QUALITY CHARACTERISTICS OF YOGURT ADDED WITH KARAMUNTING (Rhodomyrtus tomentosa) AQUEOUS EXTRACT AS
NATURAL COLORANT AND SOURCE OF ANTIOXIDANT
Hotman Manurung1), Ferlando Jubelito Simanungkalit1), Anggriani Silitonga2)
1) Department of Agricultural Product Technology, Faculty of Agriculture, University of HKBP Nommensen Medan
2) Undergraduate Student of Agricultural Product Technology, Faculty of Agriculture, University of HKBP Nommensen Medan
*Corresponding email: [email protected] Submitted 12 November 2021; Accepted 3 March 2022
ABSTRACT
The aims of this research are to determine the effect of the concentration addition level of karamunting (Rhodomyrtus tomentosa) fruit extract on the quality of yogurt during 9 d storage period to increase the functionality of yogurt as a probiotic food, a source of antioxidants and the use of karamunting as a natural colorant for food. This research used a completely randomized design consisting of two factors, that is the concentration of karamunting fruit extract which consisted of 4 addition levels (0%, 12%, 15% and 18% w/w) and the storage period of yogurt which also consisted of 4 levels (0 d, 3 ds, 6 d and 9 ds). The parameters that have been observed in this research were pH, total acid, water content, fat content, protein content, color analysis, antioxidant activity and organoleptic tests (aroma, taste, viscosity and color) of the yogurt. The results showed that karamunting fruit extract had a significant effect on pH, total acid, color L*, a* and b*, and organoleptic (aroma, viscosity and color) of the yogurt, but had no significant effect on water content, fat content, protein content and flavor of the yogurt. Storage period had a significant effect on pH, total acid, protein content, color L*, a* and b*, and organoleptic (aroma, taste, viscosity and color) of the yogurt, but had no significant effect on water content and fat content of the yogurt. The addition of 18% (w/w) karamunting fruit extract and 9 d of storage period resulted in yogurt with the characteristics as follows pH 4.2; total acid 1.57%; water content 87.05%; fat content 3.66%;
protein content 2.7%; color L* 72,24; a* 8.28; and b* 9.38 and organoleptic (aroma, taste, thickness and color) which were quite favorable, as well as a strong antioxidant activity value of 85.35 ppm IC50.
Keyword: Karamunting; natural colorant; source of antioxidants; yogurt.
INTRODUCTION
Karamunting (Rhodomyrtus tomentosa) is a type of non-cultivated plant that is often found in forests or marginal lands in the Toba Batak region, North Tapanuli Regency. For the Batak Toba, karamunting is one of 10 types of forest plants that have been used as a food source (Harianja, 2016; Silalahi et al., 2018).
However, along with the entry of fast food types that are increasingly easy to obtain and buy in the local market, karamunting as a type of food originating from the forest has begun to be forgotten by the Toba Batak people.
Karamunting contains anthocyanins which have high antioxidant properties, also contains flavonoids, phenolics and saponins (Hilma and Cendrakasih, 2018).
Karamunting can be used as a new source of antioxidants (Wu et al., 2015). According to Vo and Ngo, (2019) karamunting contains bioactive metabolites that can be used as new functional food compounds. Functional foods provide many benefits and advantages, one of which is to increase the body's immunity (Cong et al., 2020).
According to Ickowitz et al., (2016) forests can be used as a source of micronutrient food, especially for people who live around the forest.
Yogurt is an example of a functional food product because the probiotic bacteria inside the yogurt can help to boost the immune system (Galdeano et al., 2019), and also to kills bad bacteria in the digestive tract (Widagdha and Nisa, 2015). Various studies to increase the functionality of yogurt have been carried out. The Slamet and Kanetro, (2017) research was produced yogurt from the isolation of winged bean
protein which can reduce total cholesterol and LDL cholesterol, on the other hand it can increase HDL cholesterol. In the research of Wulandani et al., (2017) the inclusion of Ficus glomerata leaf extract in yogurt was able to increase antioxidant activity and was able to increase the formation of peptides with anti- Angiotensin-1 Converting Enzyme (ACE) ability. According to Cui et al., (2013) The purplish red color of karamunting fruit is caused by anthocyanin pigments.
Anthocyanins have high antioxidant properties. In this study, the use of karamunting fruit extract as a colorant and a source of antioxidants in yogurt drinks will be investigated. The choice of yogurt is based on the fact that yogurt in general has a low pH, which ranges from 3.8 to 4.6 (Wijayanti, 2017), so that it matches the characteristics of anthocyanin pigments which are more stable in acidic conditions (Rifkowaty et al., 2018).
