A novel method for determination of peroxide value and acid value of extra-virgin olive oil based on fluorescence internal filtering effect correction

Peroxide value (PV) and acid value (AV) are widely used indicators for evaluating oxidation degree of olive oils. Fluorescence spectroscopy has been extensively studied on the detection of oil oxidation, however, the detection accuracy is limited due to internal filtering effect (IFE). Due to the primary and secondary IFE, at least two wavelengths of absorption information are required. Least squares support vector regression (LSSVR) models for PV and AV were established based on two absorption coefficients (μa) at 375 nm and emission wavelength and one fluorescence intensity at corresponding wavelength. The regression results proved that the model based on 375 and 475 nm could reach the best performance, with the highest correlation coefficient for prediction (rp) of 0.889 and 0.960 for PV and AV respectively. Finally, the explicit formulations for PV and AV were determined by nonlinear least squares fitting, and the rp could reach above 0.94 for two indicators.

Preparation and characterisation of kaempferol composite carrier solid dispersion: evaluation of its application in preventing soybean oil spoilage

Kaempferol (KPF) can be used as a natural antioxidant and food additive in food processing. However, the poor solubility of KPF limited its bioavailability and application. In order to improve the solubility of KPF, kaempferol composite carrier solid dispersion (KPF-CC-SD) was prepared and the process was optimised. When the ratio of KPF: CA (citric acid): Soluplus reached 1:4:6, the dissolution rate was the highest, and the sample was stable over 12 weeks. The characterisation results indicated that KPF-CC-SD exists in an amorphous form. Peroxidation value and acid value of soybean oil showed that the preservation effect of KPF-CC-SD was better than that of KPF, and the inhibition effect of KPF-CC-SD on acid value was better than that of butylated hydroxytoluene. In conclusion, KPF-CC-SD can change the solubility, crystal form and spatial stability of KPF through the carrier, which has a great application prospect in the field of food preservation.

Comparative evaluation of physicochemical and antimicrobial properties of rubber seed oil from different regions of Bangladesh

In Bangladesh, the annual production of rubber seeds is typically left untapped although the seeds contained a high percentage of oil but underutilized without any value-added utilization. This study aims to evaluate the geographical effect on physicochemical properties, fatty acid composition and the antimicrobial activity of oil extracted from rubber seeds. Seeds were collected from three different regions of Bangladesh and the oil was extracted by the soxhlet method using n-hexane as a solvent. Results demonstrated that the geographical regions have some significant effect on the properties of rubber seed oil (RSO). The physicochemical properties of RSO varied from region to region. For example, the percent of yield, higher heating value, and flash point varied from 50.0 to 50.8 %, 31.8-33.3 kJ/g, and 237-245 °C, respectively. The chemical parameters, such as acid value, iodine value, and hydroxyl value varied from 13.3 to 18.2 mg KOH/g, 132-137 g I2/100g, and 47.7-55.8 mg KOH/g, respectively. Chromatographic analysis showed that RSO mainly contains palmitic, linoleic, linolenic, and stearic acid. Regional variations were also seen in the composition of these fatty acids. Most notably, regardless of the rubber seeds collected from various locations, RSO exhibited inhibitory activity against only gram positive bacteria. The zone of inhibition range for different tested gram positive bacteria was 2.33-11.17 mm irrespective of different RSO samples.

How heated vegetable oil age? Effect of the container of heating on ageing

This study compares the ageing process of heated oil with unheated oil and assesses the effect of container used in heating on ageing. Four types of oils were heated on glass, copper and iron. The samples were allowed to age for 1 year. Unheated oils generally produce peroxide faster (for unheated maximum increase in 6-month is 2907 % from 1.351 to 40.627 but for heated maximum increase is 6574 % from 1.91 to 127.476). But they develop secondary oxidation products slowly (for unheated maximum increase in 6-month is 884 % from 1.553 to 15.29 but for heated maximum increase is 191 % from 6.42 to 18.72). For most oil heating in copper produce more p-anisidine value during ageing. The acid value of only unheated oils decreases between 6 months to 1 year. For the 1st six-month rate of increase in saponification value in unheated oil is much higher. The DPPH inhibition activity also changes differently.

