Impact of adding flour from Jerusalem artichoke (topinambur, Helianthus tuberosus L.) tubers to wheat flour on the nutritional value of bread

Being a source of proteins, dietary fibers, vitamins, micronutrients and antioxidants, bread is considered to be of global importance in nutrition [7]. Contrary to whole bread, which is relatively high in fiber content (7÷8% of dry matter), white bread contains only 2÷3% fiber on a dry matter basis [11]. Fibers, and more particularly the soluble ones, like inulin and oligofructose, might help to prevent diseases like intestinal infections, colorectal cancers, obesity, cardiovascular diseases and type II diabetes [9]. Fructo and gluco- oligosaccharides stand out for their prebiotic characteristics that positively influence the host by stimulating the growth and/or activity of a limited number of Bifidobacteria and/or Lactobacilli that can improve the host fitness [10].

Therefore, to improve the nutritional quality of white bread, new formulae enriched in dietary fibers can be developed.

Helianthus tuberosus L. (Asteraceae), a perennial plant commonly known as Topinambur or Jerusalem artichoke, contains a big amount of fructose polymers- inulin, around 80% d.b. [15]. Jerusalem artichoke tubers (with 14÷19% inulin) can be a valuable source of inulin [18].

The functional effects of inulin on humans and experimental animals include relief of constipation lower blood glucose levels, improved absorption of calcium, reduced fasting triglycerides, LDL cholesterol, and inhibition of the growth of various kinds of tumors [14]. Marchetti [16] reported that, inulin is a natural polymer that not hydrolysable by the intestinal enzymes, because it has β (2-1) link which is not be hydrolyzed. So it could be considered a calorie free fiber, although some calories may occur due to the digestible fermentation of these by products in the colon. Inulin is such carbohydrates have a high potential nutritional advantage as low energy dietary supplements. It can be used as a source of carbohydrates for diabetic patients and more generally as dietary fiber. During 4 to 6 weeks improves glucose tolerance, decreases glycemia, and partially restores insulin secretion [6].

The flour from Jerusalem artichoke tubers is rich in bioactive components not only inulin type polysaccharides but also pectin, macro-(potassium, calcium, phosphorus) and microelements (silicon, iron, magnesium, zinc, copper, nickel, manganese) and vitamins.

The present study aimed at development of floury mixes with flour from Jerusalem artichoke tubers, intended for production of bread enriched in dietary fibers.

Materials and Methods

Raw Materials. Two commercial types of wheat flour (type 500 and type 1150) and wheat bran were used. The flour from the Jerusalem artichoke tubers, was supplied by a Bulgarian company, trading with products from Jerusalem artichoke. In appearance, it is pale beige-creamy colored powder, with specific sweet taste and odour. Three floury mixes were investigated. The first mix was consisting of 100 g wheat flour type “500”, 3 g artichoke flour, 2 g dry yeast and 1.5 g salt. The second mix-100 g wheat flour type “500”, 10 g wheat bran, 6 g artichoke flour, 2 g dry yeast and 1.5 g salt. The third mix-100 g wheat flour type “1150”, 6 g artichoke flour, 2 g dry yeast and 1.5 g salt. The control mixes consisted of no artichoke flour. The ingredients of every particular floury mix were preliminary mixed all in one and stored as a ready to use mix.

Baking. The floury mixes were stirred for 1 min in the farinograph bowl, after that, the water was added. The amount of water to be used was determined by the farinograph absorption value. The dough was then mixed for 5 min, formed and placed in baking plates (pan-free), and fermented at 30ºC and 80÷90% relative humidity. Baking for each 400 g dough piece was at 230ºC for 17 min. During baking, some water was vaporized in the oven to avoid any extreme dryness of the bread crust. The baked bread was cooled for an hour at room temperature, before being prepared for the consequent analyzes.

Chemical determination and calculations. The moisture content values were obtained by heating a 5-g ground sample at 130ºC for 1 hour using oven method. The fat content determination was carried out using automatic Sohxlet extraction apparatus with petroleum ether [2]. Nitrogen content was determined using Kjeldahl method and was multiplied by a factor of 5.7. The determination of ash content was carried out in accordance with ICC Standard № 104/1 [12]. A total carbohydrate was calculated by difference. The content of fibers was evaluated by the ICC Standard № 156 [13], the content of fructans- by the AOAC Method 999.03 and AACC Method 32.32 [3]. The energy values are calculated by NME (Net Metabolizable Energy) factors. The conversion factor for 1 kcal is 4.184 kJ [8].

Results and Discussion

The chemical constituents of the raw materials used, are shown in Table 1.

Table 1 - Composition of wheat flours, wheat bran and artichoke flour (per 100 g product)

Material	Moisture content [%]	Dietary fibers [% ]	Total carbohydrates [%]	Protein content [%]	Fat content [%]	Ash content [%]
Wheat bran	13.8	32.43	66.12	13.40	3.00	3.68
Wheat flour "500"	14.0	4.41	74.57	10.00	0.90	0.53
Wheat flour "1150"	12.3	8.28	71.80	12.30	2.50	1.10
Artichoke flour	7.0	83.69	84.14	4.32	0.37	4.17

The artichoke flour is rich in dietary fibers and minerals as well, presumably of the high value of the ash content.

The total carbohydrates, the fat content and the protein content (Table 2) are not influenced by the artichoke addition.

