Reduction In Peroxide Value Research Articles

Functional characteristics and storage stability of hot air assisted radio frequency treated pearl millet

Nutricereals, pearl millet flour consumption is hardly limited to a few specific regions of the world owing to the development of early rancidity on storage. Hot air assisted radio frequency technology (HARF) was used to improve the storage stability of pearl millet flour. Pearl millets at different moisture levels of 10.5±0.5, 12 & 15% were subjected to HARF for 5-, 10- & 15-min exposure period under fixed electrode position. The results revealed that significant reduction in peroxide value and free fatty acid values of flours from treated pearl millet was found compared to decorticated raw flour; thereby, the storage stability enhancement of pearl millet flour up to 180 days was achieved. No significant difference was found for emulsifying, foaming and cooking properties between treated pearl millet at 15% moisture, 15 min exposure and decorticated raw one. In contrast, the bulk density of flour from treated pearl millet was found higher. Significant increase in hardness of cooked grains after the treatment was observed while the springiness, cohesiveness and gumminess values did not vary. In FTIR analysis, no difference was observed between the peaks of whole and decorticated pearl millet flours in both untreated and treated samples.Graphical

Effects of oleuropein-rich olive leaf extract on the oxidative stability of refined sunflower oil

The aim of this study is to investigate the ability of oleuropein-rich olive leaf extract (OLE) to improve the quality and oxidative stability of sunflower oil subjected to accelerated thermal oxidation. Oleuropein was the major phenolic compound determined by HPLC-DAD with a content ranging from 20.81 to 32.56 mg·g-1 of dry extract (DE). The evaluation of the in vitro antioxidant capacity of OLE showed good scavenging capacity of the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and hydrogen peroxide (H2O2) (1.01 and 0.96 mmol Trolox equivalents (ET·g-1 DE, respectively). The enrichment of sunflower oil with 0.1, 0.25 and 0.5% OLE (w/v) significantly inhibited thermal-induced peroxidation in a dose-dependent fashion. 0.25% OLE was the most effective concentration and showed a significant reduction in peroxide value and conjugated dienes by 61.4 and 17.4%. These results indicate that OLE can be considered a good natural alternative for extending the shelf-life of polyunsaturated vegetable oils.

Assessment of the potential of algae phycobiliprotein nanoliposome for extending the shelf life of common carp burgers during refrigerated storage

This study is focused on the effect of phycobiliprotein extraction of Gracilaria on the quality of common carp burgers, and the application of nanoliposomes containing pigment in the improvement of its antimicrobial and antioxidant activity of burgers during refrigerated storage in 18 days. Burgers were incorporated with phycobiliprotein and liposomal phycobiliprotein (2.5% and 5% w/w), and their chemical and microbial changes in terms of pH, peroxide value (PV), thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N), total viable counts (TVC), psychrotrophic bacterial counts (PTC), and sensory characteristics were evaluated. Results presented a nanoliposome size of about 515.5 nm with capable encapsulation efficiency (83.98%). Our results showed non-encapsulated phycobiliprotein could delay the deterioration of common carp burgers, as a reduction in PV, TBA, and TVB-N, TVC, and PTC values in burgers treated with free and nano encapsulated phycobiliprotein. Moreover, the potential of phycobiliprotein was improved when it was encapsulated into chitosan coated liposomes. Burgers treated with 5% nanoliposomes displayed the lowest amount of lipid oxidation and microbial deterioration in comparison to others during storage. According to chemical, microbial and sensory evaluation, the shelf life of common carp burgers was increased in samples treated with encapsulated phycobiliprotein at 2.5% and 5%, as compared to the control (p ≤ 0.05).

Combination of natural strategies to improve the oxidative stability of echium seed oil.

