Bread lipids

In our study, consumption of rye bread or rye bread with phloem did not have an effect on serum lipids (total, LDL or HDL cholesterol or triglycerides) (Table 14.4). This is contrary to a recent finding suggesting that soluble fiber from rye bread decreased the concentrations of cholesterol (Leinonen et al., 2000). In that study ingestion of rye bread (220 g/d) with naturally high amounts of insoluble (18 g/d) and soluble fiber (4 g/d) decreased the LDL concentrations by 8% in hypercholesterolemic men. The researchers speculated that soluble fiber, maybe P-glucan, was responsible for the hypocholesterolemic effect. The amount of rye bread (70 g/d vs 220 g/d), the amount of total (5.9-11.8 g/d vs 22.1 g/d) and soluble fiber (0.6-1.3 g/d vs 4 g/d) ingested in this study was considerably less, and could explain the lack of effects on blood lipids in our study. 

Although most naturally occurring lipids contain fatty acids with an even number of carbon atoms, fatty acids with an odd number of carbons are common in the lipids of many plants and some marine organisms. Cattle and other ruminant animals form large amounts of the three-carbon propionate (CH3—CH2—COO ) during fermentation of carbohydrates in the rumen. The propionate is absorbed into the blood and oxidized by the liver and other tissues. And small quantities of propionate are added as a mold inhibitor to some breads and cereals, thus entering the human diet. 

In terms of human dietary requirements, much of the wheat for breadmaking in the United States is produced in selenium-adequate sections of the country. Bread is generally a good source of dietary selenium, Selenomethionine decomposes lipid peroxides and inhibits in vivo lipid peroxidation in tissues of vitamin-E-deficient chicks. Selenocysdne catalyzes the decomposition of organic hydroperoxides. Selenoproteins show a high degree of inhibition of lipid peroxidation in livers of sheep, chickens, and rats, Thus, some forms of selenium exhibit in vivo antioxidant behavior,... 

The flavor compounds of the crust from the chemically leavened model bread were then compared to those recently identified (6) in the crust of a standard wheat bread which was leavened by addition of yeast (Table I). One striking difference was that Acp (No. 16), which showed the highest FD-factor in the yeast-leavened bread showed a very low FD-factor in the chemically leavened bread. This indicated, that the flour contained only minor amounts of the precursor (s) for the formation of Acp. On the other hand, 2(E),4(E)-decadienal, 2(E),4(E)-nonadienal, l-octen-3-one and 2(Z)-nonenal, which are undoubtedly formed by a heat-induced oxidative degradation of the flour lipids, became predominant odorants in the chemically leavened compared to the yeast-leavened bread. 

In the food industry, lipases are used in lipid modification processes. In these processes the texture, digestibility, or physical properties of natural lipids are modified by lipase-catalyzed transesterification reactions with lipids other than the original fatty acids. In the baking industry, lipases are used to influence the quality of bread through modification of the wheat flour lipids. Finally lipases are used for flavor enhancement of cheese in the dairy industry. 

The significance of starch-lipid complexes in bread has been reviewed.866 Earlier, the role of lipids and other emulsifiers was also reviewed.852,867-869... 

For such starchy foods as noodles, cakes, pastries, processed potato food, and puddings, lipids improve the texture. The tendency of bread to staling is also related to the presence of lipids and emulsifiers. In order to satisfy market demands, it is important to optimize the water-binding capacity, the rate of water sorption, and the swelling power. The effects of lipids on these properties is under ongoing study. The mode of application of lipids is also a factor which controls functional properties.851-853 869 The effect of all these factors on bread quality has been recognized.870-873... 

Li, W., Dobraszczyk, B.J., and Wilde, P.J. (2004). Surface properties and locations of gluten proteins and lipids revealed using confocal scanning laser microscopy in bread dough,... 

The lipids, although present in a very small amount, are also of critical importance for the bread making process. The lipids themselves form Hu, La and L3 liquid-crystalline and liquid phases respectively with increasing water content. 

The most important category of polar lipids used in European bread making are DATEM (Diacetyl tartaric acid esters of monoglycerides). 

Today, more than 2300 different enzymes are catalogued by the Enzyme Commission of the International Union of Biochemistry (TUB). The enzyme nomenclature proposed by the lUB uses the name of the substrate (the material that is affected by the enzyme) followed by the suffix ase . For example, the enzymes affecting amylum (Latin for starch ) are called amylases. Enzymes affecting lipids, cellulose and proteins are named lipases, cellulases and proteases, respectively. However, many enzymes are still named by their original names. Diastase, trypsin, papain, lactase, etc. are examples of old names which were used before the official TUB names were proposed. Names of proteases originally had the suffix in and are still in use in the traditional industries such as breweries and bread bakeries. 

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