KR100362965B1 - Preparation Method for Yogurt from Milk Added with Purple Sweet Potato - Google Patents

Abstract

The present invention relates to a method for preparing yogurt using purple sweet potato. More specifically, in order to increase the solid content in yogurt production, by replacing a part of skim milk powder with purple sweet potato, it hides the unpleasant taste of skim milk powder and adds anthocyanin pigment, a natural pigment of purple sweet potato, which is highly stable in aqueous solution. The present invention relates to a method for preparing yogurt with improved palatability and functionality while adding purple sweet potato instead of skim milk powder added as a solid content increasing agent.

The purple sweet potato of the present invention can increase the viscosity of the yogurt by using natural pigments and to diversify the color and taste of the yogurt, while lowering the manufacturing cost while improving palatability by using purple sweet potato instead of skim milk powder.

Description

Preparation method of yogurt with purple sweet potato {Preparation Method for Yogurt from Milk Added with Purple Sweet Potato}

The present invention relates to a method for preparing yogurt using purple sweet potato. More specifically, in order to increase the solid content in yogurt production, by replacing a part of skim milk powder with purple sweet potato, it hides the unpleasant taste of skim milk powder and adds anthocyanin pigment, a natural pigment of purple sweet potato, which is highly stable in aqueous solution. It relates to a method for producing a potato flavored yogurt by adding purple sweet potato instead of skim milk powder added as a solid content increasing agent.

Yogurt is fermented with lactic acid bacteria, such as Lactobacillus or Bifi dobacterium , to enhance acidity and flavor. Due to the small amount of active substances, lactic acid bacteria and intestinal growth of lactic acid bacteria, the food and nutrition are very good foods. Years ago, the demand for staple yogurt with high milk content and lactic acid bacteria has been increasing. Staple yogurt recommends 14-18% by weight of milk solids to prevent casein from coagulating by lactic acid during fermentation to form soft gel-like tissues and to prevent tissues from becoming too thin or whey separated. In Korea, dairy companies add 3 to 4% by weight of skim milk powder, or concentrate whole milk or skim milk to increase the milk solids content.In addition to the addition of dairy products such as skim milk powder, soy protein, cereals, sweet potatoes, pumpkins, wolfberry, etc. In addition to the addition of pectin or flesh, and as a fermentation substrate has been attempted to develop a new fermented beverage by using rice, malt, corn, sugar cane, etc. in addition to milk. In addition, yogurt not only varies in quality during storage, lactic acid bacteria can survive at low pH in the stomach to exert an intestinal action, and a high lactose decomposition rate is preferable for digestion of lactobacillus beverages.

The purple sweet potato, which has recently attracted attention as a new natural color pigment, is a cultivar known as Sancheonja, which was native to Kyushu, Japan. It is targeted. The purple sweet potato is dark purple not only in the epidermal layer but also in the flesh because it contains a large amount of anthocyanin, a water-soluble pigment. It can be seen that the anthocyanidin pigment of the purple sweet potato is slightly different depending on the variety, but it is known to have a high stability because it has an aromatic acyl group in common.

The prior art similar to the present invention is a study on the production of yogurt added with sweet potato and pumpkin (Korean Journal of Food Science and Technology Vol. 25, No. 6, pp. 666-671, 1993), the preparation and characteristics of yogurt added with potato (Korean Journal of Food Science and Technology Vol. 26, No. 3, pp. 266-271, 1994), Preparation and Quality Characteristics of Yogurt Added with Aloe (Korean Journal of Food and Nutrition Vol. 24, No. 2, pp. 254- 260, 1995), but most of them are focused on grasping the sensory characteristics, and these yogurt products have a problem in that it is difficult to obtain the effect of raw material replacement because the number of lactic acid bacteria is reduced.

