Lipid oxidation kinetics of ozone-processed shrimp during iced storage using peroxide value measurements

In this research, in situ generated ozone exposure/wash cycles of 1, 3, and 5 min applied to shrimp samples either before (BIS) or during iced storage (DIS) has been used to study the lipid oxidation kinetics using the peroxide values (PV). The induction period (IP) as well as PV at end of the IP (PVIP) have been obtained. The rate constants (k) as well as half-lives (t1/2) of hydroperoxides formation for different oxidation stages were calculated. The results showed that both IP and PVIP were lower with BIS (IP between 4.35±0.09 and 5.08±0.23 days; PVIP between 2.92±0.06 and 3.40±0.18 mEq kg−1) compared with DIS (IP between 5.92±0.12 and 6.14±0.09 days; PVIP between 4.49±0.17 and 4.56±0.10 mEq kg−1). The k value for DIS seemed to be the greater compared to BIS. In addition, whilst decreases and increases in t1/2 were found at propagation, respectively, for BIS and DIS, decreases and increases were only found at the induction of oxidation stage(s) for BIS. Further, the PV of ozone-processed samples would fit first order lipid oxidation kinetics independent of duration of ozone exposures. For the first time, PV measurements and fundamental kinetic principles have been used to describe how increasing ozone exposures positively affects the different oxidation stages responsible for the formation of hydroperoxides in ozone-processed shrimp.

Enzymatic technology to improve oil extraction from Caryocar brasiliense camb. (Pequi) Pulp.

The present study aims to compare yield and quality of pequi pulp oil when applying two distinct processes: in the first, pulp drying in a tray dryer at 60ºC was combined with enzymatic treatment and pressing to oil extraction; in the second, a simple process was carried out by combining sun-drying pulp and pressing. In this study, raw pequi fruits were collected in Mato Grosso State, Brazil. The fruits were autoclaved at 121ºC and stored under refrigeration. An enzymatic extract with pectinase and CMCase activities was used for hydrolysis of pequi pulp, prior to oil extraction. The oil extractions were carried out by hydraulic pressing, with or without enzymatic incubation. The oil content in the pequi pulp (45% w/w) and the physicochemical characteristic of the oil was determined according to standard analytical methods. Free fatty acids, peroxide values, iodine and saponification indices were respectively 1.46 mgKOH/g, 2.98 meq/kg, 49.13 and 189.40. The acidity and peroxide values were lower than the obtained values in commercial oil samples, respectively 2.48 mgKOH/g and 5.22 meq/kg. Aqueous extraction has presented lower efficiency and higher oxidation of unsaturated fatty acids. On the other hand, pequi pulp pressing at room temperature has produced better quality oil. However its efficiency is still smaller than the combined enzymatic treatment and pressing process. This combined process promotes cellular wall hydrolysis and pulp viscosity reduction, contributing to at least 20% of oil yield increase by pressing.

Estudio analitico de especies oxigenadas en el aceite de teobroma ozonizado

Ozonization of theobroma oil at different applied ozone dosages was carried out with measurement of peroxide index values, oxygen percentage content and fatty acids composition. The comparison of peroxide values with percentage content of oxygen at different applied ozone dosages showed good correlation (r=0.9923). Unsaturated fatty acids and triacylglycerols decrease with ozone applied dosage due to ozone reaction with double bonds. Small amounts of oleic acid were consumed with applied ozone dosage at 35 mg/g, which demonstrated that peroxide values and oxygen content were not principally increased by the ozone attack on the double bonds, but other mechanisms could be involved in the reaction system.

Antioxidant activity of rosemary and oregano ethanol extracts in soybean oil under thermal oxidation

Four experiments were conducted to measure the antioxidant activity of ethanol extracts of rosemary and oregano compared with synthetic antioxidants such as TBHQ and BHA/BHT. The antioxidant activity was determined and results differed from those of the Oven test at 63º C. Peroxide values and absorptivities at 232 nm of soybean oil under Oven test were lower in treatments with 25, 50, 75, 100 and 200 mg.Kg-1 TBHQ than in treatments with 1000 mg.Kg-1 oregano extract (O), 500 mg.Kg-1 rosemary extract (R) and their mixture R+O. All the treatments were effective in controlling the thermal oxidation of oils; the natural extracts were as effective as BHA+BHT and less effective than TBHQ. The natural extracts were mixed with 25, 50, 75 and 100 mg.Kg-1 TBHQ and then added to the oil. No improvement in antioxidative properties was observed. The best antioxidant concentration could be determined from polynomial regression and quadratic equation from the experimental data.