The aims of this research are to increase the functionality of yogurt as a probiotic food as well as a source of antioxidants, and to increase the utilization of karamunting fruit as a source of antioxidants and natural colorant for food.
MATERIALS AND METHODS The research was conducted at the Laboratory of Food Analysis and Processing, Agricultural Product Technology, Faculty of Agriculture, University of HKBP Nommensen Medan;
Laboratory of Food Technology Science and Laboratory of Food Chemical Analysis, Faculty of Agriculture, University of North Sumatra; and the laboratory of Biochemistry and Laboratory of
*Corresponding author:
Ferlando Jubelito Simanungkalit
Email: [email protected]
Department of Agricultural Product Technology, Faculty of Agriculture, University of HKBP Nommensen Medan
How to cite:
Manurung, H., Simanungkalit, F. J., & Silitonga, A.
(2022). Quality Characteristics of Yogurt Added with Karamunting (Rhodomyrtus tomentosa) Aqueous Extract As Natural Colorant and Source of Antioxidant. Jurnal Ilmu dan Teknologi Hasil Ternak (JITEK), 17 (1), 41-55
Microbiology, Faculty of Mathematics and Natural Sciences, University of North Sumatra. This research was conducted from July 2021 to November 2021.
Material
The ingredients that used in this research were fresh cow's milk, full cream milk powder, sugar, mineral water, and a starter using Biokul Plain Yogurt (based on information on the packaging containing Lactobacillus achidophilus and Bifidobacterium bacteria) and karamunting fruit obtained from Bonan Dolok Tiga Village, Balige District, Toba Regency.
Tools
The equipments that used in the production of karamunting yogurt are a digital scale, a blender, glassware, filter cloth, spoon, stirrer, pan, stove, digital thermometer, label paper, plastic cup, incubator, and refrigerator. The equipments that used for laboratory analysis are a spatula, dropper, measuring cup, pH meter, erlenmeyer, petridish dish, Memmert UFB 400 oven, desiccator, burette, static pole, filter paper, glass beaker, funnel glass, Kjedahl flask, thimble, heating mantle, soxhlet App, condenser, Minolta Croma Meter CR400 (source light : pulsed xenon lamp; observer degree : 2o closely matches CIE 1931 standard observer (x̄2λ, , z̄λ);
calibration : white calibration plate CR- A43), UV/Vis spectrophotometer.
Research methods
Experimental design and statistical analysis This research was conducted by experimental method using a completely randomized design with 2 treatment factors.
Factor 1: Concentration (% w/w) of karamunting fruit juice: 0%; 12%; 15%; and
18%. Factor 2: Yogurt storage period 0 d;
3 d; 6 d; and 9 ds.
Observational and measurement data were analyzed with Univariate Two Way Anova using software SPSS version 20.
Treatments and interactions that had a significant effect were tested with Duncan's
test at level p=0.05. The research variables that would be analyzed were: pH, total acid, water content, fat content, protein content, color L* a* and b*, antioxidant power, and sensory analysis (aroma, taste, viscosity and color).
Karamunting fruit extraction
Karamunting fruits were sorted to get fruit with the same ripeness, then the results of the sorting were washed until clean and then drained. A total of 700 g of sorted karamunting fruits that have been drained were put into a blender which already contains 1,400 g of water, then blended using low speed for ± 2 min. Then the fruit pulp would be filtered using a filter cloth.
The filtering results would produce karamunting fruit extract which were used in the process of yogurt production.
The subculture of bacteria starter
To 166 g of mineral water added 26 g of full cream milk powder and 8 g of sugar.
The milk mixture then stirred until mixed evenly. The milk mixture then heated at 85oC for 1 minute, then poured into a sterile cup and then cooled until the milk temperature becomes 42oC. 10 g of yogurt bacteria starter (Yogurt Biokul Plain) was inoculated into a sterile cup that already containing pasteurized milk. Then the cup was closed tightly and incubated in the incubator box for 12 h. Yogurt that has been made is called the subculture I and then used as a starter for bacteria for the next pass. The subculture process was carried out 3 times.
The subculture results are stored in a refrigerator.
