Research Paper CHARACTERISTICS EVALUATION of SPAGHETTI

Journal of Global Biosciences ISSN 2320-1355 Volume 8, Number 6, 2019, pp. 6271-6280 Website: www.mutagens.co.in

Research Paper CHARACTERISTICS EVALUATION OF SPAGHETTI SQUASH (Cucurbita pepo) FERMENTATION BY YINKIN FERMENTED POWDER Maynanda Brigita Chrysta, Ji Hee Woo, Eun Suk Lee and Won Sik Choi

Department of Bio-Industrial Machinery Engineering, Pusan National University, Miryang 50463, Republic of Korea.

Abstract The subspecies of Cucurbita pepo fruit, which is known to contain many beneficial components, is spaghetti squash. The fruit flesh and the seeds of this fruit contain high protein and carbohydrates. Despite these many benefits, the fruit’s consumption in Korea remains lower than its production. This fruit seeds are also mostly waste material. The potential method can be used to increase fruit consumption is by fermentation. Since no one has ever produced this product as a fermented beverage, it is necessary to check the condition of the product. The purpose of this study was to describe the characteristics of spaghetti squash during its fermentation. In this study, fermentation was conducted for 30 days at 34.6 ± 1.3oC using “Yinkin” fermented powder as a starter with an initial sugar concentration of 20oBrix. The only experimental variation was to use either the whole fruit (sample A) or the seedless fruit (sample B). The pH, total soluble solids (sugar) content, and alcohol content were observed at 3-day intervals during fermentation. The total soluble solids content decreased during fermentation from 19.75oBrix to 6.45oBrix for sample A and from 20.04oBrix to 6.85oBrix for sample B. The pH decreased from 4.817 to 4.616 for sample A and 4.902 to 4.595 for sample B. Whereas, the final alcohol content of products for sample A and sample B was 13.67% and 14.65%, respectively. The results revealed that whole spaghetti squash produced better fermentation products from lactic acid bacterial (LAB) fermentation with Yinkin fermented powder than seedless fruit. Key words: fermentation, fermented powder, seedless, spaghetti squash, quality.

INTRODUCTION Edible squash and pumpkins in the world can be grouped into three main groups, namely Cucurbita moschata, C. maxima, and C. pepo. These three species are cultivated throughout the world with high production yields [1]. Most parts of the pumpkin are

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Creative Commons Attribution License 4.0 International License Journal of Global Biosciences Vol. 8(6), 2019 pp. 6271-6280 ISSN 2320-1355 consumed, including flesh of fruit, seeds, and fleshy shells. Pumpkin can be either eaten directly or after processing. Pumpkin flesh is usually made into juices, processed into soups, or used as a mixture to make food such as bread, rice cakes, and candies [2].

Pumpkin has high nutritional content, as well as rich content of proteins, antioxidants, minerals, and vitamins. The fruit’s flesh and seeds are low in fat and calories. Therefore, pumpkins are famous as ingredients for traditional medicine in many countries, including China, Korea, India, Mexico, Argentina, and Brazil [3].

The Cucurbita pepo subsp. pepo includes spaghetti squash, which is a versatile vegetable loaded with many beneficial components that promote eye and skin health, aid in wound healing, help fight off free radicals, support bone health, help abate inflammation, and promote cardiovascular health [4]. Spaghetti squash originated in China and can be consumed raw, put into a variety of dishes, such as soups, or processed into stews. When served as “spaghetti”, various pasta sauces can also be added as a topping.

Spaghetti squash contains many nutrients, such as potassium, beta carotene, folic acid, and vitamin A. This fruit is also rich in riboflavin, B vitamins, niacin, and thiamin, which improve cellular function [4]. The seeds contain high protein with a balanced amino acid composition, and also fairly high lysine content compared to wheat [5]. However, this fruit has low calories of, around 42 calories per 155 grams portion, and is also low in carbohydrates [6]. Therefore, this fruit is quite often used as a substitute for pasta ingredients. Similar to brightly colored vegetables, spaghetti squash has folate which supports the formation and development of new cells and prevents birth defects [7].

