Effects of maltodextrin level,frying temperature and time on the moisture,oil and beta‐carotene contents of vacuum‐fried apricot slices

Response surface methodology was used to investigate the effects of frying temperature, time and maltodextrin (MD) levels on the moisture, oil and beta‐carotene contents of the vacuum‐fried apricot slices. Based on the results, the moisture content of vacuum‐fried apricot slices decreases with increasing frying temperature and frying time. Generally, the oil content of vacuum‐fried apricot slices decreases with decreasing frying temperature and frying time. The beta‐carotene content of vacuum‐fried apricot slices increases with increasing frying temperature. But the trend of increase in the beta‐carotene content of the product with frying temperature was higher at lower MD level. When processing vacuum‐fried apricot slices, a frying temperature of 100 °C, frying time of 72.5 min and an MD level of 70% must be used to achieve a product of acceptable moisture, oil and beta‐carotene contents.     

Effects of processing conditions on the quality of vacuum‐fried carrot chips

The effects of pretreatment and vacuum frying conditions on the quality of fried carrot chips were studied. The moisture and oil contents of fried carrot chips were significantly (p < 0.05) reduced when blanched carrot slices were pretreated by immersion in fructose solution and freezing prior to vacuum frying. Furthermore, more uniform porosity was observed on the vertical cross‐section of carrot chips when examined by scanning electron microscopy. During vacuum frying, the moisture content, colour and breaking force of carrot chips decreased while the oil content increased with increasing frying temperature and time. However, there was no apparent change in Hunter ΔE with time when the frying temperature was below 100 °C and the frying time was below 25 min. Results of this study suggest that vacuum frying at moderate temperature (90–100 °C) for 20 min can produce carrot chips with lower moisture and oil contents as well as good colour and crispy texture. Copyright © 2005 Society of Chemical Industry     

Effects of processing conditions on the quality of vacuum fried apple chips

The effects of pretreatment and processing conditions on the quality of vacuum fried apple chips were studied. As blanched apple slices were pretreated by immersing in fructose solution and freezing prior to vacuum frying, more uniform porosity was observed on the surface (or cross-section) of apple chips as examined by scanning electron microscopy (SEM). During vacuum frying, the moisture content and breaking force of apple chips decreased with increasing frying temperature and time while the oil content increased. The L values of fried apple chips decreased apparently with increasing frying temperature. However, when apple slices were fried at 100°C for up to 20 min, both a and b values increased rapidly. Statistical analysis with the central composite rotatable design showed that the moisture content, oil content, color, and breaking force of apple chips were significantly (P⩽0.05) correlated with concentration of immersing sugar solution, frying temperature and frying time. Based on surface responses and contour plots, optimum conditions were: vacuum frying temperature of 100–110°C, vacuum frying time of 20–25 min, and immersing fructose concentration of 30–40%.     

Physicochemical Properties Changes of Donuts During Vacuum Frying

Vacuum frying was explored to cook donuts and compared to the conventional atmospheric frying. A temperature of 190°C was used for atmospheric frying. Three vacuum levels (3, 6, and 9 kPa vacuum) with three temperature levels (150, 165, and 180°C) were used for vacuum frying. The effects of initial moisture content (IMC), vacuum level and frying temperature on physicochemical properties, such as moisture loss, oil absorption, and quality were investigated. The properties of fried donuts were significantly affected by IMC. Under vacuum frying, volume and total color changes were affected by frying temperature; and oil uptake was affected by vacuum and frying temperature. Frying temperature and vacuum were not directly related to the final moisture content (MC) of donuts. There was no relationship between MC and fat content of donuts. Donut texture was directly related to the vacuum and frying temperature.     

Quality changes in chicken nuggets fried in oils with different degrees of hydrogenatation

Quality changes in chicken nuggets fried in different mixtures of hydrogenated and non-hydrogenated canola oils were studied. Colour, texture, oil and moisture contents of the chicken nugget samples fried at 190 °C for 30, 60, 90, 120, 180, 240 and 300 s were investigated. The proportions of hydrogenated to non-hydrogenated frying oils used in the study were 0%, 20%, 40%, 60%, 80% and 100%.Results indicate that increase in frying time resulted in decreased product lightness (L*) whereas redness (a*) and yellowness (b*) increased. The maximum load to puncture increased with increasing frying time. In addition, oil content increased slowly with frying time, and moisture content decreased as expected. Both frying times and oil types have significant effects on the quality parameters investigated. First-order kinetic equation was used to describe colour changes as well as oil and moisture contents of the samples. Oil and moisture contents had negative correlation relationship. With increasing degree of oil hydrogenation, the surface colour of the fried chicken nuggets samples were lighter, texture increased, oil and moisture contents decreased.     