Yogurt production
To 350 g of fresh cow's milk added 14 g of sugar, then stirred until
homogeneous. Then added karamunting fruit extract according to the treatment, consist of 0, 12, 15, and 18% (w/w). The results of the mixing were stirred until homogeneous. Milk that has been mixed with karamunting fruit extract were pasteurized at 85oC for 1 min, then would
be cooled until 42oC. Yogurt bacteria starter (subculture III result) as much as 17.5 g was inoculated into a sterile cup which already contained pasteurized milk. The cups were closed tightly and then fermented in the incubator box for 12 h. After the fermentation process is complete, the yogurt is then stored in the refrigerator for 0, 3, 6, and 9 ds. Then do the laboratory analysis to measure the quality characteristics of the yogurt.
pH measurement (AOAC, 1995)
The pH measurement was carried out using a pH meter. The pH meter was standardized first with buffers of pH 4 and
pH 7. A sample of 10 ml was put into a
100 ml volumetric flask and diluted to the tera mark with the addition of distilled water. Measurements were made by dipping the pH meter electrode into the sample solution and then observing the pH value.
Total Acid Analysis (AOAC, 2005)
The 10 ml sample was put into a 100 ml volumetric flask and diluted to the
mark with distilled water, then filtered using filter paper.
Then 5 ml was taken and transferred to a 100 ml Erlenmeyer and added 2 drops of 1% (v/v) phenolphthalein (PP) indicator and then titrated with 0.01 NaOH. The calculation is obtained from the formula below:
Total acid (%) = ml NaOH × N NaOH × DF × MW sample weight
*Note: DF = dilution factor; and MW = molecular weight of lactic acid;
Water content analysis (AOAC, 1995) A total of 20 g of sample was placed in an empty cup that had been weighed, the cup had previously been dried in the oven and cooled in a desiccator. The cup containing the sample was then placed in an oven at 100 oC for 5 h. The cup was then
cooled in a desiccator for 15 min and weighed. Then it was reheated for 1 h until the difference between the last weighing and the previous weight was about 0.05 g.
The water content is weighed by the formula:
Water content (%) = W1 − W2
sample weight x 100%
*Note: W1 = weight (sample + cup) before drying; W2 = weight (sample + cup) after drying;
Soxhlet’s method of fat content analysis (AOAC, 2005);
The fat flask to be used was dried in an oven at 100°C for 1 h. The fat flask was cooled in a desiccator for 15 min and weighed (W2). Then the sample was weighed ± 2 g (W1) and wrapped using filter paper in the form of a thimble.
Assemble extraction tools from heating mantle, fat flask, soxhlet to condenser. The sample was then put into a soxhlet and then added hexane solvent for 1½ cycles.
Extraction was carried out for 6 h until the
solvent fell back through the siphon into a clear fat flask. The fat that has been separated with hexane is then heated in an oven at 100°C for 1 h. The fat flask was cooled in a desiccator for 15 min and weighed (W3). Reheat in the oven for 1 h if the difference in weighing the last extraction with the previous weighing has not reached 0.5 g. Fat weight is calculated by the formula:
Flat content (%) =final flat flask weight (W3) − empty flat flask weight (W2)
sample weight (W1) x 100%
Protein content analysis (AOAC, 1984) 0.25 g of the sample was put into a Kjeldahl flask with concentrated sulfuric acid and a mixture of selenium and boiling stone then destroyed by heating in an acid chamber until the color became clear, then
diluted to the limit of tera. Furthermore, it is distilled and titrated with 0.01 N KH(IO3)2
solution until a color change occurs. Also worked on the determination of blanks.
Protein content is calculated by the following formula:
Protein content (%) = (A − B) × 0,01 × P × 14 × 6,38
sample weight × 100%
*Note: A = ml of titran sample; B = ml of titran blanks; P = ml of dilution Color analysis (Kaemba et al., 2017)
The Analyzes were performed using a Minolta Croma Meter CR400 (source light
: pulsed xenon lamp; observer degree : 2o closely matches CIE 1931 standard
observer (x̄2λ, , z̄λ); calibration : white calibration plate CR-A43) EZ. The color test was carried out using the Hunter L*
(white), a* (red), b* (yellow) color system.
The chroma meter was first calibrated with the white standard found on the tool. The results of the analysis of the degree of white produced were the values of L*, a*, b*. The measurement of the total degree of color used a white base as a standard.
