Consuelo Pérez

Fermentation Problem in Spanish North-Coast Honey

Twenty-one samples from the Cantabrian coast were analyzed to establish their microbiological quality and fermentation tendency. In a food with a very low free-water content like honey, microbiological growth is only possible when there is an increase in water activity. Since most of the samples studied were not extensively granulated, the risk of fermentation is mostly due to high water content. Among our samples, only two had a water content below 17.1% (no risk of fermentation), whereas the high water activity of the rest of the samples indicates the possibility of microbial growth. In fact, four of the samples analyzed showed a moisture content over the Spanish maximum legal limit, which means a high risk of fermentation. The absence of Enterobacteriaceae, coliforms, and Escherichia coli in our samples indicates an appropriate cleanliness during extractions and handling of honey. No Salmonella or Shigella were found. The relationship between water activity and mold and yeast counts found for the honeys analyzed allowed us to divide our samples in two groups: honeys with a high or a low risk of fermentation. Changes observed during storage of the samples confirmed this classification.

Bioactive properties of a propolis-based dietary supplement and its use in combination with mild heat for apple juice preservation

This study characterizes the antioxidant and antibacterial properties of a propolis-based dietary supplement (PDS) and investigates its incorporation into apple juice to decrease the intensity of the heat treatment required to inactivate 5 log10 cycles of Escherichia coli O157:H7. As the source of propolis, we used a PDS containing 0.2 mg/μL of propylene glycol-extracted propolis (propolis). The total phenolic content and antioxidant activity (IC50) of the PDS were 82.15±3.53 mg/g and 0.055±0.003 mg/mL, respectively. Regarding antimicrobial activity, propolis (0.2 mg/mL) was very effective under acidic pH against Listeria monocytogenes EGD-e, inactivating more than 5 log10 cell cycles in 1h, but hardly inactivated or sub-lethally injured E. coli O157:H7 Sakai. However, incorporating propolis (0.2 mg/mL) into acidic buffer decreased the time needed to inactivate 5 log10 cycles of E. coli O157:H7 Sakai at 51 °C by more than 40 times. Moreover, when combined with heat in apple juice, propolis (0.1mg/mL) reduced the thermal treatment time and temperature needed to inactivate 5 log10 cycles of E. coli by 75% and 3 °C, respectively. The corresponding PDS concentration did not decrease the organoleptic properties of the apple juice, which implies the possibility of obtaining a sensorially appealing, low-pasteurized apple juice with the functional properties provided by propolis.

Hexachlorobenzene Residues in Spanish Meat Products After Cooking, Curing, and Long-term Ripening

The effect of cooking, curing, and long-term ripening on hexachlorobenzene (HCB) residues in Spanish pork meat products was investigated. Twenty pork bologna samples were analyzed before and before cooking at 80-82°C for 100 min. Twenty-six fermented dry-cured pork sausage samples were initially analyzed just before filling into natural casing and at 4-, 15-, and 30-d intervals during curing process. Thirty dry-salted cured ham samples were investigated fresh, after dry-salting for 10 d, and after 6 month ripening. HCB residues were quantitated by gas-liquid chromatography with electron capture detector using packed columns. Neither cooking nor curing significantly reduced the HCB content in pork bologna and pork sausage, respectively. Ham processing yielded a significant (p<0.001) reduction of 42% in HCB levels throughout the length of maturation.

Evaluation of a Method for Rapid Detection of Listeria monocytogenes in Dry-Cured Ham Based on Impedanciometry Combined with Chromogenic Agar

The food industry is in need of rapid, reliable methodologies for the detection of Listeria monocytogenes in ready-to-eat products, as an alternative to the International Organization of Standardization (ISO) 11290-1 reference method. The aim of this study was to evaluate impedanciometry combined with chromogenic agar culture for the detection of L. monocytogenes in dry-cured ham. The experimental setup consisted in assaying four strains of L. monocytogenes and two strains of Listeria innocua in pure culture. The method was evaluated according to the ISO 16140:2003 standard through a comparative study with the ISO reference method with 119 samples of dry-cured ham. Significant determination coefficients ( R2 of up to 0.99) for all strains assayed in pure culture were obtained. The comparative study results had 100% accuracy, 100% specificity, and 100% sensitivity. Impedanciometry followed by chromogenic agar culture was capable of detecting 1 CFU/25 g of food. L. monocytogenes was not detected in the 65 commercial samples tested. The method evaluated herein represents a promising alternative for the food industry in its efforts to control L. monocytogenes. Overall analysis time is shorter and the method permits a straightforward analysis of a large number of samples with reliable results.