Oxidative stabilities of enzymatically interesterified goose fat and rapeseed oil blend by rancimat and PDSC

Goose fat (GF) and rapeseed oil (RSO) 2:3 m m^?1 blend was enzymatically interesterified at 60 °C with and without microwaves assistance. As the catalyst, a commercial preparation of the immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) containing 2 % of water was used, and the catalyst load was 8 % in each case. The starting mixture and the interesterified products were separated by column chromatography into pure triacylglycerols fraction (TAG) and a non-triacylglycerol fraction, which contained free fatty acids (FFA), mono- and diacylglycerols (MAG and DAG). The oxidative stabilities of fats studied and TAG derived from them were assessed by Rancimat at 100 °C and by pressure differential scanning calorimetry (PDSC) under oxygen at 110–140 °C. Interesterification reduced the oxidative stability of GF and RSO blend. The main factors influenced on the oxidative stabilities of fats studied were concentrations of tocopherols and the presence of FFA, MAG and DAG. The structures of TAGs were of minor importance. From the resulting PDSC exotherms, their times to reach the onset (τ _on) and peak maximum (τ _max) were measured and used for calculations of parameters of the Arrhenius type kinetics for thermaloxidative decomposition of fats studied.     

Application of the calorimetric and spectroscopic methods in analytical evaluation of the human milk fat substitutes

The aim of this paper was the analytical evaluation of human milk fat substitutes (HMFS) by the calorimetric and spectroscopic methods. The HMFS were obtained by enzymatic interesterification of blend of lard or milk fat with rapeseed oil and concentrate of fish oil. The enzymatic reactions were carried out at 60, 70, and 80 °C for 2 h. A commercially immobilized 1,3-specific lipase, Lipozyme RM IM, was used as a biocatalyst. Oxidative stability of HMFS was determined using the calorimetric method. The oxidative induction time was obtained from the pressure differential scanning calorimetry curves. Peroxide value (PV) and anisidine value were determined using spectroscopic method. Interesterification caused a decrease in oxidative stability. Samples with lower induction times were characterized by higher PV. There was also a strong relation between total polar compound content and induction time. The induction times obtained for analyzed fats can be used as primary parameters for the assessment of the resistance of tested fats to their oxidative decomposition.     

Monitoring batch lipase catalyzed interesterification of palm oil and fractions by differential scanning calorimetry

The melting profiles of palm oil, palm olein, and soft palm mid fraction were investigated by differential scanning calorimetry (DSC) before, during and after enzymatic interesterification. The DSC melting profiles of the three palm fats changed drastically due to the random redistribution of the fatty acids on the glycerol occurring upon interesterification. A high melting peak (already present for native palm oil) was observed for the three interesterified products and attributed to the increase in trisaturated triacylglycerols; modifications of the shape of the medium-melting peak (observed in the three products) were attributed to modifications within the mono-unsaturated triacylglycerols. In view of the drastic changes observed, the applicability of DSC to monitor enzymatic interesterification reactions was considered. While the degree of interesterification was supposed to be completed after 8 h according to the HPLC data, significant modifications were still observed within the DSC melting profiles. Minor changes within the structure of the medium-melting peak were selected as indicator of the reaction progress, and it was shown that intensities of DSC melting endotherms can be used to monitor the enzymatic interesterification reaction of these palm products.     

Monitoring lipase-catalyzed butterfat interesterification with rapeseed oil by Fourier transform near-infrared spectroscopy

This work demonstrates the application of FT-NIR spectroscopy in order to monitor the enzymatic interesterification process for butterfat modification. The reactions were catalyzed by Lipozyme TL IM at 70 °C for the blend of butterfat/rapeseed oil (70/30, w/w) in a packed-bed reactor. The blend and interesterified fat samples were measured in liquid form at 70 °C by transmission mode-based FT-NIR over the spectral region 12000–4000 cm⁻¹. The calibration of FT-NIR for conversion degree (evaluated by the triglyceride profile, which was represented by the triglyceride peak ratio) and solid fat content (SFC) of the interesterified products was carried out using partial least squares (PLS) regression. Good correlations were observed between the NIR spectra and ln (peak ratio), and between the NIR spectra and the SFC at 5 °C over the spectral range 5269–4513 cm⁻¹. Overall, transmission-mode FT-NIR spectroscopy performed at 70 °C yielded conditions close to those used during the interesterification process, implying that this method could be used to control the enzymatic interesterification process online.     