Analysis of antioxidant activity using DPPH method (2,2-Diphenyl-1- Picrylhydrazyl) (Brand-Williams et al., 1995). Antioxidant activity was determined by the DPPH free radical method. This antioxidant test was carried out in several stages, the first stage was making a DPPH solution by dissolving 4.7 mg of DPPH in 100 ml of ethanol to obtain a concentration of 0.12 mM, and stored in a dark room for 20 min. The second stage was making control solution by adding 1.5 ml of ethanol solution to 1.5 ml of DPPH solution in a test
tube, then determining the absorbance at the maximum wavelength of the control solution. Determination of the maximum
wavelength was measured in the range 510 – 520 nm.
The third stage was making stock solution by weighing 100 mg of sample extract, then dissolving up to 100 ml of ethanol in a volumetric flask to obtain a stock solution concentration of 1,000 ppm.
Stock extract solutions were prepared with varying concentrations in a volumetric flask. The fourth stage was making sample solutions with various concentrations, as follows 3.12 µg/ml, 6.25 µg/ml, 12.5 µg/ml, 25 µg/ml, 50 µg/ml, and 100 µg/ml from stock solution. Preparation of the solution with the above concentration was carried out by pipetting the stock solution as much as 15.6 µl, 31.2 µl, 62.5 µl, 125 µl, 250 µl, and 500 µl into a 5 ml volumetric flask, then added with 1 ml of DPPH solution and ethanol to the tera limit, then vortexed until mixed and allowed to stand in the dark
condition (avoided from sunlight) for 30 min in each sample solution. The
percentage of inhibition was calculated by the formula:
Inhibition (%) = absorbance of control − absorbance of sample
absorbance of control x 100%
Sensory analysis (Rahayu et al., 2012) Organoleptic tests were carried out to measure the aroma, taste, consistency, and
color of yogurt using a hedonic scale consisting of 5 statements and 5 rating scales (very dislike = 1; dislike = 2; quite
like = 3; like = 4; and very like = 5). All panelists were untrained panelists consisting of 25 students of the Agricultural Product Technology Department, University of HKBP Nommensen Medan.
Preparation for the panelists was done by first introducing information about yogurt products, starting from the raw materials, manufacturing process, shape, aroma and taste.
Then the panelists were also introduced to yogurt products that are generally on the market. At this introductory stage, each panelist was given a plain variant of Biokul yogurt to be tasted organoleptically.
After the preparation stage, organoleptic testing was carried out by giving each panelist 5 samples of yogurt at random condition which had been given a code label before. After that, each panelist was asked to provide an assessment of the tasted yogurt sample by filling out the hedonic test assessment form that had been provided.
RESULTS AND DISCUSSION The results showed that increasing the concentration of karamunting fruit extract in yogurt gave an increase in total acid, water content, protein content, color a* and b* as well as organoleptic aroma and taste of yogurt. But it gives a decrease in pH, fat content, L* color, organoleptic viscosity and yogurt color. The concentration factor of the karamunting fruit extract did not have a significant effect on the water content, fat content, protein content and organoleptic taste of the resulting yogurt, as shown in Table 1.
The longer yogurt was stored, would increasing the value of total acid, protein content and b* color in the resulting yogurt, but also causes would decreasing the value of pH, water content, fat content, L* and a*
color, organoleptic aroma, taste, viscosity and color of yogurt. Storage period was not affected the moisture content, fat content, color L* and b* of the yogurt produced, as shown in Table 2.
Table 1. The Effect of caramunting fruit extract concentration on the quality characteristics of yogurt.
Quality Characteristics
Karamunting Fruit Extract Concentration
0% 12% 15% 18%
pH 4,76c±0,09 4,62b±0,08 4,26a±0,11 4,20a±0,09 Total Acid (%) 0,69a±0,16 0,94b±0,15 1,46c±0,13 1,53c±0,08 Water Content
(%) 84,71 84,88 85,99 85,78
Protein Content
(%) 2,78 2,68 3,00 3,21
Fat Content (%) 4,41 4,34 4,01 4,14
Color
L* 75,11acd±5,55 76,62abc±2,16 73,97ad±5,23 72,22abc±1,34 a* 9,94acef± 1,87 11,22ef ±0,88 9,54abcde ±1,22 10,71abef ±1,69 b* 6,68abcd±0,91 6,17abc±0,60 6,69abcd±0,73 6,81abe±1,61 Aroma 3,34a ±0,31 3,50bc ±0,29 3,40ab ±0,33 3,61c ±0,28
Taste 3,05 3,16 2,96 3,10
Viscosity 3,64b±0,25 3,23a±0,29 3,55b±0,27 3,64b±0,38 Color 3,92c±0,26 3,50a±0,32 3,62ab±0,32 3,63b±0,27 Remarks: *Mean values within a column followed by the different letters are significantly
different at p<0.05 according to Duncan Test.
