Accumulation of 2-tert-Butyl-1,4-Benzoquinone in Frying Oil and Fried Food during Repeated Deep Fat Frying Processes

2-tert-Butyl-1,4-benzoquinone (TBBQ), the main oxidation product of tert-butyl-hydroquinone (TBHQ) during frying, is cytotoxic and its residual levels in frying oils and foods are unknown. In this study, TBBQ residues have been evaluated during the preparation of french fries. Results showed that frying at 140 °C resulted in the highest TBBQ peak concentration (48.42 mg kg⁻¹) compared with frying at 190 or 170 °C. This unexpected finding can be attributed to more extensive hydrolytic reaction when frying at the lower temperature, generating more peroxyl radicals. TBBQ concentrations proved to be independent of the oil type among various unsaturated oils. However, higher TBBQ levels were observed in saturated palm oil and crude soybean oil than in unsaturated oil or refined oil. Continuous frying leads to the accumulation of a large amount of TBBQ in fried food. After frying 1–5 batches, TBBQ levels in both the frying oil and fries were above 10 mg kg⁻¹, exceeding its critical cytotoxic concentration (IC₅₀ value of 10.71 mg kg⁻¹ for RAW 246.7 cells in our previous study), warranting concern with respect to the safety of fried food. FTIR has been utilized as an effective tool for visually monitoring the degree of oxidation in the frying medium with respect to its hydrogen peroxide level, which contributes to the increased level of TBBQ derived from TBHQ therein.     

Effects of Linalyl Oleate on Soybean Oil Flavor and Quality in a Frying Application

Bread pieces were fried at 180 °C in soybean oil (SBO) containing no additives (control), 0.1% linalyl oleate (LO), or 10 ppm methyl silicone (MS). After 2 h of heating, the MS-containing oil was the most stable, followed by the oil with LO and the control, based on conjugated dienoic acid percentage (CD) and the ratio of linoleate%/palmitate%. Oil extracted from the fresh fried bread showed similar, but not significant, trends for CD and PV. Fresh and stored (60 °C, 2 days) bread fried in LO-containing oil had less hexanal than the other two treatments, and the stored LO bread had less t,c- and t,t-2,4-heptadienal than the control. Fresh bread fried in LO-containing oil had a less rancid flavor than did the other two treatments, and the LO treatment had less fishy flavor than the control. In stored bread, the MS treatment was less rancid than the control. In oil extracted from the stored bread, the amounts of t,c-2,4-heptadienal and 2-decenal correlated (p ≤ 0.05) with the amounts of individual unsaturated fatty acids and with CD, but only t,c-2,4-heptadienal correlated with the PV. The t,c-2,4-heptadienal correlated with individual Polyunsaturated fatty acids (PUFA) in freshly fried bread. In general, oil and fried bread had improved flavor quality and/or oil stability when they contained MS or LO.     

Pore Development and Moisture Transfer in Chicken Meat during Deep-Fat Frying

Abstract

Changes in the structure of food products play important role in the various mass transfer processes during deep-fat frying. The relationship between moisture loss and pore formation were investigated at frying oil temperatures of 170, 180, and 190°C and frying times up to 900 s. Porosity and pore structure were characterized by using mercury intrusion porosimetry and helium displacement pycnometer. Moisture transfer in the samples was modeled using Fick's law and effective moisture diffusivity was computed from experimental data. Pore formation changes significantly (P < 0.01) in time as modulated by frying oil temperature. A peak pore fraction of 0.283 (after 360 s of frying), 0.238 and 0.220 (after 900 s of frying) at frying temperatures 190, 180 and 170°C, respectively was observed. Effective moisture diffusivity of 5.4 to 6.9 × 10^?9 m² s^?1 and activation energy of 20 kJ/mol was obtained for the frying oil temperatures. Changes in pore structure influenced moisture diffusivity and oil uptake. Eighty-four percent of the pores are capillary pores, hence moisture transfer increased.     

一种新型破伤风类毒素的理化和生物学特性的研究

对所研制的新型破类进行SDS－PAGE和HPLC分析，其主要成分为分子量大于584KD的聚合物，HPLC显示第一峰占82．09％～97．68％。此抗原的稳定性能良好，毒性逆转试验阴性，说明此种新破类解毒彻底。动物试验表明，其免疫原性大大优于常规破类，而且达到和超过了1990年版《中国生物制品规程》规定的吸附精制破伤风类毒素的要求。     

Formation of Alkylbenzenes and Tocochromanols Degradation in Sunflower Oil and in Fried Potatoes during Deep‐Frying and Pan‐Frying

