Application of Pediococcus acidilactici BK01 Microencapsulated Starter on Nutritional and Organoleptic Value of Sweet Potato Flour ( Ipomoea batatas L.) Fermented Milk

Probiotics are live microorganisms that benefit to the body's health. One of which is Pediococcus acidilactici BK01 , which is used as a microencapsulated starter in the manufacture of fermented milk. This study aimed to determine the effect of adding several types of sweet potato flour ( Ipomoea batatas L.) on the nutritional and organoleptic values of fermented milk. The research method used is an experimental method using a Randomized Group Design. The treatments were the addition of several types of sweet potato flour (Factor A): A1 (white sweet potato), A2 (purple sweet potato), C1 (yellow sweet potato), and the percentage of sweet potato addition (Factor B): B1 (0%), B2 (3%), B3 (6%). The results showed that the addition of sweet potato flour at different percentages had an effect (p < 0.05) on moisture content, protein content, fat content, and sensory value. The conclusion of this study is that fermented milk with the addition of 6% purple sweet potato (A2B3) is a treatment that can be accepted by organoleptic panelists with 84.27% moisture content, 5.67% protein content, 1.59% fat content. For the future, the results of this study are expected that fermented milk with the addition of sweet potato can increase nutritional value and be used as a functional food that is beneficial for health.


INTRODUCTION
One necessary that must be satisfied for life to exist is food.People are more likely to consume functional food because there is a greater public awareness of healthy eating, which emphasises nutritional content, sensory appeal, and other physiological aspects of bodily health.Milk is one of the food products made from animals that is useful and preferred by a variety of people, according to Sujana et al. (2022).Milk's rich mix of elements which encourage microbial development makes it susceptible to harm, even if milk has a high nutritional content (lactose, protein, fat, and minerals).
Milk must be processed in order to increase its nutritional value and make it better so that it is not easily damaged.Making fermented milk products as a useful food is one kind of milk processing.A dairy product known as fermented milk is made when lactic acid bacteria use raw milk materials that have been processed or without them.The milk is modified by breaking down lactose with lactase to lower pH and prevent coagulation (Horiuchi et al., 2022;Bintsis et al., 2022).To increase the shelf life of milk, dangerous microorganisms can be inhibited by the fermentation process (Nadirova et al., 2023).Furthermore, the nutritional value of fermented milk is beneficial to health, as it contains lactic acid bacteria that may ferment carbohydrates and generate organic acids, which give fermented milk its unique flavour, texture, and scent (Saleem et al., 2024).
Probiotics are necessary for the fermentation process in milk.When ingested in appropriate amounts, probiotics are microorganisms that can improve the balance of the gut microbiota, improve nutritional value, and impact body health (Lata and Savitri, 2023).Probiotics provide several health advantages, including lowering the risk of colon cancer, lowering blood pressure, boosting immunity, and having anti-carcinogenic properties (Zaib et al., 2024).Pediococcus acidilactici BK01 is one type of probiotic that was employed in fermented milk in this investigation.
A probiotic known as P. acidilactici BK01 was isolated from Bekasam, or swamp sepat (Tricopodus trichopterus), fish that spontaneously fermented in Banyuasin, South Sumatra.According to Melia et al. (2019), this bacteria shows antibiotic action against Escherichia coli 0157:H7, Staphylococcus aureus ATTCC25923, and Listeria monocytogenes CFSAN0044330.It can also live in settings with stomach acid and bile salt.In earlier research, P. acidilactici BK01 fermented milk with red ginger added was found to have an antioxidant content of 48.39%, pH 4.3%, titratable acidity 1.716%, moisture content of 80%, protein 3%, fat 3%, syneresis 28%, and water holding capacity (WHC) of 63%.These bacteria can be used as probiotics in fermented milk.In a different study, Melia et al. (2020) looked at the probiotic count of 9,106 log CFU/ml, total acid titration of 1.73%, pH 4.28, total plate count (TPC) of 4.012 log CFU/ml, protein 3.57%, fat 3.49%, and moisture content 85.51% of goat milk fermented by P. acidilactici BK01 at refrigerator temperature for 28 days.Moreover, a microencapsulation procedure is used to increase the shelf life of P. acidilactici BK01 bacteria so that it can be widely used.Prebiotics can be added to probiotic fermented P. acidilactici BK01 milk to create a functional meal.Lyon et al. (2023) define synbiotics as a blend of prebiotics and probiotics that have an impact on bodily functions.Sweet potato flour is one kind of prebiotic that can be added to fermented milk to raise its nutritious content.One local product that can improve the nutritional content of fermented milk is sweet potatoes.Ipomoea batatas var Ayumurasaki (purple sweet potato), Ipomoea batatas var Lam (yellow sweet potato), and Ipomoea batatas var linneaus (white sweet potato) are some of the popular varieties of sweet potatoes.
Previous studies by Mayasari et al. (2024) found that milk fermented by Levilactobacillus brevis DSM02 with up to 1% addition of pouring flour (Amorphophallus neophallus) had a nutritional composition of 82.31% water, 2.74% protein, and 0.19% fibre.According to Hasan's research (2023), panellists found that Lactococcus lactis D4 fermented milk with up to 10% of banana kepok flour (Musa balbisiana) still had a satisfactory moisture content of 80.39%, fat content of 3.93%, and protein content of 5.14%.In order to enhance the nutritional content of fermented milk, this study will employ multiple varieties of sweet potato flour as prebiotics and P. acidilactici BK01 microencapsulated starter as a functional ingredient.Local sweet potato food utilisation is still quite limited in food processing.

