Comprehensive Thermal Characteristics of Different Cultivars of Flaxseed Oil (Linum usittatissimum L.)

A crude, cold-pressed oil from elderberry (Sambucus nigra L.) seeds: Comprehensive approach to properties and characterization using HPLC, DSC, and multispectroscopic methods

The physicochemical characterization of fresh, undiluted, cold-pressed oil from elderberry seeds (EO) is presented. The results showed EO's uniqueness for the 93 % presence of essential fatty acids, including linoleic n-6 (41 %), α-linolenic n-3 (38 %), and oleic n-9 (13 %) acids with favorable ratios for human nutrition, n-3/n-6 = 0.93. A γ-tocopherol is the dominant tocopherol (96 %), with a concentration of 20.62 mg/100 g, indicating low oil oxidative stability. DSC heating and cooling traces determined the thermal properties. These results also revealed the presence of metastable triacylglycerol (TAG) structures composed of polyunsaturated fatty acids. The presence of characteristic groups for fatty acids and TAGs in EO was confirmed by FTIR-ATR spectra. For the first time, Langmuir monolayer studies on EO revealed its low compressibility, indicating its low emulsifiability, and the presence of minor components of EO, including tocopherols, phenolic acids, polyphenols, flavonoids, and carotenoids, was determined using UV-Vis absorption and fluorescence excitation-emission matrix (EEM) along with the chemometric method.

Comparing Different Chemometric Approaches to Detect Adulteration of Cold-Pressed Flaxseed Oil with Refined Rapeseed Oil Using Differential Scanning Calorimetry

Flaxseed oil is one of the best sources of n-3 fatty acids, thus its adulteration with refined oils can lead to a reduction in its nutritional value and overall quality. The purpose of this study was to compare different chemometric models to detect adulteration of flaxseed oil with refined rapeseed oil (RP) using differential scanning calorimetry (DSC). Based on the melting phase transition curve, parameters such as peak temperature (T), peak height (h), and percentage of area (P) were determined for pure and adulterated flaxseed oils with an RP concentration of 5, 10, 20, 30, and 50% (w/w). Significant linear correlations (p ≤ 0.05) between the RP concentration and all DSC parameters were observed, except for parameter h1 for the first peak. In order to assess the usefulness of the DSC technique for detecting adulterations, three chemometric approaches were compared: (1) classification models (linear discriminant analysis-LDA, adaptive regression splines-MARS, support vector machine-SVM, and artificial neural networks-ANNs); (2) regression models (multiple linear regression-MLR, MARS, SVM, ANNs, and PLS); and (3) a combined model of orthogonal partial least squares discriminant analysis (OPLS-DA). With the LDA model, the highest accuracy of 99.5% in classifying the samples, followed by ANN > SVM > MARS, was achieved. Among the regression models, the ANN model showed the highest correlation between observed and predicted values (R = 0.996), while other models showed goodness of fit as following MARS > SVM > MLR. Comparing OPLS-DA and PLS methods, higher values of R2X(cum) = 0.986 and Q2 = 0.973 were observed with the PLS model than OPLS-DA. This study demonstrates the usefulness of the DSC technique and importance of an appropriate chemometric model for predicting the adulteration of cold-pressed flaxseed oil with refined rapeseed oil.

DSC Phase Transition Profiles Analyzed by Control Charts to Determine Markers for the Authenticity and Deterioration of Flaxseed Oil during Storage

An approach of implementing X-bar and R control charts as a statistical control tool to monitor the changes in the melting profile of fresh and stored flaxseed oils by differential scanning calorimetry (DSC) was used. Phase transition melting profiles were collected after 0, 2, 4, and 6 months of storing flaxseed oils, originating from five different cultivars. Four peaks at around -36, -30, -25, and -12 °C were identified using the deconvolution analysis procedure, which enabled the data to be collected at peak temperature (T), peak height (h), the peak area (A), and the percentages of the area (P A), as well as the ratio calculated from these parameters. Control charts obtained for the second peak of the melting profile showed a significant decrease of peak height (h2) from 0.50 to 0.39 W/g and the percentage of the area (P A2) from 50 to 38%, within the storage time (p ≤ 0.05); thus, they were considered to be indicators of oil deterioration. Strong negative correlations of the unstable parameters of DSC with chemical indicators of the oils' oxidative stability (PV, p-AV, TOTOX) were found. For DSC parameters, related to the first peak (h1, A1) and the third peak (h3, A3), changes were statistically not significant within storage (p > 0.05); thus, they can be used as markers of flaxseed oil authenticity. The study demonstrated that X-bar and R control charts could effectively monitor changes in the specific peaks and calculated ratios from the DSC melting profile of fresh and stored flaxseed oils, serving as reliable indicators of oil deterioration.

