Simultaneous separation and determination of organic acids in blueberry juices by capillary electrophoresis- electrospray ionization mass spectrometry

Biosynthesis and Cellular Functions of Tartaric Acid in Grapevines

Tartaric acid (TA) is an obscure end point to the catabolism of ascorbic acid (Asc). Here, it is proposed as a "specialized primary metabolite", originating from carbohydrate metabolism but with restricted distribution within the plant kingdom and lack of known function in primary metabolic pathways. Grapes fall into the list of high TA-accumulators, with biosynthesis occurring in both leaf and berry. Very little is known of the TA biosynthetic pathway enzymes in any plant species, although recently some progress has been made in this space. New technologies in grapevine research such as the development of global co-expression network analysis tools and genome-wide association studies, should enable more rapid progress. There is also a lack of information regarding roles for this organic acid in plant metabolism. Therefore this review aims to briefly summarize current knowledge about the key intermediates and enzymes of TA biosynthesis in grapes and the regulation of its precursor, ascorbate, followed by speculative discussion around the potential roles of TA based on current knowledge of Asc metabolism, TA biosynthetic enzymes and other aspects of fruit metabolism.

Fast determination of lactic, succinic, malic, tartaric, shikimic, and citric acids in red Vranec wines by CZE-ESI-QTOF-MS

A fast and simple method with CZE coupled to ESI/QTOF-MS was optimized and validated for quantitative determination of organic acids (lactic acid, succinic acid, malic acid, tartaric acid, shikimic acid, and citric acid) in red wines. The BGE was ammonium acetate and the separation of the analytes was performed in a polybrene-coated capillary in the presence of EOF. The sample preparation included dilution and filtration of the wine. The method showed satisfactory performance characteristics: good linearity for each organic acid, with correlation coefficients ranging from r²  = 0.9902 (shikimic acid) to r²  = 0.9990 (tartaric acid). The limit of quantification was between 0.0034 mM (for shikimic acid) and 0.107 mM (for citric acid), and the recovery data fell between 95.8% (malic acid) and 102.7% (lactic acid); the total run time was less than 4 min. The RSD values for the interday repeatability and intraday reproducibility were between 3.44 and 9.50%, and between 1.75 and 8.29%, respectively. Seventeen Macedonian red Vranec wines were studied demonstrating a wide variation in the organic acids' concentration, which should be most probably due to the variation of the climate conditions in the vine areas.

Miniaturized Potentiometric Titration for Improving Portability and Accuracy in the Determination of Total Acid in Squeezed Fruit Juice

To determine the total acidity in freshly squeezed fruit juice, we miniaturized the potentiometric titrations and achieved better accuracy compared with titrations from a conventional pH probe. The improvement was the result of a higher jump in pH at the endpoint due to a reduction in the dilutions of both the titrand and titrant. A conventional pH probe requires more than 50 mL of titrand, which can lead to a 25000-fold dilution of the titrant when adding the titrant at 2 µL intervals. Conversely, when the volume of the titrand can be reduced to 1 mL, the dilution is only 500-fold, which results in a higher jump in pH at the endpoint. The concentration of the titrant, NaOH, was optimized by titrating sample solutions containing 25 and 50 mM of citric acid. The addition of 5 M NaOH in intervals of 2 µL led to a more accurate endpoint for both 25 and 50 mM citric acid solutions. Miniaturization of the titration process is advantageous in terms of portability, accuracy, and in requiring less consumption of a sample, thereby simplifying the process of repeat measurements that are helpful in evaluating the precision of analytical results. Practical samples of squeezed fruit juices were titrated via three methods that showed no significant differences: classic titrimetry with an indicator, conventional potentiometry, and miniaturized potentiometry. This process would be effective for use in the field and in developing countries. PRACTICAL APPLICATION: The total acidity of fruits and fruit juices is an important indicator of quality and is generally expressed in terms of the citric acid content. However, a standard potentiometric titration requires a large sample volume, which makes it difficult to assess dispersion of the acidity for individual fruits. The results of this study indicate that the use of miniaturized potentiometric titration could benefit food chemistry in many developing countries in addition to opening new fields of food chemistry such as on-site quality control of citrus fruit and evaluation of variations in quality.