常压煎炸和真空煎炸对中国对虾品质的影响

探究常压煎炸和真空煎炸对中国对虾理化性质和感官品质的影响。测定了不同煎炸温度下两种煎炸方式对中国对虾的水分含量、含油量、色泽、虾青素含量和感官品质的影响。结果表明：随着煎炸温度的升高,两种煎炸方式下中国对虾的水分含量均降低,含油量均增加,但真空煎炸下中国对虾的变化幅度较低;两种煎炸方式下中国对虾的虾青素含量均随着煎炸温度的升高呈现先增加后减少的趋势;相同热驱动力下,真空煎炸的中国对虾的色泽、虾青素含量和感官品质均优于常压煎炸的。相比于常压煎炸,真空煎炸的中国对虾品质更佳。     

EVALUATION OF THE TEXTURE OF FRIED POTATOES

Texture of potatoes with different shapes (slices and strips) were evaluated after frying and in some cases after baking. Blanched and unblanched potato slices (Bintje variety) were fried at four oil temperatures: 160, 170, 180 and 190C until reaching a moisture content of ∼1.7%. A puncture test with three point support for the slices was applied to measure the texture of potato chips using the following parameters extracted from the force versus distance curves: maximum force of break (MFB) and deformation of break (DB). These two parameters were useful to follow the changes in texture of the fried slices with moisture content at different frying temperatures. Blanched and unblanched potato strips were partially fried at 160C and 190C for 60, 90 and 120 s. The par-fried potatoes were frozen at -20C for one day after which they were baked at 200C for 15 min. The texture of the baked potato strips was evaluated using a bending test with two support points. From the force versus distance curves, two parameters were extracted: maximum force of deformation (MFD) and maximum deformation (MD). Significant higher MFB and lower DB values (P > 0.1) for unblanched fried slices indicate that these are crispier than blanched chips for moisture contents lower than 4% (6.59 N and 0.62 mm vs 5.74 N and vs 0.75 mm for unblanched and blanched chips, respectively, average values for the four frying temperatures employed). There was no effect of the frying temperature and the pretreatment (blanching or unblanching) on the texture of the frozen par-fried potatoes after baking when compared at the same residual moisture content, but blanched potato strips lost moisture more slowly both in frying and in baking.     

The optimization of vacuum frying to dehydrate carrot chips

The effects of pretreatment and processing conditions, such as frying temperature, absolute vacuum pressure and frying time; on the properties of fried carrot chips were studied. Statistical analysis with response surface regression showed that moisture content, fat content and breaking force of carrot chips were significantly (P < 0.05) correlated with frying temperature, vacuum absolute pressure and frying time. The optimum conditions were a vacuum frying temperature of 100–110 °C, a vacuum absolute pressure of 0.010–0.020 MPa and a frying time of 15 min.     

Effects of osmotic pretreatment and frying conditions on quality and storage stability of vacuum-fried pumpkin chips

The effects of osmotic (OP), ultrasound-assisted osmotic pretreatment (UAOP) and frying conditions on quality and storage stability of vacuum fried pumpkin chips were investigated. The pumpkin samples were pretreated in maltodextrin solution and subsequently fried at different temperatures (90–110 °C) and time periods (10–30 min). The results demonstrated that the moisture content, water activity, lightness, yellowness and carotenoid content of the fried chips decreased, while oil content, hardness and a* (dark brown colour) value increased with increasing frying temperature and time. UAOP reduced about 16.0% of oil absorption and enhanced approximately 70% of carotenoid retention in the fried chips. UAOP samples were also more stable during storage than the untreated ones, indicated by lower degradation kinetics constants of key quality parameters. The proposed pretreatment could be an effective method for food industries to develop vacuum fried pumpkin chips with improved quality and stability.     

