Ana Paula Pereira

Antioxidant and antimicrobial effects of phenolic compounds extracts of Northeast Portugal honey

Phenolic compounds of dark and clear honeys from Trás-os-Montes of Portugal were extracted with Amberlite XAD-2 and evaluated for their antioxidant and antimicrobial activities. The antioxidant effect was studied using the in vitro test capacity of scavenge the 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical and of reducing power of iron (III)/ferricyanide complex. The antimicrobial activity was screened using three Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, Staphylococcus lentus) and three Gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli). The results obtained from the partial identification of honey phenolic compounds by high-performance liquid chromatography with a diode array detector showed that p-hydroxibenzoic acid, cinnamic acid, naringenin, pinocembrin and chrysin are the phenolic compounds present in most of the samples analyzed. Antioxidant potential was dependent of honey extract concentration and the results showed that dark honey phenolic compounds had higher activity than the obtained from clear honey. In the biological assays, results showed that S. aureus were the most sensitive microrganisms and B. subtilis, S. lentus, K. pneumoniae and E. coli were each moderately sensitive to the antimicrobial activity of honey extracts. Nevertheless, no antimicrobial activity was observed in the test with P. aeruginosa.

Microbiological characterization of table olives commercialized in Portugal in respect to safety aspects

Table olives are a traditional component of the Mediterranean diet and are largely consumed in the world. There are different trade treatments that originate different types of olives. The aim of the present work was to proceed to the microbiological characterization of table olives commercialized in the Portuguese market, with respect to their microbiological safety. The microbiological characterization was made in the olive pulp and packing brine of thirty-five table olives samples of different types and trade treatments, namely natural olives Cv. Galega (NOG), natural turning colour olives (NTCO), green olives (GO), black ripe olives (BO) and natural olives purchased in the traditional market and obtained from traditional producers (NOt). Simultaneously it was verified specific legislation of the table olives in what it concerns to labeling rules, pH values and the identification of isolated yeasts. In general, table olives consumed showed acceptable security with exception of four NOt samples that presented Staphylococcus aureus. In a considerable number of samples high number of microorganisms indicators of contaminations were observed that reveals the need of optimization the hygienic procedures during production process to improve the quality and safety of table olives. During the work seven yeasts were isolated from olive pulp and brine.

Characterization of Lavandula spp. Honey Using Multivariate Techniques

Traditionally, melissopalynological and physicochemical analyses have been the most used to determine the botanical origin of honey. However, when performed individually, these analyses may provide less unambiguous results, making it difficult to discriminate between mono and multifloral honeys. In this context, with the aim of better characterizing this beehive product, a selection of 112 Lavandula spp. monofloral honey samples from several regions were evaluated by association of multivariate statistical techniques with physicochemical, melissopalynological and phenolic compounds analysis. All honey samples fulfilled the quality standards recommended by international legislation, except regarding sucrose content and diastase activity. The content of sucrose and the percentage of Lavandula spp. pollen have a strong positive association. In fact, it was found that higher amounts of sucrose in honey are related with highest percentage of pollen of Lavandula spp.. The samples were very similar for most of the physicochemical parameters, except for proline, flavonoids and phenols (bioactive factors). Concerning the pollen spectrum, the variation of Lavandula spp. pollen percentage in honey had little contribution to the formation of samples groups. The formation of two groups regarding the physicochemical parameters suggests that the presence of other pollen types in small percentages influences the factor termed as “bioactive”, which has been linked to diverse beneficial health effects.

Computational intelligence applied to discriminate bee pollen quality and botanical origin

The aim of this work was to develop computational intelligence models based on neural networks (NN), fuzzy models (FM), and support vector machines (SVM) to predict physicochemical composition of bee pollen mixture given their botanical origin. To obtain the predominant plant genus of pollen (was the output variable), based on physicochemical composition (were the input variables of the predictive model), prediction models were learned from data. For the inverse case study, input/output variables were swapped. The probabilistic NN prediction model obtained 98.4% of correct classification of the predominant plant genus of pollen. To obtain the secondary and tertiary plant genus of pollen, the results present a lower accuracy. To predict the physicochemical characteristic of a mixture of bee pollen, given their botanical origin, fuzzy models proven the best results with small prediction errors, and variability lower than 10%.

Biexciton polariton laser emission in a GaAs microcavity

Biexciton polariton emission from GaAs SQW microcavity were observed at 10K. This mode appear 0.27 meV blueshifted from the lower polariton branch, showing a laser like behavior, and also crossed polarizations for this double mode.