The effect of inulin on the shape and quality of whole wheat bread was studied with self-made whole wheat bread as experimental sample. By optimizing the formula technology of whole wheat bread with inulin, and through sensory evaluation, the sensory quality factors such as softness, size, smell, taste and texture of bread were scored to determine the best addition amount of inulin in whole wheat bread. The results showed that the specific volume of whole wheat bread first increased and then decreased, the water content first increased and then decreased, and the water retention continued to increase. On the whole, it shows a trend of rising first and then falling. When the content of inulin reached 6%, the moisture content reached 45.9 1% and the specific volume reached 6.92 ml/g. At this time, the sensory evaluation was the highest, and whole wheat bread with good flavor and texture could be produced.

Keywords: whole wheat bread; Inulin; affect

1 Introduction

Overview of Inulin 1. 1 Inulin, also known as inulin, is a kind of fructan obtained by purifying the roots of Inula inula in the early19th century, and is called inulin. In nature, inulin content in Jerusalem artichoke chicory is very rich, which are 14% ~ 19% and 15% ~ 20%[ 1] respectively.

1. 1. 1 inulin is found in all kinds of creatures in nature, but its content in natural plants is much higher than that of bacteria and fungi. Relevant scientific research results show that there are more than 30,000 kinds of herbs containing inulin, including monocotyledonous herbs such as Liliaceae and Gramineae, and dicotyledonous herbs such as Compositae, Platycodon and Gentianaceae [2]. Because chicory and Jerusalem artichoke are rich in inulin in nature, they are often used as raw materials for inulin processing industry. In foreign countries, inulin is mainly extracted from chicory, while in China, Jerusalem artichoke is mainly extracted by spray drying, and processed by hydrothermal method and microwave method [3].

1. 1.2 The structure of inulin is composed of D- fructofuran, which is a linear polysaccharide with glucose residue at the end and β(2→ 1) bond. The specific chemical formula is shown in figure 1. 1.

Fig. 1. 1 inulin chemical structure The polymerization degree (DP) of inulin is generally 2-60. Generally speaking, inulin with average moisture DP≤ 10 mainly belongs to short-chain polycyclic inulin or other short-chain fructooligosaccharides, and inulin with average DP≥23 is called long-chain inulin or fructooligosaccharides. Inulin extracted from natural plants contains short chains and polyfructose. Monosaccharide and disaccharide are very common in short-chain inulin and natural inulin products, with slightly sweet taste; Long-chain inulin basically contains no monosaccharide and disaccharide, so it has no sweetness [4].

1. 1.3 nutritional value and physiological function of inulin as a soluble dietary fiber, inulin has more prominent physiological functions than ordinary dietary fiber, fruits and vegetables, cereals, beans and fungi. , often used as a standard reference for studying the efficacy of other prebiotics. Its specific physiological functions are as follows:

(1) controlling blood lipids Inulin can effectively control human blood lipids because it can change the proportion of high-density lipoprotein in human serum total cholesterol by controlling the content of low-density lipoprotein cholesterol and serum total cholesterol. Through investigation, it was found that among people aged 50-90, the contents of triglyceride and total cholesterol in blood of people who insisted on taking 8g inulin every day were lower than those who did not [5]; Through the clinical study on the frequency change of 8g inulin daily intake in 18 diabetic patients for two weeks, it was found that the cholesterol content in human serum decreased by 7.9%, but HDL- cholesterol remained unchanged. Compared with the control group, the body function has not changed [6]. Brighenti et al. [7] found through many studies on 12 young healthy men that after 9g inulin was ingested in breakfast, the triglyceride decreased by 8.2% four weeks later [8].

(2) Hypoglycemic inulin belongs to carbohydrate, which will not directly cause the obvious increase of basic glucose hormone content in uric acid of patients. It is generally located in the upper part of human gastrointestinal tract, and will not become monosaccharide due to hydrolysis, so it plays an important role in controlling blood sugar and insulin. Relevant scientific research results confirm that the combination of fructooligosaccharides in stomach and colon cells can directly reduce the fat content in human blood sugar system by using the content of short-chain saturated fatty acids [9].