The present invention has been developed due to the development of the breeding technology of the purple sweet potato has a high pigment content and a high yield of excellent varieties, containing a lot of starch, minerals, dietary fiber components, high nutritional support effect, and contains anthocyanin, a natural pigment After saccharifying the purple sweet potato, a part of the skim milk powder is added as a solid content increasing agent to prepare yogurt by reducing the number of lactic acid bacteria.

The present invention consists of saccharification and medium preparation of purple sweet potato, preparation of starter, yogurt fermentation and will be described in more detail in the following examples.

<Example>

Step 1: saccharification of purple sweet potatoes

After peeling 1,000 g of commercially purchased purple sweet potato, steamed at 100 ° C. for 30 minutes, crushed with a stirrer, mixed with 1 liter of water, and 0.5 wt% of alpha -amylase was added as a liquefied enzyme. The solution was liquefied at 90 ° C., heated to 110 ° C. to inactivate the liquefied enzyme, and then cooled to 60 ° C. to glycosylate by adding 0.5% by weight of glucoamylase.

Step 2: prepare the badge and starter

Streptococcus thermophilus H. Prod (Wh ole milk), skim milk powder (Skim milk powder), saccharified purple sweet potato and starter in the laboratory as commercially available (negative by Triphenyl tetrazolium chloride test) -N ₂ 540652 and Bifidobacterium infantis 420 (Wiesby Co., Germany) were inoculated with 4 v / v% of Lactobacilli MRS broth and passaged at 40 ° C. three times for 24 hours and used as starters. .

Step 3: preparing yogurt

As a fermentation substrate, skim milk powder and saccharified purple sweet potato solution were added to the whole milk in the ratio as shown in Table 1, and the solid content was adjusted to 14% by weight and homogenized for 5 minutes with a wear blender, followed by 15 minutes at 121 ° C. in an autoclave. Sterilized. The sterilized substrate was allowed to cool to 40 ° C, and then inoculated (4%, v / v) with lactic acid bacteria as a mixed strain ( Streptococcus thermophilus + Bifidobacterium infantis , 1: 1, v / v) and fermented at 40 ° C. Medium composition (unit: g) division Whole milk powder Skim milk powder ²⁾ Purple sweet potato ³⁾ Control 1000 44 - A 1000 37 28 B 1000 27 48 C 1000 16 78 1) Yogurt base: 0.1 wt% gelatin, 4 wt% sugar, starter 4 v / v% 2) skimmed milk powder: 14 wt% solids 3) Purple sweet potato: Sweetened purple sweet potato solution

<Test Example>

[pH and titration acidity measurement]

To investigate the acid production of lactic acid bacteria during fermentation, 40 ml of distilled water was added to 10 g of the fermentation broth, titrated to pH 8.1 with 0.1 N NaOH using a digital burette (JENCONS, UK), and converted to lactic acid. Was measured (pH meter; ORION MODEL SA 720).

[Measuring viable cell count]

In order to measure the change in viable cell number over time, the fermentation broth was diluted with 0.85% NaCl, plated on a plate (BCP plate count agar; Eiken Co, Japan), and the yellow colonies which appeared after incubating at 40 ° C for 24 hours were counted.

[Sensory Test of Yogurt]

After homogenizing the fermented yogurt and storing it for 12 hours in a 5 ℃ refrigerator, 20 testers evaluated the overall acceptability, taste, odor and texture by 5 steps for each item. The difference in significance of the intervals was tested by Duncan's multiple range test.

[Measurement of Yogurt Viscosity]

To measure the viscosity of yogurt during fermentation, 200 ml of fermentation broth was placed in a 250 ml beaker and maintained at 8-9 ° C. while the viscosity (Brookfield viscometer; Model DV-II) was changed at 60 rpm from 4 to 8 minutes at 1 minute intervals. The viscosity change was evaluated by arithmetic mean value.

[Organic Acid Analysis]

The change of organic acid over time was analyzed by GC. After centrifugation at 9,000 × g for 20 minutes at 5 ° C, each culture solution was precisely taken with 2 ml of chloroform made by adding heptadecane, an internal standard, to 1 ml of the supernatant, and a 25 ml round bottom flask.