Influence of thermal degradation in the physicochemical properties of fish oil

Physicochemical and thermal analyses were undertaken to evaluate the influence of the temperature on the oxidation of sea fish oil once its polyunsaturated fatty acids deteriorate rapidly. Fish oil displayed four decomposition steps in synthetic air atmosphere and only one step in nitrogen atmosphere. The first step started at 189 and 222 °C for oxidizing and inert atmospheres, respectively. An OIT value of 53 min was measured at 100 °C. After the degradation process the peroxide index and the iodine index reduced from 35.38 to 9.85 meq × 1000 g^?1 and from 139.79 to 120.19 gI₂ × 100 g^?1, respectively. An increase of the free fatty acids amount from 0.07 to 0.17% was observed while viscosity increased from 57.2 to 58.0 cP. Absorption at 272 nm also increased. The thermogravimetric and spectroscopic techniques are reproducible and versatile being an option for characterization of edible oil oxidation.     

Characterization of oil from roasted hemp seeds using the PDSC and FTIR techniques

The purpose of the present work was to characterize oil extracted from roasted hemp seeds using the PDSC and FTIR techniques. Roasting was conducted in a laboratory convective dryer. DSC method was used for the determination of the oxidative stability of oil extracted from hemp seeds. Pressure differential scanning calorimetry experiments were carried out using a DSC Q20, TA Instruments, coupled with a high-pressure cell. The isothermal temperature (393 K) was used for the data collection. The oxidative induction time was obtained from the PDSC curves. Infrared spectra were registered for every sample in the classic range of 4000–400 cm^?1 with 1 cm^?1 resolution, using System 2000 PerkinElmer instrument. The Grams AI 8.0 and TQ Analyst 8 software were used for spectral data processing. The samples of oil were also characterized by standard quality parameters: fatty acids composition (with use of GC technique), free fatty acids content by titration with 0.1 M potassium hydroxide and peroxide value determined by iodometric titration technique. Samples of oil extracted from hemp seeds after roasting in higher temperatures were characterized by lower induction time than oil from hemp seeds roasted in lower temperature. The results confirm that the induction time obtained from PDSC measurements can be used as parameters for the assessment of the resistance of oils from roasted hemp seeds to their thermal–oxidative decomposition.

     

A complete evaluation of thermal and oxidative stability of chia oil

Chia (Salvia hispanica L.) seed oil is the richest natural source of α-linolenic acid, an n ? 3 polyunsaturated fatty acid (ω-3 PUFA), contributing to its use as functional and nutraceutical food in large part of Latin America. However, a food with such fatty acid composition could be highly susceptible to lipid oxidation. Thus, the present study was conducted to determine the thermal and oxidative stability of chia oil by various methods. Rancimat method was used to evaluate the effect of synthetic and natural antioxidants in the oxidative stability. Pressurized differential scanning calorimetry (PDSC), Schaal test and ¹H NMR spectroscopy were used to assess the thermal stability. The effect of frying temperature and/or heating time on fatty acid composition was assessed by ¹H NMR. The results show that tert-butylhydroquinone (TBHQ) and a mixture of TBHQ and rosemary extract were effective in increasing the oxidative stability of chia oil. Concerning the storage conditions, PDSC, Schaal test and ¹H NMR data showed that chia oil is stable at 60 °C; hence, there is no need for special storage conditions. PDSC and ¹H NMR results indicate that chia oil cannot be used in cooking and frying, because at high temperatures severe degradation of the unsaturated groups and loss of the nutritional properties of the oil occur.     

Identification of volatile aroma compounds in processed cheese analogues based on different types of fat

The simple and rapid solid-phase micro-extraction method using gas chromatography was used for the identification and quantification of volatile aroma compounds in various types of processed cheese analogues produced from different types of fat (butter, butter oil, coconut oil, palm oil, and sunflower oil). In total, 31 organic compounds belonging to five chemical groups were identified, with the alcohols and fatty acids quantitatively predominant. The contents of the aroma compounds (the so-called aroma profiles) of the analogues and corresponding fats used as raw materials were compared. Significant differences (p < 0.05) were found between samples. The highest total content of aroma compounds was found in coconut oil analogue ((547.30 ± 9.82) mg kg^?1), the lowest in palm oil analogue ((372.01 ± 16.16) mg kg^?1). The concentrations of aroma compounds in fats were substantially lower (p < 0.05) than in analogues. Hence, the largest number of aroma analogues came from Edam cheese used for production as a protein source.     