(3) Improving mineral utilization rate Inulin also helps people digest and absorb foods rich in minerals such as Ca2+, Mg2+ and Zn2+. It has been proved that if teenagers eat 8g/d (natural inulin) for a long time, the utilization rate of Ca in body bones can be improved. Enhance the lipid density and comprehensive content of minerals in human bones.

The specific ways are as follows: ① the crypt of body mucosa becomes shallow under the action of inulin, and short-chain fat is produced under the action of fermentation to promote the absorption of inulin; (2) Under the action of fermentation, the acid content is further expanded, which reduces the pH value of colon, accelerates the dissolution of minerals and improves the bioavailability; ③ Inulin can promote the secretion of phytase, release a lot of phytic acid, and further promote the absorption of minerals.

(4) Adjusting the balance of intestinal flora Inulin, as a high-quality water-soluble dietary fiber, is not directly affected by the concentration of gastric acid in human body, but effectively improves the aseptic environment of human intestine under the joint action of various microorganisms in stomach and colon. Relevant research data confirmed that the number of initial Bifidobacterium in human large intestine determines its reproduction speed. If there are fewer initial bifidobacteria, the effect of inulin is more significant, and if there are more initial bifidobacteria, the effect of inulin is worse. Intake of inulin can also effectively help to enhance the normal peristalsis of all gastrointestinal tract and large intestine, increase the digestive function of gastrointestinal tract, improve people's appetite and enhance their own immunity.

(5) Reduce the reproduction speed of toxic fermentation products, protect the liver and prevent colon cancer food from being transported to the colon. Under the action of various intestinal flora, a large number of toxic biological metabolic oxidation products will be produced rapidly, and the newly generated short-chain fatty acids will increase the acidity of the colon environment, effectively slow down the reproduction speed of saprophytic bacteria, greatly reduce the production of toxic substances, and protect the health of the intestinal wall. Under the action of inulin, toxic carcinogens can be significantly reduced. With the continuous improvement of people's quality of life in defecation, the acidity in feces increases sharply, which makes the toxic carcinogen inulin excreted quickly, promotes the production of a large number of short-chain saturated fatty acids, and effectively reduces the incidence of colon cancer.

(6) Anti-constipation and treatment of obesity Dietary fiber can make food digest faster and improve the discharge of feces, which has a significant effect on preventing constipation. The fiber in these diets may also greatly improve the digestive viscosity of these foods, so that the peristaltic speed of these foods directly entering the intestine and small intestine is obviously slowed down, thus reducing hunger and effectively controlling food intake.

(7) Inulin contains a small amount of 2-9 fructooligosaccharides. Relevant scientific research results confirmed that under the stimulation of fructooligosaccharides, the expression level of nutritional metabolic factors in cerebral cortex cells will increase rapidly, which can effectively help protect glucocorticoid-induced brain neurons and eliminate depression [10].

(8) Reduce the risk of cancer and improve immunity. Inulin may bind to the lectin receptor of pathogens, so that its receptor cannot adhere to the intestinal wall of bacteria. Inulin can also stimulate the immune system, activate phagocytes, produce antibiotics, reduce the production of toxic substances and balance the intestinal flora by promoting the growth and proliferation of Bifidobacterium [1 1]. Trans-lactic acid and short-chain trans-fatty acids produced by catalytic fermentation of inulin in human large intestine solution obviously reduce the activity of β -glucosidase and are beneficial to inhibit the reasonable excretion of carcinogens such as nitrosamines and indole in large intestine [12] [13].

1. 1.4 application of inulin in food industry inulin has good food processing performance, such as the appearance of inulin is white and white powder, which has the processing characteristics of organic powder similar to oatmeal and has no bad chemical smell. Compared with common dietary protein fibers such as oat dietary fiber and soybean dietary fiber, inulin also has good organic water solubility and is slightly sweet, and can quickly form a smooth and delicate solidified fat rubber fiber structure. Adding inulin to baked products can make dough more stable, promote water absorption, expand the volume of bread and make bread more elastic.

