Characterization ofβ-carotene thermal degradation products in a model food system

A model system developed in our laboratory for the study of thermal degradation products (TDP) of carotenoids was employed.β-Carotene (10 g) in glycerol was heated at 210 C for 4 hr, 1 hr, 15 min and 5 min. The time and temperature chosen were similar to edible oil deodorization and deep fat frying. In this study, the TDP ofβ-carotene were quantified as influenced by time and temperature of heating. Results indicate that at 210 C, degradation is almost complete after 4 hr and most of the nonvolatile products are viscous, yellow-brownish material. Shorter times (1 hr, 15 min and 5 min) cause less degradation. TDP include nonpolar as well as oxidized derivatives ofβ-carotene. The results of this study provide information on the type, amount and mechanism of formation of compounds resulting from heating carotenoids. Presented at the AOCS meeting in Dallas, Texas, in 1984.     

Capabilities of different cooking oils in prevention of cholesterol oxidation during heating

The potential of various cooking oils to prevent cholesterol degradation and/or oxidation, as measured by the production of 7-ketocholesterol during heating at different temperatures, was studied using a cholesterol model system. In the control group (without cooking oil), cholesterol was relatively stable, and 73% of its initial concentration was present after 30 min of heating at 125°C. Less than 30 and 10% of cholesterol remained at 150 and 175°C after 30 min, respectively, and 10% at 200°C after 10 min. In the treatment group, cholesterol mixed with corn, canola, soybean, or olive oil had significantly improved thermal stability. More than 60 and 40% of cholesterol remained at 150 and 175°C after 30 min, respectively. In the control group, 7-ketocholesterol was produced when samples were heated above 150°C, and levels increased consistently during 30 min of heating. At 175 or 200°C, the level of 7-ketocholesterol did not increase further after reaching the highest level after 10 min of heating. 7-Ketocholesterol is not stable above 175°C, and its degradation rate could be much faster than its production at 200°C. 7-Ketocholesterol was not found in samples of cholesterol mixed with corn oil or laboratory-prepared soybean and rice bran oils until the heating temperature was raised to 175°C for 20 min. The levels of 7-ketocholesterol in those treatment groups were greater than that in the control group at 175°C for 30 min. These oils may increase the thermal stability of 7-ketocholesterol and retard its degradation rate.     

Effects of Time and Temperature on the Viscoelastic Properties of Chinese Fir Wood

The effects of time and temperature on dynamic viscoelastic properties of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) were investigated using dynamic mechanical analysis in this study. The isothermal tests were applied to the small clear specimens with a moisture content of about 0.6% at constant temperatures ranging from 25 to 200°C for 550 min at atmospheric pressure. Changes in storage modulus and loss tangent with heating time were examined. The results indicated that heating time mainly resulted in thermal softening, thermal degradation of wood, and the reduction of wood stiffness. At more than 60°C, the reduction in storage modulus was accelerated generally as the wood was subjected to a higher temperature or longer heating time. At constant temperatures of 140 and 160°C, a relaxation phenomenon was observed with a slight change in weight, which could be attributed to the relocation of lignin molecules. At the temperature range of 140 to 180°C, the higher the heating temperatures, the earlier the tanδ peak appeared. It is suggested that the wood thermal softening occurs at higher temperatures with shorter heating times or at lower temperatures with longer heating times. At temperatures of 180 and 200°C, the loss of amorphous polysaccharides due to thermal degradation is considered to be the main factor affecting wood viscoelasticity.     

In-situ synthesis of MCM-41 on ceramic membranes and its application in transesterification as catalyst support for p-toluenesulfonic acid

In this study, a new kind of solid acid catalyst p-toluenesulfonic acid/MCM-41/ceramic membrane was synthesized by in situ synthesis and impregnation method, which has shown its favorable catalytic activity, as verified in the transesterification and catalyst characterization. The catalyst was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. The transesterification of palm oil and methanol results showed that p-toluenesulfonic acid/MCM-41/ceramic membrane had the highest catalytic activity with immersing p-toluenesulfonic acid solution concentration of 0.15 mol/L. Different operation parameters of the transesterification of palm oil with methanol, such as catalyst amount, catalytic mass ratio, reaction time, reaction temperature and methanol/palm oil molar ratio were investigated. Under the optimum conditions of 4 % of fresh catalyst (catalytic mass ratio is 4.37 %), 80 min of reaction time, reaction temperature of 120 °C and methanol to palm oil molar ratio of 12:1, a relatively high fatty acid methyl ester yield of 95.6 % was obtained.     