Spectroscopic studies on thermal degradation and quantitative prediction on acid value of edible oil during frying by Raman spectroscopy

The health risks posed by harmful substances resulting from the thermal degradation of frying oils are of great concern. Characteristic peak intensity ratios (PIRs) screened from Raman spectra were used to characterize the thermal degradation. High correlation coefficients between PIRs and acid values (AVs) of 0.972 (linear fitting), 0.984 (logarithmic function fitting), and 0.954 (linear fitting) for fried soybean oil, canola oil, and palm oil, were obtained at the PIRs of I₁₂₆₇/I₁₇₄₉, I₁₂₆₇/I₁₆₅₉, and I₁₂₆₇/I₁₇₄₉, respectively. The highly correlated PIRs common to the three oils were determined by Pearson's correlation coefficient combined with heat maps. To accommodate both linear and nonlinear features, a global model for predicting AVs of multi-varieties frying oils was constructed using a least-squares support vector machine algorithm, and the results performed well with a root mean square error of prediction of 0.016 and a ratio of prediction to deviation of 11.351. The whole results demonstrate that Raman spectroscopy could characterize the thermal degradation and has excellent quantitative analysis ability for food control based on AV in frying oils, thus providing a new approach to quality control of frying oils.

Identification of aged-rice adulteration based on near-infrared spectroscopy combined with partial least squares regression and characteristic wavelength variables

The long-term storage of rice will inevitably be involved in the deterioration of edible quality, and aged rice poses a great threat to food safety and human health. The acid value can be employed as a sensitive index for the determination of rice quality and freshness. In this study, near-infrared spectra of three kinds of rice (Chinese Daohuaxiang, southern japonica rice, and late japonica rice) mixed with different proportions of aged rice were collected. The partial least squares regression (PLSR) model with different preprocessing was constructed to identify the aged rice adulteration. Meanwhile, a competitive adaptive reweighted sampling (CARS) algorithm was used to extract the optimization model of characteristic variables. The constructed CARS-PLSR model method could not only reduce greatly the number of characteristic variables required by the spectrum but also improve the identification accuracy of three kinds of aged-rice adulteration. As above, this study proposed a rapid, simple, and accurate detection method for aged-rice adulteration, providing new clues and alternatives for the quality control of commercial rice.

Application of NIR spectroscopy for rapid quantification of acid and peroxide in crude peanut oil coupled multivariate analysis

Two key parameters (acidity and peroxide content) for evaluation of the oxidation level in crude peanut oil have been studied. The titrimetric analysis was carried out for reference data collection. Then, near-infrared spectroscopy in combination with chemometric algorithms such as partial least square (PLS); bootstrapping soft shrinkage-PLS (BOSS-PLS); uninformative variable elimination-PLS (UVE-PLS), and competitive-adaptive reweighted sampling-PLS (CARS-PLS) were attempted and assessed. The correlation coefficients of prediction (Rp), root mean square error of prediction (RMSEP) and residual predictive deviation (RPD) were used to individually evaluate the performance of the models. Optimum results were noticed with CARS-PLS, 0.9517 ≤ Rc ≤ 0.9670, 0.9503 ≤ Rp ≤ 0.9637, 0.0874 ≤ RMSEP ≤ 0.5650, and 3.14 ≤ RPD ≤ 3.64. Therefore, this affirmed that the near-infrared spectroscopy coupled with CARS-PLS could be used as a simple, fast, and non-invasive technique for quantifying acid value and peroxide value in crude peanut oil.

Development of methods for determining free fatty acid contents in red colored oils

Buah merah oil and red palm oil are red colored and unrefined edible oils. Because of this color characteristic, measuring acid value by titration method can be uncertain and subjective, so more accurate and objective methods are needed. Gas chromatography-flame ionization detector (GC-FID) and high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) methods were developed to determine acid value in 3 buah merah oils and 1 red palm oil by measuring free fatty acid contents. The acid value was high in the order of titration > GC-FID > HPLC-ELSD in all samples. GC-FID method showed accurate and reliable results, whereas HPLC-ELSD showed rough data partly due to the non-linear standard curve and high limit of detection. Difference in acid value between titration method and GC-FID might be due to unrefined components that reacted with KOH titration solution. GC-FID can be used measuring free fatty acid contents in red colored oils.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00964-2.

