Effect of olive stoning on the volatile and phenolic composition of virgin olive oil

Olive stoning during the virgin olive oil (VOO) mechanical extraction process was studied to show the effect on the phenolic and volatile composition of the oil. To study the impact of the constitutive parts of the fruit in the composition of olive pastes during processing, the phenolic compounds and several enzymatic activities such as polyphenoloxidase (PPO), peroxidase (POD), and lipoxygenase (LPO) of the olive pulp, stone, and seed were also studied. The olive pulp showed large amounts of oleuropein, demethyloleuropein, and lignans, while the contribution of the stone and the seed in the overall phenolic composition of the fruit was very low. The occurrence of crushed stone in the pastes, during malaxation, increased the peroxidase activity in the pastes, reducing the phenolic concentration in VOO and, at the same time, modifying the composition of volatile compounds produced by the lipoxygenase pathway. The oil obtained from stoned olive pastes contained higher amounts of secoiridoid derivatives such as the dialdehydic forms of elenolic acid linked to (3,4-dihydroxyphenyl)ethanol and (p-hydroxyphenyl)ethanol (3,4-DHPEA-EDA and p-HPEA-EDA, respectively) and the isomer of the oleuropein aglycon (3,4-DHPEA-EA) and, at the same time, did not show significant variations of lignans. The stoning process modified the volatile profile of VOO by increasing the C6 unsaturated aldehydes that are strictly related to the cut-grass sensory notes of the oil.     

Effect of the technological and agronomical factors on pigment transfer during olive oil extraction

The aim of this work was to determine the transfer of the chloroplast pigment fractions during the virgin olive oil extraction process, in relation to different factors: the ripening stage of the olive fruits, the irrigation water applied to the olive tree, and the addition of natural microtalc (NMT) during the oil extraction process. Results showed that the percentage of chloroplast pigments transferred from the olive paste to the oil increases with the ripening of the olive fruit (raw material). An excess of the water irrigation applied to the olive tree shows a reduction in the biosynthesis of chloroplast pigments in olive fruits, which is reflected in a low concentration in the virgin oils. Furthermore, the percentage of pigment transfer from the olive paste to the oil during the extraction process is reduced by irrigation, mainly of the chlorophyll fraction. The addition of NMT during the malaxation step produced an increase in the percentage of the total pigments transferred from the olive paste to the oil, in relation to nonaddition.     

Influence of the decrease in oxygen during malaxation of olive paste on the composition of volatiles and phenolic compounds in virgin olive oil

The sensory and health properties of virgin olive oil (VOO) are highly related to its volatile and phenolic composition. Oxygen control in the pastes during malaxation may be a new technological parameter to regulate enzymatic activities, such as polyphenoloxidase, peroxidase, and lipoxygenase, which affect the phenolic and volatile composition of VOO. In this work, we monitored CO2 and O2 concentrations during industrial-scale olive paste malaxation with various initial O2 concentrations within the malaxer headspace. Results show that the O2 concentration in the malaxer headspace did not affect CO2 production during processing, whereas a strong influence was observed on the changes of the phenolic composition of olive pastes and VOOs, with high correlation coefficient for the total phenols (R = 0.94), especially for oleuropein and demethyloleuropein derivatives (R = 0.81). In contrast, aroma production during malaxation was minimally affected by the O2 concentration in the malaxer headspace.     

Determination of esters of fatty acids with low molecular weight alcohols in olive oils

A simple and precise analytical method was developed for the simultaneous determination of squalene and methyl, ethyl, propyl, and butyl esters of fatty acids present in olive and olive pomace oils. A fraction containing squalene and fatty acid alkyl esters was isolated from the oil by solid phase extraction on silica gel cartridges and quantitatively analyzed by gas chromatography. A modification of the procedure allowed the isolation of squalene and esters separately. Repeatability and recovery of the method were good. The method was applied to extra and lampant virgin olive oil categories and also to oils obtained from olive pomace by second centrifugation and solvent extraction. Extra virgin olive oils contained low amounts of fatty acid methyl and ethyl esters, while oils obtained from altered olive or olive pomace showed high concentrations of fatty acid alkyl esters, mainly ethyl esters. Correlation between oil acidity and ethyl esters concentration was poor.     