Optimization of processing conditions for vacuum frying of high quality fried plantain chips using response surface methodology (RSM)

Optimization of processing conditions (temperature 122 to 136°C, vacuum pressure 9.91 to 19.91 cmHg, and frying time 3 to 9 min) during vacuum frying of plantain chips was investigated using a Box-Behnken experimental design with response surface methodology (RSM). Models for various responses were developed and optimized frying conditions using numerical solutions were established. Optimized vacuum fried samples were compared with atmospheric fried samples based on the concept of equivalent thermal driving force (ETDF). Frying parameters had significant (p<0.05) effects on the moisture content, texture, and color with a coefficient of determination (R ²) for quadratic model responses varying between 0.53 and 0.99. Optimum vacuum frying conditions for plantain chips were a frying temperature of 133°C, vacuum pressure of 9.91 cmHg, and frying time of 6 min based on desirability concepts. Vacuum fried plantain chips had more acceptable sensory properties, based on ETDF values, than atmospheric fried samples.     

LIMPNESS OF FRIED POTATO SLABS DURING POST-FRYING PERIOD

The rupture stress (RS) of fried potato slices (1.60 mm thick) and of the crust of fried potato slabs (FPS) having lengths of 60 mm and sides of 8, 10 and 12 mm, was determined during the post‐frying period by a puncture test. The RS of fried potato slices decreased as water activity increased from 0.22 to 0.85. The RS of FPS diminished in the first 5–6 min when exposed to ambient conditions and remained almost constant thereafter. A novel videotape technique and image analysis were used to follow deflection of FPS in the post‐frying period. An apparent modulus based on the composite structure of FPS and calculated from beam mechanics decreased with time in a trend similar to that of the textural parameters. We concluded that changes in physical properties of the crust because of moisture accumulation are the major causes of loss of texture (limpness) in FPS during the post‐frying period.     

Effect of vacuum frying on main physicochemical and nutritional quality parameters of pineapple chips

BACKGROUND: Slices of MD‐2 pineapple hybrid were vacuum fried at 24 kPa according to a central composite experimental design that simultaneously varied frying time (6.3–7.7 min) and temperature (106.3–117.7 °C). Major physicochemical and nutritional quality factors were measured and modelled using a second‐order polynomial equation. RESULTS: Moisture content, water activity a_w, colour parameters L*, C* and H* and total vitamin C content decreased while total phenolic content and dehydroascorbic acid content increased with increasing frying time and temperature. Oil content, hardness and hydrophilic antioxidant capacity reached minimum values near the centre of the experimental field. By superimposing contour curves, it was determined that processing conditions of 6.9 min frying time and 112 °C frying temperature produced pineapple chips with a golden colour (L*≥ 60, C*≥ 50, H*≥ 80), an a_w of less than 0.29, a moisture content of about 4% and a hardness of less than 1.9 N, giving rise to a crispy texture. Oil content was about 20% (d.b) and residual total vitamin C content (～90 mg per 100 g wet basis (w.b.)) was high. Phenolic compound content was about 150 mg gallic acid equivalents per 100 g w.b. and antioxidant capacity was around 22 µmol Trolox equivalents g^?1 w.b. CONCLUSION: Vacuum frying is a dehydration process that produces healthy fruit snacks which partially preserve the fruit's original colour and nutritional compounds and have a high hydrophilic antioxidant capacity. Copyright © 2008 Society of Chemical Industry     

Effect of frying time on acrylamide content and quality aspects of French fries

The effect of frying time on quality and acrylamide (AA) content of French fried potatoes, obtained simulating home-cooking practices, was studied in order to investigate the optimal conditions to minimize the amount of produced toxicant together with the maintenance of good culinary quality. French fries were obtained from fresh potatoes using a domestic fryer with static basket; a 4:1 oil:product ratio and a fixed initial oil temperature of 180 °C were used. Several batches were fried at different times (3, 4, 5, 6, 7, 8, 9 min). During frying tests the oil, the sticks surface and core temperatures were measured by thermocouples. Analysis of water removal, oil uptake, colour, texture and AA content were carried out on fried final products. AA content increased exponentially increasing the frying time. In our working conditions after around 4 min of frying, when the temperature of potato surface and the oil bath reached, respectively, 120 and 140 °C, the increase of time became a key factor in terms of the quantity of AA and its formation rate. On the basis of colour, oil content and AA level the best culinary product was obtained after 5 min of frying.     

