Lack of correlation between incidence of rice grain discolouration and panicle brown spot

Grain discolouration of rice is a serious diseases intropical countries, caused both by fungal pathogens like Cochliobolus miyabeanus, Magnaporthe grisea and Sarocladium spp., and by pathogenic and saprophytic bacteria. In Italy, the disease was reported occasionally in the past, mainly as a consequence of severe epidemics of brown spot and blast. However, incidence of discoloured grains has recently increased, in spite of improved fungal disease control. Failure of fungicides to reduce incidence of grain discoloration suggests that pathogens other than fungi may cause the disease. We identified the most sensitive rice varieties grown in Italy and searched for factors increasing disease incidence. Sensitivity of rice varieties was assessed randomly, collecting samples all over the rice-cultivated area. Forty-six percent of the samples (N=39) were of cv Selenio, 18% of cv Loto and 8% of cv Balilla, which resulted the most sensitive varieties with an average discoloured grains incidence of 13.7%, 14.6% and 8.7%, respectively. Results of two-year field trials, carried out in Rosasco (Province of Pavia) on cv Selenio (subsp. Japonica), showed that the percentage of discoloured grains decreased by delaying the date of sowing. Disease incidence was not affected by increasing the level of nitrogen or by fungicide treatments and it was not correlated to panicle brown spot incidence and severity. We are currently studying the microflora associated with discoloured rice grains in order to identify the casual agent of the disease

Encapsulation of grape seed phenolics from winemaking byproducts in hydrogel microbeads – Impact of food matrix and processing on the inhibitory activity towards α-glucosidase

Hydrogel-based encapsulation systems were developed for grape seed phenolics recovered from winemaking byproducts. Proanthocyanidins, monomeric flavanols, flavonols and anthocyanins were extracted from grape seeds with 60% ethanol. Encapsulation of solubilized grape seed phenolics in microbeads with alginate-Ca++ or alginate-chitosan-Ca++ achieved efficiency of 78 and 92%, respectively, higher than those of pure catechin and proanthocyanidins. Encapsulated phenolics showed inhibitory activity towards the brush border enzyme \u3b1-glucosidase, which was chosen as a model bioactivity assay. Grape seed phenolics were retained in the hydrogel structure after mixing of the microbeads with bovine milk or rice drink, pasteurization of these beverages to achieve 7 decimal reductions of Mycobacterium avium subsp. paratubercolosis (equivalent to 72 \u25e6C for 91 s) as well as after intense heat treatment of the rice beverage to achieve 7 decimal reductions of Bacillus cereus (95 \u25e6C for 20 min)

Kinetic study of vitamin D2 degradation in mushroom powder to improve its applications in fortified foods

The aim of this study was to develop a value chain approach to address the need for sustainable vitamin D2 food sources. A combined process of UV-irradiation and air-drying was used to produce a Pleurotus ostreatus powder with a target amount of vitamin D2 as an ingredient for functional foods. The kinetics of vitamin D2 degradation was studied as a function of water activity (aw) in the range 0.11\u20130.75 at 30 \ub0C, and temperature in the range 20\u201340 \ub0C, at aw 0.32. The Guggenheim\u2013Anderson\u2013de Boer equation was applied to model experimental data of moisture content as a function of aw at 30 \ub0C, and the resulting monolayer water activity was found to correspond to the aw level of 0.45. During storage under different environmental conditions, vitamin D2 degradation followed first-order kinetics. The rate constants ranged from 0.00308 to 0.0121 d 121 at aw 0.11 and 0.75 at 30 \ub0C, respectively. The Arrhenius equation was applied to calculate the activation energy for vitamin D2 degradation at aw 0.32, which resulted 37.6 kJ/mol. The kinetics data obtained can be used as a basis to design the best formulation strategy to deliver this vitamin with functional foods

Isolation and characterization of bacteria associated with rice grain discolouration

In Italy, in spite the widespread use of fungicides to control blast and brown spot epidemics, the incidence of discoloured rice grains has recently increased. Widely grown rice varieties like \u2018Selenio\u2019, \u2018Loto\u2019, and \u2018Balilla\u2019 are highly susceptible to grain discolouration. Disease incidence is highest in early sown crops and it is negatively correlated to panicle brown spot incidence and severity. These observations together with lack of fungicides efficacy, suggest that bacteria may cause the disease, as it occurs in tropical countries. To have a better insight into grain discolouration aetiology in Italy we analysed the bacterial population associated with discoloured grains of cv Selenio (N=43) and other varieties (N=8). More than 400 bacterial isolates were obtained. DNA Repetitive Extragenic Palindromic (REP) sequences were amplified for each isolate, using the primer BOXA1R. More than 200 isolates had unique BOX-fingerprint and were further char-acterized with molecular and physiological analyses. About 80% of the bacterial population was composed by Gram-negative species: 60% of these isolates were fermenting, and the majority was Pantoea spp., while 40% resulted strictly aerobic. About 70 isolates were identified as Pseudomonas (sensu stricto) and cluster analysis of ITS1-RFLP data showed 9 major groups. Partial sequences of 16S rDNA of representative isolates were aligned and matched with the following species: Ps. fluorescens, Ps. stutzeri, Ps. fulva and Ps. putida. Acidovorax avenae sub. sp. avenae, a seed-transmitted and highly destructive bacterium in tropical countries, was found in 25% of the rice samples (N=21). Pathogenicity tests provided additional evidence that rice grain discolouration in Italy is due to bacteria