Inulin is also the main production material of food and beverage, and almost all foods contain inulin. Inulin can be found in baked daily food, snacks, baby products, skin care cultural products and ice cream. Inulin is very stable to high temperature heating. Therefore, adding inulin or spices to other unbaked dough and flour products can effectively improve the appearance, texture and better and more effective elasticity of other baked dough, and bring better taste to dough consumers in other baked dough products. The results show that inulin can increase the spreading time of dough and make dough more elastic. Together with inulin, it can improve the emulsifying activity and β -sheet content of wheat protein and reduce its content. Inulin is a high-quality functional ingredient, which is widely used all over the world. As a main dietary supplement, it exists in various products.

1.2 whole wheat bread whole wheat flour refers to whole wheat bread made of various whole wheat bread starches with or without completely removing wheat bran and wheat germ. Wheat bran is rich in various components with high nutritional value, such as dietary protein fiber, and its nutritional value is extremely high [16]. With the steady development of China's socialist economy, people pay more attention to food health after basically solving the demand for food and clothing. Whole grain food has become people's main food. As a whole grain food, whole wheat bread tastes more mellow and has higher nutritional value than white bread. However, the water holding capacity and swelling rate of wheat bran are high, which affects the moisture distribution of dough and destroys its stability. In addition, the fiber in wheat bran will dilute the protein network structure, affect the expansion of gluten, lead to the problems of rough taste, hard texture and lack of elasticity of bread, and lead to the sensory characteristics of bread [17].

1.3 This paper focuses on the content of inulin in whole wheat bread, with the whole wheat bread as the research focus and the characteristic indexes such as volume, water retention, moisture content, specific volume and sensory evaluation as the evaluation system, to study the effects of different inulin content on the quality of whole wheat bread, so as to develop whole wheat bread with suitable taste and rich nutrition, and provide the direction for the development of new food raw materials.

2 materials and methods 2. 1 materials and reagents

Whole wheat bread flour, Xinxiang Liangrun Whole Grain Food Co., Ltd.; Yeast, Angel Yeast Co., Ltd; Natural inulin, Chongqing Wang Jiao Tian Ran Products Co., Ltd.; Vegetable oil (Arowana), Kerry Grain and Oil Co., Ltd.; Salt, Hubei Yan Guang Lantian Salinization Co., Ltd.; Hebei Gu Song agricultural and sideline products sugar co., ltd

NaOH(AR), Tianjin Beichen Fangzheng Reagent Factory; C20H 14O4(AR), Tianjin Dengfeng Chemical Reagent Factory.

2.2 Equipment MB25 moisture analyzer, Orhaus, USA; JA5003B MAX Electronic Balance, Shanghai Yueping Scientific Instrument; Elba oven of Foshan Nanhai Yang Gang Electromechanical Equipment Co., Ltd.; PHS-3C Acidimeter, Shanghai Macro Cover Instrument; BCD-206SM refrigerator, Haier/Haier; B40 mixer, Lian Heng, Guangzhou.

2.3 test methods

2.3. 1 basic formula of whole wheat bread making process: whole wheat flour 400g, dry yeast 5g, vitamin C 15μg, sugar 7g, salt 2g, vegetable oil 25g and warm water 280mL. Before baking, the temperature should be raised to 260℃ in advance and the oven should be preheated 10min[ 18].

The specific operation is shown in Figure 2. 1 below:

If the dough starts, you can remove the plastic film, put the bread 5min the oven for 5 minutes and let it stand for 5 minutes, then raise the temperature to 190℃ and bake it for about 18 to 20 minutes. Finally, take it out and check if the bread is ripe. You can knock to see if there is a hollow sound inside. Take out the bread and cool it at room temperature to get the finished product. Cover the tin mold with plastic film and ferment in a fermentation box (34-40℃) for 30 minutes. Add a bowl of hot water to increase the degree of fermentation, and ferment the dough to twice the size of your finger.

Sprinkle flour on the table and knead the dough on it 10min. In order to form gluten as fully as possible, you need to stretch the dough with the back palm and then hit the dough. Finally, cover the dough with plastic film. Put the listening mold into the oven to preheat, then take it out and clean the oil on the inner surface. Finally, the plastic film is removed and quickly kneaded and shaped. A folding incision is needed in the middle position, so that the size difference between the dough and the listening mold is not big. When you put it into the audition mold, put the smooth side up.

