Effect of Various Sodium Chloride Mass Fractions on Wheat and Rye Bread Using Different Dough Preparation Techniques

Bread is a staple food in the diet of most European countries and the United States. It is the main source of complex carbohydrate, protein, vitamin B, mineral and dietary fi bre intake; this applies especially to wholemeal bread (1). A decrease in bread consumption in Europe can be seen in the past few years; today approx. 170 g of bread per capita is consumed daily. Despite this, it is still regarded as an important source of sodium chloride in the human diet (2). A high level of bread consumption considerably contributes to exceeding the daily dose of salt of 5.8 g, recommended by the USA National Academy of Medicine, formerly Institute of Medicine (3), equivalent to 2.3 g of sodium (4). According to Brown et al. (5), the physiological daily dose of sodium (<0.6 g) is exceeded by consumers all over the world. Salt consumption in the European and North American diet is believed to depend on the amount of salt added to the most frequently consumed processed food (75 % of total consumption), which also includes cereal products, such as bread. Daily consumption of salt in most European countries ranges from 8 to 11 g per capita (6). According to the European Commission Report (7), the lowest consumption of salt (6.3– 7.3 g per day) was recorded in Germany, Bulgaria, Cyprus and Lithuania, and the highest (13.6 g per day) in the Czech Republic. Such a high consumption of salt was also observed in Slovenia, Hungary and Portugal (12.3–12.7 g per day). According to the report, more salt is usually consumed by males than by females. ISSN 1330-9862 original scientifi c paper


Introduction
Bread is a staple food in the diet of most European countries and the United States.It is the main source of complex carbohydrate, protein, vitamin B, mineral and dietary fi bre intake; this applies especially to wholemeal bread (1).A decrease in bread consumption in Europe can be seen in the past few years; today approx.170 g of bread per capita is consumed daily.Despite this, it is still regarded as an important source of sodium chloride in the human diet (2).A high level of bread consumption considerably contributes to exceeding the daily dose of salt of 5.8 g, recommended by the USA National Academy of Medicine, formerly Institute of Medicine (3), equivalent to 2.3 g of sodium (4).According to Brown et al. (5), the physiological daily dose of sodium (<0.6 g) is exceeded by consumers all over the world.Salt consumption in the European and North American diet is believed to depend on the amount of salt added to the most frequently consumed processed food (75 % of total consumption), which also includes cereal products, such as bread.Daily consumption of salt in most European countries ranges from 8 to 11 g per capita (6).According to the European Commission Report (7), the lowest consumption of salt (6.3-7.3 g per day) was recorded in Germany, Bulgaria, Cyprus and Lithuania, and the highest (13.6 g per day) in the Czech Republic.Such a high consumption of salt was also observed in Slovenia, Hungary and Portugal (12.3-12.7 g per day).According to the report, more salt is usually consumed by males than by females.Salt, as a dough ingredient, has a benefi cial eff ect on the properties of gluten, dough properties and bread taste (8)(9)(10).However, considering its health eff ects, it is believed that its consumption should be reduced.Excessive amounts of consumed salt are believed to contribute to elevated arterial blood pressure, thereby increasing the risk of stroke, heart failure, cardiac infarction, renal and gastric diseases, obesity and osteoporosis (4,8,10,11).The mass fraction of salt added during white bread making in European countries is varied: for example, in Portugal it is 1.67, in the UK 1.01 and in the Netherlands ≤1.8 % (12,13).However, the lower dose of salt in food raises the producers' concern that consumers may not accept products with a less distinctive taste (14).Dötsch et al. (15) and Girgis et al. (16) suggested that sodium chloride content in bread should be reduced gradually, which will help consumers to become accustomed to the change of taste, or which will make the change of taste imperceptible.Furthermore, Noort et al. (17) have shown that in order to reduce the amount of salt without the loss of saltiness intensity, an inhomogeneous distribution of salt in bread can be used.However, considering the fact that consumers eat bread with other food, such as salty meat or cheese, or sweet jams and honey, it is believed that an absence of salt in bread would not aff ect considerably their taste sensations.
Appreciating the need to reduce the sodium chloride content in the diet, the aim of this study is to determine the eff ect of a reduced sodium chloride content on yield, volume, crumb properties and organoleptic properties of bread.
Water absorption was determined according to a method of Gould et al. (19).A mass of 3 g of the fl our sample was weighed into a centrifugal tube, 30 mL of distilled water were added and mixed for 30 s.The sample was allowed to hydrate for 2 h at room temperature.This was followed by centrifugation using a benchtop centrifuge (type 5417R; Eppendorf AG, Hamburg, Germany) at 25 000×g for 10 min.The supernatant was discarded and the hydrated sample was weighed.

