Exploratory chemometric analysis for the characterisation of Tunisian olive cultivars according to their lipid and sterolic profiles

This study aims to evaluate some Tunisian olive genetic resources using fatty acid, triacyglycerol and sterolic compositions and to classify the cultivars according to their fruit genotype and to their respective geographical origin (North, Centre and South). manova results showed that the studied cultivars presented highly significant differences regarding all the variables (P < 0.01). The most discriminant variables of fatty acids are C17:1 (F = 98.468), C16:0 (F = 92.994), C18:1 (F = 60.865), C18:1/C18:2 (F = 44.632) and C18:2 (F = 40.167); those of triacylglycerols are POP (F = 123.34), LLL (F = 122.944), LnLO (F = 98.363), POO (F = 93.357) and LOO (F = 90.42), while sitostanol (F = 289.171), campestanol (F = 192.792) and campesterol (F = 160.724) have the higher discriminant power among sterol compounds. Principal component analysis (PCA) was performed on the data of each chemical parameter to explore their usefulness for the discrimination of eleven monovarietal olive oils. Best differentiations among cultivars were obtained with triacyglycerol and sterolic compositions. The spatial distribution of the different oil samples using all the collected data showed a good discrimination among olive cultivars. A strong resolution between the samples according to the geographical origin was obtained by means of factorial discriminant analysis (FDA) (λ = 0.002). Comparisons of the distances between classes were statistically significant (Fisher tests; P < 0.0001), and 90.91% of cross‐validated grouped cases are correctly classified. The obtained results could become an important tool for sorting out oils to a single cultivar or to a specific geographical area.     

The occurrence and bioactivity of polyphenols in Tunisian olive products and by-products: a review

Polyphenols have become a subject of intense research because of their perceived beneficial effects on health due to their anticarcinogenic, antiatherogenic, anti-inflammatory, and antimicrobial activities. It is well known that olives and their derivatives are rich in phenolic substances with pharmaceutical properties, some of which exert important antioxidant effects. The characterization and quantification of their polyphenol composition is one of the first steps to be taken in any evaluation of the putative contribution of the olive to human health. This review is concerned with polyphenols in Tunisian olive (Olea europaea L.) products (fruit and oil) and some by-products (leaves and olive-mill wastewater) with an emphasis on the analytical methods used, as well as the biological activities described in recent years.     

Potential use of extra virgin olive oil in bakery products rich in fats: a comparative study with refined oils

The lipid fraction of bakery products undergoes a significant degradation during baking, with an increase in undesirable oxidised substances, that can act as catalysts for further oxidative reactions during storage reducing the product shelf life. The use of extra virgin olive oil in bakery products rich in fat in place of refined oils was studied, assessing the evolution of the oxidative and hydrolytic degradation during storage. Two‐way analysis of variance, followed by Tukey's HSD test for multiple comparisons, covariance and principal component analyses were carried out to compare the effect of the type of oils. The data obtained showed that the evolution of the oxidation levels in the analysed samples during storage was related to the type of oil used in the production process. Particularly, the use of extra virgin olive oil led to significantly lower values of hydroperoxides, ultraviolet absorption constants, triacylglycerol oligopolymers and oxidised triacylglycerols.     

Evaluation of the bellier test in the detection of olive oil adulteration with vegetable oils

Virgin olive oil was mixed with eight vegetable oils (sunflower, soya bean, palm, linseed, cottonseed, corn, sesame, and olive residue) at various levels. The Bellier test was applied to find the minimum detectable adulteration level and the ‘sensitivity score’ for each oil. The test was inapplicable to sunflower and linseed oils regardless of the level in olive oil. It was successful in detecting olive residue, soya bean, palm, cottonseed, corn, and sesame oils at minimal levels of 730, 150, 130, 90, 60 and 10 g kg^?1, respectively. The rancidity level of the adulterant oils did not affect the performance of the test in the case of sunflower, linseed and sesame oils. The sensitivity of the test decreased considerably with increasing peroxide value of the adulterant oil: soya bean, palm, cottonseed, corn and olive residue. However, the change in sensitivity level commenced at so high a peroxide value that it has no significance for practical purposes; at such levels of peroxidation the adulterated olive would be unmarketable and rejected by inspectors due to its poor sensory quality.     