Materials
The materials used in this study were Ottawa goat milk (Capra aegagrus circus) for making starters obtained from Dairy Goat Farm in Korong Gadang, Kuranji District, Padang City, West Sumatra, Indonesia.
White, purple, and yellow sweet potatoes were obtained from traditional market in Padang City (Bandar Buat, Lubuk Kilangan, Padang).In addition, the ingredients were H2SO4 0.05 N, selenium, NaOH 0.01 N, methyl red indicator, and N-hexanes.

Methods
This research was conducted with the experimental method of Factorial Randomised Group Design.The treatments are the type of sweet potato flour (Factor A), namely A1 (white sweet potato), A2 (purple sweet potato), A3 (yellow sweet potato) and the percentage of sweet potato flour addition (Factor B) to fermented milk namely B1 (0% or control), B (3%) and C (6%), with 3 replications.

Preparation of Sweet Potato Flour (Ipomoea batatas L.)
White, purple, and yellow sweet potatoes were peeled, washed, and sliced thinly, then dried using a Food Dehydrator at 90 o for 3 hours.Pureed the dried sweet potato with a blender, then sifted with a 60 mesh sieve to produce fine sweet potato flour (Santi et al., 2023;Dhani, 2020).

Preparation of Fermented Milk Starter
100 ml of goat milk was fermented at 85 o C for 15 min, and the milk temperature was reduced to room temperature.Microencapsulated probiotic powder P. acidilactici BK01 was put into goat milk as much as 1%.Milk was incubated at 37 o C for 18 ho (Wakhidah et al., 2017).

Making Fermented Milk
UHT milk was added to each breast milk bottle.Sweet potato flour was added according to the treatment and pasteurized milk at 85 o C for 15 min.The milk temperature was lowered to room temperature.P. acidilactici BK01 starter was inoculated as much as 5% and homogenized.Incubation occurred at 37 o C for 18 h (Andriani et al., 2021).

Test Parameters 1. Moisture Content
The moisture content was tested according to the AOAC (2005) method, and the cup was baked at 110 o for 1 h.The cup was cooled in a desiccator to remove moisture and weighed; a 5-g sample was put into a porcelain cup and oven at 105 o for 8 h.
Then, the sample was cooled in a desiccator for 30 min, and the final weight was weighed.
Moisture content was calculated by subtracting the weight of the sample before and after drying divided by the weight of the sample multiplied by 100%.

Protein content
Protein content testing was carried out according to the AOAC (2005) method; as much as 1 g of sample was put into a kjeldhal flask, 1 g of selenium and H2SO4, then deconstructed until transparent.The results of deconstruction are diluted and distilled until all N from the liquid is trapped by 0.05N H2SO4, which is first mixed with three drops of methyl red.Furthermore, the distillation results are titrated with 0.01 N NaOH.

Fat Content
Fat content testing was carried out according to the AOAC (2005) method, weighing as much as 1 g of dry sample.Then, wrap with fat paper in the oven and weigh.The sample is put into a soxhlet connected with a fat flask.Pour hexane solvent until submerged and extract for 5-6 hours until the fat solvent drops into a clearcolored flask.

Statistical Analysis
All data obtained in this study were analyzed using statistical analysis of SPSS version 26, and if there were significant differences (p < 0.05) then continued with the Duncan Multiple Range Test (DMRT).