Nutritional improvement of soybean oil via lipase-catalyzed interesterification

In order to decrease the content of linoleoyl moiety in soybean oil, soybean oil that contains 22.8% oleoyl, 54.8% linoleoyl, and 7.1% α-linolenoyl moieties as molar acyl moiety composition was interesterified in hexane with oleic acid or α-linolenic acid, using an immobilized sn-l,3-specific lipase (Lipozyme® IM) fromMucor miehei. The reactions were carried out in a batch reactor at 37°C in the following system: molar ratio of fatty acid to soybean oil = 1.0 ～ 6.0, 5.0 mL of hexane/500 μmol soybean oil, and 10.0 or 15.0 batch interesterification units of enzyme/500 μmol soybean oil. Under these reaction conditions, the rates of interesterification of acyl moieties in soybean oil were of the order: stearoyl > palmitoyl > linoleoyl > oleoyl > α-linolenoyl, and the reaction with oleic acid occurred without a significant loss of α-linolenoyl moiety. At the molar ratio of 3.0 and the reaction time of 6 h, triacylglycerols (TGs), which contain 50.8% oleoyl, 38.8% linoleoyl, and 5.4% α-linolenoyl moieties, were produced in the reaction with oleic acid; TGs that contain 13.5% oleoyl, 40.8% linoleoyl, and 40.4% α-linolenoyl moieties were obtained with α-linolenic acid. Approximately 86-88% of the interesterification of linoleoyl moiety, which occurred in 10 h, took place within 1 h.     

Evaluating antioxidants efficiency during storage of ethylic and methylic biodiesel by low pressurized DSC and Rancimat methods

Efficiencies of four commercial antioxidants used during the storage of two biodiesel, BS-ethyl and BS-methyl, respectively obtained from soybean oil by ethylic and methylic routes, were evaluated by measuring their oxidative stability using a low pressurized DSC (low P-DSC) method developed by the authors and by Rancimat method, which is specified by the American ASTM D6751 and European EN 14214 standard methods. The operating temperature of the low P-DSC method was the same as that used in the Rancimat procedure (110 °C). The antioxidants, used in 500 mg kg^?1 content, have the following active components: phenol, biphenol, phenol + amine mixture, and a hydroquinone + organic acid mixture. Samples of each biodiesel–antioxidant mixture were evaluated simultaneously by the two methods, right after their preparation and 30, 60, 90, and 120 days of storage at 23 ± 1 °C. A non-dimensional oxidative induction time parameter, defined as the ratio between the oxidation induction time (OIT) or induction time (IT) values at a storage time t and at t = 0, was used to evaluate the antioxidant activity. For the same mixture, changes of this non-dimensional parameter calculated from OIT or IT show a similar trend with storage time, indicating that it can be determined either from low P-DSC or Rancimat method data. As the efficiency of the studied antioxidants depends on their composition, their interaction with each biodiesel, and on the storage time, this parameter can be used to indicate the best storage time for each antioxidant–biodiesel mixture.     

Effect of temperature on frying oils: infrared spectroscopic studies

Frying oils were studied by Fourier-transform infrared (FT-IR) spectroscopy, in the range 4,000–200 cm^?1, at different temperatures, in the liquid and solid states. The infrared spectrum at 15 °C was similar to that at 200 °C. The band at 730 cm^?1 which was assigned to the rocking mode of (–CH₂) disappeared at higher temperature because of the rotational isomerism which occurred in the oil structure. The activation energy (E _a) of the disappearing (–CH₂) band, calculated by use of the chemical dynamic method using the Arrhenius equation, is 8.45 kJ mol^?1. The enthalpy difference (ΔH) between the two rotational isomer bands of the conformational structures of the oil at 730 and 1,790 cm^?1, at different high temperatures, was also calculated, by use of the Van’t Hoff equation; the value obtained was ?10.85 kJ mol^?1.     