This fruit has a color between ivory to yellow/orange, with bright yellow or orange flesh. Orange spaghetti squash has high carotene content. The raw, fruit flesh has the same solid texture as other raw squash. But when cooked, the flesh is separated into strands that resemble spaghetti pasta. Spaghetti squash can be stored for about one month at room temperature [8].

Of all the Cucurbita species themselves, the most consumed species in Korea are C. maxima and C. moschata. The consumption of Cucurbita pepo in Korea is still reported to be quite low compared to others. In addition, research related to this type of Cucurbita is also limited in Korea [2]. Tridge (2018) reported that the production of spaghetti squash in Korea continues to increase every year, including for exports and imports [9]. Therefore, fermentation may be applied to the spaghetti squash to try to balance its production and consumption.

Fermented products are favored by Koreans. Terefe (2016) reported that in order to increase the shelf life of food products, fermentation can be an alternative. This process is also known to increase product value added [10]. In the development of spaghetti squash fermented drinks, fermentation uses microorganisms and the sugar

www.mutagens.co.in 6272 Journal of Global Biosciences Vol. 8(6), 2019 pp. 6271-6280 ISSN 2320-1355 contained in it. One of the microorganisms known to be an important substrate related to fermentation is Lactobacillus. This microorganism has also been reported to like the environment of pumpkins as a medium for growth [11, 12]. However, no one has ever produced this product as fermented beverage. Therefore, it is necessary to check the condition of the product and describe the characteristics of spaghetti squash during its fermentation. Through this study, it can be examined whether spaghetti squash fermentation works well by measuring changes in sugar content, pH level, and alcohol content.

MATERIALS AND METHODS

Materials

Spaghetti squash (Cucurbita pepo) was obtained from local farmers in Miryang, South Korea. Spaghetti squash was washed with tap water. The fruit was cut into small pieces before fermentation. Yinkin fermented powder (Yinkin, Korea) was used as the fermentation starter and other necessary materials and chemicals were used from laboratory stock.

Yinkin fermented powder was added to increase the fermentation efficiency. This fermented powder contains many microbes which are useful for accelerating fermentation. The raw materials contained in Yinkin fermented powder include Weissella koreensis BSS10, Lactobacillus salivarius SW709, L. brevis BSS04, L. casei BSS05, L.plantarum HS729, L.sakei MG521, Leuconostoc citreum BSS07, Leuconostoc mesenteroides SY1118, Streptococcus themophilus BSS08, S. cerevisiae BSS01, B. subtilis BSS09, B. subtilis BSS11, and others [13].

Fermentation

In the two experimental conditions sample A used the whole fruit and sample B used the fruit without seeds. The initial sugar content or brix was set to ±20oBrix by manipulating the sugar added to the sample. The ingredients for both samples were 5 kg spaghetti squash, 2.2 kg sugar, 10 L water, 5 g salt, and 5 g Yinkin fermented powder.

The sugar, salt, and Yinkin fermented powder were put into a fermentation jar that had been filled with water. After all the ingredients were stirred until dissolution, the fruit was added and stirred. The complete fermentation samples were stored in a fermentation room for 30 days at 34.6 ± 1.3oC. The changes of fermentation room temperature during fermentation can be seen in Table 1 below.

Table 1. Fermentation room temperature during process

Day 0 3 6 9 12 15 18 21 24 27 30 Temp (ºC) 35 33 33 34 33 35 37 36 35 35 35

www.mutagens.co.in 6273 Journal of Global Biosciences Vol. 8(6), 2019 pp. 6271-6280 ISSN 2320-1355 pH value and total soluble solids content analysis

The spaghetti squash fermentation was monitored for pH value and total soluble solids content at 3-day intervals. The pH meter type pH-250L (iSTEK, Korea) was used as a medium to measure the pH value of the product. Each sample was stirred before pH reading, and the electrode was rinsed with distilled water between readings. The total soluble solids (sugar) content was measured following ISO 2173 (2003) method [14] using a pocket refractometer PAL-1, Cat. No. 3810, capacity: 0.0-53% (ATAGO, Japan). The total soluble solids contents were expressed as degree Brix (oBrix). The examination of each condition of the fermentation samples was done in triplicate.