Moisture Content
The results of statistical analysis showed an interaction (p < 0.05) between the type of sweet potato (Factor A) and the percentage of sweet potato flour addition (Factor B) on the moisture content of P. acidilactici BK01 fermented milk.This shows that the type of sweet potato and the percentage of sweet potato flour addition affect the moisture content.Sweet potatoes contain fiber which can affect moisture content, fiber can help retain less water compared to cells rich in starch.The average moisture content of P. acidilactici BK01 fermented milk was 84.27-88.89%.The average moisture content of each treatment is presented in Table 1.
Table 1 shows an interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A2B3 treatment was significantly different (p < 0.05) from the A3B3, A1B2, A2B2, A2B2, A1B1, A2B1, A3B1 treatments, but not significantly different (p > 0.05) from the A1B3 treatment.The highest average moisture content was found in the A1B1 treatment with the addition of 0% white sweet potato flour, namely 88.89%.In comparison, the lowest average moisture content was found in the A2B3 treatment with the addition of 6% purple sweet potato flour, namely 84.27%.The A2B3 treatment with 6% purple sweet potato flour has the lowest moisture content value in P. acidilactici BK01 fermented milk.This is because purple sweet potato flour's moisture content is lower than that of yellow sweet potato and white sweet potato.The moisture content in the type of sweet potato flour is different depending on the chemical composition of the type of sweet potato.
The type of purple sweet potato contains much fiber, which can affect moisture content; fiber can help retain a little water compared to cells rich in starch.This follows the opinion of Rakhmawati et al. (2014), which states that fiber can bind water; water firmly bound in food fiber is difficult to evaporate again, even though the drying process.Olatunde et al. (2015) added that the moisture content of white and yellow sweet potatoes has a relatively higher moisture content of 10.84-12.86%.Toan and Ahn (2018) stated that purple sweet potato flour has a moisture content of 7.14% with a fiber content of 2.1%.In this study, the moisture content of purple sweet potato flour, white sweet potato, and yellow sweet potato were 5.53%, 6.35%, and 7.00%, respectively and almost the same as the research of Afiati et al. (2018) the moisture content of purple sweet potato flour was 5.14%.
The A2B3 treatment was significantly different (p < 0.05) from A3B3, where the moisture content of fermented milk with the addition of 6% purple sweet potato flour was lower at 84.27% compared to the addition of 6% yellow sweet potato flour at 84.74%.This is because the high starch content in yellow sweet potato flour is hydrolyzed by microorganisms, which causes the bound water to become free water, thus increasing the moisture content of fermented milk by adding yellow sweet potato flour.Murtius (2016) opinion states that the activity of microorganisms in breaking down starch causes bound water in the material to become free water.Added to the opinion of Zhang et al. (2024), materials rich in starch have a high ability to bind water, but after fermentation, the ability to bind water decreases.
The A1B1, A2B1, and A3B1 treatment, namely fermented milk without the addition of sweet potato flour (control), has the highest moisture content value of 88.89%, 88.65%, and 88.86%, respectively, compared to the A1B2, A2B2, A3B2, A1B3, A2B3, A3B3 treatments.The higher the percentage of sweet potato flour addition, the lower the moisture content of fermented milk.This is due to the content of dietary fiber and starch in sweet potato flour that can bind water in fermented milk.This follows the opinion of Suryana et al. (2022), which states that the addition of pouring flour containing glucomannan can bind water and form gels in large quantities, causing the space between particles to become narrower and much water is bound and trapped.Added by the research of Afiati et al. (2018) states that increasing the percentage of sweet potato flour by 4% can reduce the moisture content of yogurt from 77.22% to 70.74%, which is caused by fiber in sweet potato flour of 0.39%.Zaddana et al. (2022) added that fermented milk, with the addition of beetroot, has as much as 4% and sweet potato, as much as 6%, and has a moisture content of 84.46%.