Table 2 - Composition of different floury mixes with addition of artichoke flour (per 100 g product)

Floury mixes	Moisture content [%]	Dietary fibers [%]	Total carbohydrates [%]	Protein content [%]	Fat content [%]	Ash content [%]
Control №1	14.0	4.08	74.29	10.10	1.05	0.56
Floury mix №1	13.9	7.37	74.64	9.80	1.05	0.61
Control №2	14.0	7.71	74.07	10.10	1.10	0.73
Floury mix №2	13.8	12.23	74.52	9.70	1.15	0.83
Control №3	12.4	8.27	72.81	12.40	1.50	0.89
Floury mix №3	12.0	12.96	73.48	12.00	1.50	1.02

The ash content of the floury mixes with artichoke is slightly increased. The fiber content of the mixes is related to the presence of wheat bran and of the artichoke flour. A significant increase in the fiber content of the mixes with artichoke flour vs. controls is indicated. The increase for mixes 1, 2 and 3 was respectively with 3.29%, 4.52% and 4.69%.

The content of the total soluble fibers in the mixes with artichoke flour is higher (Table 3), if compared to the control probes.

The addition of artichoke flour does influence the content of the insoluble and the total soluble fibers. The mixes with artichoke flour have higher content of fructans, as the increase for mixes 1, 2 and 3 is respectively with 2.41, 4.25 and 4.20% dry matter basis. The most enriched in fructans floury mix is the third one, because of the type of the flour and of the quantity of the artichoke flour as we can see in Table 1.

The composition of the bread, obtained from the mixes with and without artichoke flour, is shown in Table 4.

Table 3 - Dietary fiber content of floury mixes with artichoke flours

Floury mixes	Dietary fibers, [% dry matter basis]
	Insoluble	Soluble		Total
		Total	Fructans
Control №1	1.90	2.85	0.39	4.75
Floury mix №1	3.26	5.30	2.48	8.56
Control №2	5.21	3.76	0.78	8.97
Floury mix №2	5.92	8.27	5.03	14.19
Control №3	5.62	3.82	1.56	9.44
Floury mix №3	6.46	8.27	5.76	14.73

Table 4 - Composition of bread enriched with artichoke flour (per 100 g product)

Bread	Moisture content [%]	Dietary fibers [%]	Total carbohydrates [%]	Protein content [%]	Fat content [%]	Ash content [%]	Energy value kcal/100g kJ/100g
Bread control №1	37.1	2.62	53.89	7.40	0.20	1.41	234.2 980.0
Bread floury mix №1	38.3	3.39	52.87	7.00	0.25	1.58	227.3 951.1
Bread control №2	40.9	3.70	48.64	8.20	0.40	1.86	214.8 898.6
Bread floury mix №2	39.7	4.57	49.56	8.10	0.50	2.14	216.8 907.0
Bread control №3	41.4	3.75	46.79	9.60	0.45	1.76	212.2 887.8
Bread floury mix №3	41.5	4.77	46.60	9.10	0.65	2.15	209.0 874.3

The bread with artichoke flour had higher content of dietary fibers and higher ash content, if compared to the control bread. The energy value of the enriched breads varies from 209.0 to 227.3 kcal/100 g. The bread with the lowest energy value was obtained from floury mix 3.

The results enabled the bread to be classified as light, as shown by Brasil et al. [5].

The results in Table 5 indicate higher values of the soluble fibers, respectively higher content of fructans, if the bread recipe includes artichoke flour.

Table 5 - Dietary fiber content of bread enriched with artichoke flour

Bread	Dietary fibers, [% dry matter basis]
	Insoluble	Soluble		Total
		Total	Fructans
Bread control №1	2.73	3.38	0.12	6.11
Bread floury mix №1	4.64	3.63	0.68	8.27
Bread control №2	6.48	3.27	0.26	9.75
Bread floury mix №2	6.63	5.01	1.43	11.64
Bread control №3	7.68	3.37	0.49	10.05
Bread floury mix №3	7.94	4.93	1.78	12.87

Comparing Table 3 and Table 5, one can see that the content of the soluble fibers in the baked bread is lower than the content in the floury mixes. The content of the insoluble fibers in the baked bread is higher than the content in the floury mixes.

The lower content of the soluble fibers in the bread could be attributed to the hydrolysis of the soluble fibers by enzymes produced during fermentation and because of the loss of fructans during baking, which can reach up to 38÷45% [1, 5, 17]. The thermostability of inulin has been studied, and it has been found that heating of inulin between 135 and 195ºC results in a significant degradation of inulin (20÷100%) and formation of new products like di-D-fructose [4].

The higher content of the insoluble fibers in the bread is due to processes occurring during baking, as part of the digestive starch goes to resistant starch, and because of interaction between proteins and carbohydrates, some of the soluble components of the system go to the insoluble [19].

Nevertheless, the breads from floury mix 2 and 3 contain sufficient quantity of dietary fibers, in particular fructans, and could be a part of healthy diet.

Conclusions

The results showed that adding artichoke flour to the wheat flour increases the ash content and the total fiber content of the floury mixes. The studied floury mixes contain inulin-type fructans, which act as prebiotic and have good effect on the human organism function, especially on the gut flora, and could be successfully used for producing of bread for preventive nutrition. The bread enriched with artichoke flour had higher content of fructans, as a part of the total dietary fibers, and lower energy value.