Baking experiment
The dough was prepared by the addition of 0.0, 0.5, 1.0 and 1.5 %, by mass, of sodium chloride to the fl our using three techniques: (i) with baker's yeast Saccharomy-ces cerevisiae (3 % of fl our mass).The dough with yeast was prepared with the one-phase method.All ingredients were mixed and the dough was then fermented for 2 h and kneaded for 80 min (white wheat dough) or for 1 h (wholemeal wheat, and white and wholemeal rye dough); (ii) with natural sourdough (30 % of dough mass).Dough with natural sourdough was prepared using a multiphase method for four days.In this method, a predetermined amount of fl our was added daily to the dough, which was fermented for 24 h at 30 °C and (85±2) % relative humidity in a proofi ng chamber (type PL 10; Warmia, Grudziądz, Poland); and (iii) with starter sourdough.Starter SAF Levain LV1 (Lesaff re) containing a mixture of Lactobacillus casei and Lactobacillus brevis bacterial cultures (2 % in total) with Saccharomyces chevalieri yeast (98 %) was used.Dough was prepared using a two-phase method.The fi rst step was the preparation of starter sourdough by using baking culture starter (1 % of total fl our mass), 50 % of the total amount of fl our and 75 % of the total amount of water.These ingredients were carefully mixed, then allowed to ferment for 24 h at 30 °C with continuous mixing using a laboratory water bath shaker (type 357; Elpan, Lubawa, Poland).Bread dough was prepared by adding the rest of the fl our (50 %) and water (25 %), and sodium chloride.The dough was fermented for 2 h.Bread with 1.5 % sodium chloride was used as the control in each of the dough preparation techniques.Each type of bread was baked in triplicate.
All types of dough were mixed in a laboratory dough kneading machine (GM-2; ZBPP, Bydgoszcz, Poland).Dough was fermented in a proofi ng chamber (type PL 10; Warmia) at 30 °C and (85±2) % relative humidity.The bread was baked in an electric laboratory oven (type PL 10; Warmia) at 230 °C for 30 min (wheat bread) or 35 min (rye bread).

Bread quality
The quality of bread was analysed 24 h aft er baking and the following properties were assessed: yield, loaf volume, and elasticity and porosity of the crumb.
In order to determine the bread yield, the dough yield was calculated as the amount of dough obtained from 100 mass parts of fl our with the moisture content of 15 %, expressed in mass percentage (23).The mass of the dough prepared for baking was then determined and the mass of cooled down bread was determined aft er baking.The bread yield was calculated from the following formula: /1/ where Y(bread) is the bread yield in %, Y(dough) is the dough yield in %, m(dough) is the mass of dough ready for baking in g and m(bread) is the mass of cooled down bread in g.Loaf volume of 100 g was measured by seed displacement method (23).
Elasticity of crumb was measured with a universal testing machine (type 4301; Instron Corp., Canton, MA, USA) and expressed as the force necessary to cause elastic deformation of a 2.5-cm cube cut out of the central part of a loaf (24).
Porosity of crumb was measured with a Digital Image Analysis (DIA) set (equipped with lights, camera, and a computer program) based on photographs of 1.5 cm thick slices cut out of the central part of a loaf and expressed in percentage of total cell area per total measured area (25).The light source was a Kaiser RB 5004-HF High Frequency Daylight Copy Light set with 4×36 W fl uorescent light tubes (colour temperature about 5400 K; Kaiser Fototechnik GmbH & Co.KG, Buchen, Germany).Images of bread slices were acquired with a Nikon DXM-1200 (Nikon Inc., Melville, NY, USA) charge-coupled device (CCD) colour camera at a resolution of 1280×1024 pixels.The centre of each slice was converted to grey scale and aft er adjusting the threshold, total cell area was determined using the LUCIA G v. 4.8 soft ware (Laboratory Imaging, Prague, Czech Republic).

