Process of making muffin from modified sweet potato flour made from sustainable raw material based Indonesian local resources

Modified sweet potato flour is sweet potato flour that has been enhanced to maintain and improve its quality, thereby reducing the overall consumption of sweet potato flour in Indonesia. Muffins, being a type of quick bread that requires only a small amount of gluten, are highly suitable for use with modified sweet potato flour. This research was carried out in two stages: Stage I involved the modification of sweet potato flour, and stage II consisted of formulating a mixture of wheat flour and modified sweet potato flour. The research employs a non-factorial Completely Randomized Design (CRD) for both of these two stages and the determine of the best treatments are conducted using De Garmo effectiveness index method. The modified flour (annealing, instant yeast fermentation, LAB fermentation, and acetic acid) was analyzed for various quality parameters. Once the best method for modifying sweet potato flour was determined, the second stage involved the preparation of muffins. The muffin (100:0, 75:25, 50:50, 25:75, and 0:100) were also analyzed for various quality. The final results indicated that the J3 treatment (LAB fermentation) was the most effective for modifying the flour, and the F2 treatment (75:25 ratio) was the best formulation for muffins.


Introduction
Sweet potatoes come in various types.Theres is one characteristic that categorically stands out: the color of their tuber flesh.Sweet tuber flesh comes in several types, including purple, white, yellow, and orange.This difference in flesh color also impacts the content and offers various advantages [1].In Northern Sumatra, various varieties of sweet potatoes are distributed.Among these distributed varieties are Japanese, Sibolu, and Taiwan varieties [2].In this study, sweet potatoes of the Taiwanese variety were utilized in Brastagi.The characteristics of Taiwan varieties sweet potatoes in Dairi Regency include an average tuber diameter of 3.06 cm, tuber length of 16.31 cm, orange skin color, and orange fleshed color [3].
Sweet potatoes are an agricultural product prone to damage and require additional treatment to extend their shelf life.One viable treatment option is the development of sweet potatoes into flour.The quality of sweet potato flour undergoes physical and chemical degradation during processing, and thus, modifying the production of sweet potato flour is expected to either maintain or enhance its quality.These modifications can be categorized into three main types: physical, chemical, and fermentation.In the physical category, sweet potato flour can be modified using annealing methods, In the chemical category, the application of acetic acid can be employed, while in the fermentation category, instant yeast and lactic acid bacteria can be utilized.By adopting these modified approaches in sweet potato flour production, it is expected that the reliance on wheat flour in Indonesia can be reduced.
In the preparation of biscuits and various types of cakes, flour is typically the main ingredient.Sweet potato flour can also be used as a substitute for wheat flour in these products, as they often serve as fillers.However, for specifically bakeries, sweet potato flour is still challenging to substitute.This is because some bakeries requires the dough to expand during the baking process.Muffin is a type of quick bread known for their practicality in preparation, as they do not require fermentation.The method employed in making muffin is the quick method, which involves simply combining all ingredients, followed by mixing.Muffin production requires only a minimal amount of gluten to achieve a softtextured muffin [4].Consequently, the use of modified sweet potato flour is anticipated to impart desirable characteristics that align with consumer preferences.

Materials
The material used were orange fleshed sweet patato Taiwan varieties from Sidikalang.The ingredient for muffin including baking powder, UHT milk, margarine, salt, sugar, and wheat flour were obtained from local market in Medan, North Sumatera.

Making Modified Sweet Potato Flour
Sweet potato washed, peeled, and sliced into chips by slicer.Modification was carried out with the first treatment, annealing (J1) by soaking the chips in distilled water in a 1:2 ratio at a temperature of 50°C for 16 hours [5].Second and third treatments involved instant yeast (J2) and Lactic Acid Bacteria (LAB) (J3) fermentation, specifically soaking the chips in a starter solution (bread yeast [6] and Biologically Modified Cassava Flour (BIMO-CF) [7]) in a 1:2 ratio for 24 hours.The dose of starter solution used was 1 gram per 1 liter of distilled water.The fourth treatment involved soaking the chips in a 2.5% acetic acid solution (J4) [8] for 2 hours with a 1:2 ratio.The chips were then washed and drained before being dried in the oven at 60°C.Subsequently, the dried chips were crushed with a disk mill and sieved in 80-mesh sieve.

Making Muffin
The modified flour obtained from the best treatment (determined by De garmo methods) was used in muffin, following the modified [9] literature.Melted margarine, sugar, eggs, UHT milk, and vanilla essence are stirred together.Then, mix wheat flour and sweet potato flour, milk powder, baking powder, and salt until smooth.Pour the batter into muffin tins and bake at 180°C in 30 minutes.The formulation of muffin is shown in Table 1.

