Effect of low temperature on the microwave-assisted vacuum frying of potato chips

The objective of this study was to investigate the effect of low temperature on the microwave-assisted vacuum frying of potato chips. A newly built, in-house, microwave-assisted frying machine was developed and used in this study. The effect of low temperature on the microwave-assisted vacuum frying of potato chips was investigated via comparing sample properties prepared with frying temperatures of 90°C, 95°C, and 100°C. The experience was taken at the same vacuum degree in every frying process. Parameters of included moisture content, oil content, color parameters (lightness, redness, and yellowness), and textures (hardness, crispness) were used to evaluate the effect of different frying temperatures on the microwave-assisted vacuum frying of potato chips. Results showed that with lower temperature in microwave-assisted frying, the rate of moisture evaporation of potato chips was slowed down and the time of the ending of frying was prolonged from 10 min with a frying temperature of 100°C to 14 min with 90°C and 12 min with 95°C. Meanwhile, the oil content in fried potato chips was increased with lower temperature in microwave-assisted vacuum frying. The breaking force of final products are not significantly (p > 0.05) affected in different frying temperatures of microwave-assisted vacuum frying. Also, the frying temperature of 100°C in microwave-assisted vacuum frying had better preservation of natural color than the lower frying temperature with prolonged frying time. Results showed that the temperature is one of the main factors that affect the quality of microwave-assisted vacuum frying of potato chips and the producer could find suitable temperature conditions according to experience.     

Use of rosemary extract in preventing oxidation during deep-fat frying of potato chips

The effect of using a rosemary extract on the stability of oil used for frying potato chips has been evaluated. Sliced potatoes were fried intermittently in soybean oil containing a natural extract from rosemary. The conditions used for frying were 185°C for 90 s. Two separate experiments, with and without replenishment of oil, were carried out. Oil samples were taken each day, not only from the frying pans but also by extraction with hexane from the chips. Changes in the induction period of the oil samples (Rancimat method) were determined. The induction period decreased as frying progressed. The reduction in the induction period was higher in the oil free of rosemary extract, and the chips were much darker in color. The oil containing the extract showed greater antioxidant activity, and reduced darkening and rancidity of the oil. Potato chips fried in the oil with added rosemary extract were more acceptable than chips fried in oil containing no extract until the last frying. The free radical scavenging activity of rosemary extract in comparison to other natural antioxidants was also determined by the reduction of O₂ ^.- in a hypoxanthine/xanthine oxidase system.     

Ultrasonically enhanced low-temperature microwave-assisted vacuum frying of edamame: Effects on dehydration kinetics and improved quality attributes

Abstract

Using ultrasound (US) at microwave-assisted vacuum Frying (MVF) program was investigated to acquire better process efficacy and bodily high-quality attributes of fried edamame. Different power degrees of US (0, 150, 300, 600 W) and temperature (80, 90, and 100?°C) were utilized in a constant microwave power and frequency of 1000 W and 28?kHz during ultrasound and microwave-assisted vacuum frying (USMVF) process. Ten different mathematical models were employed to describe dehydration kinetics of the fried edamame, and nonlinear regression analysis was used to determine model parameters. Concerning fitting performance, the most suitable model was the two-term model. Drying kinetics, effective moisture diffusivity (D_e), activation energy (E_a), and physical properties of fried samples were evaluated in this newly designed USMVF equipment using different ultrasound power to the studied temperature range. By increasing the US power level, the calculated D_e increased from 1.947?×?10^?9 to 4.742?×?10^?9 m²/s. The results have revealed that the E_a of this fried edamame decreased significantly with increasing the US power level. The USMVF process at every frying temperature increased the drying kinetics and D_e when compared to the non-USMVF process. The USMVF samples always gave lower oil content and water activity in contrast to the non-USMVF samples. The color and texture properties of fried edamame were significantly improved and higher the US power level in the USMVF produced a better progress. Vitamin C and chlorophyll retention of fried edamame was highest in US600MVF process.     