Protein Content
The statistical analysis revealed an interaction (p < 0.05) between the protein content of P. acidilactici BK01 fermented milk and the combination of sweet potato type (Factor A) and the percentage of sweet potato flour addition (Factor B).This suggests that the protein level is influenced by the kind of sweet potato and the amount of sweet potato flour added.The lactic acid bacteria that are stimulated to thrive by the prebiotic content of sweet potatoes produce protein coagulation, which alters the protein of the fermented milk that results.The average protein content of P. acidilactici BK01 fermented milk was 3.65-5.67%.The average protein content of each treatment is presented in Table 2. Table 2 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A2B3 treatment was significantly different (p < 0.05) from the A3B3, A1B2, A2B2, A3B2, A1B1, A2B1, A3B1 treatments, but not significantly different (p > 0.05) from the A1B3 treatment.
The highest average protein content was found in the A2B3 treatment with the addition of 6% purple sweet potato, namely 5.67%.In contrast, the lowest average protein content was found in the A1B1, A2B1, and A3B1 treatments with the addition of 0% white, purple, and yellow sweet potatoes (control), namely 3.65%, 4.25%, and 4.04%, respectively.The A2B3 treatment, the addition of 6% purple sweet potato has the highest protein content in P. acidilactici BK01 fermented milk.This is due to the high content of dietary fiber, fructooligosaccharides, resistant starch, and inulin in purple sweet potato flour.The prebiotic content can stimulate LAB growth, most of which cell components are proteins.This follows the statement of Grosu et al. (2023), which states that lactic acid bacteria cells have a plasma membrane layer and cell walls containing S layer proteins.In addition, the high protein content as part of the total solids is also related to the low moisture content of fermented milk in the treatment combination of sweet potato flour types with the highest concentration of 6%.Added to the research of Melia et al. (2022) The A1B1, A2B1, and A3B1 treatments, adding 0% white, purple, and yellow sweet potato flour (control), had the lowest protein levels in P. acidilactici BK01 fermented milk.This is because sweet potato flour is not an addition, a prebiotic source that stimulates LAB growth, and no protein content in sweet potato flour ingredients can increase protein levels.The low protein content in fermented milk is also related to the high moisture content in fermented milk (control).The higher the moisture content, the lower the fermented milk's total solids (protein).In this study, the respective protein contents in purple, white, and yellow sweet potato flour were 1.39%, 2.07%, and 1.53%.This follows the statement of Purwantiningsih et al. (2022), which states that the more protein, the higher the protein content.
Added by Kusumaningsih et al. (2022) the protein content in white sweet potato starch is 3.91%, purple sweet potato starch is 4.77%, and yellow sweet potato starch is 5.21%.In the research of El-Attar et al. (2022), the supplementation of yellow sweet potato flour, as much as 0.5-4%, has a protein content of 3.07-4.03%.In this study, the protein content of fermented milk is between 3.65 and 5.67%, according to the Codex Alimentarius (2003) standard of 3.2%.

Fat Content
The results of statistical analysis showed an interaction (p < 0.05) between several types of sweet potato (Factor A) and the percentage of sweet potato flour addition (Factor B) on the fat content of P. acidilactici BK01 fermented milk.This shows that the type of sweet potato and the percentage of sweet potato flour addition affect the fat content.The average fat content of P. acidilactici BK01 fermented milk was 1.59-3.47%.The average levels of each treatment are presented in Table 3. Table 3 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A2B3 treatment was significantly different (p < 0.05) from the A1B2, A2B2, A3B2, A1B1, A2B1, A3B1, but not significantly different (p > 0.05) from the A1B3 and A3B3 treatments.The highest average fat content was found in the A2B1, A1B1, and A3B1 treatments with the addition of purple, white, and yellow sweet potato flour as much as 0% (control), namely 3.47%, 3.26%, and 3.10%, respectively.The lowest average fat content was found in the A2B3, A1B3, and A3B3 treatments with the addition of purple, white, and yellow sweet potato flour as much as 6%, namely 1.59%, 1.69%, and 1.72%, respectively.The A2B1, A1B1, and A3B1 treatments, namely fermented milk with the addition of purple, white, and yellow sweet potato flour as much as 0%, have the highest moisture content in P. acidilactici BK01 fermented milk.
This is due to the low-fat content in sweet potato flour and the absence of added sweet potato flour, so the total amount of solids does not increase.The fat content in fermented milk remains constant, so there is no contribution.This is the opinion of El-Attar et al. (2022), who state that low sweet potato fat content can reduce the fat content of fermented milk.The added opinion of Siti et al. (2022) states that raw materials influence fat content; the higher the fat content of the material, the greater the fat content of the resulting yogurt.In this study, the fat content of purple, white, and yellow sweet potato flour was 0.25%, 0.26%, and 0.30%, respectively.Lower than the research of Toan and Ahn (2018) in his research the fat content of purple sweet potato flour was 0.44%.Fadli et al. (2023) added that the fat content of purple sweet potato flour was 2.11%, orange sweet potato flour was 1.87% and white sweet potato flour was 1.04%.
The A2B3, A1B3, and A3B3 treatments, namely fermented milk with the addition of purple, white, and yellow sweet potato flour as much as 6%, have the lowest moisture content in P. acidilactici BK01 fermented milk.This is because the higher percentage of sweet potato flour addition will increase the proliferation of LAB, which also increases the lipase enzyme that can hydrolyze fat, thereby reducing the fat content of fermented milk.This is the opinion of Burgain et al. (2014), who states that lactic acid bacteria will produce lactase, lipase, and protease enzymes during the fermentation process.Garcia-Cano et al. (2019) added that LAB isolated from dairy products is essential to their research.Namely, P. acidilactici SRCM101189 has a high lipolytic activity, which has the potential to produce aromatic compounds and sensory characteristics in fermented foods.Daniatur et al. (2024), synbiotic yoghurt with 1-4% taro starch added has a fat content of 0.54-3.37%., respectively.Lower than this study, the fermented milk with sweet potato flour addition was 1.59-3.47%and met the standard of maximum yogurt fat content of 3.8% (SNI 01-7552-2009).