Table 2. The Effect of storage period on the quality characteristics of yogurt.
Quality Characteristics
Storage Period (Days)
0 3 6 9
pH 4,58c±0,27 4,46b±0,23 4,41ab±0,25 4,38a±0,26 Total Acid (%) 0,97a±0,44 1,17b±0,35 1,22b±0,35 1,26b±0,35
Water Content (%) 85,46 85,78 84,67 85,45
Protein Content
(%) 3,40b±0,87 3,01ab±0,37 2,73c±0,29 2,53c±0,26
Fat Content (%) 4,36 4,07 4,33 4,16
Color
L* 76,30bcd±3,88 75,31acd±5,45 71,02a±0,13 71,29ab±0,70 a* 11,45af±2,02 10,18ae±1,52 10,60de±0,50 9,18abce±0,93 b* 6,20abc±0,57 6,47abcd±1,11 6,37abcd±0,48 7,31abcde±1,41 Aroma 3,92c±0,14 3,42b±011 3,27a±0,13 3,24a±0,20 Taste 3,51b±0,20 2,93a±0,12 2,91a±0,21 2,91a±0,19 Viscosity 3,93c±0,23 3,48b±0,25 3,34ab±0,20 3,31a±0,24 Color 4,08c±0,17 3,64b±0,16 3,48a±0,19 3,46a±0,29 Remarks: *Mean values within a column followed by the different letters are significantly
different at p<0.05 according to Duncan Test.
pH
The concentration of karamunting fruit extract and storage period had a significantly different effect (p<0.05) on the pH of yogurt as shown in Tables 1 and 2.
The increasing of karamunting fruit extract concentration would resulted in a significantly lower pH from 4.76 at 0%
(w/w) concentration of karamunting fruit extract to 4.20 at 18% (w/w) concentration of karamunting fruit extract.
The decrease in yogurt pH was caused by the lower pH of the karamunting fruit extract (5.5) than the pH of cow's milk (6.7).
Karamunting fruit extract using water as a solvent has a pH of 5.50 (Rifkowaty et al., 2018). The decrease in pH due to the addition of karamunting fruit extract, can increase the activity of lactic acid bacteria (LAB) to break down lactose into lactic acid. The more lactic acid formed, would resulted the lower pH value (Sutedjo and Nisa, 2014).
The decrease in pH was caused by the activity of LAB which converts lactose into lactic acid. Lactic acid produced from carbohydrate metabolism will be able to reduce the pH value of the growth environment and cause a sour taste. The longer storage period, the more lactose will
be converted into lactic acid. However, as in Table 2, until the 9th d of storage it was seen that the increase in pH was not significant.
This condition was caused by the decrease in pH could inactivate lactic acid bacteria as said by Jay, (2000) that the growth of Lactobacillus bulgaricus can be stopped at pH 3.5 – 3.8, while Streptococcus thermophillus will stop at pH 4.2 – 4.4.
Total Acid
The concentration of karamunting fruit extract and storage period had a significantly different effect (p<0.05) on the total acid as shown in Table 1 and Table 2.
From Table 1 it can be seen that the total acid increased from 0.69% to 1.53%. The increase in the total acid value in the yogurt produced was due to the addition of karamunting fruit extract which was acidic.
According to Vo and Ngo, (2019) karamunting fruit contains organic acids such as citric acid 5.62 mg / 150 g karamunting and fatty acids such as linoleic and palmitic acids which account for 85.81% of the total acid contained in karamunting fruit.
LAB contained in yogurt converts milk lactose into lactic acid. A high amount of lactose will produce high lactic acid,
thereby increasing the total acid value. A high total acid value will lower the pH due to an increase in the concentration of H+ ions which can produce a sour taste. In conditions that are influenced by storage period, the total acid produced in yogurt also increases, starting from 0.97% at 0 d storage to 1.26% at 9 d storage. The highest increase in the acidity level of karamunting yogurt occurred at the beginning of storage (0 – 3 ds), and the longer the storage period, the total acid content continued to increase, but not as much as at the beginning of storage.
The increase in total acid levels during storage is related to the amount of LAB in yogurt. The longer the storage period, the more lactic acid produced by LAB will result in a decrease in the pH of yogurt. The decreasing pH of yogurt causes the amount of LAB in yogurt to also decrease. A decrease in the amount of LAB in yogurt will cause LAB activity in breaking down lactose into lactic acid to also decrease. That's what causes the
increase in total acid on storage period of 3 – 9 d only slightly.