Influence of the extraction method and storage time on the physicochemical properties and carotenoid levels of pequi (Caryocar brasiliense Camb.) oil

The objective of this study was to analyze the physicochemical properties and carotenoid levels of pequi oil obtained by different extraction methods and to evaluate the preservation of these properties and pigments during storage time. The pequi oil was obtained by solvent extraction, mechanical extraction, and hot water flotation. It was stored for over 180 days in an amber bottle at ambient conditions. Analyses for the determination of the acidity, peroxide, saponification and iodine values, coloration, total carotenoids, and β-carotene levels were conducted. The oil extraction with solvents produced the best yield and carotenoid levels. The oil obtained by mechanical extraction presented higher acidity (5.44 mg KOH.g-1) and peroxide values (1.07 mEq.kg-1). During the storage of pequi oil, there was an increase in the acidity and the peroxide values, darkening of the oil coloration, and a reduction of the carotenoid levels. Mechanical extraction is the less advantageous method for the conservation of the physicochemical properties and carotenoid levels in pequi oil.

Changes in Protein, Carbohydrate and lipid content of cashew kernels during storage under two humidity conditions

The changes occuring to cashew kernels during storage at two humidity levels - 80% to 20% with respect to organoleptic characteristics, protein content, carbohydrate content, oil content, iodine and peroxide values were studied. From the present study it is concluded that organoleptic characteristics of cashew kernels deteriorates with increase in humidity. Decrease in protein and carbohydrate content of stored cashew kernel is dependent on humidity. Humidity increased oxidative rancidification.

Bovine serum albumin produces a synergistic increase in the antioxidant activity of virgin olive oil phenolic compounds in oil-in-water emulsions

Virgin olive oil is valued for its flavor, but unacceptable off-flavors may develop on storage in food products containing this oil due to oxidation. The oxidative stability of oil-in-water emulsions containing bovine serum albumin (BSA) and virgin olive oil phenolic compounds was studied. Four oil-in-water emulsions with and without BSA and phenols isolated from virgin olive oil were prepared. These model systems were stored at 60 degrees C to speed up lipid oxidation. Primary and secondary oxidation products were monitored every three days. Peroxide values and conjugated diene contents were determined as measures of the primary oxidation products. p-Anisidine values and volatile compounds were determined as measures of the secondary oxidation products. This latter determination was carried out by headspace solid-phase microextraction coupled with gas chromatography. Although olive oil phenolic compounds and BSA contributed some antioxidant activity when present as individual additives, the combination of BSA with phenols in an emulsion showed 58-127% synergy, depending on which analytical method was used in the calculation. The emulsion containing phenolic compounds and BSA showed a low level of deterioration after 45 days of storage at 60 degrees C.

Albumin causes a synergistic increase in the antioxidant activity of green tea catechins in oil-in-water emulsions

Model oil-in-water emulsions containing epicatechin (EC) and epigallocatechin gallate (EGCG) showed a synergistic increase in stability in emulsions containing added albumin. EGCG showed a stronger synergy (35%) with ovalbumin than did EC. Oxidation of the oil was monitored by determining peroxide values and hexanal contents. The effect of bovine serum albumin (BSA) on model oil-in-water emulsions containing each of the green tea catechins [epicatechin gallate (ECG), EGCG, EC and epigallocatechin (EGC)] was studied during storage at 30 degrees C. The green tea catechins showed moderate antioxidant activity in the emulsions with the order of activity being ECG approximate to EGCG > EC > EGC. Although BSA had very little antioxidant activity in the absence of phenolic antioxidants, the combination of BSA with each of the catechins showed strong antioxidant activity. BSA, in combination with EC, EGCG or EGC, showing the strongest antioxidant activity with good stability after 45 days storage. Model experiments with the catechins stored with BSA in aqueous solutions confirmed that protein-catechin adducts with antioxidant activity were formed between the catechins and protein. The antioxidant activity of the separated protein-catechin adducts increased strongly with storage time and was stronger for EGCG and ECG than for EC or EGC. (c) 2006 Elsevier Ltd. All rights reserved.

