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%.     

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.     

Application of Vacuum Frying as a Furan and Acrylamide Mitigation Technology in Potato Chips

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 _abs 29.92 inHg) and vacuum conditions (P _abs 3.00 inHg), using equivalent thermal driving forces (T _{water boiling point} ? T _oil = 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.     

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 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.     

Vacuum frying of high-quality fruit and vegetable-based snacks

Sweet potato, green beans, Tommy Atkins mango, and blue potato were fried in a vacuum frying process at a temperature of 120-130 ± 1°C. Before frying, green beans and mango slices were soaked in a 50% maltodextrine 0.15% citric acid solution. The products were also fried in a traditional (atmospheric pressure) fryer at 160-165 ± 1°C for 4 min. A 30-member consumer panel rated the sensory quality of both types of fried snacks using a 1-9 hedonic scale. Compared with traditional frying, oil content of vacuum-fried sweet-potato chips and green beans was 24% and 16% lower, respectively. Blue potato and mango chips had 6% and 5% more oil, respectively, than the traditional-fried samples. Anthocyanin (mg/100 g d.b.) of vacuum-fried blue potato chips was 60% higher. Final total carotenoids (mg/g d.b.) were higher by 18% for green beans, 19% for mango chips, and by 51% for sweet-potato chips. Sensory panelists overwhelmingly preferred (p < 0.05) the vacuum-fried products for color, texture, taste, and overall quality. Most of the products retained or accentuated their original colors when fried under vacuum. The traditional-fried products showed excessive darkening and scorching. These results support the applicability of vacuum frying technology to provide high-quality fruit and vegetable snacks.     

Comparison of vacuum and atmospheric deep-fat frying of wheat starch and gluten based snacks

Vacuum frying was compared with atmospheric frying in the development of wheat starch and gluten based snacks in terms of oil uptake, texture, expansion, and color development. The comparison was based on the concept of equivalent thermal driving force (ETDF) (i.e., keeping a constant difference between the oil temperature and boiling point of water at the working pressure). Vacuum fried snacks were observed to absorb lower oil content at all ETDFs and as low as 27% less of atmospherically fried samples and lighter in color. A very strong relationship existed between texture and oil content on one hand; and expansion and oil content on the other hand for fried matrices from both technologies. SEM was used in validating the result. Vacuum frying can be used for the development of acceptable fabricated fried snacks from wheat starch and gluten with lower oil content and acceptable textural and color properties.

     

Quality changes of edible oils during vacuum and atmospheric frying of potato chips

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.Industrial relevanceFood 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.     

Reduction in hydroxymethylfurfural content in ‘churros’, a Spanish fried dough,by vacuum frying

This work explores the advantages of vacuum frying of ‘churros’, a Spanish dough pastry, compared to standard deep‐fat frying. Oil uptake, texture change, colour development, nonenzymatic browning and hydroxymethylfurfural (HMF) concentration were analysed at different frying conditions. The results obtained during vacuum frying at 100, 120 and 140 °C and 21 kPa were compared with those obtained at atmospheric pressure at 140 and 180 °C. For the same final water content, the vacuum fried ‘churros’ showed no significant differences in the fat uptake compared to those fried at atmospheric pressure (P > 0.05). However, the vacuum fried dough had a much crunchier texture. The evolution of the CIELab a* coordinate and the browning measurement at 280 nm show that vacuum frying is able to slow down the development of browning tones. Furthermore, products can be obtained with an HMF content <1 mg kg^?1 of dry dough.     

Effect of Osmotic Dehydration and Vacuum-Frying Parameters to Produce High-Quality Mango Chips

ABSTRACT:  Mango ( Mangifera indica  L.) is a fruit rich in flavor and nutritional values, which is an excellent candidate for producing chips. The objective of this study was to develop high-quality mango chips using vacuum frying. Mango (" Tommy Atkins ") slices were pretreated with different maltodextrin concentrations (40, 50, and 65, w/v), osmotic dehydration times (45, 60, and 70 min), and solution temperatures (22 and 40 °C). Pretreated slices were vacuum fried at 120, 130, and 138 °C and product quality attributes (oil content, texture, color, carotenoid content) determined. The effect of frying temperatures at optimum osmotic dehydration times (65 [w/v] at 40 °C) was assessed. All samples were acceptable (scores > 5) to consumer panelists. The best mango chips were those pretreated with 65 (w/v) concentration for 60 min and vacuum fried at 120 °C. Mango chips under atmospheric frying had less carotenoid retention (32%) than those under vacuum frying (up to 65%). These results may help further optimize vacuum-frying processing of high-quality fruit-based snacks.     

