Deterioration of palm oil olein and partially hydrogenated soybean oil during deep-fat frying

The deterioration of palm oil olein (POO) and partially hydrogenated soybean oil (PHSO) during deep-fat frying of fish and potato was compared. Deterioration of the oils during use was assessed by fast analytical tests (dielectric constant, DC, and foam height, FH, measurements) and changes in the fatty acid composition, smoke point (SP), levels of free fatty acids (FFA), dienoic acids (DA) and total polar materials (TPM). The study consisted of four treatments: (1) potatoes fried in POO, (2) fish fried in POO, (3) potatoes fried in PHSO, and (4) fish fried in PHSO. The statistical design of the experiment was a 4 x 4 Latin Square with a split in each square. The design was represented by four replications and four fryers with the split being sampling time from each fryer. The frying oils were used in the following manner. The oil in each fryer was held at 180 C for 8 hours a day for 5 consecutive days with a batch of food being fried every 2 hours starting 1 hour after the fat had reached 180 C. At the end of each day the frying oil was cooled, filtered through cheese cloth and stored covered until the next day. DC and FH were measured on all frying oils every day, and SP, FFA, DA, TPM and fatty acid composition of the frying oils were determined after 1, 3 and 5 days of use. Moisture and fat levels were measured in the last batch of food fried each day at 1, 3 and 5 days of use. Levels of DA, FH, FFA, and SP were significantly affected by the type of frying oil used and the type of product fried. Across 5 days of frying, PHSO had higher levels of FH, DA and SP and a lower level of FFA than POO. The frying of fish in either oil resulted in a higher DC, FH, DA, FFA and SP than did the frying of potatoes. DC was not affected (P \u3c 0.05) by type of frying oil used. Levels of TPM did not differ (P \u3c 0.05) between types of oil used or types of product fried. The fatty acid composition of the frying oils was affected by the type of oil used and the type of product fried. Used POO had higher levels of saturated fatty acids (12:0, 14:0, 16:0 and 18:0) and lower concentrations of the unsaturated fatty acids (18:1ω9, 18:1 isomers, 18:2ω6 and 18:2 isomers) than the used PHSO. The frying of fish caused higher concentrations of 18:2ω6. 18:3ω3 and 20:0 than did the frying of potatoes. All measurements of the frying oils were significantly affected by the amount of time the frying oils were used. Levels of DC, FH, DA, FFA and TPM generally increased in a curvilinear fashion with increasing time of frying oil use while the SP decreased. The level of TPM was 30.7 percent by the third day of use which is higher than the 27 percent recommended as the point at which a frying oil should be discarded. The average percentage of 18:0, an 18:1 isomer, an 18:2 isomer and 20:2ω6 increased significantly across frying time, while the average percentage of 18:2ω6, 18:3ω3, 20:1ω9, 18:2ω7 (diene) and 24:0 decreased. Results of this study indicate that both oils deteriorated during use; however, compared with PHSO, POO had higher levels of FFA, a lower smoke point and might cause problems in commercial frying operations. Results also indicate that the frying of fish caused a greater deterioration of frying fats than the frying of potatoes. Results also confirm that 27 percent TPM as a level at which a frying fat should be discarded is probably applicable to most frying fats and situations, since the level of TPM was not affected by the type of frying fat used or the type of product fried. Although other measurements such as levels of DC, FH and FFA were highly correlated with levels of TPM, they were affected by one or both of these parameters

Stability of high oleic acid sunflower oil, regular sunflower oils and a sunflower-corn oil blend during frying of a plain yeast-raised doughnut as a simulated model for Swaziland small food vendors and sensory evaluation of the doughnuts