Kinetic study of the microwave-induced thermal degradation of cv. Arbequina olive oils flavored with lemon verbena essential oil

The effect of typical domestic microwave heating (0–15 min, at 800 W) on the thermal degradation of unflavored and flavored olive oils' minor bioactive compounds and related antioxidant activity was studied. Olive oils from cv. Arbequina were flavored with lemon verbena essential oil (0%, 0.2% and 0.4%, w/w) leading to a linear increase of total phenols (112–160 mg gallic acid kg⁻¹ oil, R-Pearson = +0.9870), total carotenoids (2.19–2.56 mg lutein kg⁻¹ oil, R-Pearson = +0.9611), and, to a less extent, of chlorophyll (2.32–3.19 mg pheophytin kg⁻¹ oil, R-Pearson = +0.8238). However, no such linear trend was observed for the oxidative stability (6.5–7.8 h) or the radical scavenging activity (inhibition rates: 40%–43%). The contents of total phenols, total carotenoids, and chlorophyll decreased with the rise of the microwave heating time, following their thermal degradation, a second-order kinetic model (0.8784 ≤ R-Pearson ≤ 0.9926). The essential oil addition did not influence the estimated second-order rate reaction constants of total phenols (0.00070–0.00072 kg oil min⁻¹ mg⁻¹ gallic acid)and total carotenoids (0.14–0.17 kg oil min⁻¹ mg⁻¹ lutein), with a broader variation observed for chlorophyll (0.014–0.022 kg oil min⁻¹ mg⁻¹ pheophytin). Globally, total carotenoids degraded faster than total phenols and chlorophyll (half-life of 2.3–3.4, 8.8–12.8, and 14.5–30.8 min, respectively). Moreover, except for chlorophyll, the half-life of total phenols and carotenoids linearly decreased with the essential oil addition (R-Pearson: −0.9999 and −0.9421, respectively), showing that flavoring did not have a protective effect against degradation when subjected to a microwave heating.     

Influence of Resin Molecular Weight on Curing and Thermal Degradation of Plywood Made From Phenolic Prepreg Palm Veneers

The present work evaluates curing and the thermal behavior of different molecular weight phenol formaldehyde (PF) resins used to prepare PF prepreg oil palm stem veneers. The physical properties (solid contents, gelation time, pH, and viscosity) of PF resins were determined. The molecular weight of resins was characterized by gel permeation chromatography, whilst thermal properties were determined by differential scanning calorimetry and thermogravimetric analyses. The average molecular weight of PF resins were 526 g/mole (low), 1889 g/mole (medium), and 5178 g/mole (control - commercial). Among the resins, medium (MMwPF) gives better thermal stability with a retained weight of 48.9% at 300°C. High (Commercial PF) had a low decomposition temperature (109.3°C) which occurred within 11 min. Both low (LMwPF) and MMwPF started to melt at ≥120°C. Based on strength and shear values, phenolic prepreg palm veneers can be prepared using either low or medium molecular weight PF but with varying results. In all cases, the mechanical properties of palm plywood made from PF prepreg veneers were superior to those made from PF-bonded plywood using the commercial process.     