Effect of vacuum frying on the oxidative stability of oils

The purpose of this study was to evaluate frying oil quality with different assessment methods during vacuum frying of carrot slices. In six consecutive days, palm oil, lard, and soybean oil were fried under vacuum at 105°C for 20 min each hour in an 8-h shift. Peroxide value, acid value, carbonyl value, total polar components, dielectric constant (Food Oil Sensor reading), viscosity, and fatty acid composition were used to evaluate the quality of these oils. Results showed that palm oil and lard possess greater thermal stability than soybean oil. The decrease in C_18:2/C_16:0 ratio was greater for soybean oil than the other two oils. Of the assessment methods used, peroxide value, carbonyl value, total polar components, and dielectric constant all showed good correlation with frying time and between each other. Viscosity was suitable to assess vacuum-fried lard and soybean oil, but not palm oil. The measurement of dielectric constant, on the other hand, appeared to be unsuitable to assess vacuum-fried soybean oil.     

Dehydration of asparagus cookies by combined vacuum infrared radiation and pulse-spouted microwave vacuum drying

ABSTRACT

The restructured cookies were made from old stalks of asparagus (Asparagus officinalis). Combination of vacuum infrared radiation drying and pulse-spouted microwave vacuum drying (VIRD–PSMVD) was studied as a potential mean for dehydration of restructured cookies. The samples were first dried by VIRD and then by PSMVD to final moisture content less than 6%. Expansion ratio, texture, color, flavor, and other attributes of samples dried by this method were evaluated and compared with those dried by PSMVD and VIRD. Results showed that the samples dried by VIRD–PSMVD showed higher overall acceptability, crisper texture, and higher expansion ratio.     

Comparison of flavor compounds of potato chips fried in palmolein and silicone fluid

The importance of the frying oil as a heat-transfer medium and as a source of flavor precursors for the formation of potato chip flavor was investigated. Potato slices were fried in palmolein or silicone fluid, and the volatile flavor compounds of the resulting chips were isolated onto Tenax and analyzed by gas chromatography-mass spectrometry. Although the heat-transfer coefficients of the oils did not differ significantly, their temperature profiles during frying were different, probably due to greater turbulence on placing potato slices in palmolein, leading to more efficient heat transfer. Levels of Strecker aldehydes and sulfides in chips fried in the two media were not significantly different, but levels of pyrazines were significantly higher in palmolein-fried chips. Amounts of 2,4-decadienal were also significantly higher in palmolein-fried chips, but there was no significant difference in hexanal levels between the samples.     

Study of oil uptake and some quality attributes of potato chips affected by hydrocolloids

The use of coating agents is one effective way to reduce oil absorption in fried products. Reducing the fat content of fried foods by application of coatings is an alternative solution to comply with both health concerns and consumer preferences. The aim of this study was to analyze the effect of hydrocolloids as coating agent on the quantity of oil uptake and on sensory attributes of potato chips. The effect of the coating composition showed that the minimum fat content was related to 1% carboxymethyl cellulose (CMC), 0.5% xanthan, 0.3% guar and 1% xanthan with 21.2, 21.7, 22.4 and 24.8%, respectively, and the highest of fat content was related to blank sample (non-coated), 2% tragacanth, 0.5% guar gum with 49.4, 41.7 and 33.2% of oil content, respectively (p <0.05). The most effective coating agent reduced the oil uptake by 57.03, 55.94, 54.67 and 49.71%, respectively (p <0.05). Sensory evaluation showed that the best color was related to 1% CMC, 0.3% guar and 2% tragacanth, and with respect to flavor evaluation the best flavor was observed in tragacanth 2%, CMC 0.5% and CMC 0.1%, and the best texture referred to tragacanth 2%, CMC 0.5% and CMC 1%. In sensory evaluation, all coated chips got high scores compared with blank (non-coated chips) samples (p <0.05).     

