Avocado oil is a food product of high commercial and nutritional value. As a result, it can be a subject of adulteration similar to other high-value edible oils, such as olive oil. For olive oil and ...many other foods products, NMR spectroscopy has been successfully used for authentication and quality assessment. In this study, we apply NMR analysis to avocado oil to differentiate it from other oils including olive, canola, high-oleic (HO) safflower, HO sunflower and soybean oil using commercial and lab-made samples of avocado oils. NMR allowed the rapid analysis of the fatty acid profile and detection of minor compounds, such as sterols, oxidation products, and hydrolysis products, which can be used to assess oil quality and authenticity. The NMR assignment was conducted using traditional 2D NMR and the novel NOAH super-sequences. Combining chemometrics with NMR enabled us to differentiate between avocado oil and other oils. Avocado oil has compositional similarities with other vegetable oils, such as HO sunflower and HO safflower oil, which can be used as potential adulterants. Despite these similarities, NMR-based metabolomics captured differences in the levels of certain compounds including fatty acids, terpenes, sterols, and oxidation products to detect adulteration and for quality control purposes.
Walnuts are grown in various countries, and as product origin information is becoming more important to consumers, new techniques to differentiate walnut geographical authenticity are needed. We ...conducted bulk stable isotope analysis (BSIA) and compound-specific stable isotope analysis (CSIA) on walnuts grown in seven countries. The BSIA consisted of δ13Cbulk, δ15Nbulk, and δ34Sbulk, and CSIA covered δ2Hfatty acid, δ13Cfatty acid, δ13Camino acid, δ15Namino acid, and δ2Hamino acid. Analysis of variance (ANOVA) and linear discriminant analysis (LDA) were used for statistical analysis to compare samples from the USA and China. Parameters that yielded significant variations are δ2HC18:1n–9, δ13CC18:2n–6, δ13CC18:3n–3, δ13CGly, δ13CLeu, δ13CVal, δ2HGlu, δ2HIle, δ2HLeu, and δ2HThr. Our findings suggested that CSIA of fatty acids and amino acids can be useful to differentiate the geographical provenance of walnuts.
With innovations and advancements in analytical instruments and computer technology, omics studies based on statistical analysis, such as phytochemical omics, oilomics/lipidomics, proteomics, ...metabolomics, and glycomics, are increasingly popular in the areas of food chemistry and nutrition science. However, a remaining hurdle is the labor-intensive data process because learning coding skills and software operations are usually time-consuming for researchers without coding backgrounds. A MATLAB
coding basis and three-in-one integrated method, 'Ana', was created for data visualizations and statistical analysis in this work. The program loaded and analyzed an omics dataset from an Excel
file with 7 samples * 22 compounds as an example, and output six figures for three types of data visualization, including a 3D heatmap, heatmap hierarchical clustering analysis, and principal component analysis (PCA), in 18 s on a personal computer (PC) with a Windows 10 system and in 20 s on a Mac with a MacOS Monterey system. The code is rapid and efficient to print out high-quality figures up to 150 or 300 dpi. The output figures provide enough contrast to differentiate the omics dataset by both color code and bar size adjustments per their higher or lower values, allowing the figures to be qualified for publication and presentation purposes. It provides a rapid analysis method that would liberate researchers from labor-intensive and time-consuming manual or coding basis data analysis. A coding example with proper code annotations and completed user guidance is provided for undergraduate and postgraduate students to learn coding basis statistical data analysis and to help them utilize such techniques for their future research.
Walnuts undergo rigorous grading before being sold to customers. There are multiple parameters used for the grading, including skin lightness. Walnuts with light skin receive superior grades while ...walnuts with dark skin are given poor grades or even rejected. However, information on the quality and physicochemical properties of walnuts with varying skin lightness levels is minimal. Therefore, we studied the quality of kernels of varying skin lightness from three common cultivars grown in California, USA (Chandler, Howard, and Tulare). The samples were subjected to size and weight, fat content, free fatty acid, peroxide value, oxidative stability, volatiles, tocopherols, fatty acid profile, and phenol measurements. The dark kernels had significantly lower weight and fat content, higher oxidative stability, and more volatiles than their light counterparts. The dark kernels had higher concentrations of some phenolics but low procyanidin B1 and non‐existent epicatechin gallate, compared to the light kernels, indicating that these two phenolics were likely involved in an antioxidant mechanism. Oxidation and depletion of epicatechin gallate likely contributed to the darkening of walnut color.
The impact of cultivar, harvest time, and crop season on olive fruit characteristics and olive oil quality and minor components composition is assessed for super‐high‐density “Arbequina”, “Arbosana”, ...and “Koroneiki” in California, United States, during 2016, 2017, and 2018. Fruit oil content reaches a plateau in November for “Arbequina” and “Arbosana,” while the accumulation rate keeps constant until early December for “Koroneiki.” Free fatty acids, diacylglycerols, pyropheophytins, and ΔK are not affected by any of the considered factors. Peroxide value, K232, and K270 decreases with harvest time. Chlorophylls content decreases with harvest time, more rapidly in “Arbequina” and “Arbosana” than in “Koroneiki”. Cultivar is the main factor affecting the fatty acid profile. “Koroneiki” has the highest oleic acid content, followed by “Arbosana” and “Arbequina.” Phenolic and volatile compounds are profoundly affected by cultivars and crop seasons, suggesting the relevance of these factors on the sensory and nutritional properties of virgin olive oil from super‐high‐density cultivars. Stepwise linear discriminant analysis allows selecting suitable markers among fatty acids, phenolic, and volatile compounds for cultivar, crop season, and harvest time discrimination.