Organoleptic evaluation
The sensory att ributes including crust, colour, taste, texture and general acceptance were evaluated by untrained 30-member panel, using a 5-point hedonic scale according to Watt s et al. (26) with 1 representing the lowest score (dislike extremely) and 5 the highest score (like extremely).

Statistical analysis
The results of the study (three parallel repetitions) were statistically analysed with STATISTICA v. 10.0 PL (StatSoft , Cracow, Poland) (27).In order to identify the signifi cance of diff erences between samples, a one-way analysis of variance (ANOVA) was used with Tukey's test with the critical level of signifi cance assumed at p≤0.05.

Results
The fl our used to make the bread had normal colour, taste and smell.All fl our types had good baking value, which was indicated by the calculated quality parameters (Table 1).Rye fl our was characterised by the highest water absorption and the lowest falling numer.The values of falling number, wet gluten yield and Zeleny sedimentation number were the highest in white wheat fl our.Wet gluten yield and Zeleny sedimentation number were not characterised in white and wholemeal fl our.
It was shown that the yield of white wheat bread made with yeast and natural sourdough with a decreased addition of sodium chloride was similar in comparison with the control sample.The greatest increase in bread yield (by 2.59 %) was observed in saltless white wheat bread made with yeast (Table 2).
A similar relationship was observed in saltless white rye bread made with yeast, whose yield was greater by 5.5 % than of the control sample with the addition of 1.5 % of sodium chloride.The yield of the other samples of white rye bread prepared with natural sourdough or starter sourdough was not aff ected by the reduction of the mass fraction of sodium chloride.Also, the yield of all the wholemeal wheat bread loaves prepared with yeast, natural sourdough and starter sourdough was similar, regardless of the mass fraction of added sodium chloride.
Decreasing the mass fraction of sodium chloride affected the bread volume depending on the type of fl our and the technique of dough preparation (Table 3).
The volume of white wheat bread made with each technique of dough preparation increased with decreasing sodium chloride content.The largest volume increase (approx.26 % compared to the control sample) was observed in saltless white wheat bread, both made with yeast and with starter sourdough (Table 3).The volume of saltless wholemeal wheat bread prepared with yeast and starter sourdough was found to decrease by 7.1 and 7.5 % compared to the control sample and the sample prepared with natural sourdough, which increased by 2.4 % (Table 3).The relationship between the volume of white rye bread and sodium chloride addition was inconclusive.A  The values are mean±standard deviation Diff erent lett ers in superscript represent signifi cant diff erences between mean values signifi cant decrease was found of the loaf volume of bread prepared with yeast (maximum decrease by 4.1 %), while with natural sourdough maximum increase was 2.3 %.The volume of white rye bread made from dough prepared with starter sourdough without the addition of sodium chloride decreased by 17 % compared to the bread made with 1.5 % of sodium chloride.Wholemeal wheat bread made with yeast or starter sourdough without the addition of sodium chloride had 7 % smaller volume, while the volume of bread prepared with natural sourdough increased only slightly.A decrease in sodium chloride mass fraction reduced the volume of wholemeal rye bread prepared with yeast by 4-6 % and of that prepared with natural sourdough by approx.3 %, whereas it did not change the volume of bread made with starter sourdough (Table 3).
Firmness of bread crumb was the most aff ected by decreasing sodium chloride content, with the trend varying from one bread type to another (Table 4).