Composition and thermal profile of crude palm oil and its products

Gas-liquid chromatography and high-performance liquid chromatography (HPLC) were used to determine fatty acids and triglyceride (TG) compositions of crude palm oil (CPO), refined, bleached, and deodorized (RBD) palm oil, RBD palm olein, and RBD palm stearin, while their thermal profiles were analyzed by differential scanning calorimeter (DSC). The HPLC chromatograms showed that the TG composition of CPO and RBD palm oil were quite similar. The results showed that CPO, RBD palm oil, RBD olein, and superolein consist mainly of monosaturated and disaturated TG while RBD palm stearin consists mainly of disaturated and trisaturated TG. In DSC cooling thermograms the peaks of triunsaturated, monosaturated and disaturated TG were found at the range of −48.62 to −60.36, −25.89 to −29.19, and −11.22 to −1.69°C, respectively, while trisaturated TG were found between 13.72 and 27.64°C. The heating thermograms of CPO indicated the presence of polymorphs β₂′, α, β₂′, and β₁. The peak of CPO was found at 4.78°C. However, after refining, the peak shifted to 6.25°C and became smaller but more apparent as indicated by RBD palm oil thermograms. The heating and cooling thermograms of the RBD palm stearin were characterized by a sharp, high-melting point (high-T) peak temperature and a short and wide low-melting point (low-T) peak temperature, indicating the presence of occluded olein. However, for RBD palm olein, there was only an exothermic low-T peak temperature. The DSC thermograms expressed the thermal behavior of various palm oil and its products quite well, and the profiles can be used as guidelines for fractionation of CPO or RBD palm oil.     

Effect of repeated heating on thermal behavior of crude palm oil

Thermal behavior of crude palm oil (CPO) is important to determine the optimal fractionation process and product yield. In this study, the effects of repeated heating on thermal behavior of CPO were examined by differential scanning calorimetry. CPO was heated at 80°C for 5 min, and heating was repeated five times to simulate the common conditions experienced by an oil before reaching the refinery. The result revealed that the thermal behavior of CPO changed after heating. The change, however, occurred only in the behavior of the high-melting stearin peak but not in the low-melting olein peak. Overheating split the stearin peak at 17.30°C to two peaks at 18.88 and 17.30°C and formed a new peak at 11.28°C. Apparently, a new substance has been synthesized.     

Effects of Pilot Plant-Scale Ultrasound on Palm Oil Separation and Oil Quality

The effects of ultrasonic standing waves on palm oil separation of ex-screw press feed from the mesocarp of the palm oil fruit, oil recovery and oil quality were determined. The ex-screw press feed at 85 °C was pumped simultaneously into two identical vessels. One vessel was the control (non-ultrasound) and the other vessel (ultrasound) was fitted with two 400 kHz transducer plates operating at 13.4 kJ/kg, which were placed in direct contact with the feed. Oiling-off by gravity settling occurred at faster rates after sonication. The total recoverable oil after 30 min gravity settling and upon centrifuging the underflow sludge (remaining colloidal fraction) at 1000×g was higher after sonication. Total recoverable oil was 30.7 ± 2.9 % and 43.5 ± 8.6 % (w/w original feed basis) for the non-sonicated and sonicated samples respectively. Sonication reduced the oil content of the sludge ex-centrifuge, demonstrating that higher recovery of palm oil was obtained with ultrasound application. Sonication did not affect the DOBI (deterioration of bleachability index) value, and vitamin E and free fatty acid contents of the separated oil. High-frequency ultrasound enhances the separation rate of palm oil and increases oil recovery without compromising oil quality.     

Oxidative degradation kinetics of lycopene, lutein, and 9-cis and all-trans β-carotene

The thermal and oxidative degradation of carotenoids was studied in an oil model system to determine their relative stabilities and the major β-carotene isomers formed during the reaction. All-trans β-carotene, 9-cis β-carotene, lycopene, and lutein were heated in safflower seed oil at 75, 85, and 95°C for 24, 12, and 5 h, respectively. The major isomers formed during heating of β-carotene were 13-cis, 9-cis, and an unidentified cis isomer. The degradation kinetics for the carotenoids followed a first-order kinetic model. The rates of degradation were as follows: lycopene>all-trans β-carotene≈9-cis β-carotene>lutein. The values for the thermodynamic parameters indicate that a kinetic compensation effect exists between all of the carotenoids. These data suggest that lycopene was most susceptible to degradation and lutein had the greatest stability in the model system of the carotenoids tested. Furthermore, there was no significant difference in the rates of degradation for 9-cis and all-trans β-carotene under the experimental conditions.     