Enhancing the recovery of tiger nut (Cyperus esculentus) oil by mechanical pressing: moisture content, particle size, high pressure and enzymatic pre-treatment effects

Tiger nut (Cyperus esculentus) tuber contains oil that is high in monounsaturated fatty acids, and this oil makes up about 23% of the tuber. The study aimed at evaluating the impact of several factors and enzymatic pre-treatment on the recovery of pressed tiger nut oil. Smaller particles were more favourable for pressing. High pressure pre-treatment did not increase oil recovery but enzymatic treatment did. The highest yield obtained by enzymatic treatment prior to mechanical extraction was 33 % on a dry defatted basis, which represents a recovery of 90 % of the oil. Tiger nut oil consists mainly of oleic acid; its acid and peroxide values reflect the high stability of the oil.

Edible oil from Tiger nut (Cyperus esculentus L.): mechanical pressing and aqueous enzymatic extraction methods

The tiger nut tuber of the Cyperus esculentus L. plant is an unusual storage system with similar amounts of starch and lipid. The extraction of its oil employing both mechanical pressing and aqueous enzymatic extraction (AEE) methods was investigated and an examination of the resulting products was carried out. The effects of particle size and moisture content of the tuber on the yield of tiger nut oil with pressing were initially studied. Smaller particles were found to enhance oil yields while a range of moisture content was observed to favour higher oil yields. When samples were first subjected to high pressures up to 700 MPa before pressing at 38 MPa there was no increase in the oil yields. Ground samples incubated with a mixture of α- Amylase, Alcalase, and Viscozyme (a mixture of cell wall degrading enzyme) as a pre-treatment, increased oil yield by pressing and 90% of oil was recovered as a result. When aqueous enzymatic extraction was carried out on ground samples, the use of α- Amylase, Alcalase, and Celluclast independently improved extraction oil yields compared to oil extraction without enzymes by 34.5, 23.4 and 14.7% respectively. A mixture of the three enzymes further augmented the oil yield and different operational factors were individually studied for their effects on the process. These include time, total mixed enzyme concentration, linear agitation speed, and solid-liquid ratio. The largest oil yields were obtained with a solid-liquid ratio of 1:6, mixed enzyme concentration of 1% (w/w) and 6 h incubation time although the longer time allowed for the formation of an emulsion. Using stationary samples during incubation surprisingly gave the highest oil yields, and this was observed to be as a result of gravity separation occurring during agitation. Furthermore, the use of high pressure processing up to 300 MPa as a pre-treatment enhanced oil yields but additional pressure increments had a detrimental effect. The quality of oils recovered from both mechanical and aqueous enzymatic extraction based on the percentage free fatty acid (% FFA) and peroxide values (PV) all reflected the good stabilities of the oils with the highest % FFA of 1.8 and PV of 1.7. The fatty acid profiles of all oils also remained unchanged. The level of tocopherols in oils were enhanced with both enzyme aided pressing (EAP) and high pressure processing before AEE. Analysis on the residual meals revealed DP 3 and DP 4 oligosaccharides present in EAP samples but these would require further assessment on their identity and quality.

Influência da relação superfície/volume e do tempo de fritura sobre as alterações da mistura azeite de dendê-óleo de soja

Objetivou-se com este estudo determinar a influência dos fatores relação superfície/volume (S/V) e tempo de fritura sobre a alteração da mistura azeite de dendê-óleo de soja em frituras descontínuas de batatas chips.Foram realizados dois procedimentos de fritura com relações S/V de 0,5 e 1,0 cm-1 e temperatura média de 180°C. O óleo foi aquecido por um período de 7,25 horas. As amostras obtidas durante o processo de fritura foram analisadas pelas determinações de índice de peróxidos, compostos polares totais, ácidos graxos livres e índice de refração. Todas as determinações analíticas foram influenciadas pelo tempo de fritura, verificando-se aumentos significativos destes parâmetros ao longo do processo de fritura. O fator relação S/V apresentou influência sobre os valores dos índices de peróxidos e de refração. A mistura azeite de dendê-óleo de soja apresentou alteração acima do limite recomendado para óleos de fritura (compostos polares totais > 25%) a partir de 6,25 horas de fritura.