Review of the use of phytosterols as a detection tool for adulteration of olive oil with hazelnut oil

Adulteration of virgin olive oil with less expensive oils such as hazelnut oil is a serious problem for quality control of olive oil. Detection of the presence of hazelnut oil in olive oil at low percentages (<20%) is limited with current official standard methods. In this review, various classes of phytosterols in these two oils are assessed as possible markers to detect adulterated olive oil. The composition of 4-desmethyl- and 4-monomethylsterols is similar in both oils, but the 4,4′-dimethylsterols differ. Lupeol and an unknown (lupane skeleton) compound from 4,4′-dimethylsterols are exclusively present in hazelnut oil and can be used as markers via GC–MS monitoring to detect adulteration at levels as low as 2%. The phytosterol classes need to be separated and enriched by a preparative method prior to analysis by GC or GC/MS; these SPE and TLC methods are also described in this review.     

Olive tree (Olea europaea L.) leaf as a waste by‐product of table olive and olive oil industry: a review

Research into finding new uses for by‐products of table olive and olive oil industry are of great value not only to the economy but also to the environment where olives are grown and to the human health. Since leaves represent around 10% of the total weight of olives arriving at the mill, it is worth obtaining high added‐value compounds from those materials for the preparation of dietary supplements, nutraceuticals, functional food ingredients or cosmeceuticals. In this review article, olive tree (Olea europaea L.) leaf is reviewed as being a potential inexpensive, renewable and abundant source of biophenols. The importance of this agricultural and industrial waste is emphasised by means of describing its availability, nutritional and therapeutic effects and studies conducted on this field. © 2017 Society of Chemical Industry     

Virgin olive oil (VOO) production in Tunisia: The commercial potential of the major olive varieties from the arid Tataouine zone

The commercial potential of olive oils from three consecutive crop years, derived from the main autochthonous olive varieties Chemlali Tataouine, Fakhari Douirat, Zarrazi Douirat and Dhokar Douirat grown in the arid region of Tataounine (Tunisia) was examined with regards to stability and nutrition aspects. Several characteristics such as fatty acid composition, the extremely high phenol-type antioxidant content, and the low levels of green pigments suggested that these oils, the only fat source for the local people, are of promising composition. Efforts to develop commercial products from these varieties could improve antioxidant intake of the local population. The introduction of Good Manufacturing Practices is a prerequisite so that the quality observed for oils obtained by an Abencor system to be achieved also in real life. This can be feasible through appropriate oleoculture, which is often the only viable agricultural activity in remote arid regions such as Tataouine.     

Use of encapsulated natural compounds as antimicrobial additives in food packaging: A brief review

BackgroundSynthetic chemical preservatives in food can be harmful to human health. These problems have increasingly attracted concern and interest from researchers, which has led to the study and application of non-toxic essential oils with preservative ability in food products and food packaging. A great challenge in this sense is their facile degradation during processing of the food and manufacturing processes during food packing.Scope and approachEncapsulation is an interesting technique to improve the physical-chemical and microbiological stability of these essential oils, as well as to achieve controlled release. This review provides a detailed overview of encapsulation in the food industry, focusing on the application of procedures to encapsulate antimicrobial essential oils.Key findings and conclusionsThis review focuses on recent studies related to nanotechnology and the nano and microencapsulation of essential oils. This study provides valuable insight that may be useful for identifying trends in the commercialization of nanotechnological products or for identifying new research areas. The results published to date confirm that the encapsulation promotes the protection of active compounds, enabling industrial applications of active packaging.     

Use of lambda DNA as a marker to assess DNA stability in olive oil during storage

Filtered olive oil samples spiked with three different concentrations of λDNA were stored at 25 °C under a 12 h photoperiod for up to a year. These samples were used for DNA extraction and PCR amplification of λDNA amplicons of 107, 415 and 691 bp length. The amplification signal was gradually decreased with longer storage periods, while the strength of the signal was related to the initial concentration of spiking λDNA particularly during longer storage periods. The 107 bp amplicon was the only one successfully amplified from all the samples, regardless of both concentration of spiking λDNA and storage period. The amplification of 415 and 691 bp amplicons was not successful for samples stored longer than a threshold period of 20 and 10 days, respectively. These results suggest that detection of polymorphic markers requiring DNA templates shorter than 100 bp might have a wider range of applications in DNA fingerprinting of olive oil. In addition, the DNA extracts were tested for the presence of inhibitors in PCR amplification reactions of yeast DNA amplicons. The inhibitory effect of olive DNA extracts was partial and gradually increased with the storage period of the olive oil samples used for the DNA extraction.     

Tocopherol speciation as first screening for the assessment of extra virgin olive oil quality by reversed-phase high-performance liquid chromatography/fluorescence detector

A method based on reversed-phase high-performance liquid chromatography with fluorescence detector has been developed for the determination of tocopherols in vegetable oils. Oils were diluted in acetonitrile/tetrahydrofuran (THF) and injected directly onto HyPurity C₁₈ column. Methanol and THF (90:10) mixture was used as a mobile phase. Tocopherols were detected by fluorescence detector. The method had good limit of detection (LOD) (7 ng/g for α-tocopherol and 6 ng/g for β-, γ- and δ-tocopherols) and reproducibility (CV% < 2.8%).     

