An updated review of extraction and liquid chromatography techniques for analysis of phenolic compounds in honey

Freezing-assisted sugaring-out liquid-liquid extraction coupled with LC-MS/MS for quantitative determination of perchlorate in honey

For the first time, a simple, quick, sensitive, and low cost method for quantification of perchlorate in honey using liquid chromatography-tandem mass spectrometry was developed. Through freezing-assisted sugaring-out liquid-liquid extraction, one-step simultaneous extraction and clean-up of perchlorate from honey were perfectly achieved. Glucose and fructose, the most abundant sugars in honey, were almost completely removed from the extract without use of any clean-up materials. Under optimum conditions, the proposed approach exhibited satisfactory linearity, negligible matrix effects, and low detection limit of 0.05 µg/kg, providing recoveries of 96.7 %-102.3 % with relative standard deviation of < 9 % for honey samples. The validated method was applied to the analysis of perchlorate in 36 honey samples, and detection rate was 94.4 %. This work provided a simple and reliable method for extensive monitoring of perchlorate in honey and opened- up new insights for analysis of contaminants in honey matrixes.

Ultrasonication for honey processing and preservation: A brief overview

Honey is a food product consumed all over the world. Besides its nutritional properties, honey presents antibacterial, antioxidant, and wound-healing properties. To ensure that the final product meets qualitative and microbiological standards, honey treatment is of great importance. Conventional honey treatment is based on the heating of honey samples for decrystallization and bacteria and yeast inactivation. However, conventional heating can cause negative effects on honey quality, such as the formation of toxic compounds, reduction of enzyme activity, and loss of antioxidant and antimicrobial properties. The application of ultrasonic waves has demonstrated interesting effects on honey processing. Ultrasound (US) treatment can lead to the fragmentation of glucose crystals in crystalized honey and has little effect on its properties. In addition to inactivating microorganisms, US-assisted honey processing also preserves phenolic compounds content and antimicrobial properties. However, there is still limited information about honey sonication. The aim of the present review is to comprehensively show the possibilities of US application in honey processing and its effects on honey properties.

Use of polyphenolic fingerprints established by comprehensive two-dimensional liquid chromatography for the classification of honeys according to their floral origin

In this work, the polyphenolic composition of honeys from three different floral origins (chestnut, heather, and thyme), coming from different geographical areas of Spain was investigated. First, samples were characterized in terms of total phenolic content (TPC) and antioxidant capacity, which was established by three different assays. The results revealed that the studied honeys presented similar TPCs and antioxidant capacities, with a wide variability within each floral origin. Next, a comprehensive two-dimensional liquid chromatography method was developed for the first time to establish polyphenol fingerprints of the three types of honeys, after optimizing the separation in terms of column combination and mobile phase gradient programs. After that, the detected common peaks were used for the construction of a linear discriminant analysis (LDA) model able to discriminate honeys according to their floral origin. The LDA model obtained was adequate for the classification of the floral origin of the honeys based on polyphenolic fingerprint data.

Characterization and Classification of Spanish Honeydew and Blossom Honeys Based on Their Antioxidant Capacity

Honey is a very appreciated product for its nutritional characteristics and its benefits for human health, comprising antioxidant, anti-inflammatory, antifungal, and antibacterial activities. These attributes depend on the specific composition of each honey variety, with the botanical origin as one of the distinctive features. Indeed, honeydew and blossom honeys show different physicochemical properties, being the antioxidant capacity, mainly relying on the phenolic compound content, one of the most important. In this work, Folin-Ciocalteu (FC) index, total flavonoid content (TFC), and the antioxidant capacity based on the ferric reducing antioxidant power (FRAP) assay were determined for a total of 73 honeys (50 blossom honeys and 23 honeydew honeys). Mean content of oxidizable species (FC index) ranges from 0.17 to 0.7 mg eq. gallic acid g^-1, with honeydew honeys being the ones with higher values. Regarding TFC, mean values above 1.5 mg eq. quercetin g^-1 (method applied in the absence of NaNO₂) were obtained for honeydew honeys and heather honey. Lower and not discriminatory values (below 0.3 mg eq. epicatechin g^-1) were obtained in the presence of NaNO₂. The maximum antioxidant capacity was observed for thyme honeys (2.2 mg eq. Trolox g^-1) followed by honeydew and heather honeys. Individually, only the FC index was able to discriminate between honeydew and blossom honeys, while the other spectroscopic indexes tested allowed the differentiation of some honey types according to the botanical origin. Thus, a holistic treatment of the results was performed using partial least square discriminant analysis (PLS-DA) for classification purposes using FC, TFC, and FRAP results as data. Honeydew and blossom honey were satisfactorily discriminated (error 5%). In addition, blossom honeys can be perfectly classified according to their botanical origin based on two-class PLS-DA classification models.