Suomalaisessa leivonnassa tapahtuvista tiamiinihäviöistä

Authors

• L. H. Pulkki OTK:n myllylaboratorio, Helsinki
• K. Puutula OTK:n myllylaboratorio, Helsinki
• U.-R. Laurila OTK:n myllylaboratorio, Helsinki

DOI: https://doi.org/10.23986/afsci.71281

Abstract

The investigation comprised a number of different types of wheat and rye bread. They could be considered to represent the most common types of bread in Finland. A part of the flours were still of the standard conditioned by the war-time regulations, a part can be regarded as normal. Customary baking technique was employed. The vitamin content of the crumb and of the crust of the loaf were determined separately in each case. The bread types examined were as follows:
Soft types of wheat bread
1. The so-called French bread (weight of the loaf 400 g., volume 1530 ml., height 65 mm., length 335 mm., breadth 90 mm.) made from half-white wheat flour of war-time qaulity (ash content 0.85 %, dry basis).
2. The so-called yeast bread, leavened with yeast, round loaf (weight 446 g., volume 920 ml., height 65 mm., diameter 145 mm.) made from dark high-extraction flour (mill stream BM3, ash content 4.00 %).
3. Yeast bread, round loaf (weight 389 g., volume 730 ml., height 67 mm., diameter 135 mm.) from the same flour as the previous one (2) but vitaminized with thiamine hydrochloride.
4. Whole-meal yeast bread, round loaf (height 60 mm., diameter 158 mm.).
5. Sweet bread (weight of the loaf 460 g., height 55 mm., length 330 mm., breadth 100 mm.) made from fine white flour (mill stream 82, ash content 0.70 %). In addition to flour, the dough contained 3.5 % eggs, 13 % butter, 10 % sugar, 1 %*salt, 3 % yeast ,35 % milk, and 5 % water colculated on the weight of flour.
Soft types of rye bread
6. Whole-meal sour bread, leavened with acid ferment, round loaf (height 60 mm., diameter 143 mm.).
7. Whole-meal sour bread, leavened with acid ferment, round loaf with a hole in the centre (weight 378 g., volume 580 ml., height 24 mm., diameter 195 mm.)
8. Whole-meal bread, leavened with yeast, round loaf) weight 370 g., volume 530 ml., height mm., diameter 143 mm.).
9. Strongly fermented bread (height of the loaf 70 mm., diam. 193 mm.) made from a mixture of rye whole-meal and high-extraction wheat flour (97; 3).
10. Sour bread (weight of the loaf 470 g., volume 645 ml., height 55 mm., diam. 146 mm.) made from a mixture of rye whole-meal and high-extraction wheat flour (85 : 15).
Hard thin bread (crisp bread)
11. Whole-meal wheat bread, leavened with yeast (thickness of the loaf 9 mm., diam. 230 mm water content 8.4 %) (same dough as in n:o 4).
12. Sout bread from a mixture of rye whole-meal and highextraction wheat flour (same as no. 9) (thickness of the loaf 6 mm., diam. 230 mm., water content 9.1 %).
13. Whole-meal rye bread, leavened with yeast, commercial quality (Elanto's bakery, size of the loaf 7,5x240x265 mm., water content 9.7 %).
14. Whole-meal rye bread, leavened with yeast, commercial quality (Elanto's bakery, size of the loaf 6.5x240x280 mm., water content 8.4 %).
Customary baking procedure, adapted to each bread type, was followed. The additional ingredients were: common salt 1—2% and yeast 3 % of the weight of the flour. In making the sour bread (loaves nos. 6,7, 9, 10, 12) and acid ferment was used, instead of yeast, in 1.3—1.7 % of the weight of flour to raise the dough. The pH of the sour bread was 3.32—3.95. Baking was carried out in this laboratory, except that two of the hard thin loaves were made in a big Finnish bakery (Elanto). There the baking was performed in a wire-net travelling oven, the temperature being, with no 3, at the start 270°C and at the end 230°C, and with no 6, 280°C and 230°C respectively. The baking temperature of the wheat loaves was 225—240°C, that of the rye loaves 240—260°C Vitamin B1 was determined in the soft loaves, from which the crust could be removed, in the entire loaf, and besides, in the crumb and in the bottom and top crust separately. For this purpose the crust was very carefully removed from the loaf. It weighed 20—30 % of the total weight of the loaf. Determination of vitamin B1 was made according to the method of Feilenberg and Bernhard (9, 10). For the enzymatic hydrolysis diastase and papain were used and in some experiments cysteine for reduction of the disulphide form of thiamine. However, cysteine was not found to affect the results. Before oxidation to thiochrome the solution to be examined was purified by shaking it twice with 2.5 volumes of isobutanol (12). This because we had previously noted that the extracts of rye-meal and ryebread have a strong fluorescense of their own (19). The same is true of the extracts obtained from the crust of wheat bread. The method of Andrews and Nordgren (1) was also tested for determination of thiamine. The results obtained were in fairly good agreement with these obtained by the first mentioned method. The loss of vitamin B1 occuring in baking was 10—25 % of the initial amount (Table 2). In the group of soft wheat bread the loss was smaller (11 %) in the whole-meal loaves than in the others (16 —20 %). The difference between wheat and rye bread was not great. The loss was 15—25 % in the soft rye bread, or slightly higher than in the wheat bread. This may be due, for instance, to differences in the baking temperature or in the acidity. The loss was regularly greater in the crust of bread than in the crumb, in certain cases 3, even 4 times greater. In the bottom crust the loss was always greater than in the top crust. In particular, the attention was drawn to the fact that in the hard thin crisp bread which in fact consists of crust only, the losses of vitamin B1 were of the same order as in the corresponding soft-bread loaves. Thus, for instance, the loss was 11 % in a yeast bread loaf (no. 4) made from wheat whole-meal and 14 % in the hard thin loaf (no. 11) from the same material. In the loaf (no. 9) made from mixed rye meal the loss was 21 %, while in the corresponding crisp bread (loaf no. 12) it was 15 %- For the sake of comparison some data have been collected from the literature concerning the losses of thiamine in baking (Table 1).