M. Teresa Sancho

Significance of nonaromatic organic acids in honey.

Although organic acids represent < 0.5% of honeys constituents, they make important contributions to the organoleptic, physical, and chemical properties of honey. To date, approximately 30 nonaromatic organic acids have been identified in honey, but relatively little attention has been paid to these components. This article reviews the current literature related to the significance of nonaromatic organic acids in honey; it was written with a goal of attracting researchers to study these interesting honey components. Previous research contributions on nonaromatic organic acids in honey may be classified into five main areas: (i) the antibacterial activities of these acids, (ii) the antioxidant activities of these acids, (iii) the use of these acids as possible indicators of incipient fermentation, (iv) the use of these acids for treatment of Varroa infestation, and (v) the use of these acids as factors for the characterization of both botanical and geographical origins of honeys. We conclude that nonaromatic organic acids are of interest for diverse reasons and that there is a particular need for studies regarding their possible antibacterial and antioxidant activities.

Analytical Methods for the Determination of Organic Acids in Honey

Although organic acids represent less than 0.5% of honeys constituents, they make important contributions to organoleptic, physical, and chemical properties of honey. They could be used as fermentation indicators, for the treatment of Varroa infestation, and to discriminate among honeys according to their botanical and/or geographical origins. This article reviews the current literature related to the analytical methods (enzymatic, chromatographic and electrophoretic) that have been applied recently to the determination of honeys organic acids. The advantages and disadvantages of all the procedures described are also discussed. This review has been written to make the study of these interesting honey component easier.

Enzymatic determination of L-malic acid in honey

Abstract l -Malic acid determination has been carried out in honey using a direct enzymatic method. The sample solution was prepared from 2.5 g honey in 100 ml Milli-Q water. The enzymatic determination was measured spectrophoto metrically at 340 nm, using glutamate-oxaloacetate transaminase and l -malate dehydrogenase. The direct method combines precision (CV was 3.5%, at worst), good recovery (100 ± 3.5%), zero interference, simplicity, and low cost (cost was reduced by 50% using a microtest). This direct enzymatic method was applied to 20 floral honeys of Galicia (northwestern Spain) and the results ranged between 94 and 596 mg kg −1 (mean 246 mg kg −1 ) of l -malic acid, which is in keeping with value ranges obtained by other authors. Different clarifications [as polyvinyl-polypyrrolidone (PVPP), Carrez, Carrez with NaOH, Carrez with KOH, Carrez together with PVPP and activated charcoal] and a pair of controls have also been used but the precision and the recovery of direct enzymatic method of l -malic acid in honey did not improve.

High-pressure liquid chromatographic determination of ascorbic acid in cooked sausages.

The purpose of this paper was to study and optimize both extraction and high-pressure liquid chromatography (HPLC)-UV detection procedures to develop a proper method for the determination of ascorbic acid content in cooked sausages. A simple and sensitive reversed-phase HPLC method for the NH2-bonded phase has been described for the determination of ascorbic acid content in cooked sausages. Various extracting agents were tested to solubilize the vitamin, with 5% (wt/vol) metaphosphoric acid giving the best results. Samples were chromatographed with UV detection at 248 nm on a 25-cm Spherisorb NH2 cartridge with a 0.4-cm inside diameter with a mixture of 0.02 M potassium phosphate buffer solution (pH 3.6) and acetonitrile (40:60, vol/vol) for the mobile phase. The methods precision within a day was 1.2%, and its precision between days was 3.8%. The detection limit was 1.6 mg/100 g. Recovery ranged from 91.4 to 96.2% for ascorbic acid added to meat samples. Twenty samples of six different products were analyzed in duplicate. For the samples analyzed, the mean value for ascorbic acid ranged between 21.555 and 24.899 mg/100 g of fresh weight.

Evolution of hydroxymethylfurfural content of honeys from different climates: influence of induced granulation.

Knowing the ‘best-before period once opened’ is of paramount importance for consumers, because it gives information about how long a given food keeps its quality. The hydroxymethylfurfural (HMF) content is related to honeys aging and heating. We researched the evolution of HMF of 60 unheated honeys originating from continental and oceanic climate areas, recording the moment at which the HMF increase begins to speed up. We also researched the influence of induced granulation on HMF evolution. All samples were stored at room temperature and analysed every 5 months throughout 30 months. Storage had an effect on HMF contents. On the contrary, induced granulation did not show any influence on this parameter. HMF constantly increased in all samples but much more markedly after 20 months. At 20 months, the percentages of samples with HMF higher than 40 mg/kg ranged between 2.9% and 8.0%. Nevertheless, at 25 months these percentages clearly increased, ranging from 22.9% to 72.0%. For honeys from both the continental and oceanic climate areas, taking HMF contents into account, 20 months could be proposed as the ‘best-before period once opened’.