远红外油炸对鸡肉品质的影响

主要研究了远红外辅助油炸和普通热传导式油炸两种方式对鸡肉油炸品质的影响。实验选用新鲜市售鸡胸肉,油炸温度为(165±2)℃,考察其在70～110s油炸时间段内色泽、质构、中心温度、水分含量、含油量和失重率的变化规律。结果表明:除鸡肉的硬度值外,不同的油炸方式和油炸时间对鸡肉各项测定指标均影响显著(P<0.05)。以普通热传导式油炸为对照,远红外油炸的鸡肉明度(L*)降低,红度(a*)和黄度(b*)增加;硬度值变化不显著,弹性值略有增加;内部的温度上升均匀、波动小;最高含油量降低33%,最大失重率降低10.21%。因此,远红外油炸促进了鸡肉色泽的变化,使内部受热均匀,降低了含油量,减少油炸损失,对油炸品质的提高起到积极作用。     

Comparison between atmospheric and vacuum frying of apple slices

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.     

Vacuum frying as a route to produce novel snacks with desired quality attributes according to new health trends

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. PRACTICAL APPLICATION: 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.     

Effects of different batter formulations on the quality of deep-fat-fried carrot slices

The effects of batter coating containing pregelatinized tapioca starch or maltodextrin at different concentrations (1, 3 or 5%) on product quality of deep-fat-fried carrot slices were evaluated. Coated slices were fried for 2, 3 and 4 min at 170 °C. Coating pickup of batter formulations and moisture and oil contents, porosity, texture and colour of fried slices were determined. Batter without pregelatinized starch or maltodextrin addition was used as the control. Addition of 5% pregelatinized tapioca starch to the batter formulation provided the crispiest product with the lowest oil content. Increasing maltodextrin concentrations enhanced the crispness and colour development of the fried product but had an adverse effect on porosity, moisture and oil contents of carrot slices.     

Oil uptake and texture development in fried potato slices

The objective of this work was to study oil absorption and the kinetics of texture development of fried potato slices during frying. Prior to frying, potato slices were blanched in hot water at 85 °C for 3.5 min. Unblanched slices were used as the control. Control and blanched potato slices (Panda variety, diameter: 37 mm, width: 2.2 mm) were fried at 120, 150 and 180 °C until reaching moisture contents of 1.8% (total basis) and their texture and oil content were measured periodically. Oil uptake was higher in 15% for blanched samples than for control samples after 20 s of frying. Besides, the higher the frying temperature, the lower the oil absorption in control samples. Textural changes in fried potato slices were followed by the parameter maximum force (MF) extracted from the force vs. distance curves corresponding to different sampling times. Normalized maximum force (MF*) was used in modeling textural changes in the potato slices during frying in both the initial tissue softening process and the later crust development process. Higher temperatures accelerated these processes; however neither the temperature nor the pre-treatment had a significant effect (P > 0.05) over the final texture of the fried potato chips.     

Mechanisms of oil uptake during deep frying and applications of predrying and hydrocolloids in reducing fat content of chips

Deep frying resulting in high-fat content is extensively used in the food industries and domestic households, and becoming an integral diet globally. The physical and chemical changes and oil uptake contributes to the unique taste and texture of fried food. Consumption of food high in fat is a health concern due to the increasing rate of obesity and cardiovascular diseases. Consumer awareness has led food industries to aim at fat reduction while maintaining the organoleptic properties of fried foods. This article reviews recent findings in reducing fat content emphasising on pretreatments. Modification of product surface was proven to lower fat content, reducing moisture content by 10% after predrying results in 54% fat reduction, while hydrocolloids coating in potato chips reduces fat content by 57% after deep frying. Although current technology, vacuum frying and air frying have a promising result in using less oil, but the initial cost is high.     

Effects of vacuum frying on structural changes of bananas

Effects of oil temperature, frying time, and ripeness on dimensional changes of vacuum fried bananas were studied. Banana slices with cross section diameters of 25-30 mm and a thickness of 3.5-4.5 mm were fried at temperatures of 100, 110, and 120 °C and 8 kPa for 20 min to determine which temperature produced the highest degree of expansion. Using this temperature, the width and thickness of the product were measured at 0, 5, 10, 15, and 20 min to model the dimensional changes as a function of moisture ratio. Sensory evaluation was conducted using a 7-point hedonic scale test to determine the effect of ripeness on acceptability of the product. Scanning electron microscopy (SEM) was used to analyze the structure of the vacuum fried bananas.The experimental results under this vacuum pressure revealed that frying temperature of 110 °C on bananas at the second day of ripeness yielded the highest volume expansion. Sensory evaluations did not unveil any significant difference (p > 0.05) in acceptability of the products based on ripeness. Results from SEM exhibited, as a function of frying time, a dramatic increase in the pore size of the bananas, while the Heywood shape factor indicated an overall increase in the product volume.