The role of the consumer in the reduction of Listeria monocytogenes in lettuces by washing at home

Lettuce is highly appreciated for its nutritional properties; however microbial contamination through the food chain and its raw consumption may jeopardize these known benefits to the diet. The objective of this study was to determine the role of the consumer at the stage of washing at home, in relation to the probability of illness due to the presence of Listeria monocytogenes in lettuce. Survival curves of L. monocytogenes after washing (dipping with and without addition of bleach, and washing under a running tap) were studied. A mathematical model for each washing method was calculated by fitting experimental data. The obtained models were used to estimate the probability of illness after washing at home. Results show that although consumers can only deal with low loads of L. monocytogenes, their role is essential to reduce the normal contamination level of lettuces and ensure their safety.     

Sensory analysis integrated by palynological and physicochemical determinations plays a key role in differentiating unifloral honeys of similar botanical origins (Myrtaceae honeys from southern Spain)

Myrtaceae honeys produced in Sierra Morena (southern Spain, Andalusia) are obtained from both Eucalyptus camaldulensis and Myrtus communis, and honeys can be easily confused when classified as they come from the same botanical family. The characterisation was intended on the basis of their physicochemical, sensory and palynological properties. Cluster analysis (CA) and principal component analysis (PCA) allowed us to make a distinction between two honey profiles. The first one corresponds to the European sensory profile described for Eucalyptus unifloral honeys. The second profile, which sensory characteristics are absolutely different, has not been previously described. Classification of samples is proposed to be based on their pollen type and content and sensory attributes. Therefore, pollen type and content in E. camaldulensis and M. communis are required to distinguish Eucalyptus honey type from other honeys coming from Myrtaceae family. Sensory analysis identifies honey botanical source as well as palynological analysis: Eucalyptus sensory profile requires over 50% of E. camaldulensis and under 30% of M. communis pollen. Previously undefined sensory profile of myrtle honey is showed under 50% of E. camaldulensis and over 30% of M. communis pollen.     

Antimicrobial activity of food-compatible plant extracts and chitosan against naturally occurring micro-organisms in tomato juice

BACKGROUND: Chitosan (AC) and five hydroalcoholic extracts from Lithospermum erythrorhizon (SE), Rheum palmatum (RE), Thymus vulgaris (AT), Lippia citriodora (PLX) and a mixture of Rosmarinus officinalis, Salvia lavandulifolia and Thymus mastichina (LA) were tested for antimicrobial activity against bacteria, yeasts and filamentous fungi using two broth dilution methods. The effects of adding single extracts on naturally occurring micro‐organisms and sensory qualities of raw tomato juice were also evaluated. RESULTS: SE extract exhibited the strongest activity, with minimum inhibitory concentrations (MICs) of 100–400 µg mL^?1 for Gram‐positive and 1600–3200 µg mL^?1 for Gram‐negative bacteria. Enterobacter aerogenes showed the greatest susceptibility to AC (MIC 1600 µg mL^?1). Lethal effects of extracts and AC were achieved at a minimum bactericidal concentration (MBC)/MIC ratio of 2 in 88% of assays. SE and RE extracts and AC also exhibited antifungal effect against yeasts, but they had no activity on filamentous fungi. Control and 100 mg L^?1 SE‐added tomato juices did not differ in acceptance, but this SE concentration was not effective in the control of microbial load throughout cold storage. CONCLUSION: Results confirm the antimicrobial potential of the plant extracts, but additional research is needed until the agents responsible for the activities have been determined in order to use them as natural constituents of multiple‐barrier food preservation systems. Copyright © 2012 Society of Chemical Industry     

Changes on indigenous microbiota,colour, bioactive compounds and antioxidant activity of pasteurised pomegranate juice

Juices prepared from arils of ‘Mollar’ pomegranates were analysed for naturally occurring microorganisms, CIE Lab colour parameters, total phenols, anthocyanins and punicalagins, ellagic acid content and antioxidant capacity before and after low-, mild- and high-temperature pasteurisations (LTPs, MTPs and HTPs): 65, 80 and 90 °C for 30 or 60 s. Mean aerobic plate count (APC), yeast and mold count (YMC), and lactic acid bacteria (LAB) for fresh juices were 5.7, 5.36 and 4.0 log CFU/mL, respectively. MTPs and HTPs were sufficiently effective to decrease APCs to nil or negligible levels. An increase in CIE a values and decrease in CIE b values were the characteristic colour changes in heat-treated juices. The effect of pasteurisations showed that total phenols, punicalagins and ellagic acid were not much affected by thermal processing. Total anthocyanin content and antioxidant capacity were substantially and significantly influenced by the heat treatment applied. A linear relationship was observed between Trolox equivalent antioxidant capacity (TEAC) values and total anthocyanins, suggesting that they contributed strongly to the antioxidant capacity of pomegranate juice.     

Characterisation of Sierra Morena citrus blossom honey (Citrus sp)

The citrus blossom honey of Sierra Morena (a mountain chain located in the south of Spain) has been characterised by melissopalinological, physicochemical and sensorial analyses with the aim of establishing criteria for a future Protected Designation of Origin, which includes citrus blossom honey as one of the monofloral types produced in that region. Thus, a content in pollen of Citrus sp. ≥5%, Maurizio classes I and II was established, the accompanying pollen spectrum characteristic being that composed by the Myrtus, Echium, Lavandula, Reseda, Quercus, Olea, Crataegus and Cistus pollen types. The physicochemical parameters set were electrical conductivity ≤0.27 mS cm^?1; diastase activity≥ 6 diastase number; colour ≤20 mm Pfund and coordinate CIE‐Lab L = 89.72–95.18, a = ?1.28 to 1.05, b = 16.99–21.79, C = 17–21.82, H = 87.23°–92.01°; hydroximethylfurfural ≤10 mg kg^?1; free acidity ≤28 milliequivalents/litre and moisture ≤18.5%. From the sensorial study, the following profile, based on the evaluation of attributes on a five‐point scale, was obtained: colour white–pale yellow, fluidity (4.22), odour intensity (3.55), citrus blossom aroma/odour intensity (3.6/3.8), sweetness (3.14), acidity (2.36), freshness (61.5%) and persistence (2.9).     

Approaches to understanding the contribution of anthocyanins to the antioxidant capacity of pasteurized pomegranate juices

Influence of processing and storage conditions on anthocyanin stability and antioxidant activity of clarified and cloudy juices from arils of the ‘Mollar’ pomegranate variety was studied. Clarification process reduced the content of total monomeric and individual anthocyanins, and increased the antioxidant activity of pomegranate juice. Thermal treatments (65 and 90 °C for 30 or 5 s) decreased the percentage of polymeric anthocyanin form, increasing on the contrary the monomeric one. In any case, storage temperature was the main factor affecting all the parameters tested. Cyanidin 3-O-glucoside (Cy3G) was more instable than delphinidin 3,5-di (Dp3,5dG) and cyaniding 3,5-diglucosides (Cy3,5dG). A linear relationship was observed between oxygen radical absorbance capacity (ORAC) and total monomeric anthocyanins, suggesting that they contributed strongly to the antioxidant capacity. Results presented in this study show that hurdle technology (heating plus refrigeration) may help to reduce anthocyanin degradation in pasteurized pomegranate juice, avoiding a dramatic impact on its colour and preserving the beneficial effects of this specific bioactive compounds on human health.