Yeast bread made from white wheat fl our with the reduced mass fraction of sodium chloride had lower fi rmness.The oposite was observed for the bread sample prepared from wholemeal wheat fl our.The other types of yeast bread, wholemeal wheat bread and white rye bread, had increased fi rmness aft er the reduction of the mass fraction of sodium chloride (Table 4).The fi rmness of rye bread prepared with natural sourdough changed similarly; moreover, the fi rmness of saltless wholemeal bread was found to increase threefold (as measured by the crumb compression force).Furthermore, the fi rmness of wheat bread made from white and wholemeal fl our with natural sourdough decreased with the reduction of sodium chloride mass fraction.The fi rmness of white and wholemeal wheat bread and wholemeal rye bread made with starter sourdough signifi cantly increased when sodium chloride content was reduced (Table 4).
The porosity of crumbs of wheat and rye bread depended mainly on the fl our type, as well as on the technique of dough preparation (Fig. 1).
A reduced mass fraction of sodium chloride aff ected the porosity and appearance of crumb diff erently.It was found that the saltless white wheat bread prepared with baker's yeast, compared to a control sample with 1.5 % sodium chloride, was characterised by tough crumb with small pores (Fig. 2).No eff ect of various doses of sodium   chloride on the porosity of crumbs was observed in white wheat bread prepared with natural sourdough and starter sourdough (Fig. 2).A similar relationship was demonstrated for all wholemeal wheat bread types (Figs. 1 and 3).
Porosity of crumbs of white rye bread prepared with yeast and wholemeal rye bread made with natural sourdough increased with the decrease of sodium chloride content (Fig. 1).Moreover, the pores were of various sizes and irregular shapes (Figs. 4 and 5).The opposite relationship was observed in the white rye bread made with natural sourdough (Fig. 1).The porosity of white and wholemeal rye bread made with starter sourdough and wholemeal rye bread containing yeast did not depend on the addition of sodium chloride (Fig. 1).
Reduced mass fractions of sodium chloride changed the results of organoleptic assessments (scores for crust, colour, taste, texture and general acceptance) of bread made with yeast and bread made with starter sourdough to a greater extent than of bread prepared with natural sourdough (Tables 5-7).The sensory properties of bread made from white wheat fl our and white and wholemeal rye fl our with yeast without added sodium chloride were improved (Table 5).The reduction of the mass fraction of sodium chloride did not aff ect the sensory properties of white and wholemeal rye bread and it had litt le eff ect on the properties of white wheat bread when dough was made with natural sourdough (Table 6).An adverse eff ect of reduced amount of sodium chloride was observed only in wheat bread made from wholemeal fl our with natural sourdough, in which the appearance of the crust deteriorated.The reduction of the amount of sodium chloride added to the dough prepared with starter sourdough perceptibly improved the sensory properties of white wheat bread by making it taste bett er, while the deterioration of organoleptic properties was observed in white rye bread (Table 7).

Discussion
Wheat bread made from white fl our can be baked even without the addition of sodium chloride using each 8±0.6) b (188.3±0.5)d (145.3±0.6)c

Fig. 1 .
Fig. 1.Porosity of bread crumbs made with diff erent types of fl our using yeast, natural sourdough and starter sourdough

Table 1 .
Q uality characteristics of fl our types used for dough preparation b (140.9±0.

Table 3 .
Volume of bread loaves made from diff erent fl our types with diff erent leavening agents

Table 4 .
Firmness of bread crumbs made from diff erent fl our types with diff erent leavening agents

Table 7 .
Organoleptic properties of bread made from diff erent types of fl our using starter sourdough