Echium seed oil is an alternative source of omega 3 fatty acids but it is highly susceptible to oxidation. A combination of three natural strategies was proposed in this study aiming to improve the oxidative stability of echium oil obtained by pressing (PO) or solvent extraction (PSO), kept in the storage condition for 180 days or during the consumption for 30 days. Our results showed that the reduction of temperature was sufficient to keep the oil stable during storage for both samples. During the consumption time, the best stability was achieved by adding a mixture of antioxidants, composed of sinapic (500ppm), ascorbic (250ppm), and citric (150ppm) acids, and/or 20% of high oleic sunflower oil. The combined strategies promoted a 34 to 80% reduction of peroxide value and 0 to 85% reduction of malondialdehyde concentrations in the samples, showing to be a feasible and natural alternative to improve the oxidative stability of echium oil. PRACTICAL APPLICATION: Our study successfully applied an optimized combination of simple and low-cost strategies to enhance the chemical stability of echium seed oil. As the use of echium oil expands around the world, the oil industry and final consumers may benefit from our results to increase the oil shelf-life.

A Green Enzymatic Extraction Optimization and Oxidative Stability of Krill Oil from Euphausia Superba.

Krill oil enriched with polyunsaturated fatty acids is in the form of phospholipid. However, its application as a dietary supplement is limited, because of its rapid deterioration. Thus, this study aims to investigate the oxidative stability of krill oil extracted from Euphausia superba. Under optimal conditions (enzyme concentration 0.16%, enzymolysis time 2.9 h, and enzymolysis temperature of 45 °C) designed by response surface methodology, the extraction yield of krill oil is 86.02%. Five assays, including peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), pH value, and turbidity were used to determine the oxidative stability of krill oil nanoliposomes during storage. Carboxymethyl chitosan (CMCS) nanoliposomes showed a significant reduction in POV and TBARS values, a prevention of pH value decrease and turbidity increase. This study indicated that CMCS nanoliposome can effectively improve the oxidative stability of krill oil during storage. Furthermore, the release profile in vitro illustrated that the controlled release of krill oil carried out by CMCS nanoliposomes is feasible.

Improving the Quality of Locally Produced Vegetable Oils in Ghana Using Zeolite ZSM-11

The local vegetable oils (Coconut and Palm Kernel Oils) are usually faced with short shelf-life which has been associated with the presence of some unwanted materials present in them. This study explores the potential of using locally manufactures Zeolites in removing these impurities to improve the shelf life of these oils. The Zeolite used in this study was synthesized using locally available raw materials such as bauxite and kaolin through the hydrothermal process X-ray diffraction studies of the synthesized Zeolite were found to be part of the ZSM-11 Zeolite type group. FTIR analysis of the sample showed a weak vibrational peak at 1642cm-1 and a strong band at 987cm-1. Batch process for the removal of these unwanted materials was performed. Percentage reduction of 85.71%, 89.22%, 89.36% and 83.81% was recorded for impurities, moisture content, free fatty acid and peroxide value reduction in Palm Kernel Oil and 85.71%, 83.33%, 93.26%, 90.57% for Coconut Oil. Kinetic studies showed the process favored the Pseudo-first order with R2 of 0.956 and 0.971 for Coconut and Palm Kernel Oil respectively for impurities The plot of (t / qe) vs. t exhibits a very high linearity and can be concluded that the adsorption rate of the moisture content, impurities, FFA and peroxide value is dependent on the adsorbate used and contact time. The final oils had very good physicochemical parameters with improved qualities. It can be concluded that the synthesized Zeolite was effective for the refining of locally produced Coconut and Palm Kernel Oils and can be accessed for commercial applications.

PEMURNIAN MINYAK GORENG BEKAS MENGGUNAKAN ADSORBEN BIJI ALPUKAT TERAKTIVASI

Abstract This research had been conducted in the use of avocado seed powder (Persea americana Mill) as an adsorbent to reduce peroxide and free fatty acids of the used cooking oil. The aim of this research was to determine the best activator of avocado seed powder as an adsorbent to reduce peroxide and free fatty acids of the used cooking oil. This research used the variation of activators, consist of hydrochloric acid (HCl), citric acid (C6H8O7), sodium chloride (NaCl) and sodium hydrogen phosphate (Na2HPO4) solutions. The result showed that the best activator of avocado seed powder by HCl which gave the highest free fatty acid reduction was 0,26%. Meanwhile, the best activator of avocado seed powder by C6H8O7 which gave the highest peroxide value reduction was 1,8 Meq/Kg . These results had qualified as the maximum limits of SNI cooking oil were 0.3% for the concentration of free fatty acids and 2 Meg/kg for the peroxide value of cooking oil. Keywords: adsorbent, avocado seed powder, used cooking oil

