Optimization of Matrix Solid-Phase Dispersion Method for Extraction of Aflatoxins from Cornmeal

An extraction method for simultaneous determination of aflatoxins (AFLAs) G2, G1, B2, and B1 in cornmeal, based on vortex-assisted matrix solid-phase dispersion (MSPD) and high-performance liquid chromatography (HPLC) with fluorescence detection was optimized by a central composite design, validated and applied. Multivariate analysis was performed to evaluate the effect of cornmeal composition on AFLA extraction. The amount and proportion of solid support (celite and C18) and volume of elution solvent (methanol and acetonitrile) were the variables tested. The mobile phase of methanol/acetonitrile/water (24:14:62, v/v/v) in isocratic elution mode provided satisfactory AFLA separation. The best recoveries (85.7 to 114.8%) were obtained when the sample preparation contained 25 mg C18 as solid support and 10 mL of elution solvent. The limits of detection ranged from 0.01 to 0.04 ng g^?1, and the limits of quantification varied from 0.02 to 0.1 ng g^?1. The optimized method was suitable for coarse and medium grind cornmeal. Multivariate correlation analysis showed that the main interferers for AFLA recovery were proteins and sugars.     

Winery grape-residue extract: Effects on quality and sensory attributes of cooked chicken meat

Sensory analysis, instrumental color, pH, and thiobarbituric acid reactive substances (TBARS) were determined on cooked chicken meat with and without grape seed extract during refrigerated storage. The effectiveness of extracts of winery grape residue from the grape varieties ‘Isabel’ and ‘Niagara’ were tested to evaluate their effectiveness at delaying lipid oxidation in cooked chicken meat and stored under refrigeration (4±1°C). The samples were aerobically and vacuum packaged and stored for 14 days. ‘Isabel’ grape extract (IGE) and ‘Niagara’ grape extract (NGE) proved effective at promoting oxidative stability when applied at concentrations of 40 or 60 mg of gallic acid equivalents (GAE)/kg, with results similar to the synthetic antioxidant butylated hydroxytoluene (BHT). The antioxidant efficiency of the extracts was highly dependent on the concentration used. The addition of grape-residue extracts combined with vacuum packaging proved to be a good method for increasing lipid stability in cooked chicken meat stored under refrigeration.     

Orientationability analyses of a special class of the Stewart–Gough parallel manipulators using the unit quaternion representation

This paper addresses the orientation-singularity and orientationability analyses of a special class of the Stewart–Gough parallel manipulators whose moving and base platforms are two similar semi-symmetrical hexagons. Employing a unit quaternion to represent the orientation of the moving platform, an analytical expression representing the singularity locus of this class of parallel manipulators in a six-dimensional Cartesian space is obtained. It shows that for a given orientation, the position-singularity locus is a cubic polynomial expression in the moving platform position parameters, and for a given position, the orientation-singularity locus is an analytical expression but not a polynomial directly with respect to the mobile platform orientation parameters. Further inspection shows that for the special class of parallel manipulators, there must exist a nonsingular orientation void in the orientation space around the orientation origin for each position in the position-workspace. Therefore, a new performance index referred to as orientationability is introduced to describe the orientation capability of the special class of manipulators at a given position. A discretization algorithm is proposed for the computation of the orientationability of the special class of manipulators. Moreover, effects of the design parameters and position parameters on the orientationability are investigated in details. Based on the orientationability performance index, another novel performance index referred to as practical orientationability is presented which represents the practical orientation capability of the manipulator at a given position. The practical orientationability not only can satisfy all the kinematic demands and constraints of such class of manipulators, but also can guarantee that the manipulator is nonsingular.