Effect of energy transfer conditions on the chemical degradation of frying oil

The effects of temperature, heating time (continuous or discontinuous mode), and water steam on sunflower oil deterioration have been investigated. Oil was heated at three temperatures, 120, 150, and 190 °C, during a total period of 60 h to achieve a wide range of degradation degrees. At 190 °C, 9 h of discontinuous heating were achieved, and oil degradation was compared to the previous treatment. Water steam treatment was investigated at two oil temperatures, 120 and 150 °C, by frying food model samples that provided a vapor flow of 1.2 g/min during about 30 h. Energy consumptions of the fryers have been measured for each experiment. Thermooxidative degradation of heated oils was evaluated by the measurement of conjugated dienes, viscosity and total polar compounds. All these indicators showed that for the same heating time, oil degradation was more important at 190 °C, and most of all for an intermittent heating. However, the results showed a good correlation between oil degradation and the fryer energy consumption for all the heating experiments, continuous or discontinuous. The presence of water seemed to modify this correlation. These results highlight the complexity of oil degradation during frying, depending on oil temperature, heating mode and presence of water, which can be expressed in energy consumption.     

Effect of heating rate on pyrolysis of low-grade pyrolytic oil

The low-grade pyrolytic oil produced from pyrolysis of municipal plastic waste in a commercial rotary kiln reaction system cannot be an acceptable fuel oil due to its low quality. Thus, the degradation of pyrolytic oil was conducted in a bench scale batch reactor, which was done by two experiment conditions of high heating rate (about 7 °C/min) and low heating rate (1.5–3.6 °C/min) up to 420 °C of reaction temperature. The characteristics of raw pyrolytic oil were examined and also the characteristics of products obtained by different heating rates were compared. Raw pyrolytic oil had higher H/C ratio and higher heating value than commercial oils, and also its peak range in GC analysis showed wide distribution including all the range of gasoline, kerosene and diesel. In the upgrading of pyrolytic oil, cumulative amount profile of product oil, as a function of reaction time, was similar in shape to the degradation temperature profile. All product oils obtained by different degradation temperature had higher H/C ratio and slightly higher heating value than those of raw pyrolytic oil. Also, the characteristics of product oils were influenced by heating rate and reaction temperature.     

Acceleration of the thermoxidation of oil by heme iron

Transition metals, including iron, occur naturally at significant concentrations in meat. Iron can be extracted from the food into the oil and potentially decrease the stability of the oil during frying by accelerating thermoxidation. The objective was to examine the thermoxidative stability of partially hydrogenated soybean oil after addition of heme iron. Heme iron (2.7 ppm) was added to the oil, and then oil samples were heated continuously at 160, 180, or 200°C for 72 h. Oil samples were removed for analysis every 12 h. The acid values, color, food oil sensor readings, and TAG polymer content of the heated oil samples were compared with oil samples containing no added iron that were held at the same temperatures. Generally, each oxidative index increased with (i) an increase in temperature, (ii) an increase in heating time, and/or (iii) the addition of iron. Generally, the extent of oxidation was greater for samples heated at 200°C than for oil samples heated at 160 or 180°C. The oil samples heated at 200°C reached the target polymer content of 20% after 27 h of heating. If heme iron accumulates in the oil, it will increase the rate of oxidation and thermal degradation and reduce the frying life of the oil.     