Quality Analysis of Modified Sweet Potato Flour and Muffin
The research model consists of two stages.The first stage employs a non-factorial Completely Randomized Design (CRD) to create modified sweet potato flour (J).The modified flour were analyzed for quality.Once the best method for modifying sweet potato flour is determined, the best method of flour will be used for the second stage involves making muffins (F), using the non-factorial completely randomized design (CRD) method to compare sweet potato flour and wheat flour.The modified sweet potato and muffin was analyzed for quality, including moisture content, ash content, fat content [10], protein content [11], carbohydrate content [10], crude fiber content [12], and specific volume [13].

Analysis of Data Modified Sweet Potato Flour and Muffin
The obtained data is loaded into the excell software, to determine the best treatments in both Stage I and Stage II using the De Garmo effectiveness index method [14].

Physicochemcal properties of modified sweet potato flour
The annealing treatment (J1) had lower water content than the others (Figure 1).Water content is influence by large amounts of evaporation [15] due to enlarged starch granule pores.The large the pores, the larger amount of evaporation.The acetic acid treatment (J4) resulted in the lowest ash content (Figure 2).The higher water content, the lower ash content in the product [16].Instant yeast treatments (J2) and LAB treatments (J3) shows higher protein levels compared to annealing treatment (J1) and acetic acid treatment (J4) (Figure 3).It is because microorganisms take a role as single-cell proteins, leading to an increase in protein levels in the flour [17].Annealing treatment (J1) exhibited the highest carbohydrate content (Figure 4).Carbohydrate content is measured using 'by different' method, which means that as other physicochemical properties increase, the carbohydrate content will decrease.The modification treatment did not show significant differences in of fat content and crude fiber content in the product.

Functional properties of modified sweet potato flour
Modification treatment with annealing (J1) provides the highest water absorption capacity (Figure 5).The water content in a product influences its absorption capacity, with lower water content resulting in Modification Methods (J) higher water absorption capacity.Beside water content, carbohydrate content in flour also has an effect on water absorption capacity [18].According to that, a high carbohydrate content will increase the water absorption capacity of a material because starch granules can absorb water very effectively.The modification treatment did not show significant effect at oil absorption capacity of the modified flour.
LAB fermentation showed a higher baking expansion value compared to other treatments (Figure 6).It is because lactic acid bacteria produce enzymes that can break the -1,6 glycosidic bonds in amylopectin, increasing the amylose content of the flour.When exposed to heat, flour with higher amylose content expands more than flour with more amylopectin [19].
The selection of the best flour treatment is determined through the results of Garmo's analysis on baking expansion, water absorption capacity, oil absorption capacity, water content, carbohydrate content, ash content, and fiber content.Based on the analysis results, the best treatment was obtained through fermentation treatment with LAB (J3) and this treatment was subsequently applied in the manufacturing of muffins.

Physicochemical properties of muffins
Increasing proportion of modified sweet potato flour shows a decrease in water content (Figure 7), fat content (Figure 8), and protein content (Figure 9) in muffins with an increasing proportion of modified sweet potato flour.This is because "Kunci Biru" flour has higher water content (14.53%), fat content (0.98%), and protein content (8%) [20] compared to the water content (19.55%), fat content (0.61%), and protein content (3.81%) in modified sweet potato flour.LAB (J₃) Acetic Acid (J₄) Baking Expansion (mL/g) Modification Methods (J) Significant differences in carbohydrate (Figure 10) and crude fiber (Figure 11) content in muffins as the proportion of modified sweet potato flour increases.This increase is attributed to the higher carbohydrate and crude fiber content in modified sweet potato flour compared to wheat flour, specifically 75% and 84.66% for carbohydrate content ("Kunci Biru" flour and modified sweet potato flour) and 0.4-0.5% [21] and 2.40% for crude fiber content ("Kunci Biru" flour and modfied sweet potato flour).Therefore, the higher the proportion of modified sweet potato flour in the formulation, the greater the fiber and carbohydrate content in the muffin.Meanwhile, in terms of ash content parameters, muffins did not exhibit any significant differences with the increasing inclusion of modified sweet potato flour.
Flour treated with F5 yields the lowest specific volume compared to other treatments (Figure 12).During the baking process, baking powder generates gas, which becomes trapped in the muffin, causing an increase in its volume specific.Gluten plays a crucial role in gas absorption.According to literature [22], sweet potato flour lacks gluten.Consequently, as the proportion of wheat flour decreases, so does the muffin's gluten content.This results in the muffin dough having a reduced capacity to absorb the produced gas, leading to a lower specific volume The selection of the best muffin treatment is determined through de Garmo's analysis of specific volume, water content, crude fiber content, protein content, and fat content.Based on the analysis results, the best treatment for muffins is achieved using a formulation of 75:25 (F2).