1 ml of 1N-sulfuric acid and 0.5 g of salt were added to the mixture, and 2 ml of 14% BF ₃ / MeOH was accurately added to the mixture, and then a round bottom flask was attached to the reflux condenser for 30 minutes in a 60 ° C. water bath. After cooling, the mixture was allowed to stand for cooling, a chloroform layer was taken, passed through 0.5 g Na ₂ SO ₄ (anhydrous), and 2 µl of the filtrate was taken as a GC analysis sample.

[Color Measurement]

The chromaticity of yogurt added with purple sweet potato is measured by the colorimeter (CR-300, Minolta), the L value indicating the lightness, the a value indicating the redness, and the b value indicating the yellowness. (yellowness) and the difference in chromaticity (△ E) between control and purple sweet potato added The difference in chromaticity was evaluated based on Table 2.

Table 2. Total Chromaticity Difference (ΔE) and Sensitivity Difference

Total color difference (△ E) Sensual difference 0 to 0.5 trace 0.5 to 1.5 slight 1.5 to 3.0 noticeable 3.0 to 6.0 appreciable 6.0-12.0 much over 12.0 very much

The change of acid production of yogurt by adding purple sweet potato from the above test was measured by inoculating lactic acid bacteria into yogurt adjusted to solid content of 14 wt% using skim milk powder and purple sweet potato, and measuring pH and total acidity while fermenting at 40 ° C. Changes in acid production over time were evaluated (Table 3).

Table 3. Change of pH ¹⁾ and Total Acidity by Lactic Acid Bacteria Fermentation Time

Hours (hr) pH % Total acidity Control A B C Control A B C 0 6.53 6.52 6.51 6.50 0.154 0.154 0.150 0.144 3 6.35 6.71 6.19 5.86 0.200 0.228 0.214 0.306 6 4.80 4.69 4.69 4.61 0.832 0.768 0.770 0.752 12 4.28 4.21 4.21 4.20 1.106 1.068 1.032 0.970 24 4.04 3.98 3.98 3.97 1.268 1.228 1.180 1.114

* Total acidity is lactic acid concentration.

As the fermentation time passed, the pH decreased in all the groups, and ranged from 4.04 to 3.97 at 24 hours of fermentation. The change in total acidity increased with all fermentation time as the pH change, and ranged from 1.268 to 1.104% after 24 hours of fermentation. In contrast to the pH value, purple sweet potato was added even though the pH value was high. The total acidity of uncontrolled controls was higher.

Table 4 shows the results of measuring the viable cell count of purple sweet potato yoghurt according to fermentation time. The number of viable cells showed a sharp increase in all the experimental groups up to 6 hours, reached a steady state at 12 hours, and changed significantly after that. At 24 hours of fermentation, the viable cell count was 9.08 to 9.62 log cfu / ml, and all of them maintained at least the number of lactic acid bacteria (8.0 cfu / ml) prescribed by the Food Code. It is believed that this is because monosaccharides and trace proteins, which are easy to use by lactic acid bacteria, are easily used by lactic acid bacteria because they sweeten purple sweet potatoes.

Table 4. Changes in Lactic Acid Bacteria during Fermentation (Unit: log cfu / mL)

Hours (hrs) Samples Control A B C 0 6.63 6.63 6.63 6.63 6 8.34 8.36 8.04 8.01 12 9.60 9.31 9.00 8.98 24 9.62 9.33 9.19 9.08

Twenty well-trained sensory test personnel evaluated the sensory performance (dunca n's multiple test) based on the overall acceptability, taste, texture and aroma of the yogurt added with purple sweet potato. The results are shown in Table 5. Overall acceptability, taste, odor and color of purple sweet potato added group were superior to the control group.