Assessment of Hemp Seed Oil Quality Pressed from Fresh and Stored Seeds of Henola Cultivar Using Differential Scanning Calorimetry

Cold-pressed hemp (Cannabis Sativa L.) seed oil has become very popular amongst consumers and researchers, due to its manifold application in food and medicine industry. In this study, oils pressed from stored and fresh hemp seeds of the Henola cultivar were analyzed. Determination of the acid value (AV) and color of oil (a* parameter) revealed significant differences between the two groups of oils (fresh and stored seeds) in contrast to the peroxide value (PV), p-anisidine value (p-AV), and fatty acid composition. On the other hand, isothermal and non-isothermal assessments of the thermo-oxidative stability by differential scanning calorimetry (DSC) showed no significant differences in oxidation induction time (OIT) as well as in onset temperature (Ton) between two groups of oils (p > 0.05). The DSC isothermal test (OIT 160) showed significant correlations with mono- and polyunsaturated fatty acids as well as with values of AV and a* (p ≤ 0.05), in contrast to the non-isothermal test, for which correlations were not significant (p > 0.05). However, the best distinction of both groups of oils was obtained analyzing all results together (DSC, fatty acid and tocochromanols composition, color, and oxidative stability results) by principal component analysis (PCA).

Revealing seed color variation and their possible association with yield and quality traits in a diversity panel of flax (Linum Usitatissimum L.)

Seed color is a vital quality determinant of flax, significant for consumers' acceptability, and determines the commercial values of seeds. Also, seed color as a phenotypic marker may be a convenient way to select the plants with desired traits. This study assessed a diversity panel representing 144 flax genotypes from diverse geographical origins for the existence of genetic variability for luminosity (L*) and chromaticity (a* and b*) seed color parameters, seed yield, and quality traits over two years. The genetic variance was significant for seed color parameters, demonstrating the presence of significant genetic variability, which provides a resource to objectively evaluate and select flax genotypes based on seed color according to the market demand. High heritability combined with the high genotypic coefficient of variation observed for seed yield, oil, and protein content suggested a better genetic gain upon selecting these traits. Seed yield, seed quality traits, and phenological traits showed significant negative correlation with L* and b* parameters and positive correlation with a* suggesting that the seeds' dark background and brown color can serve as marker characters to prescreen early-flowering, high-yielding and oil and protein-rich genotypes. Interestingly 48 brown-seeded genotypes were identified as early-flowering with short height, large seeds, high thousand seed weight, and capsule diameter. In addition, 34 genotypes were characterized by light-colored yellow seeds, large seeds, late-flowering with shorter height, and high branch numbers. Our results highlighted that North America and Australia-belonged genotypes were lighter yellow-seeded than the ones from other continents. Flax genotypes from South America and Asia were high-yielding, while genotypes from North America were low-yielding genotypes. Moreover, darker brown-seeded genotypes have prevailed in the South American continent.

Differential scanning calorimetry for authentication of edible fats and oils-What can we learn from the past to face the current challenges?

Fats and oils authentication has become an important issue recently, due to the growing interest in consumption of cold-pressed oils. Therefore, it is becoming more and more difficult to maintain official control over the growing assortment of new cold-pressed oils. Authenticity of plant oils is also an important issue for religious or cultural reasons. This review article focuses on the application of differential scanning calorimetry (DSC) in the field of assessing authenticity of various fats and oils (e.g. olive oil, palm oil, confectionery fats, butter). Extra virgin olive oil (EVOO) is the most comprehensively tested oil by means of the DSC technique in terms of the authenticity of origin as well as the adulteration with foreign oils. In most of the studies on DSC applicability for authentication, crystallization and melting curves were analyzed by the conventional DSC, although other modified DSC methods were also applied, such as isothermal freezing, modulated temperature DSC (MT-DSC) and fast DSC. However, the most promising are the melting profiles, which, due to the complexity of transitions, need advanced chemometric tools as well as tools for peaks deconvolution. The future prospect of using DSC in the authenticity assessment lies also in the use of DSC techniques along with other complementary chromatographic or spectroscopic techniques.