The stabilities of 4 oils, high oleic sunflower (HOS) and regular sunflower (RCO) oils from the USA and a regular sunflower-corn oil blend (SOS) and regular sunflower (SVS) oil, processed in the Republic of South Africa (RSA) and used in Swaziland, were evaluated during frying. For each oil, 24 batches of 2 plain, yeast-raised doughnuts/batch were fried for 4 hr/day for 5 days. Samples taken from each oil during TIME (fresh, break-in heated and on each of the 5 days) were evaluated by measuring levels of a- and Y~tocopherols, total polar components (TPC), Food Oil Sensor reading (FOS), free fatty acids (FFA), conjugated dienes (DIENES), C18:2/C16:0 ratio, and Hunter color values, L, a, b and AE. Crust flavor and color likability, crust color intensity, mouthfeel (greasiness) and overall acceptability of doughnuts fried on days 2 and 4 in each oil were evaluated by a 48-member consumer panel. When fresh, USA oils contained lower levels of tocopherols and were less yellow than RSA oils; HOS contained the lowest amount of tocopherols of all oils. Levels of each tocopherol decreased while levels of TPC, DIENES, C18:2/C16:0 ratio, b and AE increased over TIME (p\u3c0.05), but the change in any one component differed among the oils. Levels of FFA and a increased and L decreased (p\u3c0.05) across TIME similarly for each oil. Levels of TPC (19.5-20.9%), FOS (1.75-2.13) and FFA (0.058-0.067% oleic acid) on day 5 were the same in all oils and were below recommended levels for oil discard. Although HOS had lowest levels of tocopherols and had a greater AE than RCO or SVS, it was comparable in stability with the other oils. None of the sensory scores were affected (p\u3c0.05) by type of oil or time. Mean (n=192) crust flavor and color scores were midpoint on 9-point hedonic scales. Overall acceptability was midpoint on an extremely unacceptable to extremely acceptable scale. Crust color and mouthfeel scores were midpoint on 9- point scales (light brown and dark brown and not at all greasy - extremely greasy). Results show that HOS is feasible as a frying oil for small food vendors in Swaziland

Soybean and palm olein oils : frying performance and characteristics of fried prawn crackers

Four different frying oils: unhydrogenated soybean oil (SO), palm olein (POO) and blends of 80:20 and 60:40 w/w SO:POO were used to fry prawn crackers (PC) intermittently for five days. The degradation of the oils/blends (O/B) were followed by daily measurement by the food oil sensor (FOS), RAU and Fritest, of color (L, a, b and ΔE) and levels of conjugated dienes (DIENES), fatty acid composition, C18:2/C16:0 fatty acid ratio (RATIO), free fatty acids (FFA) and total polar components (TPC). PC fried in each O/B were stored at 25°C for 0 wk (fresh) and 4 wk in the dark (4D) and in the light (4L) and analyzed for flavor volatiles and color, flavor and overall likability scores. FOS, Fritest and TPC values were not different among frying O/B, and each measurement for each O/B reached maximum value or oil discard point before or by day 5 of frying. The TPC level at discard point (25-27%) was reached by frying day 3 in all O/B mainly because of high TPC (12-14%) in fresh oils. Levels of DIENES and RATIO were higher in SO than in blends or POO and decreased with decreasing SO level in the blends. DIENES and RATIO of each O/B also decreased with increasing frying time. Although FFA content increased with increasing frying time in all 0/B and was higher in POO than in other O/B, after frying day 5, it was still below the level (0.5%) recommended for discard of potato chip frying oil. SO had highest levels of 018:2 and C18:3 fatty acids of all O/B while PO had the highest levels of C16:0 and C18:1. Levels of C18:2 decreased in all O/B during frying while levels of C12:0, C20:2 and C22:4 increased. RAU value, a measure of oxidized products, reached discard point by frying day 4 in the blends compared to day 5 in pure SO and POO. Indicating the pure oils were more stable than the blends during frying. POO had a lower L value (was darker) and higher b value (more yellow) than SO when fresh. All O/B darkened and became more yellow with increasing frying time. After five days frying, POO was still darker than SO or the blends, but SO had similar b values as POO (42.3 versus 43.9) and the greatest color change (ΔE) of all O/B. The darker color of POO could cause early discard in institutions using dark color to judge when a frying oil is fully deteriorated. The color, flavor and overall likability scores of the fried PC were not different among the O/B and averaged 5.9 ( were liked moderately). However, 4L PC received a lower flavor and overall likability score (4.9) than that (5.8) of fresh or 4D PC. The 4L PC also had much higher levels of 21 of 23 identified flavor volatiles than those present in the fresh or 4D PC. These latter results indicate that for stored fried PC to maintain acceptable flavor, they must be stored in a light barrier package

Rapid and innovative instrumental approaches for quality and authenticity of olive oils