Oxidative stability of soybean oil added to Lentinus edodes and Agaricus blazei mushrooms extracts in an accelerated storage test

Purpose: The purpose of this paper is to evaluate the oxidative stability of soybean oil added by Lentinus edodes and Agaricus blezei extracts in accelerated storage test. Design/methodology/approach: The following treatments were subjected to accelerated storage test in an oven at 60°C for 15 days: Control (soybean oil without antioxidants), TBHQ (soybean oil + 100 mg/kg of TBHQ), BHT (soybean oil + 100 mg/kg of BHT), L. edodes (soybean oil + 3,500 mg/kg of L. edodes extract) and A. blazei (soybean oil + 3,500 mg/kg of A. blazei extract). The samples were taken every three days and analyzed for peroxide values and conjugated dienes. Findings: At the end of 15 days, the treatments TBHQ, A. blazei, L. edodes, Control and BHT showed 6.47, 8.81, 41.53, 71.28 and 78.40 meq/kg, respectively, for peroxide values and 0.37, 0.40, 0.67, 1.07 and 1.00 per cent, respectively, for conjugated dienes. Originality/value: The research indicates that mushrooms may be a promising source of natural antioxidants. Therefore, natural extracts of mushrooms can be applied to vegetable oils as a way to reduce the degradation caused by lipid oxidation. © Emerald Group Publishing Limited.

Protective effect of oregano (Origanum vulgar L.) and thyme (Thymus vulgaris L.) oleoresins in stored soybean oil

Purpose: The objective of this study was to evaluate the antioxidant effect of oregano and thyme extracts isolatedly and combinedly applied in soybean oil. Design/methodology/approach: Soybean oil containing 3,000 mg/kg of oregano and thyme oleoresins and the mixture of both, as well as soybean oil containing TBHQ (50 mg/kg) and soybean oil free of antioxidants, were subjected to accelerated oven test (60°C/10 days). Samples were collected every two days and analyzed as to their peroxide and conjugated diene values. Findings: The mixture of oleoresins and consequent increase of concentration were as effective as the antioxidant TBHQ. Practical implications: These studies may prove to be beneficial to the exploitation of natural antioxidant sources for the preservation and/or extension of raw and processed food shelf life. Therefore, they could also be applied in the area of pharmaceuticals for the protection of human life. Originality/value: This study offers information on the use of natural antioxidants as an alternative to the use of synthetic antioxidants, which might be considered toxic. © Emerald Group Publishing Limited.

Caracterização e estudo do comportamento térmico do óleo extraído da semente de mamão formosa (Carica papaya L.)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of contact surfaces on the thermal and photoxidation of dehydrated castor oil

The effect of stainless steel, glass, zirconium and titanium enamel surfaces on the thermal and photooxidative toughening mechanism of dehydrated castor oil films deposited on these surfaces was investigated using different analytical and spectroscopic methods. The conjugated and non-conjugated double bonds were identified and quantified using both Raman spectroscopy and 1D and 2D NMR spectroscopy. The disappearance of the double bonds in thermally oxidised oil-on-surface films was shown to be concomitant with the formation of hydroperoxides (determined by iodometric titration). The type of the surface had a major effect on the rate of thermal oxidation of the oil, but all of the surfaces examined had resulted in a significantly higher rate of oxidation compared to that of the neat oil. The highest effect was exhibited by the stainless steel surface followed by zirconium enamel, titanium enamel and glass. The rate of thermal oxidation of the oil-on-steel surface (at 100 °C, based on peroxide values) was more than five times faster than that of oil-on-glass and more than 21 times faster than the neat oil when compared under similar thermal oxidative conditions. The rate of photooxidation at 60 °C of oil-on-steel films was found to be about one and half times faster than their rate of thermal oxidation at the same temperature. Results from absorbance reflectance infrared microscopy with line scans taken across the depth of thermally oxidised oil-on-steel films suggest that the thermal oxidative toughening mechanism of the oil occurs by two different reaction pathways with the film outermost layers, i.e. furthest away from the steel surface, oxidising through a traditional free radical oxidation process involving the formation of various oxygenated products formed from the decomposition of allylic hydroperoxides, whereas, in the deeper layers closer to the steel surface, crosslinking reactions predominate.