Organoleptic Analysis of Fermented Milk
The results of statistical analysis showed an interaction (p < 0.05) between several types of sweet potato (Factor A) and the percentage of sweet potato flour addition (Factor B) on the organoleptic value of taste, color, texture, and aroma of P. acidilactici BK01 fermented milk.This shows that the type of sweet potato and the percentage of sweet potato flour addition affect the organoleptic value.
The average organoleptic values of taste, color, texture, and aroma of each treatment are presented in Table 4.

Taste
Table 4 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A2B3 treatment was significantly different (p < 0.05) from the A1B1, A1B2, A3B3, A2B1, A2B2, A3B1, A3B2, A3B3 treatments.The A2B3 treatment, namely fermented milk with purple sweet potato flour, has the lowest taste sensory value of 2.62 (neutral).This is because fermented milk with purple sweet potato flour has a very sour taste, which causes consumers to dislike it.This follows the opinion of Alzahra (2023), who states that consumers prefer fermented drinks with a less sour taste and still taste sweet.Added by the opinion of Costa and Junior (2016) stated that lactose fermentation produces lactic acid sourced from the conversion of carbohydrates in proportion to the presence of lactic acid produced by LAB during the fermentation process and causes the distinctive taste of fermented milk.Added by Patel and Parikh (2016), the increase in acidity value in fermented milk products is produced by LAB production due to the fermentation process.It can affect the level of consumer acceptance of fermented milk.Added by Rahmawati and Kusnadi (2017), the sour taste in yogurt is produced by lactic acid during fermentation, releasing H + ions that can reduce the pH value.

Color
Table 4 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A1B1 treatment was significantly different (p < 0.05) from the A3B1, A1B2, A2B2, A3B2, A1B3, A2B3, A3B3 treatments, but not significantly different (p > 0.05) from the A2B2 and A1B2 treatments.
In the A1B1 treatment, A2B1, namely the addition of 0% white and purple sweet potato flour (control), and A1B2 treatment, namely the addition of 3% white sweet potato flour, has the highest color sensory value, namely A1B1 3.84 (like), A2B1 3.88 (like) and A1B2 3.88 (like) respectively.This is because panelists prefer fermented milk that is naturally white.
This follows the opinion of Najih et al. (2018), which states that the whiter color of milk in tempeh fermented milk causes panelists to like it.Added to the opinion of Teichert et al. (2020), maintaining the white color of fermented milk can provide a natural taste, which still creates a nutritious and attractive product through fermentation processing.Added by Spence (2015), the white color gives the impression that it matches the color of fermented milk to provide consumer expectations about fermented milk products.The A3B3, A1B3, and A2B3 treatments, namely the addition of yellow, white, and purple sweet potato flour as much as 6%, have the lowest sensory value, namely A3B3 2.98 (neutral), A1B3 3.12 (neutral), 3.46 (neutral) respectively.
The higher percentage of sweet potato flour addition causes the color of fermented milk to be pale.The A3B3 treatment is pale yellow, A1B3 is pale white, and A2B3 is pale purple.This follows the opinion of Umar et al. (2022), which states that the carotenoid component in yellow sweet potatoes is beta-carotene, which is provitamin A and can be converted into vitamin A, causing a yellowish pigment.Added by Rizki et al. (2019), the addition of purple sweet potato flour makes the yogurt product purplish in color due to the anthocyanin content contained in purple sweet potato.