Formation of toxic alkylbenzenes, total polar compounds (%TPC) and degradation of tocochromanol are monitored. Analyses of the oil extracted from fried potatoes confirm the trend observed in the frying oil. The fresh oil has a TPC content of 3%, which increases with the frying time, exceeding the acceptable value (25%) after about 25 h for deep‐frying and 1.5 h for pan‐frying. During deep‐frying, total tocochromanol decreases to about half (25 mg per 100 g) of the initial value, pan‐frying shows faster, degradation (complete after 1.5 h). Toluene concentration increases with the frying time reaching a maximum, and afterwards gradually decreases. Except for butylbenzene during pan‐frying, pentylbenzene and butylbenzene concentration, increase with the frying time, but remain much lower than toluene. Practical Applications: This is the first systematic work comparing alkylbenzenes evolution under different frying conditions. Different from previous works, frying experiments are carried out following the indication of many European countries that recommend using temperature lower than 180 °C. The amount of alkylbenzenes assumed through a standard portion of fried potatoes (200 g) is assessed, which is relevant for evaluating dietary exposure to these contaminants.     

胡萝卜真空油炸脱水工艺和优化研究

研究了不同预处理条件哒展油炸温度、真空度、时间对胡萝卜脆片品质的影响。通过响应面分析可知：油炸温度、真空度以及时间显著影响胡萝卜片中水分与脂肪含量以及脆度（P≤0．05）;其最佳油炸工艺为温度100℃-110℃、真空度0．08—0．09MPa、时间15min。     

改善液压油水解安定性、放气性及破乳化性的研究

就改善液压油的水解安定性、放气性及破乳化性进行了研究,试验表明金属减活剂和高碱度清净剂能改善液压油的水解安定性,清净剂还可改善液压油的破乳化性,硅型和非硅型抗泡剂对放气性和抗泡性的影响不同,需从配方技术上进行平衡,才能达到效果.     

Relationship Between Oil Uptake and Water Content During Deep-Fat Frying of Potato Particulates Under Isothermal Temperature

The purpose of this study is to correlate water content and oil uptake with the structural changes of potato particulates during deep-fat frying. Raw potato particulates were sliced to form cylinders of 0.006 m diameter × 0.006 m length and subjected to deep-fat frying at isothermal oil temperatures of 160, 190 and 220 °C. The microstructure properties were assessed using a field emission scanning electron microscope (FESEM). Previous results showed that a simultaneous two first-order kinetic model adequately predicted water loss of potato particulates during isothermal frying. In this study, a simple rational model with two parameters in which regression squared (Rsqr) reaches 0.983 shows that oil uptake can be expressed by water content. The cross-sectional structure of potato particulates observed using FESEM is different from the surface structure. Regardless of the frying temperature, pores not only become larger but also increase in number after the transition time. The observations of structural changes at the surface and inner section of potato particulates through the pictures of FESEM are critical. This physical evidence supports our previous assumption that the mechanisms of water loss (two-stage rate processes) before and after transition time are different.     

Deterioration Kinetics of Crude Palm Oil,Canola Oil and Blend During Repeated Deep-Fat Frying

The oxidation of vegetable oils is generally treated as an apparent first order kinetic reaction. This study investigated the deterioration of crude palm oil (CPO), refined canola oil (RCO) and their blend (CPO:RCO 1:1 w/w) during 20 h of successive deep‐fat frying at 170, 180 and 190 °C. Kinetics of changes in oil quality indices, namely, free fatty acid (FFA), peroxide value (PV), anisidine value (p‐AV), total polar compounds (TPC) and color index (CI) were monitored. The results showed that FFA and PV accumulation followed the kinetic first order model, while p‐AV, TPC and CI followed the kinetic zero order model. The concentration and deterioration rate constants k, increased with increasing temperatures. This effect of temperature was modeled by the Arrhenius equation. The results showed that PV had the least activation energies E_a (kJ/mol) values of 5.4 ± 1 (RCO), 6.6 ± 0.7 (CPO) and 11.4 ± 1 (blend). The highest E_a requirement was exhibited by FFA with a range of 31.7 ± 3–76.5 ± 7 kJ/mol for the three oils. The overall E_a values showed that the stability of the blend was superior and not just intermediate of CPO and RCO. The correlation of the other oil quality indices with TPC indicated a positive linear correlation. The p‐AV displayed the strongest correlation, with mean correlation coefficient r_s of 0.998 ± 0.00, 0.994 ± 0.00 and 0.999 ± 0.00 for CPO, RCO and blend, respectively.     