Alkyl esters of fatty acids a useful tool to detect soft deodorized olive oils

Fatty acid alkyl esters (FAAEs) are a family of natural neutral lipids present in olive oils and formed by esterification of free fatty acids (FFAs) with low molecular alcohols. Inappropriate practices during the olive oil extraction process and bad quality of the olive fruits promote their formation. Quantification can be done by isolation with a silica gel solid phase extraction cartridge followed by analysis on a gas chromatograph equipped with a programmed temperature vaporizer injector using a polar capillary column. The application of the method to more than 100 Spanish olive oils from different categories, varieties, and geographical origin allowed for establishing the average content of FAAEs and distinguishing the Spanish protected denomination of origin (PDO) and extra virgin olive oils from other categories of olive oils. Those other categories of oils can be subjected to a mild refining process, which leads to blending with extra virgin olive oils. Studies on low quality oils subjected to mild refining showed that FAAEs remain after that process. Thereby, blends of extra virgin olive and mildly refined low quality olive oils can be detected by their alkyl ester concentrations.     

Strength of interparticle bonds in soil pastes and aggregates

The dynamics of the strength of the soil structure in the course of drying of soil pastes and aggregates have been studied in a loamy gray forest soil using the cone-plastometer method suggested by Rebinder. It is shown that the paste consistence and the corresponding rheological model can be determined from the paste strength loading curves at different values of the moisture content. The dynamics of the strength of the structural bonds in both the pastes and the aggregates are nonuniform and depend on the prevailing forms of soil water. The strength of the soil pastes considerably exceeds the strength of the natural aggregates in the range of moisture contents from the hygroscopic moisture to the liquid limit. This is caused by the more dense packing of the soil particles and, hence, more intensive interparticle interaction. The ratio of the aggregate strength to the paste strength upon equal levels of moistening makes it possible to quantitatively compare the strengths of the interparticle bonds in aggregates and pastes.     

Retrogradation of Starches from Different Botanical Sources

Retrogradation in 2% pastes prepared from unmodified commercial starches by cooking at 98–100°C under low shear, then held at 4°C for 56 days, was examined by turbidometric analysis and light microscopy. Turbidometric analysis revealed that retrogradation rates followed the order of wheat, common corn > rice, tapioca, potato ≫ waxy maize. Microstructures of stored pastes were examined both before and after centrifugation. Granule remnant morphologies and fresh and stored paste microstructures were unique to each starch examined. Fresh pastes from amylose-containing starches were dominated by networked amylose that condensed into higher density aggregates upon storage. Unique phenomena seen in some stored pastes included interactions of granular remnants with aggregated amylose, composite networks of co-associated amylopectin and amylose, and slight birefringence regained by granule remnants. Microstructural changes in stored pastes could be related to changes in turbidity and to the results of other methods used to quantitate retrogradation.     

Comparison of static headspace, headspace solid phase microextraction, headspace sorptive extraction, and direct thermal desorption techniques on chemical composition of French olive oils

Static headspace (SHS), headspace solid phase microextraction (HS-SPME), headspace sorptive extraction (HSSE), and direct thermal desorption (DTD) were applied to the analysis of four French virgin olive oils from Corsica. More than 60 compounds were isolated and characterized by GC-RI and GC-MS. SHS was not suited to the characterization of olive oil volatile compounds because of low sensitivity. The SPME and HSSE techniques were successfully applied to olive oil headspace analysis. Both methods allow the characterization of volatile compounds (mainly C(6) aldehydes and alcohols), which contribute significantly to the "green" flavor note of virgin olive oils. The PDMS stir bar showed a higher concentration capacity than a DVB/CAR/PDMS SPME fiber due to the higher volume of polymeric coating. DTD was a very good tool for extracting volatile and especially semivolatile compounds, such as sesquiterpenes, but requires a significant investment like that for HSSE. Finally, SPME may be a more appropriate technique for routine quality control due to its operational simplicity, repeatability, and low cost.     