Molecular Mechanism and Health Role of Functional Ingredients in Blueberry for Chronic Disease in Human Beings

Functional ingredients in blueberry have the best health benefits. To obtain a better understanding of the health role of blueberry in chronic disease, we conducted systematic preventive strategies for functional ingredients in blueberry, based on comprehensive databases, especially PubMed, ISI Web of Science, and CNKI for the period 2008⁻2018. Blueberry is rich in flavonoids (mainly anthocyanidins), polyphenols (procyanidin), phenolic acids, pyruvic acid, chlorogenic acid, and others, which have anticancer, anti-obesity, prevent degenerative diseases, anti-inflammation, protective properties for vision and liver, prevent heart diseases, antidiabetes, improve brain function, protective lung properties, strong bones, enhance immunity, prevent cardiovascular diseases, and improve cognitive decline. The anthocyanins and polyphenols in blueberry are major functional ingredients for preventive chronic disease. These results support findings that blueberry may be one of the best functional fruits, and further reveals the mechanisms of anthocyanins and polyphenols in the health role of blueberry for chronic disease. This paper may be used as scientific evidence for developing functional foods, nutraceuticals, and novel drugs of blueberry for preventive chronic diseases.

Rapid screening and quantification of major organic acids in citrus fruits and their bioactivity studies

Organic acids (OAs) are small non-volatile molecules with widespread usage in processed foods, feeds and instant beverages. The prime aim of this study was to explore major OAs in local citrus fruits (Citrus limetta, Citrus aurantifolia, Citrus nobilis, Citrus karna, Citrus medica, Citrus ichangensis and Citrus aurantium) and assessment of their bioactivities. A RP-HPLC-DAD method was developed using buffer free solvent system for rapid detection and quantification of major OAs from citrus fruits and derived products. Method validation studies showed good linear calibration curve (0.985-0.998) for all OAs. The values of %RSD ranged between 0.0001-1.129 and 0.142-1.941 for interday and intraday variability respectively. The limit of detection and limit of quantification values for different OAs were ranged between 1.5-12 and 5-40 µg mL^-1. The juice of above mentioned citrus fruit cultivars were assessed for OAs, total phenolics, free radical scavenging antioxidants and their antimicrobial potential against selected bacterial and fungal strains. The results showed variable contents of phenolics [0.28 ± 0.001-1.17 ± 0.014 mg (GAE) mL^-1] and antioxidant compounds (1.26 ± 0.009-2.84 ± 0.006 mg of trolox equivalents mL^-1) in all juice samples besides significant antifungal activity against C. albicans and A. niger strains. However, in case of antibacterial activity, only C. aurantifolia showed inhibitory effects against selected strains. It was found that citrus fruits have immense potential for their utilization as economic source of natural OAs and development of value added products, beverages and bio-preservatives.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics

This review work presents and discusses the main applications of capillary electromigration methods in food analysis and Foodomics. Papers that were published during the period February 2015-February 2017 are included following the previous review by Acunha et al. (Electrophoresis 2016, 37, 111-141). The paper shows the large variety of food related molecules that have been analyzed by CE including amino acids, biogenic amines, carbohydrates, chiral compounds, contaminants, DNAs, food additives, heterocyclic amines, lipids, peptides, pesticides, phenols, pigments, polyphenols, proteins, residues, toxins, vitamins, small organic and inorganic compounds, as well as other minor compounds. This work describes the last results on food quality and safety, nutritional value, storage, bioactivity, as well as uses of CE for monitoring food interactions and food processing including recent microchips developments and new applications of CE in Foodomics.