Effects of spice extracts on lipid fraction oxidative stability of cookies investigated by DSC

The addition of natural antioxidants to the bakery products containing fats can extend their shelf life, and it may be more attractive to consumers. In this research, the antioxidant effect of spice extracts and synthetic antioxidant on oxidative stability of fat extracted from cookies was evaluated by differential scanning calorimetry (DSC). The results revealed that addition of spice extracts to the cookies in comparison to cookies without additives reduced the oxidation as evidenced by higher the onset oxidation temperature (t _ON) of antioxidant-treated samples. Using the Ozawa–Flynn–Wall method, the activation energies (E _a/kJ mol^?1) and pre-exponential factors (Z/min^?1) and then induction times (τ/min) were calculated and also used for evaluation of antioxidants efficiency. After baking, cookies were also subjected to sensory studies and to instrumental measurements of colour changes. Among the samples studied, cookies with 0.02 % of rosemary or 0.2 % thyme extracts showed good sensorial acceptability. Cookies fortified with spice extracts also characterised greater lightness compared to the control sample.     

Characterization of Pentaclethra macroloba oil

The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing.     

Determination of SFC, FFA, and equivalent reaction time for enzymatically interestified oils using NIRS

The use of near infrared spectroscopy (NIRS) for rapid determination of the degree of interesterification of blends of palm stearin, coconut oil, and rapeseed oil obtained using an immobilized Thermomyces lanuginosa lipase at 70 °C was investigated. Interesterification was carried out by applying both fixed bed and batch reactors. Calibrations were developed for quantitative determination of solid fat content (SFC) at 10, 20, 30, 35, and 40 °C and free fatty acid (FFA) resulting in root mean square errors of prediction of 1.0, 1.3, 1.4, 1.6, 1.7, and 0.19% (w/w), respectively. The data showed that NIRS could be used to replace the traditional methods for determining FFA and SFC in vegetable oils.It was possible to monitor the activity of the immobilized enzyme for interesterification of margarine oils by predicting the equivalent reaction time in a batch reactor from NIR spectra. Root mean square errors of prediction for two different oil blends interesterified for 300 and 170 min were 21 and 12 min, respectively.     

Interesterification of butter fat by lipase fromRhizopus niveus in cosurfactant-free microemulsion system

Butter fat was interesterified in a cosurfactant-free microemulsion system containing nonionic and ionic surfactants, using commercial lipase obtained fromRhizopus niveus, at different concentrations of surfactant mixtures and hydrophilic-lipophilic balance (HLB) values. The results indicated that the interesterification yield (IY) of lipasecatalyzed interesterified butter fat reached its maximum in the microemulsion system prepared with the surfactant mixture of HLB value of 9, followed by that of HLB value of 10. In addition, increasing concentrations of surfactant mixtures, from 3 to 6 mM, resulted by an increase in the IY. The interesterification of butter fat in the microemulsion prepared with 3 mM of surfactant mixture of HLB value of 10 showed a minimum hydrolytic activity. The results showed that the interesterified selected triacylglycerol molecules were enriched with the hypocholesterolemic fatty acid C18:l, originally located onsn-1,3 positions, on theirsn-2 positions; this fatty acid was favorably interchanged with the hypercholesterolemic fatty acid C16:0, originally located onsn-2 position. The results also indicated that the use of 6 mM of surfactant mixtures increased the acyl exchange reaction toward the long-chain saturated fatty acid C16:0 on the sn-2 position of triacylglycerol molecules.     

Electrochemical studies of copper fatty amides complex in organic medium

The electrochemical behavior of complexes of fatty amides, synthesized from vegetable oil, with Cu(II) has been investigated. In this study, a platinum electrode was used in presence of DMSO as a medium. Reduction of Cu(II)/fatty amides complex was found with quasi-reversible reaction. The peak potential of voltammetric behavior of fatty amides is about ?0.77 V at a scan rate v = 0.1 V s^?1 versus Ag|Ag⁺ electrode. This study shows that Cu(II)-fatty amides complex is poorly adsorbed on the electrode surface. Additionally, the copper complex form of fatty amides has a more stable structure than pure fatty amides to form the electrochemical reduction of the complex.     