Kinetic study of β‐carotene and lutein degradation in oils during heat treatment

The kinetics of trans‐β‐carotene and trans‐lutein degradation were individually investigated in palm olein and Vegetaline®, at four temperatures ranging from 120 to 180 °C. HPLC‐DAD analysis was carried out to monitor trans and cis carotenoid variations over the heating time at each temperature. In both oils, initial trans‐β‐carotene and trans‐lutein degradation rates increased with temperature. Trans‐lutein was found to degrade at a slower rate than trans‐β‐carotene, suggesting a higher thermal resistance. The isomers identified were 13‐cis‐ and 9‐cis‐β‐carotene, and 13‐cis‐, 9‐cis‐, 13'‐cis‐, and 9'‐cis‐lutein. In spite of the higher number of lutein cis isomers, their total amount was lower than that of β‐carotene cis isomers. Trans and cis carotenoids were involved in degradation reactions at rates that increased with temperature. All degradation rates were generally found to be lower in Vegetaline® than in palm olein. These results were explained by the initial composition of the two oils and especially their peroxide and vitamin E contents.     

Reactions of palm oil‐based mcl‐PHAs with epoxidized natural rubber

A palm oil‐based medium‐chain‐length polyhydroxyalkanoate (mcl‐PHA) was allowed to react with epoxidized natural rubber (ENR). There was no noticeable reaction at ambient temperature for short reaction times. However, after 30 min at 170°C, the mcl‐PHA underwent thermal degradation to generate carboxylic terminal groups that attacked the epoxy groups of the ENR. Evidence of the ring‐opening reaction was provided by both FTIR and ¹H‐NMR. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Experimental characterization and modeling of microwave heating of oil palm kernels,mesocarps, and empty fruit bunches

The current work investigates the microwave heating and drying behavior of oil palm fresh fruits and bunches. Dielectric, thermal, and mechanical properties of oil palm kernels (OPKs), mesocarps, and empty fruit bunches (EFBs) were determined. New empirical models of the dielectric constant, loss factor, elastic modulus, and yield stress as functions of moisture content were obtained for OPKs, mesocarps, and EFBs. The thermal conductivity of the mesocarps and EFBs was 0.458 and 0.0285?W/(m K), respectively. Thermal analyses showed that decomposition of OPKs, mesocarps, and EFBs started when the temperature exceeded 100°C. Multiphysics models that consider electromagnetic waves, moisture, and heat conservation as well as material deformation were developed for OPKs, mesocarps, and EFBs. The simulation results show that an EFB sample with high moisture content generated a high moisture gradient during heating, causing high stress that exceeded its yield stress. However, this effect occurred only during the initial heating. Our results show that microwave heating can aid the detachment of oil palm fruit from bunches before EFBs harden because of moisture loss.     

Effect of short thermal treatment on cotton degradation

Cotton fabric was subjected to thermal treatment for durations ranging from 0.5 to 5 min at a temperature range of 160°C. In comparison with the untreated cotton, the copper number (measure of the aldehyde content) decreased after heating cotton for up to 3 min at 160°, 180°, and 190°C but increased when heating was prolonged to 5 min. Thermal treatment at 200°C or above caused an appreciable increase in the copper number. The carboxyl content increased with time of heating, attained a maximum, and then fell down to reach values which in some cases were lower than that of untreated cotton. Thermal treatment at 180°C caused a substantial reduction in the D. P.; this reduction increased with time of treatment. At the other temperatures there was no significant decrease in D. P. when cotton was heated up to 3 min. The D. P. decreased in these cases only when the thermal treatment was conducted for 5 min. The tensile strength remained practically unimpaired after thermal treatment of the cotton for up to 2 min, regardless of the temperature used within the range studied. A loss in tensile strength of ca. 9% and 13% was observed with fabrics treated for 5 min at 160° and 180°C, respectively. This contrasts with a loss of ca. 4% at 190°C, 7% at 200°C, and 8% at 220°C. The highest dye exhaustion was obtained on cotton which was thermally treated at 180°C prior to dyeing, while the lowest dye exhaustion was obtained on cotton heated at 220°C. Thermal treatment at 160°C left the susceptibility of cotton toward the dyestuff practically unaltered.     