Edible coatings and lipid oxidation data in walnuts

The information presented is part of an investigation that seeks a better understanding of lipid oxidation in walnuts. The data shown regarding edible coating, are one of the strategies used to investigate the effect over oxidation stability. For the present experiments, unshelled walnuts were coated with different formulations, and then stored at 37 °C, 20% RH for 6 weeks. After that time, coated nuts were taken out, cold pressed to extract the oil and analysed. The main data obtained from the oil analysis of walnuts were acid value, peroxide value, and thiobarbituric acid reactive substances (TBARS). Data show the variation of the parameters during the storage time at 37 °C, considering the different formulations of edible coatings and the control. These data are relevant to walnuts exporters to have a comparison point.

Quantitative and qualitative assessment on the suitability of seed oil from water plant (Trichilia emetica) for soap making

Despite widespread and its local available as a naturalized hedge and shade plant, the potential of Trichilia emetica was not utilized in soap making by the majority of local community in various parts of Dodoma, Tanzania. This study aimed to assess the quantity (yields) and quality (Acid Values (AVs), %Free Fatty Acids (%FFAs) and Saponification Values (SVs) of seed oil from water plant (T. emetica), suitable for soap making application. Solvent extraction method was used during oil extraction, where by 50gm of preheated and powdered seed materials were immersed in 250 ml of n-hexane in 1:5 (w/v) to dissolve the oil contained in the seed cake. The oil was collected by vaporizing solvent out through Rotary evaporation at 60 °C. Also standard titration methods were used to obtain SVs, AVs and %FFAs of the extracted oil. Results showed that T. emetica seeds contained higher quantity of oil (48.4%-50.2%) than many reported commercial plant seed oils. Also, the study found higher AV (7.4 mgKOH/g-7.8 mgKOH/g), %FFA (3.7% to 3.9%) and SVs (189.5 mgKOH/g - 191.4 mgKOH/g) than the maximum acceptable limits of 0.50 mg KOH/g, 0.020% and 175 mgKOH/g - 187 mgKOH/g prescribed by ASTM standards (2002). The obtained results showed that, T. emetica seeds yielded high oil quantity with low qualities due to higher levels of acidity. But high SVs guarantees the possibility of using T. emetica seed oil in soap making. However, the oil requires purification in order to bring levels of acidity to acceptable standards and guarantee its normal use in soap making.

Characterization of physico-chemical properties and antioxidant activity of oil from seed, leaf and stem of purslane (Portulaca oleracea L.)

Purslane (Portulaca oleracea L.) is a member of the family of portulacaceae and is a very good source of alpha-linoleic acid. Alpha-linoleic is an omega-3 fatty acid which plays an important role in human growth, development and in preventing diseases. Characterization of the physicochemical properties and antioxidant activity of oil from seeds, leaves and stems of purslane, and appraisal of its viability is the main purpose of this study. In this work, physicochemical properties of oil from seed, leaf and stem of purslane were characterized and the highest oil content was observed in seed (11.25 %) using solvent extraction method. The highest specific gravity was recorded for seed oil (1.10 w/w) followed by leaf oil (0.73 w/w) with non-significant difference. Moreover, oil extracted from purslane stem was found to be the least in oil content (2 %) and specific gravity (0.14 w/w); but the highest in acid value (13.32 w/v) and percentage free fatty acid. The peroxide value was found to be the highest for seed oil and the least for stem with significant difference. The highest ascorbic acid content was recorded for purslane seed oil (41.67 %) followed by leaf oil (32.29 %). Likewise, the highest 1, 1- diphenyl-2-picrylhydrazine activity was obtained for leaf oil (12.55 %) followed by seed oil (2.05 %). The plot for PC2 vs PC1 showed the oil content, specific gravity, peroxide value, ascorbic acid and 1, 1- diphenyl-2-picrylhydrazine having close PC1 and PC2 scores with vector angle < 90 0 showing correlated effects. Characterizing physical and chemical properties and antioxidant activity of oil from seeds, leaves and stems of purslane is crucial in providing necessary information for the utilization of the oil content.