Water content
The increase in concentration of karamunting fruit extract and storage period had no significant effect (p>0.05) on the water content. This is because the sugar content that can bind water inside the karamunting fruit is very low, only 4.79%
so that the water contained in the karamunting extract all turns into water vapor (Sinaga et al., 2019).
Fat content
The increase in concentration of karamunting fruit extract and storage period gave no significant effect (p>0.05) on fat content. This is because the karamunting fruit has a very low fat content, as stated by Lai et al., (2015) that the fat content of karamunting is only about 0.07 g in 100 g of karamunting. Therefore, increasing the
concentration of karamunting fruit extract had no significant effect on the fat content of the yogurt produced. During storage, yogurt fat content also did not change. This shows that during storage, milk fat is not damaged by chemical reactions.
Protein content
The concentration of karamunting fruit extract had no significant effect (p>0.05) on the protein content of yogurt.
This is because the protein content of caramunting is very low, which is around 0.98% of the fruit weight (Lai et al., 2015).
So that the addition of karamunting fruit extract according to the treatment did not have an effect on the protein content of the yogurt produced. These results also indicate that the majority of protein in yogurt still comes from milk protein. From Table 1 it can be seen that the protein content is in accordance with SNI, which is an average of 2.92%.
Yogurt storage period had a significantly different effect (p<0.05) on yogurt protein content. From Table 2 it can be seen that the protein content in yogurt decreased from 3.40% to 2.53%. The decrease in protein content was caused by a protein denaturation process caused by the formation of acids during storage (Sari et al., 2016). The decrease in protein content can also be caused by the breakdown of protein into dipeptides and so on into NH3
compounds which are lost through evaporation (Raharjo et al., 2019).
L* value (brightness)
The concentration of addition of karamunting fruit extract and storage period had a significantly different effect (p<0.05) on the value of L* (brightness) of yogurt.
The results of the analysis also showed that there was a significantly different interaction (p<0.05) between the addition of karamunting fruit extract with different concentrations and storage period on the L*
(brightness) value of yogurt as shown in Table 3.
Table 3. The interaction effect of karamunting fruit extract concentration and storage period on the value of L* (brightness) yogurt.
Concentration of Karamunting Fruit
Extract
Storage Period
0 d 3 ds 6 ds 9 ds
0% 74,98c 83,58d 70,83a 71,11a
12% 73,70bc 74,98c 71,07a 70,56a
15% 82,45d 71,22a 71,04a 71,18a
18% 74,15c 71,26a 71,15a 72,34ab
Remarks: *Mean values within a column followed by the different letters are significantly different at p<0.05 according to Duncan Test.
In Table 3 it can be seen that during storage period there was a significant decrease in the value of L* at each concentration level of the karamunting fruit extract. Likewise, there was a decrease in the value of L* due to an increase in the concentration of karamunting fruit extract at each storage period. The highest L* value was at the addition of karamunting fruit extract at the level of 15% (w/w) with a storage period of 0 d and the lowest L* was at the addition of 12% (w/w) concentration of karamunting fruit extract which was stored for 9 ds. The decrease in the brightness value of the yogurt occurs because the anthocyanin red pigment affects the brightness of the yogurt. The chromophore group is a color-carrying group in a pigment where the higher the pigment concentration, the more the number of chromophore groups resulting in a darker color. (Delgado-Vargas et al., 2000).
The value of L* (brightness) in yogurt decreased with increasing yogurt storage time. The decrease in the value of L* in the resulting yogurt occurred due to an oxidation reaction that occurred in the yogurt. The reaction is triggered by the presence of oxygen or storage conditions that trigger oxidation, thereby reducing the brightness of the product's color.
Karamunting fruit extract anthocyanins can undergo oxidation and their levels decrease during storage (Priska et al., 2018).
a* value (redness)
The concentration of the addition of karamunting fruit extract and storage period had a significantly different effect (p<0.05) on the a* (redness) value of yogurt. The interaction of the addition of karamunting fruit extract with different concentrations and storage time on the a* (redness) value of yogurt showed a significantly different effect (p<0.05) as shown in Table 4.
Table 4. The interaction effect of karamunting fruit extract concentration and storage period on the value of a* (redness) yogurt.