The effects of vacuum package combined with tea polyphenols (V+TP) treatment on quality enhancement of weever (Micropterus salmoides) stored at 0 °C and 4 °C

The effects of vacuum package combined with tea polyphenols (V + TP) on the quality of weever stored at 0 and 4 °C were evaluated for 18 and 12 days. Changes of sensory score, volatile spoilage products, total viable counts (TVC) and physiochemical indexes including total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), peroxide value (PV), pH and texture were examined. The results indicated that V + TP presented better quality preservation than vacuum package and control group in maintaining the good quality and it presented optimal quality enhancement effects, such as volatile spoilage inhibition, TVB-N, TBA and PV reduction, TVC and pH control, texture and sensory acceptability maintenance, which could extend the shelf life by 4–6 and 3–4 days at 0 and 4 °C, respectively compared with the control group. Therefore, V + TP is promising in weever shelf life extension.

Reduction of Chlorophyll in Cold‐Pressed Hemp (Cannabis sativa) Seed Oil by Ultrasonic Bleaching and Enhancement of Oxidative Stability

The effects of ultrasonic bleaching on chlorophyll reduction and oxidative stability of cold‐pressed Cannabis sativa (hemp) seed oil is investigated using three different clays, Sepiolite, activated Bentonite, and an industrial clay. The chlorophyll content is significantly reduced (p < 0.05) from 56.3 μg g−1 in the untreated oil to 14.8 μg kg−1, 9.9 μg kg−1, and 7.8 μg kg−1 in oils treated with Sepiolite, activated Bentonite, and industrial clay, respectively. Oxidative stability is enhanced in all ultrasonically‐treated oils by a significant (p < 0.05) reduction in Peroxide Value (PV) with the highest reduction (97%) observed in the presence of industrial clay (PV = 0.11 mEq kg−1). A corresponding reduction in Conjugated Dienes (CD) is also found in the treated samples ranging from 0.073–0.095% compared to 0.102% for the control. During accelerated storage at 60 °C, increase in PVs and CDs are significantly (p < 0.05) slower for the ultrasonically treated oils in the presence of clays compared to the control. Accelerated storage at 40 °C shows that the PV is greater in hempseed oil bleached with Sepiolite clay compared to a combination of Sepiolite and ultrasonic bleaching. Based on these results it is evident that the rapid removal of chlorophyll from cold pressed hempseed oil is enhanced by a combination of bleaching clay and ultrasonic treatment.Practical Applications: Ultrasonic treatment of cold pressed hempseed oil combined with bleaching clays proves very effective in reducing chlorophyll content. The method is not only rapid and clean but requires significantly less bleaching clay. Hempseed oil treated in this way exhibits greater oxidative stability making it more attractive for industrial and consumer use. The results of ultrasonic bleaching suggest its potential for prolonging the shelf‐life. Utilizing the ultrasonic bleaching technique as an alternative to conventional bleaching would be beneficial to the edible oil industry.The results of ultrasonic bleaching prove effectiveness in reducing chlorophyll content in cold‐pressed hempseed oil and suggest its potential for prolonging the shelf‐life.

Physicochemical Property and Oxidative Stability of Whey Protein Concentrate Multiple Nanoemulsion Containing Fish Oil.