Variation of apparent ethanol content of unspoiled northwestern Spanish honeys during storage

Abstract This paper describes, for the first time, the variation of apparent ethanol content during storage of 33 honey samples. Moisture content was determined by measuring refractive index at 20°C. Apparent ethanol content was determined in a double cuvette, according to a modification of the Boehringer–Mannheim enzymatic method. Four different types of apparent ethanol evolution were observed: constant increment, increment followed by decrease, values oscillation and constant decrease.

Direct Enzymatic Analysis of Glycerol in Honey: a Simplified Method

The glycerol content of honey has been determined using a Boehringer Mannheim enzymatic method simplified for this purpose. The solution of honey was employed directly, without clarification and without addition of NaOH solution. With these conditions, there were no observed interference effects. It is necessary to use a 1.5 ml micro-cuvette. The enzymatic determination was measured spectrophotometrically at 365 nm using the enzymes in quadruple the quantities recommended by the supplier. The method combines precision, good recovery, sensitivity, simplicity and low cost.

Methods of analysis of honey

A thorough updated review of both standardized and the most used and novel analytical methods for the analysis of honey is presented. The methodologies applied to honey in the analysis of the physical parameters (electrical conductivity, rheological properties, specific rotation, color and water activity), the analysis of the properties and the most important components of honey (moisture, sugars, enzymes, HMF, types of acidity and pH, formol index, insoluble solids, organic acids, proteins, amino acids, vitamins, minerals, volatile and semi-volatile compounds and polyphenols), and the antioxidant and antimicrobial activities are described. Finally, the most applied methods for multicomponent analysis and/or for honey authenticity verification (both the botanical and/or geographical origin honey classification and the detection of honey adulteration) are provided.

Analysis of Polyphenols in Honey: Extraction, Separation and Quantification Procedures

Polyphenols are secondary plant metabolites playing a major role as potentially functional components. They can also be used for honey authentication. This review gathers the recent literature references about honey extraction procedures, as well as instrumental analysis of phenolic compounds found in honey. Liquid-Liquid extraction is widely used for both extraction and purification purposes, with adequate recovery percentages. However, the use of high solvent volumes is a major disadvantage. More environmentally friendly methods include accelerated solvent extraction, and dispersive and inverse dispersive liquid-liquid microextraction. Solid phase extraction is the most common method for honey polyphenols’ isolation. Polyphenol isolation by a combination of liquid-liquid and solid phase extraction allows good recoveries for a variety of different compounds. High-performance liquid chromatography with ultraviolet or mass spectrometry detectors is by far, the most commonly employed instrumental procedure to separate and quantify polyphenols in honey although capillary electrophoresis has been also successfully used for these purposes. The use of new sorbents, the optimization of current procedures and the development of other simple and rapid analytical techniques are challenges for future analysis of polyphenols found in honey.

Design of a food product composed of honey and propolis

Propolis is a natural bee hive product with potential functional activities. Nowadays, many propolis products are available on the market, including cosmetics and food commodities. However, it is still unknown if edible products with propolis are fully accepted by consumers and are thus commercially viable, due to the bitter and resinous flavor and taste of propolis. This work is focused on the design of a “honey with propolis” foodstuff that can be welcomed by consumers, and, if possible, provide added benefits compared to the honey itself. Propolis tinctures containing three different concentrations of ethanol and times of maceration were prepared, giving the best results with 90% ethanol and two days of maceration. Then, in order to study the maximum amount of propolis in honey that could be accepted by a representative group of consumers, a forced choice paired comparison preference test with 69 people was carried out, giving the best results with a honey product containing 0.3-0.5% propolis extract. Phenolic and flavonoid contents, as well as TEAC antioxidant and antimicrobial activities of propolis, honey, and the product “honey with propolis” were then analyzed. As expected, propolis showed the highest phenolics and flavonoids contents, as well as the highest antioxidant and antimicrobial activities. The product “honey with propolis” showed a significantly higher antimicrobial activity, however, when compared to honey alone. In conclusion, the commercialization of a food product of “honey and up to 0.5% propolis” is promising, interesting and viable, as such a product is greatly appreciated by consumers, as well as being potentially healthy.