Comparison of the oxidative stability of soybean and sunflower oils enriched with herbal plant extracts

The present study was conducted to determine and compare the oxidative stability of soybean and sunflower oils using differential scanning calorimetry (DSC). These edible oils were enriched with marjoram (Origanum majorana L.), thyme (Thymus vulgaris L.), and oregano (Origanum vulgare L.) extracts at three different concentrations and synthetic antioxidant (BHA). The fatty acid composition of studied oils was determined by gas chromatography mass spectrometry to evaluate the content of unsaturated fatty acids that are sensitive to oxidation process. Oil samples were heated in the DSC at different heating rates (4.0, 7.5, 10.0, 12.5, and 15.0 °C min^?1) and oxidation kinetic parameters (activation energy, pre-exponential factor, and oxidation rate constant) were calculated. The results showed that the oxidative stability of sunflower oil samples enriched with oregano extracts and soybean oil supplemented with thyme extracts was improved compared to samples without the addition of herbal plant extracts and the synthetic antioxidant.     

Mixed,lipase-catalyzed inter-esterified fats and hemp oil as a fatty base of model emulsion products with different emulsifiers

The aim of the study was to perform modification of fats to obtain new products, which were used as a fatty basis of model emulsions. The second objective was to assess the stability of the prepared emulsions. For this purpose, turkey fat, chicken fat, and mutton tallow were used and enzymatically inter-esterified with hemp oil. Enzymatic interesterification was performed using a selective catalyst – Lipozyme IR RM. The obtained fat mixtures before and after interesterification were assessed by determining their acid value, peroxide value (PV), anisidine value (AV), polar fraction (PF), and slip melting point (SMP). Later, the fats were used as a fatty basis of emulsions. The variable component in the emulsions was the emulsifier. The emulsions were evaluated for droplet size and viscosity and by the Turbiscan test. It was concluded that the dispersion systems containing mutton tallow and the emulsifier formed during the enzymatic reaction, as well as the one containing the same fat and lecithin, showed the best stability. In the case of emulsions with enzymatically modified mutton tallow, the authors are planning to extend the range of usable properties under examination. In the authors’ opinion, the proposed systems can be used in the cosmetic and food industries.     

Rancimat and PDSC accelerated techniques for evaluation of oxidative stability of soybean oil with plant extracts

Taking into account the importance of natural antioxidants in the preservation of oils and fats, the present study evaluated the antioxidant action of five plant extracts in the control of soybean oil stability, by means of the accelerated techniques Rancimat and PDSC. These plants are rosemary (Rosmarinus officinalis L.), chamomile (Matricaria recutita L.), coriander (Coriandrum sativum L.), fennel (Foeniculum vulgare), and senna (Cassia angustifolia Vahl). The plant extracts and also the synthetic antioxidant BHT were added to the samples of crude soybean oil at the concentration of 1,000 mg kg^?1. The values of total phenolic contents ranged from 8.7 ± 0.4 to 63.0 ± 2.3 mg GAE g^?1 extract and a strong positive correlation was observed between the total phenolic contents and the overall antioxidant activity of the plant extracts. Such high values indicate a good protection of the analyzed soybean oil, moreover for the Rosemary extract that was superior to the remaining extracts. In the Rancimat technique the rosemary extract was more effective than the synthetic BHT antioxidant. The OIT values of Rosemary extract and the BHT antioxidant were equivalent, and the former, showed the highest phenolic contents among the extracts, for all the performed tests, confirming that it is a powerful natural source of antioxidants.     

Fatty Acid Content and Profile of the Aerial Microalga Coccomyxa sp. Isolated from Dry Environments

Aerial algae are considered to be highly tolerant of and adaptable to severe conditions including radiation, desiccation, high temperatures, and nutrient deficiency, compared with those from aquatic habitats. There are considerable variations in the fatty acid (FA) composition of aerial microalgae from dry environments. A new species with a high lipid level was found on concrete surfaces and was identified as Coccomyxa sp. KGU-D001 (Trebouxiophyceae). This study characterized its FA content and profile in a bath culture. The alga showed a constant specific growth rate (0.26 day^?1) ranging in light intensity from 20 to 80 μmol photons m^?2 s^?1. The algal cells started to form oil bodies in the early stationary phase of growth, and oil bodies occupied most of the cells during the late stationary phase when the cells accumulated 27 % total fatty acids (TFA). The process of lipid body formation accumulating large amounts of triacylglycerols (TAG) appeared to be very unusual in response to stress conditions persisting for a relatively long culture time (50 days). This study could indicate that aerial microalgae will be a candidate for biodiesel production when a new cultivation method is developed using extreme stresses such as nutritional deficiency and/or desiccation.