The objectives of this research were to produce whey protein concentrate (WPC) multiple nanoemulsion (MNE) and to study how whey protein concentration level and antioxidant type affected the physicochemical properties and oxidative stability of fish oil in MNE. The morphological and physicochemical characteristics of MNE were investigated by using transmission electron microscopy and particle size analyzer, respectively. The oxidative stability of fish oil in MNEs was assessed by measuring peroxide value (PV), p-anisidine value, and volatile compounds. The spherical forms of emulsions with size ranging from 190 to 210nm were observed indicating the successful production of MNE. Compared with free fish oil, fish oil in MNE exhibited lower PV, p-anisidine value, and formation of maker of oxidation of fish oil indicating the oxidative stability of fish oil in MNE was enhanced. PV, p-anisidine value, and makers of oxidation of fish oil were decreased with increased WPC concentration level. The combined use of Vitamin C and E in MNE resulted in a reduction in PV and p-anisidine value, and development of maker of oxidation. In conclusion, WPC concentration level and antioxidant type are key factors affecting the droplet size of MNE and oxidative stability of fish oil.

Reduction of Peroxide Value and Free Fatty Acid Value of Used Frying Oil Using TiO2 Thin Film Photocatalyst

The quality of used frying oil degraded due to the presence of products degradation, such as; PV and FFA which formed during the frying process. PV and FFA are harmful to human health. The photocatalytic activity of TiO2 thin film has been applied in various fields, especially in the environment. The aim of this study is to evaluate photocatalytic activity of TiO2 thin film for reducing PV and FFA in used frying oil. The TiO2 thin films were deposited on glass substrate by spray coating method at a temperature of 450 oC. The TiO2 precursor solution was prepared by mixing TTiP, AcAc, and ethanol. The thin films were varied into two conditions; as-deposited and annealed at a temperature of 500 oC. The morphology, crystalline structure, and optical properties of the thin films were characterized by scanning electron microscope (SEM), X-ray Diffraction (XRD), and UV-VIS spectrophotometer, respectively. The photocatalytic process was carried out by putting TiO2 thin film in used frying oil and irradiated by sunlight. The result showed that both of TiO2 thin films were still amorphous in nature. However, there was a peak with low intensity for annealed TiO2 thin film which corresponding to the TiO2 anatase crystals plane of (101). Annealing process improved crystallinity and changed the shape morphology of TiO2 thin films. The band gap was found to be 3.59 eV for as-deposited TiO2 thin film and 3.49 eV for the annealed-TiO2 thin film. The photocatalytic process shows that TiO2 thin films reduced FFA and PV of used frying oil up to 67.10% and 79.15%, respectively. Photocatalytic activity of annealed TiO2 thin film was higher than as-deposited TiO2 thin film. The results indicated that TiO2 thin film photocatalyst potential as the new alternative method to purify used frying oil.

Refining Ostrich Oil and its Stabilization with Curcumin

Ostrich Oil is particularly known for its cosmetic and therapeutic use. Being rich in polyunsaturated fatty acids, it is prone to oxidation causing undesirable changes in peroxide value, color, flavour and odor, which deteriorates its nutritional value. The objective of the study is to establish an efficient separation method to refine ostrich oil and stabilize it with curcumin or the extract of Curcuma longa. The reduction in peroxide value, color intensity, moisture content and odor were used as indicators of the purity of the oil. The modified refining process developed saw a reduction of 75% free fatty acid, 90% peroxide value, 54% moisture content, 60% in color intensity and odor. Curcumin, a natural antioxidant, prevented lipid peroxidation by 56% while vitamin E by only 8%, when tested at the same concentration (0.04%). Curcumin proved to be an effective stabilizer in a 6-month accelerated stability test. This study presents a method to refine ostrich oil efficiently and the ability of a natural antioxidant, curcumin, to stabilize the refined ostrich oil.This simple and straight forward method to refine and stabilize the oil can be adapted to be used for any ratite oils. The use of a natural alternative, curcumin as the anti-oxidant is not only safe but provides further added health benefits.