The quality of virgin olive oils is assessed through the determination of several analytical parameters, whose values must be within the ranges established by the different institutions involved. In addition to official methods, there is a strong need for simple, rapid, and environmentally friendly techniques for the quality control of virgin olive oils and for addressing the challenging task of determining geographical origin and detecting adulterants. Toward this purpose, some of the most interesting applications based on optical spectroscopic techniques, on the measurement of electrical characteristics and on the use of instruments equipped with electronic chemical sensors, including also other promising techniques are herein discussed. These techniques, adequately coupled with an appropriate statistical approach, appear to be promising for assessment of several quality-related parameters. The prediction of sensory attributes and of the oxidative status of virgin olive oils have also been reviewed by adopting these selected techniques, which are also considered to be potentially appropriate solutions for identification of the geographical origin of virgin olive oils and to assess their adulteration with cheaper oils. Overall, the techniques discussed are promising and cutting-edge approaches for the establishment of useful portable instruments for in situ monitoring of the quality of virgin olive oils. Practical applications: The simple, rapid, and environmentally friendly analytical approaches discussed herein represent promising analytical tools for assuring the authenticity and monitoring the quality of virgin olive oils. Such innovative techniques and tools need to be ring-tested and validated. Some innovative reviewed approaches will permit to develop useful portable instruments able to perform in situ appropriate controls also by small laboratories or olive oil mills with limited technical facilities. These equipments will be potentially usable also by trained \u201cnon-professional analytical skilled\u201d people. Some other approaches, rapid but more expensive, will be applicable mainly by quality control labs and will increase the number of samples analyzed per day, thus fostering laboratory proficiency and an effective fighting against olive oil fraud

Analog interface based on capacitance multiplier for capacitive sensors and application to evaluate the quality of oils

Currently, interdigital capacitive (IDC) sensors are widely used in science, industry and technology. To measure the changes in capacitance in these sensors, many methods such as differentiation, phase delay between two signals, capacitor charging/discharging, oscillators and switching circuits have been proposed. These techniques often use high frequencies and high complexity to measure small capacitance changes of fF or aF with high sensitivity. An analog interface based on a capacitance multiplier for capacitive sensors is presented. This study includes analysis of the interface error factors, such as the error due to the components of the capacitance multiplier, parasitic capacitances, transient effects and non-ideal parameters of OpAmp. A design approach based on an IDC sensor to measure the quality of edible oils is presented and implemented. The quality relates to the total polar compounds (TPC) and consequently to relative electrical permittivity ${\varepsilon }_{r}$ of the oils. A measurement system has been implemented to measure the capacitance of the IDC sensor, which depended on ${\varepsilon }_{r}$. The simulation and experimental results showed that, for a capacitance multiplication factor equal to 1000, changes of 3.3 µs/100 fF can be achieved with an acceptable level of noise, which can be easily measured by a microcontroller

A Portable Battery-Operated Sensor System for Simple and Rapid Assessment of Virgin Olive Oil Quality Grade

Virgin olive oil quality is assessed by chemical as well as sensory analysis. Two of the most important parameters that define the quality of virgin olive oils are the free acidity and the peroxide index. These chemical parameters are usually determined by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to support the quality grade assessment of virgin olive oil is presented. The system is battery operated and characterized by small dimensions, light weight and quick measurement response (about 30 s). The working principle is based on the measurement of the electrical conductance of an emulsion between a chemical reagent and the olive oil sample. Two different chemical reagents have been investigated: (1) a hydro-alcoholic solution (HAS), made of 60% ethanol and 40% distilled water; (2) 100% distilled water (DW). Tests have been carried out on a set of 40 olive oil samples. The results have shown how, for most of the fresh virgin olive oil samples (31 samples out of 40), the free acidity can be estimated with good accuracy from the electrical conductance of the emulsion using HAS as the reagent. In the case of the full set of samples, the emulsion electrical conductance, using HAS as the reagent, is a function of both the sample free acidity as well as the compounds produced by oil oxidation, and a compensation method based on the measured electrical conductance, using DW as the reagent, has been introduced to improve the accuracy in the estimated free acidity. Tests have also been carried out on the full set of samples, using a k-nearest neighbors algorithm, to demonstrate the feasibility of olive oil classification according to the quality grade. The results have shown how measurements carried out using only the HAS reagent provide better classification accuracy than measurements carried out using both the HAS and DW reagents. The proposed system can be a low-cost alternative to standard laboratory analyses to evaluate the quality grade of virgin olive oil