Lactonic Acidity Research Articles

Microbiological and physico-chemical properties of some commercial Nigerian honey

A total of 10 honey samples from different geographical locations of Nigeria were evaluated for their physico-chemical properties and microbiological quality. The honey samples were examined for antimicrobial activity against Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Bacillus cereus, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella spp, Shigella spp, Clostridium sporogenes and Candida albicans. The study revealed that the honeys had an average pH of 3.86, moisture content of 14.09%, ash content of 0.28% and electrical conductivity of 34.09 µS/cm. The free acidity was about 27.00 meq/kg, lactone acidity 10.55 meq/kg and total acidity of about 37.20 meq/kg. Results of the microbiological characteristics showed total coliform counts of 0 - 3.0 ◊ 10 cfu/g and total aerobic mesophilic bacteria (TAMB) between 1.0 ◊ 10 3 and 5.0 ◊ 10 3 cfu/g. Yeasts and moulds were not detected. The Bacillus species detected were identified as B. cereus, B. megaterium, B. polymyxa, B. licheniformis, B. firmus, and B. pumilus. The honey samples showed inhibitory activity at the various concentrations against Salmonella spp, Shigella spp, E. coli and Proteus vulgaris with the zones of inhibition increasing with honey concentration. B. cereus, K. pneumoniae and Clostridium sporogenes were inhibited at higher concentrations (50 - 100%) of the honey samples. The honey samples showed no inhibitory activity against S. aureus, P. aeruginosa and C. albicans.

Honey from Luso region (Portugal): Physicochemical characteristics and mineral contents

This work was conducted to evaluate the quality of 38 honey samples from Luso region (Portugal), and to study the relation between Eucalyptus pollen and chemical properties of honey. Mean values obtained for physicochemical parameters were: pH 3.83; 16.65% moisture; 80.7 °Brix sugar; 0.35% ash; 419.6 μS cm − 1 electrical conductivity; 21.5 meq/kg free acidity; 9.6 meq/kg lactonic acidity; 31.2 meq/kg total acidity; 9.41 mg/kg HMF and 18.3° Gothe diastase activity. The mineral content was determined by atomic absorption spectrometry, and in the analysed samples, potassium was the major element, being magnesium the minor one. Mean values obtained were (mg/kg): Ca, 59.88; K, 1150.10; Mg, 35.57; Na, 261.43. Among the overall determined parameters, only Mg, ash and electrical conductivity were influenced by the presence of Eucalyptus pollen in the honey samples: the values obtained for Mg, ash and electrical conductivity in multifloral honey without Eucalyptus were lower than those of either monofloral or multifloral honey with Eucalyptus. The results obtained for physicochemical characteristics of Luso honey indicate a good quality level, adequate processing, good maturity and freshness.

Composition and Antioxidant Activity of Trigona carbonaria Honey from Australia

Stingless bees (Tribe Meliponini) are a diverse group of highly eusocial bees distributed throughout the tropics and subtropics. Trigona carbonaria honey, from Australia, was characterized by traditional physicochemical parameters (acidity, sugars, diastase, electrical conductivity, hydroxymethylfurfural, invertase, nitrogen, and water content) and other compositional factors (flavonoids, polyphenols, organic acids, and water activity), as well as total antioxidant capacity and radical scavenging activity. For the Australian T. carbonaria, the traditional analytical parameters were similar to those previously reported for neotropical stingless bee honey and confirm that honeys produced by Meliponini bees possess several physicochemical properties that are distinctly different from Apis mellifera honey, with higher values of moisture (26.5 +/- 0.8 g of water/100 g of honey), water activity (0.74 +/- 0.01), electrical conductivity (1.64 +/- 0.12 mS/cm), and free acidity (124.2 +/- 22.9 mEq/kg of honey) and a very low diastase activity (0.4 +/- 0.5 diastase number) and invertase activity (5.7 +/- 1.5 invertase number). The sugar spectrum was quite different from that of A. mellifera honey, with 20.3 +/- 2.9 g of maltose/100 g of honey. The values of pH (4.0 +/- 0.1), lactonic acidity (4.7 +/- 0.8 mEq/kg of honey), sucrose (1.8 +/- 0.4 g/100 g of honey), and fructose/glucose ratio (1.42 +/- 0.13) fell in the same ranges as those of A. mellifera honey. Citric (0.23 +/- 0.09) and malic (0.12 +/- 0.03) acid concentrations (in g/kg of honey) of T. carbonaria honeys were in the range described for A. mellifera honey. D-Gluconic was more concentrated (9.9 +/- 1.3 g/kg of honey), in the range of Italian Castanea, Thymus, Arbutus, and honeydew honeys. Flavonoid content was 10.02 +/- 1.59 mg of quercetin equivalents/100 g of honey, and polyphenol contents were 55.74 +/- 6.11 mg of gallic acid equivalents/100 g of honey. The antioxidant activity, expressed as percentage of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) cation (ABTS(*+)) decolorization, was 233.96 +/- 50.95 microM Trolox equivalents, and free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH(*)) depletion was 48.03 +/- 12.58 equivalents of ascorbic acid. All reported values are averages +/- standard deviation. The antioxidant activity can represent an important added value for T. carbonaria honey, to initiate a medicinal approach for both nutritional and pharmaceutical applications, besides further physicochemical characterization.