Baseline characterization data for raw rice husk

There is a significant interest in using agricultural wastes such as rice husk as a precursor for the synthesis of adsorbents and catalysts. In this article, readers will find valuable baseline characterization data related to physical and chemical properties of raw rice husk including BET specific surface area, acid value, the point of zero charge, elemental analysis, Time-of-Flight Secondary Ion Mass Spectrometric Analysis X-Ray Photoelectron Spectroscopic Analysis, and Scanning Electron Microscope-Energy Dispersive Spectroscopic Analysis. It is expected that the baseline raw data presented in this article will be useful for researchers around the world who are working on chemically modifying rice husk for valorizing them for applications in adsorption, catalysis, and energy storage.

Enhanced lipid extraction from oleaginous yeast biomass using ultrasound assisted extraction: A greener and scalable process

Soaring demand for alternative fuels has been gaining wide interest due to depletion of conventional fuel, increasing petroleum prices and greenhouse gas emissions. Biodiesel, an alternative fuel, derived from oleaginous microbes has been promising because of short incubation time and easy to scale up. Oleaginous yeast Trichosporon sp. is capable of utilizing glycerol and agro-residues for enhanced lipid synthesis. Lipid extraction from Trichosporon sp. biomass showed highest lipid content with ultrasonic assisted extraction (43 ± 0.33%, w/w) coupled with process parameters than the conventional Soxhlet (30 ± 0.28%, w/w) and Binary solvent [choloroform:methanol, (2:1, v/v)] methods (36 ± 0.38%, w/w), respectively. The standardized process parameters of ultrasonic assisted extraction coupled with chloroform/methanol solvent system resulted 95-97% of conversion efficiency in 20 min at 30 °C with a frequency of 50 Hz and 2800 W power, respectively. Enzymatic transesterification of yeast biomass lipid obtained 85% of fatty acid methyl esters that are predominant with oleic acid methyl ester followed by palmitic and stearic acid methyl esters, respectively. These results substantiate that the ultrasonic assisted extraction is a potential green extraction technique that had reduced time, energy and solvent consumption without compromising on lipid quality. Deploying this green extraction technique could make the biodiesel production process inexpensive and eco-friendly.

Utilization of high FFA landfill waste (leachates) as a feedstock for sustainable biodiesel production: its characterization and engine performance evaluation

In present study, biodiesel was produced from landfill waste-derived oil by chemical transesterification process, to evaluate its potential as a renewable energy source for the first time. The free fatty acid percentage (FFA) in landfill waste oil is considered to be high, which was reduced by treating it with two different acids as catalyst, muriatic acid and phosphoric acid, in order to build a comparison between fatty acid methyl ester (FAME) contents. Further, it was treated with a base catalyst potassium hydroxide (KOH) to produce the final product. The FAME value of landfill oil when treated with muriatic acid was found to be 92.59%. The quality of biodiesel produced was analyzed by gas chromatography (GC), which indicated above 25.7% of conversion of oil into biodiesel when muriatic acid was used as a catalyst. The properties of the produced biodiesel were found to be in good agreement with ASTM D 6751 and EN 14214 standards. Various test fuels were prepared for the engine test by blending 10%, 20%, and 100% of landfill waste biodiesel in diesel on volumetric basis and designated as B10, B20, and B100, respectively. The brake thermal efficiency (BTE) of the engine was more while the exhaust emission was less except NOx with biodiesel and its blend (B10 and B20). Thus, landfill waste is a potential source of biodiesel, and blends of landfill waste up to 20% can be used for realizing better performance from the engine.

