, and therefore, the color and nutrients of samples can be largely preserved. Many food research projects involving snack food industries therefore attempt to understand oil uptake during the vacuum-frying process in order to control and reduce the fat content of fried products without deteriorating their desirable organoleptic characteristics. This article is an update of the state-of-the-art in vacuum-frying technology, showing the effect of pretreatments and frying conditions on quality characteristics of the products. Facts pertaining to equipment and operation conditions are included. On the other hand, mathematical models to describe oil uptake and water loss are also mentioned. The effect of this treatment on color, texture, and nutritional value of the final products is also discussed. [ABSTRACT FROM AUTHOR]

Consumers look for products that contribute to their wellness and health, however, even health-conscious consumers are not willing to sacrifice organoleptic properties, and intense full-flavor snacks remain an important trend. The objective of this study was to examine most important quality parameters of vacuum (1.92 inHg) and atmospheric-fried carrot, potato, and apple slices to determine specific advantages of vacuum technology. Slices were fried using equivalent thermal driving forces, maintaining a constant difference between oil temperature and the boiling point of water at the working pressure (ΔT = 60 and 80 °C). This resulted in frying temperatures of 160 and 180 °C, and 98 and 118 °C, for atmospheric and vacuum frying, respectively. Vacuum-fried carrot and potato chips absorbed about 50% less oil than atmospheric-fried chips, whereas vacuum-fried apple chips reduced oil absorption by 25%. Total carotenoids and ascorbic acid (AA) were greatly preserved during vacuum frying. Carrot chips vacuum fried at 98 °C retained about 90% of total carotenoids, whereas potato and apple slices vacuum fried at 98 °C, preserved around 95% of their initial AA content. Interestingly, results showed that the antioxidant capacity of chips may be related to both the presence of natural antioxidants and brown pigments developed at elevated temperatures. A way to reduce detrimental effects of deep-fat frying is through operating-pressure reduction, the essence behind vacuum deep-fat frying. In this way, it is possible to remove product moisture at a low temperature in a low-oxygen environment. The objective of this research was to study the effect of oil temperature reduction when vacuum frying traditional (potatoes) and nontraditional products (carrots and apples) on most important quality attributes (vitamins, color, and oil uptake). Results are promising and show that vacuum frying can be an alternative to produce nutritious and novel snacks with desired quality attributes, since vitamins and color were greatly preserved and oil absorption could be substantially reduced. [ABSTRACT FROM AUTHOR]

Abstract: Recent consumer trends towards healthier and low fat products have had a significant impact on the snack industry. The objective of this study was to examine the most important quality parameters of vacuum and atmospheric fried carrot slices in order to identify the specific advantages of vacuum technology. Said parameters include oil uptake, colour changes, and trans α and β-carotene degradation. Equivalent thermal driving forces were used (ΔT =60°C and 80°C) to compare the processes, maintaining a constant difference in temperature between the oil and the boiling point of water at the working pressure. The results showed that vacuum frying can reduce oil content by nearly 50% (d.b.) and preserve approximately 90% of trans α-carotene and 86% of trans β-carotene. This process also allowed for the raw carrot colour to be preserved, which was reflected by good correlations between a∗ and trans β-carotene content, b∗ and trans α-carotene content, and hue and total carotenoid content. [Copyright &y& Elsevier]

Abstract: 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 (24.9kPa). Various combinations of draining times (30, 60, and 90s) and vacuum break velocity, VBV (0.75, 2.21, 4.43 and 12.43kPas−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. [Copyright &y& Elsevier]

Abstract: The objective of this research was to determine the kinetics of water loss and oil uptake during frying of pre-treated potato slices under vacuum and atmospheric pressure. Potato slices (diameter: 30mm; width: 3mm) were pre-treated in the following ways: (i) raw potato slices “control”; (ii) control slices were blanched in hot water at 85°C for 3.5min; (iii) blanched slices were dried in hot air until reaching a moisture content of ∼0.6g water/g dry basis. The slices were fried under vacuum (5.37kPa, absolute pressure, at 120, 130 and 140°C) and atmospheric conditions (at 180°C). Two models based on the Fick''s law were used to describe water loss: (i) with a constant effective diffusive coefficient; and (ii) with a variable effective diffusive coefficient. Oil uptake data were fitted to an empirical model, with a linear behavior for short times whereas the model was time independent for long times. The variable diffusivity model better fitted experimental water loss, giving values of effective diffusivity between 4.73×10−9 and 1.80×10−8 m2/s. The proposed model for the study of the kinetics of oil uptake fitted the experimental data properly. Control and blanched vacuum fried potato chips increased their final oil contents to 57.1% and 75.4% respectively, when compared with those fried at atmospheric pressure. However, the oil absorption of dried vacuum fried potato chips diminished by ∼30%. [Copyright &y& Elsevier]

Abstract: Vacuum deep-fat frying is a new technology that can be used to improve quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper atmospheric and vacuum frying of apple slices were compared, in terms of oil uptake, moisture loss and color development. In addition, some apple slices were pre-dried (up to 64% w.b.) before vacuum frying to determine the overall effect. To carry out appropriate comparisons between both technologies equivalent thermal driving forces were used in both processes (ΔT =40, 50, 60°C), keeping a constant difference between the oil temperature and the boiling point of water at the working pressure. Vacuum frying was shown to be a promising technique that can be used to reduce oil content in fried apple slices while preserving the color of the product. Particularly, drying prior to vacuum frying was shown to give the best results. For instance, when using a driving force of ΔT =60°C, pre-dried vacuum fried slices absorbed less than 50% of the oil absorbed by atmospheric fried ones. Interestingly, a strong relationship between water loss and oil content was observed in both technologies, allowing the extension of observations that have been made for atmospheric frying. [Copyright &y& Elsevier]