Texture
Table 4 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The treatment of A3B1 was significantly different (p < 0.05) to the treatment of A2B1, A1B1, A1B2, A2B2, A3B2, A1B3, A2B3, A3B3.In the A3B1, A3B3, A2B3, A1B3 treatments, namely fermented milk adding yellow sweet potato flour as much as 0% (control) and fermented milk adding yellow, purple and white sweet potato flour had the lowest texture sensory value, namely A3B1 2.56 (dislike), A3B3 2.92 (neutral), A2B3 2.96 (neutral), A1B3 2.88 (neutral).In the A3B2, A2B2, and A1B2 treatments, namely fermented milk with the addition of yellow, purple, and white sweet potato flour as much as 3% has the highest texture sensory value, 3.84 (like), 3.66 (like), and 3.54 (like) respectively.This is because adding sweet potato starch to fermented milk can increase the viscosity and softness of fermented milk texture.This is the opinion of Rizki et al. (2019), who states that adding sweet potato flour causes viscosity and softness of texture due to the carbohydrate content that can function as a filler.Gohar et al. (2024) added that fillers such as polysaccharides are needed in making yogurt, which can affect the texture.The A3B3, A2B3, and A1B3 treatments, namely fermented milk with the addition of yellow, purple, and white sweet potato flour as much as 6%, have the lowest sensory value, namely A3B3 2.92 (neutral), A2B3 2.96 (neutral), A1B3 2.88 (neutral).This is due to the very thick texture that reduces the level of panelists' liking.This is in accordance with the opinion of Hertina (2022) that fermented milk with the addition of pouring flour of as much as 1% has a high viscosity and produces a very high viscosity that reduces the level of panelists' liking.Sari (2016) added that the texture of fermented milk is related to the decrease in moisture content in fermented milk; the viscosity of fermented milk, which is increasing, causes the texture to thicken.
Research by Yolanda et al. (2022) added that fermented milk with sweet potato flour and as much as 4% is more favorable than 10%.

Aroma
Table 4 shows the interaction (p < 0.05) between the type of sweet potato flour (Factor A) and the percentage of sweet potato flour addition (Factor B).The A3B3 treatment was significantly different (p < 0.05) from the A1B3, A2B3, A2B2, A3B2, A1B1, A2B1, A3B1 treatments, but not significantly different (p > 0.05) from the A1B2 treatment.The A3B3 treatment, namely fermented milk with the addition of 6% yellow sweet potato flour, has the highest aroma sensory value of 3.62 (like), while in the A3B1 treatment, namely, the addition of 0% yellow sweet potato flour (control) has the lowest sensory value of 3.00 (neutral).This is because increasing sweet potato flour will produce a sour aroma from sweet potato and lactic acid from fermentation by breaking down carbohydrates and lactose by lactic acid bacteria.This is in accordance with the opinion of Yolanda et al. (2022), which states that adding sweet potato flour produces a distinctive sour aroma in yogurt.Anjarwati et al. (2022) added that aroma is the smell that is generated so that it provides delicacy, which will then affect the attractiveness of panelists to certain food products.Adding sweet potato to yoghurt results in a characteristic sweet potato aroma that may affect sensory properties.Purple sweet potato has anthocyanins that not only enhance the colour but also contribute to the aroma and taste of the yoghurt.(Hariadi et al., 2023).

CONCLUSION
The results concluded a significant interaction between the type of sweet potato (Factor A) and the percentage of sweet potato flour addition (Factor B) on moisture content, protein content, and organoleptic in

Table 1 .
Average moisture content (%) of fermented milk with the addition of several types of sweet potato flour (Factor A) and the percentage of sweet potato flour addition(Factor  B) abcd Different superscripts in the columns indicate significant differences (p < 0.05).

Table 2 .
Average protein content (%) of fermented milk with the addition of several types of sweet potato flour (Factor A) and the percentage of sweet potato flour addition(Factor  B)

Table 3 .
Average fat content (%) of fermented milk added with different types of sweet potato flour (Factor A) and percentage of sweet potato flour added(Factor B)

Table 4 .
Average sensory analysis scores of fermented milk with the addition of different types of sweet potato starch (Factor A) and percentage of sweet potato starch addition (Factor B) Note: abcde Different superscripts in the columns indicate significant differences (p < 0.05).