First, prepare a vessel, put vitamin C, yeast, sugar, water and other materials into it, and then stir it quickly and evenly. Secondly, put it in a warm place (34-40℃), and then let it stand for 10min until foam is generated.

Then prepare a plastic box, put salt, flour, oil, inulin and unused sugar in it, and mix and stir the unused water and foamed yeast liquid until the dough is formed.

Fig. 2. 1 whole wheat bread process flow chart

2.3.2 Determination of inulin addition amount Seven groups of whole wheat bread were made, and 0%, 2%, 4%, 6%, 8%, 10% and 12% inulin were added respectively. After cooling, the volume, moisture, acidity and sensory evaluation of bread were measured with the finished product, and the optimum amount of inulin was obtained through analysis.

2.3.3 Quality inspection of whole wheat bread

2.3.3. 1 moisture content the whole wheat bread is cooled at room temperature and then quickly sliced and extracted, and 3-4g whole wheat bread cores are weighed and dried to constant weight at 105℃, and the weight difference and moisture content are calculated.

2.3.3.2 water retention rate is usually used to indicate the water retention capacity of food. The bread core of whole wheat bread is placed in a naturally ventilated room temperature environment, and the inside is cooled at room temperature. 1h, the whole wheat bread core was quickly sliced and extracted, weighed with test paper and recorded. Put the bread in a double glass bag or paper bag in a naturally ventilated environment, and weigh the bread quality every 24 hours.

Calculate the water loss rate according to formula 2. 1

2.3.3.3 bread volume Choose a suitable container and filler, such as millet, cover the bread, take out the filler, measure the filler volume, and calculate the difference between the container volume and the filler volume [19].

2.3.3.4 bread specific volume P= formula 2.2 According to the experimental method of national standard GB/T 2098 1-2007, various indexes such as bread volume and bread quality were experimentally determined. According to Formula 2.2, the specific volume of each bread is comprehensively calculated [20].

The letters in the above formula indicate:

—— Specific volume of bread, in milliliter/gram (ml/g);

—— Volume of bread, in milliliter (ml); M-quality of bread, g.

The acidity of 2.3.3.5 was determined according to GB/T2098 1-2007 [20]. Specific determination steps are shown in Figure 2.2:

Prepare a 200ml triangular flask, put 25ml filtrate into it, add 2-8 drops of phenolphthalein indicator, then titrate it to reddish color with sodium hydroxide standard solution (0. 1mol/L), keep it for 30s, and record the consumed solution volume. At the same time, distilled water was selected for comparative test.

Let stand for 10 minute, then shake for 2 minutes, let stand for 10 minute, and then filter with filter paper or gauze.

Take 25g bread crumbs, which should be accurate to 0. 1g, then put them into 60ml distilled water without carbon dioxide, mash them, transfer them to a 250mL volumetric flask, adjust the volume to the scale, and shake well.

Figure 2.2 Acidity determination method

Calculate the bread acidity according to Formula 2.3.

T=c×V 1-V2m× 1000 (formula 2.3)

Among them:

-acidity, with? ;

—— concentration of sodium hydroxide standard solution in mol/L;

—— The volume of sodium hydroxide standard solution consumed when titrating the test solution, in milliliter (mL);

—— Volume of sodium hydroxide standard solution consumed in blank test, ml; M-mass of the sample, g.

2.3.3.6's sensory evaluation standard refers to GB/T2098 1-2007 "Method for Sensory Evaluation of Bread". Evaluation team 12 people, all of whom are professionals in sensory evaluation, rated bread from color, texture, shape, smell and other aspects. [20]. See Table 2. 1 for specific evaluation criteria.