Practical Application: This paper constitutes the first report of a multiyear study considering quality and composition in bioactive compounds of super‐high‐density “Arbequina,” “Arbosana,” and “Koroneiki,” planted in California, USA. This information helps processors understand the differences in oil made from the most common super‐high‐density cultivars along harvest times and for growers to make planting and harvesting decisions.
Olive oil production is increasing outside the Mediterranean Basin. In this study, olive fruit characteristics, olive oil quality, and chemical composition during maturation are described for the three most common super‐high‐density cultivars, “Arbequina,” “Arbosana,” and “Koroneiki,” planted in Central Valley region of California.
Reducing acrylamide in foods is an important scientific and regulatory goal. Black ripe olives contain significant levels of acrylamide. However, unlike cereal and potato products, there are no ...standardized methods or certified reference materials for olives and no harmonization between laboratories performing routine analyses. The industry has observed inconsistencies between laboratories using different analytical methods. To narrow the cause of this variability, acrylamide was extracted from olives using a single protocol and analyzed with the most commonly used routine methods: liquid chromatography with ultraviolet detection (LC–UV) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) without bromination and LC–UV and gas chromatography–mass spectrometry (GC–MS) following bromination. This design specifically evaluated the effects of sample derivatization and detector on acrylamide measurements, which has not been documented for any food. Accuracy, precision, sensitivity, linearity, and reproducibility were assessed, and 10 commercial olive samples were analyzed. LC–MS/MS demonstrated the best overall performance. Although derivatization decreased precision and reproducibility, all detection methods had comparable accuracy and calculated acrylamide values. The results suggest that harmonization of extraction protocols across laboratories is the most important area of future study. This study provides the framework for a standardized method for acrylamide analysis in olives. Reliable measurements are essential for aiding the decision making of the industry and regulatory agencies.
Extra virgin olive oil (EVOO), with high unsaturation degree (oleic acid, linoleic acid, and linolenic acid), is prone to oxidation during production and storage even with the presence of abundant ...antioxidants (e.g., phenolic compounds, alpha-tocopherol, and chlorophyll). The level of oxidation degradation is greatly affected by the EVOO chemical composition (free fatty acids, saturated and unsaturated fat ratio, total phenol content, etc.) and storage conditions (packaging material, oxygen, temperature, and light). With the increasing demand on qualitative acceptability and food safety of an EVOO product, consumers rely heavily on “shelf life” as a good indicator. Hence, it is critical for olive oil producers to provide accurate and practical information on shelf-life prediction. This review analyzes ten shelf-life prediction models that used various parameters and approaches for model establishment. Due to the complexity of chemical interactions between oil phase and environment under real-time storage and rapid accelerated testing conditions, further investigation is needed to scrutinize and minimize the discrepancies between real-time shelf life and predicted shelf life of EVOO products.
Avocado oil is a nutritious, edible oil produced from avocado fruit. It has high commercial value and is increasing in popularity, thus powerful analytical methods are needed to ensure its quality ...and authenticity. Recent advancements in low‐field (LF) NMR spectroscopy allow for collection of high‐quality data despite the use of low magnetic fields produced by non‐superconductive magnets. Combined with chemometrics, LF NMR opens new opportunities in food analysis using targeted and untargeted approaches. Here, it was used to determine poly‐, mono‐, and saturated fatty acids in avocado oil. Although direct signal integration of LF NMR spectra was able to determine certain classes of fatty acids, it had several challenges arising from signal overlapping. Thus, we used partial least square regression and developed models with good prediction performance for fatty acid composition, with residual prediction deviation ranging 3.46–5.53 and root mean squared error of prediction CV ranging 0.46–2.48. In addition, LF NMR, combined with unsupervised and supervised methods, enabled the differentiation of avocado oil from other oils, namely, olive oil, soybean oil, canola oil, high oleic (OL) safflower oil, and high OL sunflower oil. This study showed that LF NMR can be used as an efficient alternative for the compositional analysis and authentication of avocado oil.
Practical Application
Here, we describe the application of LF‐NMR for fatty acid analysis and avocado oil authentication. LF‐NMR can be an efficient tool for targeted and untargeted analysis, thus becoming an attractive option for companies, regulatory agencies, and quality control laboratories. This tool is especially important for organizations and entities seeking economic, user‐friendly, and sustainable analysis solutions.
Kernel oxidation susceptibility and pellicle darkening are among the biggest concerns regarding walnut quality. Monitoring oxidation is crucial to preserve quality from production to consumption. ...Chemical oxidation parameters (peroxide value and UV absorbances), fatty acid profile, tocopherols, phenols, and volatiles in 'Chandler' and 'Howard' kernels were studied at different time points during 28 weeks of storage to evaluate potential oxidation markers. During storage, peroxide value, UV absorbances, and volatiles concentration increased; oxidative stability, phenols, and tocopherols decreased, while fatty acid profile was unaffected. 'Chandler' had a lower peroxide value, K
, and K
; and higher kernel and oil oxidative stability compared to 'Howard'. Phenols and tocopherols decreased 1.2-fold in 'Chandler' and 1.3-fold in 'Howard'. Using multivariate analysis, samples were discriminated in three groups according with their oxidative levels. Increases of volatiles in oil and kernel were associated with higher oxidative levels. Pentanal, 2-methylpropanal, hexanal,
-2-pentenal, 3-octanone, octanal,
-2-penten-1-ol, hexanol,
-2-octenal, 1-octen-3-ol, benzaldehyde,
-2,4-nonadienal, and hexanoic acid in kernels were adequate at distinguishing oxidation levels and as oxidative markers in walnuts. Kernel volatiles is a useful measurement for walnut oxidation during storage without any prior fat extraction.
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