Assessment of the phenolic profile, antimicrobial activity and oxidative stability of transgenic Perilla frutescens L.overexpressing tocopherol methyltransferase (γ-tmt) gene

This study evaluated the effects of enhanced concentrations of α-tocopherol and phenolic compounds on the resistance and stability of Perilla oil in transgenic Perilla frutescens plants against various tested pathogenic bacteria by over-expressing the γ-tmt gene. The concentration of phenolic compounds in the non-transgenic samples was 9313.198 ± 18.887 μg g^-1 dry weight (DW), whereas the total concentration of the transgenic samples ranged from 9118.015 ± 18.822 to 10527.612 ± 20.411 μg g^-1 DW. The largest increases in phenolic compounds in the transgenic plants in comparison with the control plants were observed in gallic acid, pyrogallol, 5-sulfosalicylic acid, catechin, chlorogenic acid, vanillin, syringic acid, naringenin, salicylic acid, quercetin, o-coumaric acid, kaempferol, and hesperetin. o-coumaric and benzoic acid acid were the most abundant phenolic acids found in the transgenic plants. Gram-negative bacteria (Salmonella typhimurium) were the most susceptible microorganism against transgenic ethyl acetate extracts with lower measurement of minimum inhibitory concentration (MICs) (0.25 ± 0.03 mg/ml) at an extract concentration of 2 mg/ml in dried plant material. The same extracts were more effective against gram-positive bacteria (Bacillus subtilis) when compared to control plants with MICs values of 0.52 ± 0.02 mg/ml. The suplementation of 20 μg of α-tocopherol (1000 ppm) in combination with ethyl acetate extracts enhanced the antimicrobial activity against S. typhimurium and B. subtilis, compared to the non-transgenic plants. The acid value of transgenic Perilla oil improved by 91.2% and 35.54% relative to the non-transgenic control oil and commercial Perilla oil, respectively. The low acid value suggests that the oil will be less susceptible to lipase action, and more economically viable and thus, may also improve the oil quality for industrial purposes. In addition, extracts obtained from transgenic plants could be a potential source of antimicrobial agents for the treatment of bacterial infections.

Antioxidant (Tocopherol and Canolol) Content in Rapeseed Oil Obtained from Roasted Yellow-Seeded Brassica napus

In this study, the effect of temperature (140, 160, 180 °C) and roasting time (5, 10, 15 min) on the bioactive compound content (canolol, tocopherol and plastochromanol-8) of cold-pressed oil from yellow-seeded rapeseed lines of different colors was investigated. Roasting increased the peroxide value in the seed oils compared to the oils from the control samples. However, roasting did not affect the acid values of the oils, which were 1.15–1.47 and 1.30–1.40 mg KOH/g, for line PN1 03/1i/14 (yellow seeds) and line PN1 563/1i/14 (brown seeds), respectively. In this study, the seeds of line PN1 03/1i/14 were characterized by different changes in canolol content during roasting than the seeds of PN1 563/1i/14. There was a 90-fold increase in canolol for the line PN1 03/1i/14 (768.26 µg/g) and a 46-fold increase for the line PN1 563/1i/14 (576.43 µg/g). Changes in tocopherol and PC-8 contents were also observed. There was an increase in the contents of γ-T and PC-8 in the oils obtained from the seeds roasted at 180 °C for 10 and 15 min. γ-T content increased by 17–18% after 15 min of roasting, whereas the PC-8 content increased twofold.

Improvement of efficiency of oil extraction from wild apricot kernels by using enzymes

An experiment was conducted to evaluate and standardize the protocol for enhancing recovery of oil and quality from cold pressed wild apricot kernels by using various enzymes. Wild apricot kernels were ground into powder in a grinder. Different lots of 3 kg powdered kernel were prepared and treated with different concentrations of enzyme solutions viz. Pectazyme (Pectinase), Mashzyme (Cellulase) and Pectazyme + Mashzyme. Kernel powder mixed with enzyme solutions were kept for 2 h at 50(±2) °C temperature for enzymatic treatment before its use for oil extraction through oil expeller. Results indicate that use of enzymes resulted in enhancement of oil recovery by 9.00-14.22 %. Maximum oil recovery was observed at 0.3-0.4 % enzyme concentration for both the enzymes individually, as well as in combination. All the three enzymatic treatments resulted in increasing oil yield. However, with 0.3 % (Pectazyme + Mashzyme) combination, maximum oil recovery of 47.33 % could be observed against were 33.11 % in control. The oil content left (wasted) in the cake and residue were reduced from 11.67 and 11.60 % to 7.31 and 2.72 % respectively, thus showing a high increase in efficiency of oil recovery from wild apricot kernels. Quality characteristics indicate that the oil quality was not adversely affected by enzymatic treatment. It was concluded treatment of powdered wild apricot kernels with 0.3 % (Pectazyme + Mashzyme) combination was highly effective in increasing oil recovery by 14.22 % without adversely affecting the quality and thus may be commercially used by the industry for reducing wastage of highly precious oil in the cake.