Recovery of triglycerides from used frying oil by extraction with liquid and supercritical ethane

The extraction of triglycerides from used frying oil with liquid and supercritical ethane has been studied in a semibatch system at different temperatures (25-80 °C) and pressures (150-250 kg/cm²). It has been found that isobaric decreases of temperature and isothermal increases of pressure lead to both increasing extraction yields and decreasing separation efficiencies. Lipid fractions recovered in the high density region had acceptable concentrations of polar compounds.Results with ethane have been compared to those reported for CO₂ in earlier works. At similar reduced densities of the solvents, oil solubility in ethane was higher than in CO₂, being the separation efficiency of polar fractions slightly better when using ethane.The extraction process was further analyzed in a packed countercurrent column. At optimum conditions (250 kg/cm², 25 °C, and solvent-to-oil ratio 45 g:g) about 85% of the triglycerides were recovered, being 11.2% the polar content of the triglyceride fraction recovered.     

Effect of after-cooking darkening inhibitors on stability of frying oil and quality of french fries

The effect of two after-cooking darkening inhibitors, sodium acid pyrophosphate (SAPP) and calcium acetate (CaAc), and their combined effect on frying oil stability and quality of french fries produced were evaluated over a period of 72 h. Samples of frying oil and par-fried french fries were taken at 3-h intervals through each experiment and analyzed for selected chemical and physical parameters. As the frying time increased, all the oil samples contained increased amounts of deterioration products. The color index and free fatty acid (FFA) values were highly correlated with frying time. There were no significant effects on oil properties in terms of FFA until 9 h of frying among the 4 pretreatments. However, from 12 to 72 h of frying, oil used to fry potatoes treated with SAPP contained less FFA than oils exposed to CaAc alone or in combination with SAPP. The fat content of par-fried french fries was approximately 0.11 g/g dry matter and remained relatively constant during extended frying. After-cooking darkening of par-fried french fries and final color of the fries were affected by the pretreatment, but not by the frying time.     

Frying oil and fat quality measured by chemical,physical, and test kit analyses

The performance of soybean oil (SBO) and a partially hydrogenated soybean oil (PHSBO) was monitored by chemical, physical, and test kit analyses during 50 h of deep-frying of potatoes in SBO and 50 h of deep-frying of potatoes in PHSBO. The oxidative stability of SBO and PHSBO was measured by the iodine value, color index, FFA content, total polar compounds, and FA analysis of deep-frying SBO and PHSBO. SBO, with higher levels of unsaturated FA, had the faster rate of formation of geometric and positional isomers of unsaturated FA as measured by GC with standards. PHSBO performance under deep-frying conditions was significantly better than SBO with respect to iodine value, color index, and total polar compounds. The results from analyses using test kits had a good correlation with analytical parameters.     

Rapid method for determining moisture content in crude palm oil by Fourier transform infrared spectroscopy

A simple, rapid, and direct Fourier transform infrared (FTIR) spectroscopic method was developed for the determination of moisture content of crude palm oil (CPO). The calibration set was prepared by adding double-distilled water to dried CPO in ratios (w/w) between 0 and 13% moisture. A partial least squares (PLS) regression technique was employed to construct a calibration model followed by cross-validation step. The accuracy of this method was comparable to the accuracy of the American Oil Chemists' Society's vacuum oven method, which is used for determination of moisture and volatile matter, with mean difference (MD_a) of 0.0105, a coefficient of determination (R ²) and a standard error of calibration (SEC) of 0.9781 and 0.91, respectively. It is also comparable to the accuracy of the International Union of Pure and Applied Chemistry's distillation method with MD_a, R ², and SEC of 0.0695, 0.9701, and 0.65, respectively. The study showed that midband FTIR spectroscopy combined with the PLS regression calibration technique is rapid and accurate for determination of moisture content of CPO samples with a total analysis time of less than 2 min and less than 2 mL of sample.     