A Chemometric Approach to Assess the Frying Stability of Cottonseed Oil Blends During Deep-Frying Process: I. Polar and Polymeric Compound Analyses

The main goal of the present study was (i) to determine the formation of degradation products in cottonseed oil (CSO) blends during deep frying process by adsorption and high performance size exclusion chromatography techniques and (ii) to evaluate the impacts of food additives on total polar (TPC) and polymeric compound (PTAG) formation using a chemometric approach. In order to prepare the frying CSO blends; ascorbic palmitate, mixed tocopherols, dimethylpolysiloxane, lecithin and sesame oils were used as additives. To determine the real impacts of additives, a quarter-fraction factorial experimental design with two levels and five factors was used. The changes in TPC and PTAG data were carefully evaluated during 10 h of frying at 170 ± 5 °C with normal distribution (ND) graphs and analyzed using a one-way analysis of variance (ANOVA), followed by Tukey’s Post-hoc test (α = 0.05). The results indicated that the increasing values for TPC and PTAG during the frying processes for all blends, TPC and PTAG contents reached maximum levels of 16.37 and 6.01 % respectively, which are below the limit values stated by official authorities for the quality assessment of frying oils. The ANOVA test results were in good agreement with ND graphs and data indicated that the impact of mixed tocopherols was significant for TPC formation, meanwhile the impact of lecithin and ascorbic palmitate × dimethylpolysiloxane were significant for PTAG formation. Thus, the present study should be considered to be a very useful guide for developing new frying oil formulations based on CSO by using food additives.     

Oxidative Stability and Changes in Chemical Composition of Extra Virgin Olive Oils After Short‐Term Deep‐Frying of French Fries

We aimed at investigating oxidative stability and changes in fatty acid and tocopherol composition of extra virgin olive oil (EVOO) in comparison with refined seed oils during short‐term deep‐frying of French fries, and changes in the composition of the French fries deep‐fried in EVOO. EVOO samples from Spain, Brazil, and Portugal, and refined seed oils of soybean and sunflower were studied. Oil samples were used for deep‐frying of French fries at 180 °C, for up to 75 min of successive frying. Tocopherol and fatty acid composition were determined in fresh and spent vegetable oils. Tocopherol, fatty acid, and volatile composition (by SPME–GC–MS) were also determined in French fries deep‐fried in EVOO. Oil oxidation was monitored by peroxide, acid, and p‐anisidine values, and by Rancimat after deep‐frying. Differential scanning calorimetry (DSC) analysis was used as a proxy of the quality of the spent oils. EVOOs presented the lowest degree of oleic and linoleic acids losses, low formation of free fatty acids and carbonyl compounds, and were highly stable after deep‐frying. In addition, oleic acid, tocopherols, and flavor compounds were transferred from EVOO into the French fries. In conclusion, EVOOs were more stable than refined seed oils during short‐term deep‐frying of French fries and also contributed to enhance the nutritional value, and possibly improve the flavor, of the fries prepared in EVOO.     

Physicochemical,Antioxidative, and Sensory Properties of Refined Rapeseed Oils

Physicochemical characteristics, antioxidant capacity (AC), and sensory quality of rapeseed oils available on the Polish market were analyzed and compared. The fatty acid composition (saturated fatty acids = 6.91–7.58%, monounsaturated fatty acids = 64.14–66.14%, and polyunsaturated fatty acids = 27.22–30.17%), color (T420 = 54.5–83.8%), amounts of free fatty acids (0.02–0.07%), primary (PV = 0.04–2.04 meq O₂ kg⁻¹) and secondary (AV = 1.02–3.21) oxidation products, phosphorus (0.38–1.62 mg kg⁻¹), chlorophyll (0.002–0.068 mg kg⁻¹), and polycyclic aromatic hydrocarbons (Σ4PAH = 0.00–2.50 μg kg⁻¹) in the commercial rapeseed oils meet the requirements of the European Food Regulation and Codex Alimentarius standards. Moreover, total phenolic content (TPC = 40.3–467.9 mg SA kg⁻¹) in the studied oils significantly differs from each other. However, the AC of rapeseed oils was analyzed using the novel iron oxide nanoparticle-based (IONP = 5552.1 − 18,510.2 μmol TE/100 g) method and the modified ferric reducing antioxidant power (FRAP = 55.7–280.3 μmol TE/100 g), cupric reducing AC (CUPRAC = 79.6–784.0 μmol TE/100 g), 2,2-diphenyl-1-picrylhydrazyl (DPPH = 185.7–516.7 μmol TE/100 g), and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS = 465.6–2142.6 μmol TE/100 g) assays. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied for discrimination of the refined rapeseed oils based on fatty acid composition, physicochemical parameters, AC, and sensory properties.     

Investigation of a Model-Based Deep Reinforcement Learning Controller Applied to an Air Separation Unit in a Production Environment

The need for load flexibility and increased efficiency of energy-intensive processes has become more and more important in recent years. Control of the process variables plays a decisive role in maximizing the efficiency of a plant. The widely used control models of linear model predictive controllers (LMPC) are only partly suitable for nonlinear processes. One possibility for improvement is machine learning. In this work, one approach for a purely data-driven controller based on reinforcement learning is explored at an air separation plant (ASU) in productive use. The approach combines the model predictive controller with a data-generated nonlinear control model. The resulting controller and its control performance are examined in more detail on an ASU in real operation and compared with the previous LMPC solution. During the tests, stable behavior of the new control concept could be observed for several weeks in productive operation.     

