The effect of roasting on the antioxidant status and phenolic profiles of seven commercial Turkish hazelnut varieties (namely, Çakıldak, Foşa, Karafındık, Mincane, Palaz, Sivri, and Tombul) was assessed. Samples were examined for their total phenolics, oxygen radical absorbance capacity (ORAC) values, condensed tannins, and phenolic acids (free and bound forms). Significant losses (p < 0.05) in total phenolics (~66.3%), ORAC values (~41.6%), condensed tannins (~75.2), and phenolic acids (~42.7) were noted when the hazelnuts were roasted. Some variations both between and within natural and roasted hazelnuts were observed (p < 0.05). Phenolic acids were mainly found in the bound form. Gallic, protocatechuic, p-coumaric, and ferulic + sinapic acids were present in all hazelnut varieties, albeit to different extents, and the first two were dominant. Mincane, in roasted form, had the highest total phenolics, ORAC values, condensed tannins, and phenolic acids. This was due to the presence of some skin in roasted Mincane. No skin was left in all other varieties upon roasting. The present work suggests that roasting results in a significant loss in the antioxidant status and phenolic profiles because of the removal of the skin, which is a rich source of phenolics. It is highly recommended to consume natural hazelnut instead of the roasted counterpart to take advantage of all of the functional benefits of this nut.

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SummaryThe oxidation of ammonium ion to nitrite and nitrate ion (nitrification) has been studied in a laboratory scale fluidized sand bed reactor with attached microbial growth. The undefined population of Nifrobacteracea organisms were immobilized on the sand particles by natural attachment after 2-3 months of adaptation. General balance equations have been formulated for a recycle reactor and oxygenation tank system. Kinetic experiments in the reactor and in a microrespirometer have been analyzed in terms of double Michaelis-Menten rate expression for the nitrogenous reactants and dissolved oxygen. Dynamic simulation of the batch integral reactor system was used to establish the error in the kinetic constants which arose due to assuming differential behavior. Design guidelines have been developed for the oxygen requirements in terms of oxygen transfer coefficients, oxygen enrichment, and liquid recycle rate.

A four-component, diffusion-reaction model with double Michaelis-Menten kinetics was used to describe the experimental data obtained from a laboratory biofilm, fluidized-bed nitrification reactor. Theory and experiment demonstrated that the stoichiometric ratio (3.5 mg O(2)/mg NH(4)(+)-N) can be employed as a criterion to determine whether the limiting substrate is oxygen or ammonia. For the present work, in the range of concentrations where limitation occurred, 4 mg/L NH(4)(+)-N and 14 mg/L O(2), the ratio of oxygen to ammonia in the bulk liquid determined which substrate was penetration-limiting-O(2) if <3.5 and NH(4)(+) if > 3.5. Half-order kinetics with respect to the limiting substrate described the apparent overall rates. Simulations provided biofilm concentration profiles which demonstrated the role of the oxygen-ammonia ratio. Experiments indicated that, generally, high NO(2)(-) concentrations can be expected. These depend on the residence time, biofilm area, and oxygen concentration. This dependency was investigated with the model, as was the parametric sensitivity with respect to the saturation constants. Particularly important for the NO(2)(-) levels were the ratios of the saturation constants for oxygen.