Assessing the Potential of Organic Solvents on Total Petroleum Hydrocarbon Extraction from Diesel-Contaminated Soils

The total petroleum hydrocarbon (TPH) extraction potential of organic solvents including dichloromethane (DCM), pentane, hexane, methanol, ethanol, propanol, and acetone was investigated along with the effect of water content in solvents for their efficiency of extraction. The extent of TPH extraction was analyzed using various extraction schemes (i.e., solvent/solid ratio, treatment time, extraction method, solvent/water ratio) to better understand the physical and chemical factors controlling TPH release from contaminated soils. More TPH was extracted with increasing solvent/solid ratio and increasing time. The extent of TPH extracted also varied depending on the extraction method, solvent type, and solvent/water ratio, but was highest when using the total extraction method and 100% DCM. However, the efficiency of TPH extraction decreased dramatically with the increase in the water content in organic solvents. The results also showed that TPH extraction using DCM was the best option for achieving cost-effective, eco-friendly outcomes along with remediation goals. DCM used in solvent extraction to remediate diesel-contaminated soils showed low toxicity, low cost, high recycling potential, and high efficiency compared to the other solvents tested in this study.     

Excitation-emission fluorescence spectroscopy combined with three-way methods of analysis as a complementary technique for olive oil characterization

This paper shows the potential of excitation-emission fluorescence spectroscopy (EEFS) and three-way methods of analysis [parallel factor analysis (PARAFAC) and multiway partial least-squares (N-PLS) regression] as a complementary technique for olive oil characterization. The fluorescence excitation-emission matrices of a set of Spanish extra virgin, virgin, pure, and olive pomace oils were measured, and the relationship between them and some of the quality parameters of olive oils (peroxide value, K232, and K270) was studied. N-PLS was found to be more suitable than PARAFAC combined with multiple linear regression for correlating fluorescence and quality parameters, yielding better fits and lower prediction errors. The best results were obtained for predicting K270. EEFS allowed detection of extra virgin olive oils highly degraded at early stages (with high peroxide value) and little oxidized pure olive oils (with low K270). The proposed methodology may be used as an aid to analyze doubtful samples.     

玉米淀粉与黄原胶复配体系流变和凝胶特性分析

为考察胶体对淀粉流变及凝胶特性的影响,该文以玉米淀粉为原料,加入不同比例黄原胶,研究两者复配后流变及凝胶特性的变化,对其相互作用机理进行了初步探讨。结果表明,玉米淀粉及两者复配体系属于屈服-假塑性流体,随着黄原胶比例的提高,复配体系的稠度系数显著增加,流体指数降低,假塑性增强,但黄原胶比例大于10%时,增加不再显著。动态流变学试验显示,复配体系具有更为优越的黏弹性,黄原胶可与淀粉分子间相互作用形成氢键,使得分子链段间的缠结点增加,同时,可延缓及阻止部分直链淀粉分子间的重新排列,从而抑制淀粉凝胶体系的回生,复配体系形成了质地更为柔软的凝胶。综合考虑,在实际应用中选择玉米淀粉与黄原胶质量比为9.0∶1.0 g/g较为适宜。研究结果可为更好的在食品工业中应用玉米淀粉/黄原胶复配体系及品质控制提供参考。     

融合双线性网络和注意力机制的油橄榄品种识别

为解决自然条件下的油橄榄品种识别问题,该研究以油橄榄品种佛奥、莱星、皮削利和鄂植8号为研究对象,融合双线性网络与注意力机制,提出双线性注意力EfficientNet模型。针对不同品种油橄榄表型差异很小的特点,搭建双线性网络以充分提取油橄榄图像中的特征信息。在此基础上,选用兼顾了速度和精度的EfficientNet-B0网络为特征提取网络。针对自然条件下油橄榄品种识别易受复杂背景干扰的问题,将CBAM（convolutional block attention module,CBAM）注意力与双线性网络结合,使模型在提取油橄榄图像特征时,能够聚焦到对油橄榄品种识别起关键作用的特征上。经测试,所提模型对4个油橄榄品种识别的总体准确率达到90.28%,推理时间为9.15 ms。Grad-CAM（gradient-weighted class activation mapping,Grad-CAM）热力图可视化结果也表明,所提模型在识别油橄榄品种时重点关注了果实以及部分叶子区域。消融试验结果表明,在EfficientNet模型中引入CBAM注意力和搭建双线性网络后,总体准确率分别提高了5.00和10.97个百分点。并且,对比试验结果表明,与双线性ResNet34、EfficientNet-SE注意力、双线性ResNet18、双线性VGG16和双线性GoogLeNet等模型相比,所提模型的总体识别准确率分别高12.78、11.53、11.11、10.70和5.00个百分点。该研究为解决自然条件下的油橄榄品种识别提供了依据,同时也可为其他作物的品种识别提供参考。     