Concentration of Karamunting Fruit
Extract
Storage Period
0 d 3 ds 6 ds 9 ds
0% 12,30f 7,75a 10,77e 8,96c
12% 12,61f 10,63e 11,06e 10,60e
15% 8,23a 11,23e 9,83d 8,87bc
18% 12,67f 11,14e 10,77e 8,28ab
Remarks: *Mean values within a column followed by the different letters are significantly different at p<0.05 according to Duncan Test.
In Table 4, it can be seen that an increase in the concentration of karamunting fruit extract resulted in the a*
value increasing at each level of storage time and conversely a decrease in the a*
value during storage at each concentration level of the karamunting fruit. The highest a* value was found in the concentration of 18% karamunting fruit and 0 d storage.
The increase in a* value in yogurt occurred because the amount of anthocyanin red pigment was increasing.
Rifkowaty et al., (2018) states that karamuting is red because it contains anthocyanins. Anthocyanin content in karamunting fruit 0.65 mg (cyanidin-3- glucoside equivalent, CGE)/g dry weight (Jumiati et al., 2017). The increase in a*
value can also be caused by the pH of yogurt decreasing from 4.76 at 0% concentration of karamunting fruit to 4.20 at 18%
concentration of karamunting fruit. Pratiwi and Priyani, (2019) stated that anthocyanins are more stable in acidic conditions, therefore the lower the pH value, the a* value of the purple sweet potato solution increases. The decrease in a* value occurred due to the degradation of
anthocyanin pigments caused by the photooxidation process. The use of transparent and translucent sterile cups as yogurt storage packaging causes the oxidation of anthocyanin pigments to occur.
This is in line with the research of Tamaroh et al., (2018) which informed that there was a decrease in purple sweet potato anthocyanin levels during storage which was probably caused by a photooxidation reaction. The anthocyanins of karamunting fruit extract can undergo oxidation and their levels decrease during storage (Priska et al., 2018). During the storage period also allows the occurrence of a copigmentation reaction. For example, research by Sangadji et al., (2017) which informed that the storage of rose and hibiscus ornamental plants in room conditions resulted in a large change in the intensity of the dye due to the copigmentation reaction.
b* value (yellowish)
The interaction of the addition of karamunting fruit extract with different concentrations and storage time on the value of b* (yellowness) of yogurt showed a significantly different effect (p<0.05) as shown in Table 5.
Table 5. The interaction effect of karamunting fruit extract concentration and storage period on the value of b* (yellowness) yogurt.
Concentration of Karamunting Fruit
Extract
Storage Period
0 d 3 ds 6 ds 9 ds
0% 6,43abc 7,99d 6.40abc 5,91a
12% 5,75a 6,58abc 5,83a 6,52abc
15% 6,59abc 5,68a 7,06bcd 7,43cd
18% 6,25ab 5,63a 6,21ab 9,38e
Remarks: *Mean values within a column followed by the different letters are significantly different at p<0.05 according to Duncan Test.
From Table 5 it can be seen that there was a significant increase in the value of b*
due to an increase in storage time at each level of concentration of caramunting extract. This is probably because during the storage process the amount of anthocyanin pigment which is red is reduced due to oxidation reactions so that the yellow color which was initially covered by
anthocyanins becomes visible. The color of yogurt is influenced by the yellow pigment anthoxanthin found in mulberry fruit (Morus alba L). Anthoxanthins bind to anthocyanins (Rahmawati and Kusnadi, 2017). According to Gonnet, (1998) the color of anthocyanins is the interaction of various color components (L*, a*, and b*) so that the level of yellowness plays a role
in composing the color of anthocyanins. In Table 5, it can be seen that the highest b*
value was 9.38 at the use of 18%
karamunting extract and 9 d of storage.
Aroma organoleptic value
The concentration of karamunting fruit extract addition and storage period had a significantly different effect (p<0.05) on the organoleptic value of yogurt aroma.
From Table 1, it can be seen that the organoleptic value of yogurt aroma increased with the increase in the concentration of karamunting fruit extract used in making yogurt. This can be seen from the resulting value increasing, starting from 3.34 to 3.61.
This increase was caused by karamunting contains phenolic compounds that produce a distinctive aroma in karamunting (Abd Hamid et al., 2017).
Meanwhile, storage resulted in decreased organoleptic aroma from 3.92 to 3.24. This decrease occurred because the distinctive aroma of caramunting decreases with the increase in yogurt storage period.