Reduction of Acrylamide Formation in Potato Chips by Low-temperature Vacuum Frying

ABSTRACT: Potatoes and other foods that have a high content of the amino acid asparagine and a high accumulation of reducing sugars are subject to the formation of acrylamide upon frying. The objectives of this research were (1) to analyze the level of acrylamide formed during deep-fat frying of potato chips and (2) to evaluate means of reducing acrylamide in potato chips by using different potato cultivars and vacuum frying. Several potato cultivars were used in this research, including Innovator (I), NDTX 4930–5W (N), ATX 854 04–8W (ATw), Atlantic (A), Shepody (S), ATX847806–2Ru (ATr), and White-Rose (W). An electric bench-top (atmospheric conditions)-type fryer was used to fry the potatoes. Three temperatures were used: 150 °C, 165 °C, and 180 °C. The vacuum frying experiments were performed at 118 °C, 125 °C, and 140 °C and a vacuum pressure of 10 Torr. The potatoes were sliced (1.5-mm thick) and fried for different lengths of times. For potatoes fried at 165 °C (for 4 min) at atmospheric conditions, the acrylamide contents were 5021 ± 55 ppb (W), 552 ± 25 ppb (I), 358 ± 50 ppb (N), 397 ± 25 ppb (ATw), 646 ± 55 ppb (A), 466 ± 15 ppb(S), and 537 ± 14 ppb (ATr). Vacuum frying reduced acrylamide formation by 94%. Results showed that both cultivar and modified frying systems can play an important role in reducing acrylamide formation in fried potatoes. As the frying temperature decreased from 180 °C to 165 °C, acrylamide content in potato chips reduced by 51% during traditional frying and by 63% as the temperature decreased from 140 °C to 125 °C in vacuum frying. Increased frying time increased acrylamide formation during traditional frying for all temperatures and frying methods analyzed. However, the effect on acrylamide concentration was greater for the traditional frying than the vacuum frying. Keywords: acrylamide, vacuum, frying, potato, temperature     

KINETICS OF ACRYLAMIDE FORMATION DURING TRADITIONAL AND VACUUM FRYING OF POTATO CHIPS

Acrylamide is considered a carcinogen in animals and a possible carcinogen in humans. It has been found in starch‐rich foods cooked at high temperatures. Vacuum frying (10 Torr) was investigated as a possible alternative to reduce acrylamide formation in potato chips. The cultivar Atlantic was used to determine the kinetics of acrylamide formation during traditional and vacuum frying at different temperatures. There was a 94% decrease in acrylamide content when potatoes were fried to the same final moisture content (1.5% ± 0.3% w.b.) under vacuum compared to those fried under atmospheric conditions. Acrylamide accumulation under vacuum frying was modeled using first‐order kinetics (during traditional frying, the logistic kinetic model was used). The behavior of the kinetics of acrylamide content in potato chips fried under the two processes was different mainly because of the different temperatures used. During traditional frying, higher temperatures are used (150 to 180C) and acrylamide after some time is produced but starts degrading, producing a constant level of acrylamide content at longer times. During vacuum frying (10 Torr), acrylamide increased exponentially (but at lower levels) for all frying times.     