PEMANFAATAN ADSORBEN DARI BIJI ASAM JAWA UNTUK MENURUNKAN BILANGAN PEROKSIDA PADA CPO (CRUDE PALM OIL)

This study was aimed to discover the effectiveness of tamarind seeds as adsorbent for the reduction of PV (Peroxide Value) in CPO (Crude Palm Oil) at the best adsorbent dose and contact time. Materials used were CPO, tamarind seeds, nitric acid, and distilled water. Variables observed were adsorbent : nitric acid ratio and oven temperature in adsorbent activation process, and contact time and adsorbent dose in adsorption process. This study was began with adsorbent modification, where the cleaced and crushed tamarind seeds to pass through 140 mesh were activated with 4 N nitric acid at 1:1, 1:2, 1:3 and 1:4 of adsorbent : nitric acid ratio while heated at 80 oC for 2 hours. Adsorbent was then dried in oven at 110 oC, 120 oC, 130 oC and 140 oC. Adsorbent with the higher iodine number was used in adsorption process that was carried out by heating 100 grams of CPO on hot plate at 90 oC with 1000 rpm of stirring speed, and followed by adsorbent addition of 0.5 %, 1,0 %, and 1,5 % (of CPO used) and 25, 35, and 45 minutes of contact time, and after that oil was filtered using vacuum pump. The study results showed that the best ratio of adsorbent : nitric acid 4 N was 1:2 at 130 oC of oven temperature with 511.773 mg/g of iodine number. The best adsorbent dose was 1.0 % at 35 minutes of contact time that gave higher reduction of PV with peroxide value of 0,00868 meq/kg with the reduction percentage was 39,72 %. This study showed that nitcic acid-activated adsorbent from tamarind seeds was effective to reduce PV in CPO.

Deacidification of High-acid Olive Oil

The objective of the present work was to improve the quality of high-free fatty acid olive (HFFAO) oil. Silica gel (SG) was used as adsorbent by applying filtration and stirring techniques. Chemical treatments with alkali using NaOH and/or Ca(OH)2 were also conducted to neutralize the acidity of HFFAO oil. The percentages of linoleic acid (C18:2) in the neutralized oils were lower than those in the reference olive oil. Untreated and treated HFFAO oil samples were stored under accelerated conditions for 30 days. The progress of oxidation at 60°C was followed by measuring acid value (AV), the formation of oxidative products (peroxide value (PV) and p-anisidine value (AnV)), total phenolic compounds (TPC), recording radical scavenging activity (RSA) toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibition of β-carotene in a linoleate model system. The results indicated that SG and alkali treatments were effective in reducing the acidity of HFFAO oil. Generally, alkali treatments reduced the AV of HFFAO oil, while treatments with SG induced variable degrees of improvements in HFFAO oil acidity. Alkali treatments resulted in increasing the PV levels to 35 and 28 meq peroxide kg−1 oil for HFFAO treated with soda and lime, respectively. The corresponding improvement in the PV reduction (%) for HFFAO oil using SG was in the range of 10.5% to 47.3%.Treatments with SG or alkali resulted in reduction of AnV, wherein filtration with SG had a remarkable effect on AnV. Levels of TPC were reduced (ca. 70%) with alkali treatments, while treatments with SG resulted in reduction of about 22-48%. Antiradical properties of HFFAO oils were compared using stable DPPH free radicals. After 60 min incubation with DPPH, 78% of DPPH radicals were quenched by control sample, while HFFAO oils treated with SG or alkali were able to quench from 48 to 56%. Different SG and alkali treatments were not effective in inhibiting the oxidation of linoleic acid and the subsequent bleaching of β-carotene in comparison with the control. During autoxidation experiments the same trends of results was noted for both control and treated oils. Practical application: Olive oil is one of the most important edible oils in the world. Crude vegetable oils refined to remove free fatty acids (FFA) as well as other impurities that affect flavor, odor and appearance of oils. Deacidification process significantly influences the economics of oil production. Several methods to remove FFA have been developed to enhance the value of degraded vegetable oils, for example, physical refining based on distillation and chemical refining with sodium hydroxide. In this work, the quality of high-free fatty acid olive (HFFAO) oil was improved using silica gel (SG) as an adsorbent by applying filtration and stirring methods. The results stated that SG with small particle size permitted high adsorbing capacity and close to that induced with chemical treatments which are used commercially in a large scale to improve oil quality.