Correlation between physicochemical analysis and radical‐scavenging activity of vegetable oil blends as affected by frying of French fries

The main goal of the present work was to compare and correlate the results of physicochemical parameters and antiradical performance of some oil blends during deep‐frying, which will be an initial indicator for applying antiradical tests for monitoring deep‐frying oils. Two oil blends were prepared. The first blend was a mixture (1 : 1, wt/wt) of sunflower seed oil and palm olein (SO/PO) and the second was a mixture (1 : 1, wt/wt) of cottonseed oil and palm olein (CO/PO). The oil blends were evaluated during intermittent frying of French fries on two consecutive days for 16 h, with oil replenishing after 8 h. Changes in the fatty acid profile and some physicochemical parameters (peroxide value, color index, viscosity, total polar compounds and UV absorbance at 232 and 270 nm) were used to evaluate the alterations during frying. A quick spectrophotometric method was developed to assess deep‐frying oil quality. With the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) method, the neutralization of the stable radical DPPH by antioxidants present in the oil during frying was measured. Radical‐scavenging activity (RSA) of both oil blends was recorded during frying, wherein the results showed that the SO/PO blend had the highest RSA. It was evident from the results that a proportional correlation and positive relationship existed between the levels of fatty acids and the physicochemical characteristics of the vegetable oil blends and their RSA. The initial results obtained allow us to suggest that antiradical measurements could be used to quantify the oxidative and hydrolytic deterioration of vegetable oils upon frying.     

委内瑞拉减渣热转化及其残渣油反溶剂造粒研究

研究在间歇釜式反应装置上委内瑞拉渣油的热转化,在常温常压下,选择甲苯为溶剂,正戊烷为反溶剂,选取反应温度为420℃,反应时间为30～90 min的热反应残渣油进行反溶剂造粒。残渣油浓度从20.0%～66.7%,剂油比从2∶1至8∶1进行反溶剂造粒,随着溶液浓度的减小和剂油比的增大,不溶物沥青颗粒收率呈下降趋势;随着溶液浓度的减小和剂油比的增大,不溶物沥青颗粒的粒度减小且粒度分布趋于均匀。反溶剂比为8∶1时,戊烷可溶物和戊烷不溶物中的H/C原子比都相对较高。     

The preparation of activated carbons from chips of oil palm trunk catalysed by ZnCl2/CO2: Surface area and porosity studies

Activated carbons were prepared by ZnCl₂/CO₂ activation of the chips of oil trunk. The surface area and the nature of the porosity of the resulting activated carbons were found to be related to the concentration of the impergnated zinc solution to the precursor. It is possible to prepare activated carbons with a fairly high surface area (more than 2000 m² g^?1) from chips of oil palm trunk.     

Motor oil classification by base stock and viscosity based on near infrared (NIR) spectroscopy data

In this paper we have tried to build effective model for classification of motor oils by base stock and viscosity class. Three (3) sets of near infrared (NIR) spectra (1125, 1010, and 1050 spectra) were used for classification of motor oils into 3 or 4 classes according to their base stock (synthetic, semi-synthetic, and mineral), kinematic viscosity at low temperature (SAE 0W, 5W, 10W, and 15W) and kinematic viscosity at high temperature (SAE 20, 30, 40, and 50). The abilities of three (3) different classification methods: regularized discriminant analysis (RDA), soft independent modelling of class analogy (SIMCA), and multilayer perceptron (MLP) - were also compared. In all cases NIR spectroscopy was found to be quite effective for motor oil classification. MLP classification technique was found to be the most effective one.     

