THE THERMAL DESTRUCTION OF VITAMIN B₁

Abstract

The only attempt thus far to determine the effeet of temperature on the rate of destiHu-tiou of aneurin is that of Riee and Beuk (1945), wlio studied the rate of destruction of aneuriu in pork at temperatures from 121° 0. to 49° C. Tlicy show a doviaiinii ffom the Arrhcuins etiuation (whieh relates lop; /.• and 1/T) below 77" C. which could bo related to enzyme activity. It has been shown iti the earlier papers of this series that the effect of various faetors on the rate of destruction of aneurin can be motlifled by the eleeti'olytP system, i.e. by the various buffer solutions used to establish the pll, and, consequently, the effect of temperature on the reaction velocity of aneurin (iestructioii has beeu studied in three different buffers. This work thus forms a continuation of the earlier investi{?ations but opportunity was takeu to determine whether there was any deviation from the Arrhenius equation below 77° C. in the absence of biological materials.Tho simplest method of studyiuf; buffer solutions at temperatures «;reater than 100° C. was thotight to be the use of sealed ampoules in whiv^h the solution under investigation could be heated iu an oil hath. When this procedure was adopted with the phosphate buffer, which was studied first, the anomalons results which were obtained led to the discovery that oxygen was capuhle of accelerating the rate of destruction of aneurin, though to different oxtents in different buffer solutions. Thus, in ypt another connection the importance of tlie electrolyte system is apparent. EXPERIMENTAL. Beagenis.The preparation of reagents was carried out in n similar manner to that used in earlier pnpers of this series (Farrer, 1947(Farrer, .i, 1947.Buffer aaJtg. The following solutions were made from A.R. reagenta and distilled water and purified by the CaCOa nbaorption method of Stout and Arnon (1939): 0-5 M Na2lTPO4; potassium hydrogen phtlialate, KHoPO, (0-5 M with respect to each salt). After filtriitioii. the COj was removed Iiy Iioitiiig followin}; the acidification of the fioliition with fiN ITCl (q.v.) He adjustment of the volume was carried out with twice distilled water after the solution had cooled.

Kinetics of thiamin cleavage by sulphite

“…These results indicate that in the cleavage of thiamin by sulphite, in an aqueous solution at pH 5-0 and 250 and at the concentrations of the reactants tested, the overall reaction is unimolecular with respect to thiamin. Farrer (1945) andFarrer &Morrison (1949) also found that the destruction of thiamin in boiling solutions was a first-order reaction with respect to thiamin. The specific reaction-rate constant they reported, however, varied with pH and type of buffer.…”

Thiamin Stability in Simulated Intermediate Moisture Food

“…There are conflicting reports on the effect of oxygen on thiamin degradation. Farrer and Morrison (1949) reported that oxygen can accelerate thermal destruction of thiamin in buffer solution at temperatures greater than 70°C. Williams and Spies (1938) and Mulley et al (1975) concluded that destruction of thiamin was not oxidative.…”

Catalytic effects of stainless steel, teflon, or glass on thermal degradation of thiamin in a tubular laminar-flow reactor

“…Thiamin degradation has been studied in the presence of several different contact surfaces and under diverse conditions. Thiamin solutions have been autoclaved in lacquer-lined cans Liska, 1971,1972) and in glass vials Arnold, 1972,1973;; sealed in glass tubes and immersed in hot water (Arnold et al, 1969;Higuchi, 1962,1963;Beadle et al, 1943;Mclntire and Frost, 1944); boiled and refluxed in glass systems (Booth, 1943;Farrer, 1945aFarrer, ,b, 1947aFarrer, ,b, 1948Farrer, ,1953Farrer, ,1955Farrer and Morrison, 1949); and injected directly into a steam-filled stainless steel chamber (Mulley et al, 1975a,b). The different kinetic parameters reported in these studies may be attributed partly to the catalytic effects of the contact materials on thiamin degradation.…”