Table 2. 1 sensory evaluation standard of whole wheat bread: 2020- 16. 1: uniform, without scorching or whitening; 16- 12. 1: uniform, slightly burnt; 12-0. scorching phenomenon 8. 1-0: uneven color, blanching phenomenon, shape 2020- 16. 1: intact, good shaping effect, consistent with the shape, smooth surface without unevenness and spots1. There are a few spots 12-8. 1 min: relatively complete, with cracks on the surface, with poor gloss of 8. 1-0 min: with defects, cracks and black spots, with rough smell on the surface of 2020- 16. 1 min. No odor:12-8.1; Aroma of lightly baked bread: 8.1-0; There is no obvious unique aroma texture of bread: 2020-16.1; The pores are closely arranged like a honeycomb, and the texture is clear. After pressing, it can rebound quickly without dropping slag: 18. Rebound quickly after pressing, and slag dropping is not obvious. 12-8. 1 min: local hardening, slow rebound after pressing, broken slag. 8. 1-0 score: hard, uneven in texture, not easy to rebound after pressing, with fracture and slag dropping. Taste: 2020-16.6438.200006066 No odor 16- 12. 1: soft, not too sticky, not biting, no odor12-8.

The detection of ash content adopts GB 5009.4-20 16, [2 1].

The detection of protein adopts GB 5009.5-20 16[22].

Fat was detected according to GB 5009.6-2003 [23].

The detection of dietary fiber adopts GB 5009.88-2008[24].

The detection of carbohydrate is GB/Z 2 1922-2008[25]. .

3 Results and analysis

3. The effect of1inulin on the moisture content of whole wheat bread is shown in the following figure, which is the effect of inulin on the moisture content of bread. It can be seen from the figure that the more inulin is added, the lower the moisture content of bread, which may be mainly due to the fact that inulin also contains a chemical component with good affinity and hydrophobicity, which strengthens the binding force between dough and water. When the amount of flour additive is low, the addition of inulin will make the surface fascia in the fermented dough quickly and fully form and fully expand during the fermentation softening process, and completely bind the moisture in the fermented dough. If the addition amount is too large, inulin will compete with gluten and starch for water absorption, which will affect the extension of gluten, weaken its retention of CO2 and accelerate water loss.

Fig. 3. 1 Effect of adding inulin on moisture content of whole wheat bread

3.2 The effect of inulin on the water retention rate of whole wheat bread is shown in Figure 3.2, and the effect of inulin addition on the water retention rate of whole wheat bread. From Figure 3.2, we can clearly see that the longer the bread is stored, the faster the water loss in the bread will be, and then the slower it will be. The reason is that in the initial stage of bread storage, the free water on the surface of bread is easy to lose, and with the passage of time, the free water is easy to lose completely. In the later period of storage, the free water on the bread surface has been completely lost, and the bound water in the bread structure has also begun to lose. Compared with free water, bound water is not particularly easy to lose. Under the same storage time, compared with other whole wheat bread without inulin and whole wheat bread with inulin, the water loss rate of the former is lower, and the water loss rate of the former is also positive and negative. This is mainly because inulin is an oligosaccharide with good hydrophilicity and water retention. When the chemical content of inulin is about 65438 0.2%, the water loss rate of inulin in the whole bread should be the lowest. After storing inulin for 6 days, the water loss rate of bread was 9.3%, while that of bread without inulin was 12.7%.

Fig. 3.2 Effect of Inulin on Water Retention of Whole Wheat Bread

3.3 The influence of inulin on the volume of whole wheat bread is shown in Figure 3.3 below, and the volume of each group of inulin whole wheat bread is the size.

As can be seen from the following figure, with the increase of inulin content, the volume of bread first increases and then decreases. This is because a small amount of inulin can promote gluten formation; When the addition amount is too large, inulin will dilute the protein content in gluten, which will affect the formation of gluten network, thus reducing the air holding capacity, making the holes bigger, the internal texture rougher and the volume lower.

Fig. 3.3 Effect of Inulin on the Volume of Whole Wheat Bread

3.4 Effect of Inulin on Specific Volume of Whole Wheat Bread The specific volume determination results of each group of bread are shown in Figure 3.4. With the increase of inulin content, the specific volume of bread first increased and then decreased. When the content of inulin reaches 6%, its specific volume is the largest, and its value is obviously higher than that of blank whole wheat bread without inulin. The structure of inulin dough will affect the specific volume of bread. In the case of low addition, inulin can strengthen the structure of gluten, improve strength and gas retention, so the specific volume of bread increases. If the addition amount is too large, the ingredients in inulin will make the dough system unevenly distributed, affect the formation of gluten network and reduce the structural stability of gluten, so the specific volume of bread will also decrease.

