A Spectrophotometric Microtiter-Based Assay of the Ability of UHT-Treated Milk to Reduce XTT.

Abstract

and A spectrophotometric microtiter-based assay was established for quantification of the ability of UHT-treated milk to reduce 3'-{1-L(phenylamino)-carbonyl]-3,4~tetrazolium}-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate (XTT). Under the optimized conditions, 40 pl of a milk sample was mixed with OO pl of 0.5 mM XTr solution (pH 7.0) saturated with menadione in each well of a 96-well nricrotiter plate. The formed XTT formazan in the reaction mixture was determined by an increase in the absorbance difference between that at 492 nm and at 600 nm during the incubation for 20 min at ambient temperature. The use of the absorbance at 600 um as a reference wavelength permitted the determination of XTT formazan without any interference from the turbidity caused by the addition of the milk sample. The present microtiter plate assay could differentiate two kinds of UHT-treated milk with a different extent of thermal treatment. In addition, the reducibility of the UHT-treated milk gradually decreased during storage dependent on the period or temperature. The method was very convenient and economical; it is promising as a method of estimating the extent of the heat treatment of milk and the storage conditions.

Antioxidant Effects of Maillard Reaction Products Obtained from Ovalbumin and DifferentD-Aldohexoses

“…The XTT assay was performed in a 96-well microtiter plate as described by Ukeda et al 24) XTT solution was prepared with 0.2 M potassium phosphate buffer (pH 7.0) containing menadione at the saturation level. Each well contained 40 ml of sample (2% and 4%).…”

Relationship between the XTT Reducibility and Aminoreductone Formed during the Maillard Reaction of Lactose: the Detection of Aminoreductone by HPLC

“…We proposed an assay method for determining the ability of UHT-treated milk to reduce XTT (3¢-[1-(phenylamino)-carbonyl]-3,4-tetrazolium)-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate) as a method for evaluating the extent of the Maillard reaction (Ukeda et al, 1995(Ukeda et al, , 1996(Ukeda et al, and 1998. Compared with the conventional methods, the XTT assay is more rapid and convenient and is found to be applicable for estimating not only the extent of thermal treatment but also the storage conditions.…”

Elucidation of mechanism of aminoreductone formation in the Maillard reaction of lactose

“…The formations of AR in the heated model solutions and milks were determined using an XTT assay, performed in a 96‐well microtitre plate according to the method described by Ukeda et al. (1995, 1996, 1998) and Shimamura et al.…”

“…As the determination of AR has been shown to be useful in distinguishing the extent of the Maillard reaction in milk (Ukeda et al. 1995, 1996, 1998; Shimamura et al.…”