Biosynthesis of polyhydroxyalkanoates using <Emphasis Type="Italic">Cupriavidus necator</Emphasis> H16 and its application for particleboard production

Different concentrations of palm oil and urea were used in a preliminary experiment conducted in a shake-flask to determine the optimum conditions for the biosynthesis of polyhydroxyalkanoates (PHA). The best concentration was found to be 10 g/L palm oil and 0.54 g/L urea which produced the highest concentration of PHA (8.11 g/L). A 13 L bioreactor was employed using a fed-batch fermentation with the derived optimum conditions and yielded a PHA concentration of 97 g/L. The melting temperature and thermal degradation temperature of PHA were determined to be 173 °C and 254 °C, respectively. The PHA was applied as a binder to make particleboard from para-rubber-wood flakes which were pretreated with microwaves and steam before being mixed with PHA, and control panels were also manufactured from un-pretreated flakes and without the addition of PHA. The mechanical and physical properties of the panels were determined including the modulus of rupture (MOR), internal bond strength (IB), water absorption, and thickness swelling according to the Japanese Industrial Standard for particleboard (JIS A 5908, 2003). The result showed that none of the panels produced met all the minimum requirements for Type 8 Particleboard of Japanese Industrial Standard JIS A 5908. The MOR of the control panel passed the JIS A 5908 standard for MOR (> 8.00 MPa) but did not meet the IB requirement (>0.15 MPa). The addition of PHA as a binder in proportions of 15, 20 and 30 wt% in the control panel enhanced the IB to 0.18, 0.19. 0.22 MPa, respectively. However none of the other parameters of these boards met the relevant JIS A 5908 standard. The pretreatment process was also unable to enhance the properties of the particleboard but that using PHA as a binder instead of urea formaldehyde was able to meet the relevant internal bonding standard for particleboard manufactured from para-rubber-wood flakes which are a waste product in the furniture industry.     

Carob Fruit Polyphenols Reduce Tocopherol Loss,Triacylglycerol Polymerization and Oxidation in Heated Sunflower Oil

Heated oils may contain potentially toxic altered compounds. A denatured carob fiber, very rich in non-extractable tannins (Exxenterol^®), exhibits antioxidant activities in in vitro experiments. The present study was designed to evaluate in sunflower oil (SO) heated to frying temperature, the protective effect on oil thermal oxidation and polymerization of adding 10 mg Exxenterol/kg oil (SO-10) and 50 mg Exxenterol/kg oil (SO-50). After 2, 8 and 16 h at 180 °C, SO displayed a relevant increase in triacylglycerol-derived polar material (PM) and polymer contents and a decrease in α-tocopherol concentrations. Thermal oxidation changes were significantly checked in SO-50 throughout the 16-h heating, while SO-10 only displayed protection from thermal oxidation during the first 2 h of heating. Oil frying-life was doubled because formation of PM and polymers was inhibited by more than 50%. Results clearly show that this non-extractable tannin-rich fiber can be successfully employed as an additive to significantly prolong sunflower oil frying-life, and thus decrease the potential toxicity of the heated oil.     

Thermal properties and aging characteristics of chemically modified oil palm ash-filled natural rubber composites

The chemically modified oil palm ash (OPA) with the cetyltrimethylammonium bromide (CTAB) solution was prepared prior to compounding with the natural rubber and other curing ingredients. The aging resistance and thermal stability of CTAB-modified OPA-filled natural rubber composites were evaluated in the same manner as non-modified OPA samples. The retention tensile properties after thermal aging was measured and based on the result shown, the CTAB-modified OPA-filled natural rubber composites imparted insignificant effect to aging resistance as compared to the non-modified OPA-filled natural rubber composites at very low OPA loading; however, the effect became apparent beyond 3 phr OPA loading where the CTAB-modified OPA-filled natural rubber composites provided better aging resistance than the corresponding non-modified OPA-filled natural rubber composites. The thermogravimetric analysis indicated that the CTAB-modified OPA-filled natural rubber composites exhibited lower thermal stability which showed lower temperature at their respective weight loss and lesser char residue than that of non-modified OPA-filled natural rubber composites. This was attributed to the CTAB which started to decompose at the temperature of 210 °C. However, for the range from ambient temperature to 210 °C, the CTAB-modified OPA-filled natural rubber composites produce better thermal stability than those of non-modified OPA-filled natural rubber composites.