低温真空油炸薯片生产工艺及其贮藏条件的研究

对马铃薯片进行低温真空油炸生产工艺的基础性研究,分析薯片在贮藏过程中水分、脂肪和VC含量的变化,并探讨等温吸湿规律。通过单因素试验确定最优的油炸工艺参数为温度105℃,时间20min,真空度0.090MPa;离心脱油的最佳条件为脱油转速400～500r/min,时间5～7min,真空度0.090MPa。研究结果对低温真空油炸薯片技术具有很好的指导和促进作用,同时改善了现在油炸薯片的品质和提高了能源利用率。     

Comparative study of physical and sensory properties of pre-treated potato slices during vacuum and atmospheric frying

The objective of this research was to study the effect of different processing conditions on physical and sensory properties of potato chips. Potato slices of Desirée and Panda varieties (diameter: 30 mm; thickness: 3 mm) were pre-treated in the following ways: (i) control or unblanched slices without pre-drying; (ii) blanched slices in hot water at 85 °C for 3.5 min and air-dried at 60 °C until a final moisture content of ∼0.6 kg water/kg dry solid; (iii) control slices soaked in a 3.5 kg/m³ sodium metabisulphite solution at 20 °C for 3 min and pH adjusted to 3. Pre-treated slices were fried at 120 and 140 °C under vacuum conditions (5.37 kPa, absolute pressure) and under atmospheric pressure until they reached a final moisture content of ∼1.8 kg water/100 kg (wet basis). An experimental design (3 × 2³) was used to analyze the effect of pre-treatment, potato variety, type of frying and frying temperature over the following responses: oil content, instrumental color and texture and sensory evaluation. Vacuum frying increased significantly (p < 0.05) oil content and decreased instrumental color and textural parameters. Sensory attributes, flavor quality and overall quality, were significantly improved using vacuum frying. The higher frying temperature (140 °C) increased ΔE, maximum breaking force, hardness and crispness and decreased L^* and b^* values. On the other hand, Panda potato variety improved the color of the product. A great improvement on color parameters was obtained using sulphited potato slices instead of the other pre-treatments. Although, the better flavor was obtained for control potato chips, no significant differences were found for overall quality between control and sulphited potato chips. Significant correlations (p < 0.01) between sensory and instrumental responses were found.     

Deep‐fat frying under moderate vacuum of potato cylinders

This 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.     

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.     

Modeling water loss and oil uptake during vacuum frying of pre-treated potato slices

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: 30 mm; width: 3 mm) were pre-treated in the following ways: (i) raw potato slices “control”; (ii) control slices were blanched in hot water at 85 °C for 3.5 min; (iii) blanched slices were dried in hot air until reaching a moisture content of ∼0.6 g water/g dry basis. The slices were fried under vacuum (5.37 kPa, 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%.     

Combination of Moderate Vacuum Frying with High Vacuum Drainage—Relationship Between Process Conditions and Oil Uptake

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.     

低温真空油炸山药脆片的工艺研究

对比不同油炸方式制作山药片,探究低温真空油炸山药脆片的优点及最佳生产工艺.以感官评价、含油率为考核指标,采用单因素和响应面方法对工艺进行优化,并通过色差仪和扫描电镜做色度及微观结构的观察.试验表明真空低温油炸山药脆片在色泽及含油率明显低于普通油炸方法,其最佳加工工艺为切片厚度6 mm,汽蒸5 min,油炸温度为95℃,...     

Response Surface Methodology Study for Optimization of Effects of Fiber Level, Frying Temperature, and Frying Time on Some Physicochemical, Textural, and Sensory Properties of Wheat Chips Enriched with Apple Fiber

In this study, wheat chips enriched with apple fiber were produced, and response surface methodology was used for the determination of the simultaneous effects of processing variables selected as fiber level (0–15 %), frying temperature (160–180 °C), and frying time (40–60 s) on some physicochemical, textural, and sensorial properties of chips. Ridge analysis was conducted to determine the optimum levels of processing variables. Predictive regression equations with high coefficient of determination (R ²?≥?0.728) were constructed. Addition of apple fiber increased the dry matter; ash content; L, a, and b values of samples, while increase of frying temperature caused decrease of the hardness values. Overall acceptability of chips enriched with apple fiber decreased with the increase of frying temperature, but wheat chips enriched with apple fiber and fried at low temperatures received highest sensory score. Ridge analysis showed that maximum taste score would be attained at fiber level?=?15 %, frying temperature?=?170 °C and frying time?=?40 s.