Role of olive seed in the biogenesis of virgin olive oil aroma

Results obtained in a set of experiments point to an effective participation of olive seeds in the biosynthesis of olive oil aroma through the lipoxygenase pathway during the extraction process to produce virgin olive oil. Data showed that olive seeds should contain enzymatic activities metabolizing 13-hydroperoxides other than hydroperoxide lyase, giving rise to a net decrease in the content of C6 unsaturated aldehydes during the olive oil extraction process. Olive seeds seem also to supply this process with alcohol dehydrogenase activity, being more specific for saturated C6 aldehydes and not acting on C5 alcohols. Moreover, olive seeds would be responsible for the biosynthesis of 30-50% esters during the olive oil extraction process of intact fruits. Thus, olive seeds would afford a load of alcohol acyltransferase activity that might be quite unspecific in terms of substrate, producing any kind of esters.     

Effect of Oil Content and pH on the Physicochemical Properties of Corn Starch‐Soybean Oil Composites

Starch‐lipid composites are a new category of fat replacers. The physicochemical properties of reconstituted corn starch and soybean oil composites (CSSBOC) were evaluated and compared with the properties of reconstituted jet‐cooked corn starch (JCCS). Gel firmness, thermal properties, and hot pasting properties at two pH levels and two oil content levels were studied. Amylose content of CSSBOC was unaffected by processing. Buffer pH significantly affected the firmness of the gels made with JCCS. Gels appeared to have a more ordered structure and were firmer at pH 3.4 than at pH 6.0. The firmness of gels made with CSSBOC was not affected by pH or oil content. Retrogradation enthalpy of the gels made with JCCS was significantly affected by pH. Differences in the thermal characteristics of gels made with CSSBOC were attributed to pH and oil content. Peak viscosity, cold paste viscosity, and breakdown viscosity changed significantly when CSSBOC pastes were reconstituted in different pH buffers. Only hot paste viscosity and cold paste viscosity changed significantly when JCCS pastes were reconstituted in different pH buffers. Results establish critical parameters for processing decisions and for the understanding of the behavior of CSSBOC in food system models in which pH is an important factor.     

Optimization of microwave-assisted extraction for the characterization of olive leaf phenolic compounds by using HPLC-ESI-TOF-MS/IT-MS(2)

In the present work, a simple and rapid method for the extraction of phenolic compounds from olive leaves, using microwave-assisted extraction (MAE) technique, has been developed. The experimental variables that affect the MAE process, such as the solvent type and composition, microwave temperature, and extraction time, were optimized using a univariate method. The obtained extracts were analyzed by using high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap tandem mass spectrometry (ESI-IT-MS(2)) to prove the MAE extraction efficiency. The optimal MAE conditions were methanol:water (80:20, v/v) as extracting solvent, at a temperature equal to 80 °C for 6 min. Under these conditions, several phenolic compounds could be characterized by HPLC-ESI-MS/MS(2). As compared to the conventional method, MAE can be used as an alternative extraction method for the characterization of phenolic compounds from olive leaves due to its efficiency and speed.     

