Rye breads

Subjects were randomly assigned to consume daily 70 g of normal dried rye bread (placebo group, = 30), rye bread in which 8% of the rye flour was substituted with phloem powder (low phloem, LP, group, = 30) or bread in which 14% of the rye flour was substituted with phloem powder (high phloem, HP, group, n = 15). Study breads used in our study were different in fiber, lignan and catechin content. The nutrient content of the phloem powder and... 

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. 

JUNTUNEN K S, MAZUR W M, LIUKKONEN K H, UEHARA M, POUTANEN K S, ADLERCREUTZ H C T, MYKKANEN H M (2000) Consumption of wholemeal rye bread increases sermn concentrations and urinary excreation of enterolactone compared with consiunption of white wheat bread in healthy Fiimish men and women, British Journal of Nutrition, 84, 839 6. 

LEiNONEN K s, pouTANEN K s, mykkAnen h m (2000) Rye bread decreases serum total and LDL cholesterol in men with moderately elevated serum cholesterol, Journal of Nutrition, 130, 164-70. 

VANHARANTA M, MURSU J, VOUTILAINEN S, RISSANEN T H, NURMI T, SALONEN R, ADLERCREUTZ C H, SALONEN J T (2002a) Rye bread fortified with phloem increases serum enterolactone level, European Journal of Clinical Nutrition, in press. 

In inner layers, changes are much the same as during boiling. Tocopherols and tocotrienols present in wheat and rye are partially destroyed during baking. In ordinary wheat bread, losses of a-tocopherol amount to about 25%, but in the case of rye bread, prepared by traditional technology, a loss of about 50% was reported (Piironen et al, 1987). Losses of natural antioxidants in coffee brews and tomato puree were also observed (Nicoli et al, 1997). 

Rye, like wheat, has bread making potential and rye dough can develop however, rye bread does not have the potential for expansion that wheat bread does. 

Rye will grow under much harsher conditions than wheat. In Germany and Scandinavia rye breads, either wholly rye or mixed with other grains, are eaten. In the UK, rye is little used and the somewhat bitter flavour that it imparts is in general not appreciated. The small amount of rye used is deployed in health food products, crisp breads and in making rye products to satisfy foreign tastes. 

While some of the products considered above do contain cereal other than wheat it is a small proportion of the whole. In this section the rye breads are either wheat free or contain only a small proportion of wheat. These breads are made either for an agricultural reason, i.e. making bread where wheat will not grow, or to avoid wheat for a health reason. Bread made with a proportion of wheat is known as composite bread. 

Rye Breads. The British consumer, in general, does not like the taste of rye bread. Most of the rye bread made in the UK is for the benefit of immigrant communities that traditionally eat rye bread. In Scandinavia, Central and Eastern Europe, rye breads are eaten as a delicacy not as a substitute for wheat bread. It has been recorded that the Vikings brought rye bread to Britain but they were an immigrant group. 

Types of Rye Bread. The usual descriptions are logical. Rye bread is bread made solely from rye flour, rye/wheat bread contains a minimum of 50% of rye flour while wheat/rye bread contains not less than 50% wheat flour with not less than 10% of rye flour. Some recipes for San Francisco sour dough bread have a proportion of rye flour. No doubt, originally, the prospectors used what ever was available. 

Some sour dough bread is made by using commercial yeast but with a proportion of genuine sour dough. Ordinary baker s yeast is at a disadvantage in rye sour dough because the low pH that is essential for rye bread is not the optimum pH for the yeast. 

Conventional improvers are not used in rye bread but additives are sometimes used to increase the water absorption of the dough. Examples are polysaccharide gums such as guar and locust bean gum as well as pregelatinised potato flour, rice starch or maize starch. 

Triticale flour has been extensively tested in Poland, a country where rye bread is traditional. The best results were obtained by using 90% triticale flour with 10% rye flour. The rye flour was made into a flour brew for 24 hours at 28-29°C. Half the triticale flour was made into a sour dough for 3 hours at 32°C followed by mixing with the rest of the ingredients plus 1.5% of salt on the flour weight. The bread was then scaled and proved for 30 min at 32°C followed by baking at 235-245°C. 

Juntunen, K.S., Mazur, W.M., Liukkonen, K.H., Uehara, M., Poutanen, K.S., Adlercreutz, H.C., and Mykkanen, H.M., Consumption of wholemeal rye bread increases serum concentrations and urinary excretion of enterolactone compared with consumption of white wheat bread in healthy Finnish men and women, Br. J. Nutr., 84, 839, 2000. 

Schieberle, P. and Grosch, W. 1987. Quantitative analysis of aroma compounds in wheat and rye bread crusts using stable isotope dilution assay. J. Agric. Food Chem. 35 252-257. 

A first approach to analyze such volatiles is the application of the AEDA on extracts prepared by dynamic headspace extraction. An apparatus used for the extraction especially of solid foods is shown in Figure 5 [55]. The powdered material is placed into a rotating cylinder and the volatiles are continuously flushed onto a polymer material (Tenax( )) by using a stream of helium (1 L/min). After 3 hr the volatiles are desorbed from the polymer by elution with a small amount of diethyl ether and evaluated by AEDA after concentration. Since different yields may change the composition of the volatiles during headspace extraction [7], it is essential to sensorially evaluate the flavor of the extracts in comparison with the food flavor itself. The following examples show applications of this method on fresh and stored wheat bread crust [55] and on fresh rye bread crust [P. Schieberle and W. Grosch, unpublished results]. 

In an headspace extract of fresh rye bread crust, 3-methylbutanal, (E)-2-nonenal and methional showed the highest FD-factors (Table 4), while 2-acetyl-1-pyrroline, the key odorant of wheat bread crust (cf. Table 3), did not significantly contribute to the rye (rust flavor. Quantitative measurements established [45, 55] that especially the higher odor activity (cf. 3, this chapter) of the boiled potato-like smelling methional in the rye bread crust in combination with the much lower odor activity of the roasty-smelling 2-acetyl-l-pyrroline mainly contribute to the overall flavor differences in rye and wheat bread crusts. 

Odorants showing high FD-factors in a headspace extract of fresh rye bread crust [P. Schieberle and W. Grosch, unpublished results] ... 

Pinto beans Corn flakes Crisped rice cereal Oatmeal Creamed corn White rice Oat ring cereal Noodles Cornbread (HM) English muffin Granola Pancake (mix) Pretzels (hard) Shredded wheat Bagel Rye bread Saltine crackers Whole wheat bread Cracked wheat bread Corn chips Butter crackers Sweet roll White bread Graham crackers Peanut butter... 

O Like roasted rye bread O Nut-like, bitter almond-like... 

The composition of the volatile fraction of bread depends on the bread ingredients, the conditions of dough fermentation and the baking process. This fraction contributes significantly to the desirable flavors of the crust and the crumb. For this reason, the volatile fraction of different bread types has been studied by several authors. Within the more than 280 compounds that have been identified in the volatile fraction of wheat bread, only a relative small number are responsible for the different notes in the aroma profiles of the crust and the crumb. These compounds can be considered as character impact compounds. Approaches to find out the relevant aroma compounds in bread flavors using model systems and the odor unit concept are emphasized in this review. A new technique denominated "aroma extract dilution analysis" was developed based on the odor unit concept and GC-effluent sniffing. It allows the assessment of the relative importance of the aroma compounds of an extract. The application of this technique to extracts of the crust of both wheat and rye breads and to the crumb of wheat bread is discussed. 

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