The effect of heat on the vitamin B₆ of milk: II. A comparison of biological and microbiological tests of evaporated milk

Abstract

Unsweetened evaporated milk is widely used in infant feeding. This product is subjected to drastic heat treatment during sterilization in the can. Lately there have been several reports (l, 2, 3, 4, 5, 6) that in the process of manufacture evaporated milk loses a large part of its original vitamin B 6 activity. According to Tomarelli, Spence & Bernhart(5) the loss of vitamin B 6 , as judged microbiologically, is much less than that determined with rats. We present here the results of a reinvestigation of the problem. The vitamin B 6 activities of raw, evaporated and stored evaporated milk were measured with rats, and chicks, and also microbiologically. In addition, the activities of the pure analogues for chicks and rats were determined to give a basis for comparison. The microbiological techniques have been separately studied by one of us and the findings are set out in the accompanying paper (7). EXPERIMENTAL MaterialsFrom a 36 gal. bulk of fresh mixed full cream milk from the N.I.R.D. herd, 18 gal. were freeze-dried immediately. The other 18 gal. were evaporated, canned and sterilized as described in (8). Half was freeze-dried immediately and half after 6 months storage at room temperature. The freeze-dried milks were stored at -15° C. in air-tight containers until required.Solutions of the pure vitamins, pyridoxine hydrochloride and pyridoxamine dihydrochloride (Roche Products Ltd.) and pyridoxal hydrochloride (L. Light and Co.) were made to contain 500 fig. free base/ml, and used as described below. Chick assaysThe method developed by Coates, Kon & Shepheard (9) was used. The basal diet given in Table 1 contains, with the exception of vitamin B 6 , all characterized vitamins believed to be essential for the chick. With vitamin B 6 added in sufficient quantities it supports excellent growth. As prepared, the diet is a fine powder not readily eaten by chicks and past experience has shown that it is much better granulated.The freeze-dried milk samples were incorporated into the diet to form 25,12-5 or 6-25% of it, replacing an equal weight of casein and dextrin (in the ratio 3:2). These quantities were too large to be given separately by mouth. For this reason the pure analogues were tested in the same way, being included during granulation at the rate of 250,125, 62-5 or

Relative biological activity of nonphosphorylated vitamin B-6 compounds in the rat

“…When the level of protein in the diets was increased to either 20% or as high as 50% of the total diet, growth-related parameters indicated higher responses to PN in the diet relative to PL and PM (Table V). It has been suggested in earlier work that intestinal microorganisms may preferentially utilize PL and PM in the diet, leading to decreased availability of and therefore decreased rat responses to dietary PL and PM (Waibel et al, 1952;Davies et al, 1959). Analysis of fecal vitamin B-6 indicated no differences between total vitamin B-6 in fecal samples of low-and high-protein basal diets (1.95 ± 0.12 and 1.71 ± 0.24 nmol of vitamin B-6/g of sample, respectively), regardless of dietary vitamin B-6 concentration.…”

Nutritional effects of food processing

“…I t has been shown in several foods that pyridoxine is not stable to heat (Woodring & Storvick, 1960) and that, for example, 45-70% can be lost during the evaporation of milk, with further losses on storage (Davies, Gregory & Henry, 1959).…”

Vitamin B6 content of feeds

“…The three natural forms of vitamin B6 (pyridoxine, pyridoxamine, and pyridoxal) show varying activity for poultry. Thus, pyridoxine is usually more active than pyridoxal and pyridoxamine in promoting growth (Davies et al, 1959;Luckey et al, 1945;Sarma et al, 1946). Waibel et al (1952) have reported that pyridoxal and pyridoxamine are as active as pyridoxine when autoclaved starch is the dietary carbohydrate, but less active than pyridoxine when sucrose or glucose was the carbohydrate.…”