Evaluation of peanut hulls as an alternative to bleaching clays

Peanut hulls (PNH) were carbonized at different temperatures, times, and evaluated at different concentrations as an alternative to bleaching clays. Evaluation of bleached crude soybean oil with PNH was based on their delta free fatty acids, reduction in peroxide value (PV), reduction in phospholipids (PL) and bleachability. The performance of several commercially used bleaching clays was evaluated, for comparison. Mixtures were formulated including: PNH and Tonsil -N (TN), PNH and Fuller’s earth (FE) and PNH and O-passive (OP) and examined. The oxidative stability of oils was determined. Results for the investigated commercial bleaching clays revealed: TN > FE > F > TF > OP. Highest reduction in PV and PL, and highest bleachability were achieved for soybean oil bleached with 2% PNH carbonized at 500°C for 30 min (PNH”). Mixtures of PNH” with the three chosen bleaching clays indicated that 1PNH”: 2TN gave the highest bleachability. CSO was miscella bleached in hexane using PNH” and resulted in an appreciable improvement in all oil characteristics, especially in bleachability. Oxidative stability of oils was in the following order: TN > control > FE > PNH” with Induction period values of 23,1 > 6,43 > 5,73 > 2,85 h, respectively.

Efficacy of lactic acid bacteria in the reduction of trimethylamine-nitrogen and related spoilage derivatives of fresh Indian mackerel fish chunks

Different strains of lactic acid bacteria (LAB) such as Pediococcus acidilactici , Pediococcus pentosaceous , Streptococcus thermophilus , Lactococcus lactis , Lactobacillus plantarum , Lactobacillus acidophilus and Lactobacillus helveticus were procured from the NCL (National Chemical Laboratory), Pune, India. These LAB cells were individually coated on the dressed fresh mackerel fish chunks and incubated at 37°C for two days. Different quality indices such as trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), peroxide value (PV) and free fatty acids (FFA) were estimated for 2 days period. P. acidilactici cell coat reduced 40 mg% of TMA-N, 47.66 mg% of FFA, 97 mg% of PV and 97 mg% of PV when compared with control. The TMA-N content was reduced to 20 mg% by S. thermophilus cell coat on the treated fish when compared with control, while no reduction was observed on TVB-N. Out of the seven LAB tested for TMA-N reduction, Lb. helveticus and Lc. lactis reduced 150 mg% identically. All the LAB grew in increasing and decreasing trends using available carbohydrate present in the fish. For, FFA reduction, Lb. plantarum showed the highest (188%) as compared to P. pentosaceous and P. acidilactici followed by S. thermophilus . P. pentasaceous and P. acidilactici showed the highest PV reduction as 98 and 83 milli equivalent fat/kg of fats, when compared with Lb. plantarum in the control. Out of seven LAB tested for quality indices reduction, Lb. helveticus , Lc. lactis and P. acidilactici were the best LAB to control TMA-N and TVB-N, respectively. Lb. acidophilus, showed the best in the reduction of FFA. Therefore, this study confirms that LAB can be used to preserve freshfish through controlling spoilage bacteria and amines for a short period of time. Inplace of chemical preservatives, LAB may be use to extend the shelf life of fish. Keywords: Lactic acid bacteria, reduction of spoilage indices, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), peroxide value (PV), free fatty acids (FFA), mackerel chunks

Chitosan–Whey Protein Isolate Composite Films for Encapsulation and Stabilization of Fish Oil Containing Ultra Pure Omega‐3 Fatty Acids