Table 5. Sensory Test Results

sample flavor Organization incense color Symbol Control 3.250 ± 1.070 ^{b, 2)} 3.95 ± 1.191 ^a 2.35 ± 1.040 ^b 2.950 ± 1.234 ^b 3.200 ± 1.005 ^b A 3.075 ± 0.520 ^b 3.65 ± 0.813 ^a 2.65 ± 1.040 ^b 3.275 ± 0.786 ^b 3.325 ± 0.864 ^b B 4.350 ± 0.813 ^a 3.60 ± 1.142 ^a 3.15 ± 1.182 ^a 4.550 ± 0.826 ^a 4.050 ± 1.099 ^a C 3.075 ± 1.238 ^b 3.20 ± 1.281 ^a 2.75 ± 1.372 ^b 3.150 ± 1.182 ^b 3.300 ± 1.129 ^b

The rich yoghurt was greatly influenced by the viscosity of the yogurt, and the change in viscosity during the fermentation process was observed. It increased rapidly until 12 hours of fermentation, and then all of them gradually increased until 24 hours, and the addition of purple sweet potato was significantly higher than that of the control, and it increased with increasing content of purple sweet potato. B, A and controls were 46000, 45000, 36800 and 32200 cp, respectively. The addition of purple sweet potato increased the production of acid and the pH was lower than that of the control, resulting in higher viscosity, which may be increased by the polysaccharides present in the purple sweet potato.

Table 6. Variation of Viscosity

sample Fermentation time (hr) 0 6 12 24 CTL 408.8 617.2 31720 32200 A 1352.8 1249.2 35360 36800 B 2216 8132 39000 45000 C 6016 26920 38000 46000

The results of comparing the difference in color (△ E) with Hunter L, a, and b by measuring the chromaticity of yogurt added with purple sweet potato are shown in Table 7. The L value representing the bright chromaticity decreased with increasing amount of purple sweet potato, which is thought to be lowered by the anthocyanin pigment derived from the flesh of purple sweet potato. The a value representing the red color increased slightly with the addition of purple sweet potato, but the b value representing the yellow color decreased slightly. The color difference (ΔE) of the control group showed that the purple sweet potatoes were 11.46, 19.33 and 22.77, respectively, in the yogurt added with 22.7, 38.6 and 63.6% of the solid increasing agent, and the difference was very large.

Table 7. Changes in Chromaticity

Samples L a b Total color difference (ΔE) Control 89.54 -2.98 +7.32 0 A 82.40 +5.82 +5.59 11.46 B 77.82 +12.03 +5.33 19.33 C 73.90 +13.44 +5.20 22.77

Yoghurt added with sweetened purple sweet potato of the present invention was shown to increase the number of lactic acid bacteria, which is an indicator of lactic acid bacteria beverage, and showed excellent physical and chemical properties of yogurt, such as pH, acidity, color, viscosity, etc., especially in the sensory test It is possible to provide a purple sweet potato yogurt containing a natural pigment.

Claims (5)

In the production method of yogurt using purple sweet potato, After removing the skin, the purple sweet potato was steamed and crushed with a stirrer and mixed with water to add 0.5% by weight of alpha amylase and liquefied at 90 ° C. The solution was deactivated and cooled to 60 ° C. Saccharifying by adding%, The fermentation substrate is mixed with whole milk, 1.6 to 3.7% by weight of skim milk powder and 2.8 to 7.8% by weight of the saccharified purple sweet potato solution to the weight of the whole milk to adjust the solid content to 14% by weight and homogenize Wow, Sterilizing the homogenized fermentation substrate at 121 ° C. and fermenting with a starter a strain of 1: 1 mixed Streptococcus thermophilus and Bifido bacterium infantis with 4 v / v% of the fermentation substrate. Method for producing yogurt using purple sweet potato delete delete The method of claim 1, Fermentation substrate is a method for producing yogurt, characterized in that it contains gelatin 0.1% by weight, sugar 4% by weight as an additive delete