Miguel A. Fernández-Muiño

Evolution of fructose and glucose in honey over one year: influence of induced granulation

Abstract Evolution of fructose and glucose over 1 year has been evaluated in 30 honey samples from Burgos (N. Spain). The influence of the induced granulation process in this evolution was also determined. Each sample was divided into two aliquots of 500 g and aseptically bottled. One aliquot was directly stored and the second induced to crystallise by seeding with 10% of finely crystallised honey. Analyses of moisture content, pH, fructose and glucose were carried out over 1 year, once each 4 months. Both, fructose and glucose increased in most samples. Induced-crystallised samples did not show any significant differences in the evolution of the two sugars in comparsion with directly stored samples. Linear correlations were found, for both fructose and glucose, between samples directly stored and honeys in which granulation was induced. These results are clearly different from those reported in previous papers where decrease of monosaccharides below their original values was described. pH of honey might promote reversion of monosaccharides and the formation of disaccharides and trisaccharides. This investigation has demonstrated the possibility of formation of monosaccharides, by the hydrolysis of higher sugars, as a process predominant over the reversion. No statistical relationship was found between pH of honey samples and their fructose and glucose content evolution.

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.

Bioactive properties of honey with propolis.

Nowadays, propolis is used as an innovative preservative and as a bioactive food supplement. Due to its bitter and astringent flavour, propolis is hardly accepted by consumers. The aim of this study was to obtain a likeable food product made with honey and propolis, whose antimicrobial, antioxidant and anti-inflammatory properties were enhanced in comparison with those of the base honeys used. 0.1%, 0.3% and 0.5% soft propolis extracts were added to honeys and the products that most appealed to the users were subjected to further research. Total phenolics, flavonoids, ABTS free radical and hydroxyl radicals scavenging and anti-inflammatory activities increased in all mixtures. Antimicrobial activity of the combined products showed synergic effects, resulting in higher results than those of the base honeys and propolis extracts. Therefore, honeys enriched with small amounts of propolis extracts are promising functional foods.

Acaricide Residues in Honey: Analytical Methods and Levels Found

A bibliographic review on the pollution of honey with acaricides is presented. This paper reviews methods for determining amitraz, bromopropylate, coumaphos, cymiazole, fluvalinate, malathion and phenothiazine residues in honey samples, as well as multiresidue methods. Acaricide residue levels found in European countries are also reviewed.

Expanded parameters to assess the quality of honey from Venezuelan bees (Apis melllifera)

Summary Hive samples from seven Venezuelan states were studied to determine the quality of honeys from the naturalized tropical honey bee Apis mellifera, submitted for a national honey competition. The physicochemical composition varied as follows: antibacterial activity as minimal inhibitory concentration for each of S. aureus and E. coli was 25.0-50.0 g/100 mL, antioxidant activity was 34.90-203.21 µmoles Trolox equivalents/100 g, ash was 0.03-0.13 g/100 g, diastase activity was 3.00-47.81 DN, flavonoids was 2.32-14.41 mg EQ/100 g, free acidity was 24.40-54.55 meq/kg, HMF was 17.70-631.73 mg/kg, moisture content was 17.2-20.2 g/100 g and nitrogen was 28.68-107.29 mg/100 g. Non aromatic organic acids, such as D-gluconic acid, was 13.5-69.3 g/kg, citric acid was 8.0-135.4 mg/kg, and malic acid was 11.2-60.9 mg/kg. Polyphenols were 38.15-182.10 mg EGA/100g, reducing sugars were 62.05-77.57 g/100 g, sucrose was 0.93-13.86 g/100 g, and vitamin C was 12.86-37.05 mg/100 g. Botanical origins of the nine honeys, determined by pollen analysis, indicate that these honeys often were derived from non-forest, non-native and weedy species. The results are a first step to better characterisation of honeys, and some of the parameters were determined for the first time in Venezuelan A. mellifera honey. They can be used for research, educational purposes, and to better understand market values, natural occurrence and chemistry of tropical honey harvested from Apis mellifera.

Nonacaricide pesticide residues in honey : analytical methods and levels found

A bibliographic review on honey pollution with pesticides is presented. This paper reviews the methods set up for determining pesticide residues in honey samples as well as the pesticide residue levels found in European countries.

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.