Determination of free fatty acids in pharmaceutical lipids by ¹H NMR and comparison with the classical acid value

Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this (1)H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The (1)H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.

Role of different media in Karpanpatru Taila preparation

Total six samples of Karpanpatru Taila were prepared with Murchchhita and Amurchchhita Sarshapa Taila (mustard oil) by using three different liquid media i.e. Gomutra, Takra and Kanji by following classical method and analyzed. The pharmaceutical analysis revealed that the Karpanpatru Taila prepared with Murchchhita Sarshapa taila by using Kanji, Gomutra, Takra as a liquid media showed minimum loss i.e. 4.00%, 8,33% & 8.66 respectively in comparison to Amurchchhita Sarshapa Taila by using Kanji, Gomutra, Takra i.e. 5.5%, 10.68%, 12% respectively. Pharmaceutical drawbacks like excessive frothing and burning of eyes & nose were absent during the preparation of Karpanpatru Taila with Takra and Kanji while present in batch of Gomutra. Analytical study reveals that Acid value was negligible increased after even 6 month in the samples of Murchchhita Karpanpatru Taila while significant increased in the samples of Amurchchhita Karpanpatru Taila. Saponification value was decreased in the samples of Murchhita Karpanpatru Taila while increased in the samples Amurchchhita Karpanpatru taila. Microbial growth was found absent in all the samples of Karpanpatru Taila even after 6 months.

Effect of storage conditions on microbiological and physicochemical quality of shea butter

Storage conditions are key constraints for quality assurance of the shea (Vitellaria paradoxa Gaertner) butter. In the Sudan savannah Africa, storage conditions of butter produced by women vary across and among processors, traders and consumers. These conditions could impact the quality of the products and reduced their access to international market. The present study attempted to investigate the effect of storage duration and packaging materials on microbiological and physicochemical characteristics of shea butter under tropical climatic conditions. Five packaging materials traditionally used in shea butter value chain were tested for their efficacy in storing shea butter freshly produced. Total germs, yeasts and mould varied with packaging materials and storage duration. After 2 months of storage, moisture content of butter remained constant (5%) whereas acid value increased from 3.3 to 5.4 mg KOH/g, peroxide value from 8.1 to 10.1 meq O2/kg and iodine value dropped from 48.8 to 46.2 mg I2/100 g in shea butter irrespectively to the storage materials used. The basket papered with jute bag was the less effective in ensuring the quality of butter during storage while plastic containers and plastic bags seemed to be the best packaging materials.

Lipid classes and fatty acid profile of selected Indian fresh water fishes

Lipid extracts from meat, head and viscera of Indian fresh water fishes, viz., catla, rohu, mrigal, common carp and tilapia were analyzed for lipid class distribution and fatty acid profile. The yield of meat ranged from 66.0-79.5% and total lipid content in meat was 0.8-3.8%. The total lipid content was higher (>4.0%) in head and viscera. Neutral lipids constituted 71.5-93.3% of the total lipid extract. Higher glycolipid content of 25.2% was observed in lipid extract from meat of common carp and higher phospholipid content (13.7%) was observed in lipid extract from meat of mrigal. Hydrocarbons, sterolesters and triacylglycerol were the major fractions of neutral lipids. Unsaturated fatty acids dominated in all the samples. Palmitic and oleic acids were the major fatty acids found in all the lipid extracts. Docosahexaenoic acid content was higher than 3% in lipid extract from meat of all the fishes. However, in most of the fishes, the content of eicosapentaenoic acid and docosahexaenoic acid were higher in visceral lipids.