Removal of monomeric phenols in dry mill olive residue by saprobic fungi

The dry olive residue (DOR) obtained from the olive oil extraction process has toxic components against plants and microorganism growth, particularly monomeric phenols. In this investigation nine saprobic fungi were found to be capable of completely removing these phenols from the solid after 20 weeks of growth, although the rate depended on the type of fungi and phenol. Results showed that most of the fungi tested first eliminated o-diphenols and then non-o-diphenols. However, some fungi did not follow this trend. Phanerochaete chrysosporium first removed hydroxytyrosol and tyrosol and later their glucosides and, in contrast, Paecylomyces farinosus hydrolyzed hydroxytyrosol and tyrosol glucosides at the first stage, 2 weeks of growth, and then eliminated all monomeric phenols. The behavior of this fungus seems of great interest for recovering phenolic antioxidants from the DOR. Similarly, differences in DOR decolorization capacity among the fungi tested were also observed. Coriolopsis rigida showed the highest capacity, followed by Phebia radiata, Pycnoporus cinnabarinus, and Pha. chrysosporium. Therefore, both decolorization and monomeric phenol elimination pointed out that saprobic fungi could be used to detoxify the DOR obtained from the two-phase system of the olive oil extraction process.     

Total recovery of the waste of two-phase olive oil processing: isolation of added-value compounds

A process for the value addition of solid waste from two-phase olive oil extraction or "alperujo" that includes a hydrothermal treatment has been suggested. In this treatment an autohydrolysis process occurs and the solid olive byproduct is partially solubilized. From this water-soluble fraction can be obtained besides the antioxidant hydroxytyrosol several other compounds of high added value. In this paper three different samples of alperujo were characterized and subjected to a hydrothermal treatment with and without acid catalyst. The main soluble compounds after the hydrolysis were represented by monosaccharides xylose, arabinose, and glucose; oligosaccharides, mannitol and products of sugar destruction. Oligosaccharides were separated by size exclusion chromatography. It was possible to get highly purified mannitol by applying a simple purification method.     

A vacuum extraction procedure for N,K, and conductivity evaluation of potted crop media

Abstract

An extraction procedure for potted crop media is proposed which removes under vacuum a solution from an intact pot. The vacuum extracted solution had nitrate and potassium concentrations and conductivity lower than a solution obtained by saturated paste extract procedure. A high correlation between the conductivity of solution obtained by vacuum and saturated paste extract methods permitted an interpretation of the vacuum extraction results based on ranges suggested for a saturated paste extract.     

玉米淀粉与黄原胶复配体系流变和凝胶特性分析

为考察胶体对淀粉流变及凝胶特性的影响,该文以玉米淀粉为原料,加入不同比例黄原胶,研究两者复配后流变及凝胶特性的变化,对其相互作用机理进行了初步探讨。结果表明,玉米淀粉及两者复配体系属于屈服-假塑性流体,随着黄原胶比例的提高,复配体系的稠度系数显著增加,流体指数降低,假塑性增强,但黄原胶比例大于10%时,增加不再显著。动态流变学试验显示,复配体系具有更为优越的黏弹性,黄原胶可与淀粉分子间相互作用形成氢键,使得分子链段间的缠结点增加,同时,可延缓及阻止部分直链淀粉分子间的重新排列,从而抑制淀粉凝胶体系的回生,复配体系形成了质地更为柔软的凝胶。综合考虑,在实际应用中选择玉米淀粉与黄原胶质量比为9.0∶1.0 (g/g)较为适宜。研究结果可为更好的在食品工业中应用玉米淀粉/黄原胶复配体系及品质控制提供理论依据。     

Separation of olive proteins combining a simple extraction method and a selective capillary electrophoresis (CE) approach: application to raw and table olive samples

A simple extraction method was developed to extract proteins from olive samples based on chloroform/methanol extraction followed by a protein precipitation with cold acetone. Then, a capillary electrophoresis (CE) method was carried out using an acid buffer (1 M formic acid at pH 2) to ensure a positive net charge for proteins and a neutral charge for potential interferents as polyphenols. The method developed was applied to raw and table olive samples. Interestingly, raw olive samples showed differences in protein profiles depending upon the botanical variety of olives and their geographical region. Protein profiles obtained for table olives also showed differences according to the sample treatment. Thus, a signal reduction in the electropherograms obtained for black olives was observed in comparison to those achieved for treated green olives. In this work, the use of protein profiles was demonstrated to be a powerful tool for studying variations among olive samples.