Flavor organoleptic value
The concentration of the addition of karamunting fruit extract did not have a significantly different effect (p>0.05) on the organoleptic value of yogurt taste. This is because the taste of the karamunting fruit extract is not too conspicuous or distinctive so that its effect on the taste of yogurt is very small and becomes undetectable by the five senses. From Table 2, it can be seen that the organoleptic value of yogurt during storage decreased from 3.51 to 2.91. This decrease occurred because the taste of yogurt become more sour as the storage period of yogurt increased. The more acid formed, the lower the pH value (Sutedjo and Nisa, 2014).
Viscosity organoleptic value
From Tables 1 and 2 it can be seen that the value of yogurt viscosity tends to decrease with increasing concentration of karamunting fruit extract and storage period. This decrease occurs because the
protein in yogurt is denatured, the hydrophobic groups will be on the outside of the material, while the hydrophilic groups will be on the inside. As a result, the casein protein aggregates formed are weak and tend to re-dissolve in water. This condition causes the viscosity of yogurt to decrease (Purbasari & Abduh, 2013).
Color organoleptic value
From Table 1 and Table 2 it can be seen that the organoleptic value of yogurt color decreased with increasing concentration of karamunting fruit extract and storage period. This is because the addition of karamunting fruit extract makes the color of the yogurt which was previously milky white becomes red but not bright (opaque). The bright pink caramunting color is not visible in the yogurt. Bright colors tend to be preferred by consumers because they are considered to be of higher quality compared to opaque colored foods (Andarwulan, 2013).
Determination of antioxidant power (IC50)
The antioxidant power (IC50) was determined in yogurt produced from the addition of 18% (w/w) karamunting extract and 9 d of storage. The results of laboratory analysis and assessment of the organoleptic test of yogurt with the addition of 18%
(w/w) karamunting extract and 9 d storage period were then compared with SNI 01- 2981-2009 as shown in Table 6.
Based on Table 6 above, it can be seen that yogurt with the addition of 18% (w/w) karamunting fruit extract has a total acid content, fat content, and protein content in accordance with the applicable requirements of SNI 01-2981-2009. This yogurt has a fairly low pH and a fairly high total acid because it uses 18% karamunting fruit extract. This treatment had a water content of 87.05%, a fat content of 3.66%, and a protein content of 2.7%. Then in the organoleptic test results, the resulting Karamunting yogurt has a fairly favorable aroma, taste, thickness, and color.
Table 6. The quality characteristics of karamunting yogurt with the addition of 18% (w/w) karamunting fruit extract and 9 d of storage.
Quality Characteristics Yogurt Extract 18% (w/w)
& Storage Period 9 ds SNI 01-2981-2009 Yogurt
pH 4,20 -
Total Acid (%) 1,57 0,5 – 2,0
Water Content (%) 87,05 -
Fat Content (%) 3,66 Min. 3,0
Protein Content (%) 2,7 Min. 2,7
Color
L* 72,34 -
a* 8,28 -
b* 9,38 -
Aroma 3,48 Normal/typically
Flavor 3,08 Asam/typically
Viscosity 3,40 Homogeneous
Color 3,40 -
Antioxidant activity test (IC50) of yogurt karamunting
The antioxidant activity test of karamunting yogurt was carried out on yogurt with a concentration of 18% (w/w)
addition of karamunting fruit extract and 9 d of storage. The test results showed that
the karamunting yogurt had an IC50 value of 85.35 ppm (strong), while yogurt without the addition of karamunting fruit extract and 9 d of storage had an IC50 of 178.16 ppm (weak). This shows that the addition of karamunting extract can increase the antioxidant power of yogurt. The lower the IC50 means the stronger the antioxidant potential (Molyneux, 2004).
CONCLUSION
The increase in karamunting fruit extract up to 18% (w/w) and storage period of up to 9 d still met the standard of SNI 01- 2981-2009 with yogurt quality characteristics pH 4.20; total acid 1.57%;
water content 87.05%; fat content 3.66%;
protein content 2.7%; color L* 72.34; a*
8.28; and b* 9.38 as well as organoleptic (aroma, taste, thickness, and color) which are quite favorable. The addition of karamunting extract increased the antioxidant power of yogurt from 178.16 ppm (without the addition of karamunting
fruit extract) to 85.35 ppm (the addition of karamunting fruit extract was 18% (w/w)).
ACKNOWLEDGEMENT
The authors would like to thank the University of HKBP Nommensen Medan through the 2020 Internal Research Program which was used to finance this research.
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