Chitosan (1.5%, w/v)-whey protein isolate (WPI, 5% w/v) composite films were developed for encapsulating and stabilizing fish oil (FO) containing 93.7% eicosapentaenoic acid (EPA). Chitosan-WPI film-forming solutions (FFS) were incorporated with 1.5% or 2% FO (w/v), 2% (w/v) glycerol, Tween 80 (3 times weight of FO), and 0.5% (w/v) oregano or rosemary essential oil (EO), and cast for films at room conditions. Dried films were stored at 2 °C for 30 d for evaluating encapsulation efficiency (EE), lipid stability, and film functionality. Total oil contents in films from FFS incorporating 1.5% or 2% FO were 28.1% to 32.5% and 33.4% to 37.3%, respectively, and free oil contents were 13.5% to 14.7% and 15.5% to 16.3%, respectively. EE, moisture content, and water activity of the films were 47.8% to 66%, 18.7% to 24.9%, and 0.42% to 0.50%, respectively, without significant difference among differently formulated films. Increasing FO concentration from 1.5% to 2% in FFS decreased tensile strength of the films from 0.57-0.73 to 0.34-0.44 MPa, but not the film elongation. Addition of oregano EO in FFS retarded lipid oxidation of the fish oil encapsulated in the films, in which a 43% to 53% reduction in thiobarbituric acid-reactive substances value and 39% to 51% reduction in peroxide value were achieved. Chitosan-WPI composite films with incorporation of oregano essential oil could be applied as a simple and economic means for encapsulating and stabilizing fish oil for fortifying omega-3 fatty acids in various applications.

Carbonaceous materials from seed hulls for bleaching of vegetable oils

Seed hulls, namely cottonseed, peanut, sunflower, soybean, faba bean and lupine were evaluated as carbonaceous materials for the bleaching of crude soybean oil. The six seed hulls were activated by carbonization, steam activation and acid activation. Two reference standards, Fullers earth and Tonsil clay, were used for comparison throughout the whole study. Bleaching of crude soybean oil under vacuum at 100 °C using the treated hulls was carried out. The effect of bleaching with the different hulls on the oil characteristics was evaluated by determining the % free fatty acid, % reduction in peroxide value, % removal of phospholipids, % bleachability and oxidative stability of the bleached oils. Results revealed that bleaching with carbonized hull yielded oils with least free fatty acid content and highest oxidative stability. Bleaching with acid activated hull carbons gave oils with least content of peroxides, phospholipids together with best color. Acid activation of the hulls resulted in highest increase in surface area, pore volume and least pore dimension.

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

AbstractThe effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at −20 and −30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of −20 °C compared with samples stored at −30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at −20 than −30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both −20 and −30 °C but was greater at −20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at −20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish.© 2002 Society of Chemical Industry

Effects of α‐ and γ‐tocopherols on the autooxidation of purified sunflower triacylglycerols

The antioxidant effects of alpha- and gamma-tocopherols were evaluated in a model system based on the autooxidation of purified sunflower oil (p-SFO) triacylglycerols at 55 degrees C for 7 d. Both tocopherols were found to cause more than 90% reduction in peroxide value when present at concentrations >20 ppm. Alpha-tocopherol was a better antioxidant than gamma-tocopherol at concentrations < or =40 ppm but a worse antioxidant at concentrations >200 ppm. Neither alpha- nor gamma-tocopherol showed a prooxidant effect at concentrations as high as 2000 ppm. The amount of tocopherols consumed during the course of oxidation was positively correlated to the initial concentration of tocopherols, and the correlation was stronger for alpha- than for gamma-tocopherol. This correlation suggested that, besides reactions with peroxyl radicals, destruction of tocopherols may be attributed to unknown side reactions. Addition of FeSO4, as a prooxidant, caused a 12% increase in the peroxide value of p-SFO in the absence of tocopherols. When tocopherols were added together with FeSO4, some increase in peroxide value was observed for samples containing 200, 600 or 1000 ppm of alpha- but not gamma-tocopherol. The addition of FeSO4, however, caused an increase in the amount of alpha- and gamma-tocopherols destroyed and led to stronger positive correlations between the amount of tocopherols destroyed during oxidation and initial concentration of tocopherols. No synergistic or antagonistic interaction was observed when alpha- and gamma-tocopherols were added together to autooxidizing p-SFO.