Determination of the SiH content of hydrogen silicone oil by a combination of the fourier transform near infrared,attenuated total reflectance–fourier transform infrared,and partial least squares regression models

To verify the feasibility of the determination of the Si?H content (HC) of hydrogen silicone oil (HS‐oil) with Fourier transform near infrared (FT‐NIR) spectroscopy and attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy combined with the partial least squares regression (PLS‐R) model, HS‐oil samples were synthesized from concentrated hydrosilicone oil (HC = 1.4 wt %), octamethylcyclotetrasiloxane, and hexamethyldisiloxane or prepared by the dilution of concentrated hydrosilicone oil with octamethylcyclotetrasiloxane. The FT‐NIR PLS‐R model (8695–4000 cm^?1, two principal components) was developed from the FT‐NIR spectral data, and the coefficient of determination for cross‐validation (R²) and the coefficient of determination for external validation (r²) were 0.992 and 0.995, respectively. The ATR–FTIR PLS‐R model (2302–2040 cm^?1, one principal component) was developed from the ATR–FTIR spectral data; it produced an R² of 0.995 and an r² of 0.996. This study demonstrated that the combination of FT‐NIR and ATR–FTIR spectroscopy with the PLS‐R model were successfully used to determine the HC of the HS‐oil. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40694.     

Determination of seed oil content and fatty acid composition in sunflower through the analysis of intact seeds, husked seeds, meal and oil by near-infrared reflectance spectroscopy

A methodological study was conducted to test the potential of near-infrared reflectance spectroscopy (NIRS) to estimate the oil content and fatty acid composition of sunflower seeds. A set of 387 intact-seed samples, each from a single plant, were scanned by NIRS, and 120 of them were selected and further scanned as husked seed, meal, and oil. All samples were analyzed for oil content (nuclear magnetic resonance) and fatty acid composition (gas chromatography), and calibration equations for oil content and individual fatty acids (C_16:0, C_16:1, C_18:0, C_18:1, and C_18:2) were developed for intact seed, husked seed, meal, and oil. For intact seed, the performance of the calibration equations was evaluated through both cross- and external validation, while cross-validation was used in the rest. The results showed that NIRS is a reliable and accurate technique to estimate these traits in sunflower oil (validation r ² ranged from 0.97 to 0.99), meal (r ² from 0.92 to 0.98), and husked seeds (r ² from 0.90 to 0.97). According to these results, there is no need to grind the seeds to scan the meal; similarly accurate results are obtained by analyzing husked seeds. The analysis of intact seeds was less accurate (r ² from 0.76 to 0.85), although it is reliable enough to use for pre-screening purposes to identify variants with significantly different fatty acid compositions from standard phenotypes. Screening of intact sunflower seeds by NIRS represents a rapid, simple, and cost-effective alternative that may be of great utility for users who need to analyze a large number of samples.     

Development of calibration equations to predict oil content and fatty acid composition in brassicaceae germplasm by near-infrared reflectance spectroscopy

The use of nondestructive analytical methods is critical for the evaluation of very small seed samples such as those from germplasm collections. The objective of this study was to evaluate the potential of near-infrared reflectance spectroscopy (NIRS) for the simultaneous analysis of seed oil content and concentration of major fatty acids in intact-seed samples of the family Brassicaceae. A total of 495 samples from 56 genera and 128 species were analyzed by NIRS. The fatty acid composition of the seed oil was determined in all the samples by gas-liquid chromatography (GLC). The total seed oil content was determined by solvent extraction in 129 samples from 22 genera. Calibration equations for oil content (n=97) and individual fatty acids (n=410) were developed and tested through external validation with the samples not included in the calibration sets. The calibration equations for oil content (r ²=0.97 in validation) and concentrations of C_18:1 (r ²=0.93), C_18:3 (r ²=0.95), and C_22:1 (r ²=0.94) showed very good performance and provided reliable estimations of these traits in the samples of the validation set. The calibration equations for C_16:0, C_18:0, and C_18:2 content were less reliable, with r ² from 0.67 to 0.73. There was practically no response of NIRS to differences in C_20:1 (r ²=0.31). These results demonstrated that the oil content and concentrations of C_18:1, C_18:3, and C_22:1 can be estimated reliably within the family Brassicaceae by using NIRS calibration equations integrating broad taxonomic variability.