Fig. 3.4 Effect of Inulin on Specific Volume of Whole Wheat Bread

3.5 Effect of Inulin on Acidity of Whole Wheat Bread The acidity of each bread group is shown in Figure 3.5. As can be seen from Figure 3.5, the acidity of inulin whole wheat bread has no obvious change between different addition amounts, but the values are all less than 6? T, which meets the acidity requirements of soft bread in GB/T2098 1-2007.

Fig. 3.5 Effect of Inulin on Acidity of Whole Wheat Bread

3.6 Effect of Inulin on Sensory Quality of Whole Wheat Bread The sensory scores of each bread group are shown in Figure 3.6.

Figure 3.6 Effect of inulin addition on sensory score of whole wheat bread As can be seen from Figure 3.6, with the increase of inulin addition, the food sensory score of whole wheat bread first gradually increased and then decreased, and the sensory gap score of whole wheat bread first gradually decreased and then increased. The appearance, color, flavor, taste and total score of inulin whole wheat bread with different types of variables were scored respectively.

3.7 The determination of the best formula is based on different inulin addition. It can be seen that the sensory score of bread is the highest when the inulin addition is 6%, and the water retention, water content and specific volume of inulin whole wheat bread are better than other addition. When the amount of inulin is within a certain range, the volume of whole wheat bread will increase first and then decrease with the increase of the amount. When the content of inulin is 6% and 8%, it is 0.24 and 0.22 percentage points higher than that when the content of inulin is 0%. When the amount of inulin is 1%, the specific volume will decrease and the internal texture will become. It can be concluded that when the inulin content is 6%, the comprehensive score of whole wheat bread is the highest, and the best formula is finally determined to be 6% inulin content.

3.8 Test results of nutritional components The bread with 6% inulin content was analyzed and tested, and it was found that its moisture content was 4.59g/ 100g, ash content was 1.83g/ 100g, fat content was 7.9g/ 100g and protein content was/kloc.

4 conclusion

This paper discusses the effect of inulin as a food additive on the quality of whole wheat bread. The results show that bread made with inulin can help people make bread with more balanced nutrition and higher dietary fiber content. Compared with bread with inulin, whole wheat bread with 0% inulin has higher water content, finer texture and texture, more elasticity and elasticity, better taste effect, and fuller appearance and color effect. With the increase of inulin content in whole wheat bread, the quality of whole wheat bread first increased and then gradually decreased. When the content of inulin is 6%, the quality of whole wheat bread is the best. Therefore, the quality of whole wheat bread made of inulin is the best in this experiment, and the main nutritional components of whole wheat bread made of the best formula are tested. The test results are as follows: moisture and ash are 45.9 1g/ 100g,1.83g100g, fat and protein are 7.9g/ 100g,14.5g//respectively. Therefore, inulin plays an important role in the continuous improvement of the color, taste and main nutritional value characteristics of whole wheat bread products in China, greatly improving the nutritional quality of whole wheat bread, and providing an important theoretical basis for enriching the varieties of whole wheat bread products in China and the continuous industrialized production technology of inulin whole wheat bread in the future.

At this moment, with great excitement, I would like to express my sincere thanks to my classmates, teachers and, most importantly, my tutor, Mr. Zhang Dan, who helped me finish my thesis and experiment. In the process of preparing my graduation thesis, both the help of my classmates and the professional guidance of my tutor gave me great encouragement, which made me see the dawn of hope when I was at a loss, especially my tutor, who always reminded and urged us and took pains to put forward valuable opinions and detailed comments on my thesis.

In the course of the experiment, there will inevitably be many mistakes. Here, I would like to thank the teachers of various professional courses for their careful teaching in the four years of undergraduate study and life, so that I have enough knowledge reserves to check and correct my mistakes when I resume.

I also want to thank my parents, who raised me and silently supported me behind my back. I can't repay this feeling and love. I only wish my parents good health, comfortable life and all the best!

Finally, thank the teachers for their hard work. Due to the limited knowledge and immature writing level at this stage, there may still be some imperfections in the paper. I hope the teacher can point it out.