高温油炸薄薯片过程中油的吸收和水分流失间的特性关系

Thin potato crisps (2mm) were fried at 170℃, 180℃ and 190℃ for various times from 10s to 180s inclusive. It was found that definite oil uptake, moisture loss trends exist during the frying process. No significant difference in the oil uptake or moisture loss rates between flat-cut and ridge-cut crisps exists. Also found in this study was that an increased oil temperature promoted higher moisture loss rates. In turn, the higher moisture loss rates contributed to a higher oil uptake rate. It was found, based on the volumetric plots of oil content vs. water content, that the oil uptake rate was proportional to the moisture loss rate. As a result, it has been shown that there is a possibility of having a characteristic curve of oil uptake against moisture content.     

The Characteristic Relationship Between Oil Uptake and Moisture Content during the High Temperature Immersion Frying of Thin Potato Crisps

Thin potato crisps (2mm) were fried at 170℃, 180℃ and 190℃ for various times from 10s to 180s inclusive. It was found that definite oil uptake, moisture loss trends exist during the frying process. No significant difference in the oil uptake or moisture loss rates between flat-cut and ridge-cut crisps exists. Also found in this study was that an increased oil temperature promoted higher moisture loss rates. In turn, the higher moisture loss rates contributed to a higher oil uptake rate. It was found, based on the volumetric plots of oil content vs. water content, that the oil uptake rate was proportional to the moisture loss rate. As a result, it has been shown that there is a possibility of having a characteristic curve of oil uptake against moisture content.     

Comparison of the Frying Performance of High Oleic Oils Subjected to Discontinuous and Prolonged Thermal Treatment

Frying is a popular practice because of its unique sensory characteristics and low cost. The high temperature reached with this cooking method alters molecules present in the oil. The deterioration of the oil depends primarily on its chemical composition. The aim of this study was to evaluate the thermal stability of high oleic sunflower oil (HOSO), sunflower oil (SO) and mixed oil (MIX) during deep frying of French fries. Octanoic acid and unsaturated fatty acid (UFA)/saturated fatty acid (SFA) ratio showed a good correlation with total polar compounds (TPC) for all frying samples analyzed. HOSO and MIX were characterized by reduced levels of thermal degradation, while SO resulted in the highest values of oxidation products (highest TPC values). SO was also the oil more retained by the food matrix, whereas MIX was the least absorbed. HOSO and MIX, having a high oleic acid content (77.58 and 59.92 %, respectively) and a low linoleic acid content (13.42 and 25.70 %, respectively), showed the best characteristics for the frying process.     

A Comparative Study of the Explosion Characteristics of IPN and IPN/JP‐10 Mixtures in Air Aerosols

This article presents a comparison of the explosion characteristics of mixtures of isopropyl nitrate (IPN, (CH₃)₂CHONO₂) and JP‐10 (C₁₀H₁₆, tricycle [5.2.1.0^2,6] decane) in air aerosols. The explosion pressure, flame temperature, maximum rate of pressure rise, maximum rate of temperature rise, and lower flammability limits (LFLs) were measured for two sets of IPN and mixed IPN/JP‐10 in air aerosols at different concentrations and Sauter mean diameters (SMDs) of 19 μm and 34 μm, respectively, and the values were compared with the experimental results of JP‐10/air aerosols with SMDs of 20 μm and 35 μm (from our previous research). Experiments were also performed to study various concentrations at various ignition energies for the IPN/air aerosols and the explosions of binary mixture aerosols with various mass ratios of IPN and JP‐10. The experimental results indicated that for the IPN/air and JP‐10/air aerosols with a mean SMD of ∼34 μm, the maximum peak pressure and maximum peak temperature of the IPN/air aerosols were greater than those of the JP‐10/air aerosols. The maximum rate of pressure rise of the IPN/air aerosols reached a maximum value of 395.3 MPa/s at a mean SMD of ∼34 μm, and the pressure increased more abruptly in the IPN/air aerosols than in the JP‐10/air aerosols. The LFLs of the IPN/air aerosols occurred with a total concentration of 197 g/m³ at a mean SMD of 19 μm and a total concentration of 233 g/m³ at a mean SMD of 34 μm, whereas the LFLs for the JP‐10/air aerosols with SMDs of 20 μm and 35 μm were less than 47 g/m³ and 40 g/m³, respectively. The experimental results presented here also showed that the maximum peak pressure was 1.07 MPa at a binary liquid mass ratio of IPN:JP‐10 (%) of 72 : 28 and a mean SMD of ∼34 μm.