Chemical changes in the non-volatile fraction of Brazilian honeys during storage under tropical conditions

The chemical transformations of the non-volatile fraction of Brazilian honeys during storage in tropical condition were monitored. Five systems, namely: 1 – fresh samples; 2 and 3 – samples heated for 3 and 6 months at 35–40 °C; 4 and 5 – samples left under similar conditions to systems 2 and 3, but containing sodium metabisulphite (120 ppm), were tested. The major transformations during storage occurred in the free and lactone acidity, diastase activity and 5-hydroxymethylfurfural (5-HMF) content. Storage modified diastase activity and the content of 5-HMF to an extent that the samples could not remain classified as fresh honey. The action of sodium metabisulphite in the control of the 5-HMF formation seemed to be dependent on other honey characteristics, such as its botanical origin. Sodium metabisulphite also influenced the development of the internal esterification reaction that converts gluconic acid into its corresponding lactone.

Preliminary contribution to the characterisation of artisanal honey produced on the island of Ireland by palynological and physico-chemical data

Fifty artisanal honey samples from the island of Ireland were collected over two consecutive harvest seasons, providing two sets of 25 samples each. Parameters measured for years 1 and 2 were water content, pH, electrical conductivity, ash content, free acidity, lactonic acidity, total acidity and mineral content; those from year one had melissopalynological and those from year two had HMF analyses performed. Evidence from all parameters tested is consistent with the fact that they were generally of floral origin.

Chemical and physical parameters of Andalusian honey: classification of Citrus and Eucalyptus honeys by discriminant analysis

The characterization of two types of Andalusian unifloral honey ( Citrus spp. and Eucalyptus spp.) was carried out on the basis of their physicochemical properties: moisture, hydroximetylfurfural, diastase, pH, free acidity, lactone acidity, electrical conductivity, glucose, fructose, sucrose, proline, invertase, glucose-oxidase, water activity and insoluble solids. All the data were statistically tested using analysis of variance, principal factor analysis (PFA) and stepwise discriminant analysis (SDA) with the aim of classifying the honeys and identifying the most significant parameters in the classification. Statistically, it was verified that the variables were different, depending on the type of honey. Of the six main factors obtained with a variance percentage of 78.95, it was the first one (free acidity, water, invertase, total sugars, electrical conductivity and solids) which explained the greater part of the variability (22.9%). The variables with the greatest discriminatory power were water activity and electrical conductivity with discrimination coefficients of −22.367 and 11.739, respectively. The overall proportion of accurately arranged samples was 96.6%.

Influence of the storage conditions on some physicochemical and mycological parameters of honey

AbstractThe authors studied the changes in yeast and mould counts, pH, free and lactone acidity, colour and sugar composition undergone by honeys with water contents of 169, 188 and 220 g kg‐1 on storage at refrigeration temperature (4–7°C), room temperature and 28°C for two years. Of the solid culture media assayed, honey agar and osmophilic medium fostered yeast growth while malt‐extract agar and yeast‐extract‐malt‐extract agar allowed for better development of filamentous fungi. The yeasts isolated belonged to the genera Saccharomyces, Schizosaccharomyces and Zygosaccharomyces, while filamentous moulds were of the genera Aspergillus, Penicillium, Fusarium and Alternaria. The honeys studied underwent no visible microbial alternations under any of the conditions tested, although yeast population increased significantly with time. Free and lactone acidity increased slightly but the pH was practically constant. The honeys darkened gradually with time, the effect increasing with the storage temperature. The analysis of various sugars carried out by capillary column gas chromatography of their trimethylsilyloxime derivatives indicated that all of them changed significantly after 2 years. Levels of fructose, glucose, sucrose, maltose, kojibiose, isomaltose and trisaccharides decreased with time whereas those of maltulose and turanose increased over the same period.

Alberta honey composition

Fresh honeys from the province of Alberta, Canada, were removed by filtration and stored frozen until analysis for moisture, enzymes (α- and β-glucosidase, diastase), 5-(hydroxymethyl)-2-furaldehyde, proline, free and lactone acidity, ash and carbohydrate composition to establish original values for authentic Alberta honey. These samples were found to meet all major national and international honey specifications. Generally, the samples were lower in moisture, α-glucosidase, proline, acidity and ash than many world floral honeys. Proline levels were often lower than 200 ppm which has incorrectly been used as a minimum level for honey authenticity by some honey importers. Fructose-to-glucose ratios were very consistent and averaged 1·09. All samples contained turanose and/or palatinose, and maltose in significant (averaging 1·6%) quantities.