Assessment of Pelargonium graveolens oil as plant‐based antimicrobial and aflatoxin suppressor in food preservation

BACKGROUND: Contamination of stored food commodities by moulds and mycotoxins results in qualitative as well as quantitative losses. Most of the synthetic antimicrobials used for preservation of stored food items produce side effects in the form of residual and mammalian toxicity. Recently some higher plant products have been recommended as safe alternatives of such synthetic antimicrobials. In the present investigation antifungal efficacy of some essential oils was evaluated against two toxigenic strains of Aspergillus flavus with special reference to the oil of Pelargonium graveolens to investigate its potential to inhibit aflatoxin B₁ secretion. RESULTS: Essential oil of P. graveolens exhibited absolute fungitoxicity against both the toxigenic strains of A. flavus. The minimum inhibitory concentration of the oil was found to be 0.75 g L^?1 and exhibited a fungistatic nature. It was found superior over the synthetic fungicides tested and exhibited a broad fungitoxic spectrum. The oil showed excellent anti‐aflatoxigenic efficacy as it completely inhibited aflatoxin B₁ production even at 0.50 g L^?1. CONCLUSION: This is the first report on the aflatoxin B₁ inhibitory nature of P. graveolens oil. It may be recommended as a novel plant‐based antimicrobial as well as aflatoxin B₁ suppressor over synthetic preservatives in food protection. Copyright © 2008 Society of Chemical Industry     

Use of ozone in a lettuce‐washing process: an industrial trial

Bacteria such as Escherichia coli and Salmonella spp. may cause serious problems for the quality maintenance of pre‐packaged lettuces. The aim of this study was to evaluate the bactericidal effect of ozonated water in the washing of iceberg lettuce. For this purpose an ozone generator was integrated into a commercial lettuce‐washing facility. Lettuce samples were removed from this process and analysed for mesophilic total viable count (TVC), E. coli, Salmonella spp., vitamin C and sugar content. The analyses were carried out either directly after washing or at the end of best‐before date (BBD), in which lettuces were stored at 4 °C for 6 days. Water samples were analysed for total organic carbon (TOC) content and pH. Through the addition of ozone to the wash water the quality of lettuce during storage time was unaffected while there was only a limited observed decrease in populations of microorganisms. Copyright © 2007 Society of Chemical Industry     

Effects of natural antioxidants in the improvement of corn oil quality: olive leaf vs. lemon balm

Commercially available corn oil was enriched in polyphenols by adding olive leaf and lemon balm extracts, respectively. First, dried and ground plants were extracted through homogeniser‐assisted extraction. Then, the dried extracts were partially dissolved into the corn oil by means of solid–liquid extraction method. Total phenolic content increased 9.5 and 2.5 times over the pure corn oil. The antioxidant activities of enriched oil by olive leaf and lemon balm extracts have been found almost 14 and 6 times higher than that of untreated oil, respectively. Olive leaf extract enhanced the quality better than lemon balm extract with respect to carotenoid (TCC) and chlorophyll contents. Addition of 0.12–0.15% natural antioxidants gave rise to increase in the stability of the oil (≈18%).     

Quantification of adulterant agents in extra virgin olive oil by models based on its thermophysical properties

Two methods to quantify the adulteration of extra virgin olive oil (EVOO) based on the physical characteristic of adulterated samples have been here described. Firstly, the adulterant agent concentration is determined using the density and/or refractive indices (RIs) of adulterated samples of EVOO with sunflower (SO) or corn (CO) oils by suitable linear correlations between density and/or RI. Finally, models based on the combination of differential scanning calorimetry (DSC) equipment and a chaotic parameter (lag-k autocorrelation coefficients, LCCs) is defined here to quantify adulterations of EVOO with refined olive (ROO), refined olive pomace (ROPO), SO or CO oils. This quantification was carried out using successful linear correlation of LCCs and ROO, ROPO, SO or CO concentrations in 462 adulterated samples of EVOO. The LCCs are calculated from DSC scans of adulterated EVOO samples. In both models studied, the adulterant agent concentrations are less than 14% w/w. The former is adequate to calculate the concentration of the adulterant agents (CO and SO) with a correlation coefficient (R²) higher than 0.927 and mean square error (MSE) lower than 8.9%. By the external validation process, the LCC/DSC approach estimates the adulterant agent concentrations with a R² (estimated vs. real adulterant agent concentration) greater than 0.921 and a MSE less than 4.9%.