Alcohol content analysis

The alcohol content was observed at 3-day intervals during fermentation. The sample was distilled by freeze distillation before the analysis was carried out to obtain the pure alcohol solution contained in the sample. The alcohol content was determined with a digital alcohol-meter PET-109 (ATAGO, Japan) by averaging three measurements done in triplicate.

RESULTS

Total soluble solids content during fermentation

Total soluble solids content is one of the parameters most often used to monitor the quality during fermentation. The total soluble solids content (TSS) is also commonly used to describe the sugar content in the sample. TSS content analysis can be used as the parameter for fermentation process condition because the sugar content is one of the factors that affect the fermentation process so it can run well. During the alcoholic fermentation process, the sugar content in the base material will be converted by yeasts cells into ethyl alcohol and carbon dioxide [15]. The changes of total soluble solids content during spaghetti squash fermentation can be seen in Figure 1. The total soluble solids content decreased from 19.75oBrix to 6.45oBrix for sample A and from 20.04oBrix to 6.85oBrix for sample B after 30 days of fermentation; i.e., both samples showed similar decrement.

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20 A

Brix) B o 18

6 Total Soluble Solids Content ( Content Solids Soluble Total 4 0 5 10 15 20 25 30 Time (Day) Figure 1. Total soluble solids content of product during fermentation for whole fruit (A) and seedless fruit (B) pH value during fermentation

Generally, the pH condition of solution decreased during fermentation, although there was a fairly high increase on the 15th day (Figure 2). The pH value decreased from 4.817 to 4.616 for sample A and 4.902 to 4.595 for sample B after 30 days of fermentation.

For pH condition of fermented product, Adegunloye and Famolu (2016) reported that during fermentation pH decreases as sugars are consumed and reaches a stable point when they are exhausted, at which time fermentation considered complete [16].

4.95 A 4.90 B

4.85

4.80

4.75

pH Value pH 4.70

4.65

4.60

4.55 0 5 10 15 20 25 30 Time (Day)

Figure 2. pH value of product during fermentation for whole fruit (A) and seedless fruit (B)

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Alcohol content during fermentation

Alcohol is produced through fermentation. The changes in alcohol content of the spaghetti squash during fermentation are shown in Figure 3. The alcohol content for both samples tended to undergo the same changes during fermentation. There was a high increase at the beginning of fermentation until the third day, and then slowly decreased until the 12th day. The alcohol content started to tend to be constant the next day until the end of fermentation, although there was a slight increase on the 15th day. The final alcohol content of product for sample A and sample B were 13.67% and 14.65%, respectively.

Figure 3. Alcohol content of product during fermentation for whole fruit (A) and seedless fruit (B)

DISCUSSION

Fermentation is one process that is quite often used for the purpose of extending the shelf life of a food ingredient. There are many kinds of fermented products, one of which is alcohol-based fermented drinks. In Korea, alcoholic beverages are one of the favorite and widely consumed drinks. Considering that things, if spaghetti squash fermentation runs well, it can be said that fermentation can be done to increase this fruit consumption besides extending shelf life.

In alcoholic fermentation, the four basic parameters to be monitored are temperature, pH, CO2 level, and alcohol content. These four factors are known to determine how the evolution of the original microbial population occurs in the product. The interactions of which later becomes a key factor in fermentation [17]. Therefore, the product characteristics observed were sugar content, pH value, and alcohol content.

The initial sugar level for both samples was the same, only the type of spaghetti squash differed. In general, there was decreasing in sugar content during fermentation.

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A very high decrease occurred in the first 3 days, while from day 15 to the end of process it began to be constant for both samples (Fig.1).

Sample A (with seeds) exhibited a greater decrease in sugar content than sample B (seedless) due to faster fermentation at higher sugar content. Rodaa et al. (2017) also explained that fermentation increases because of the enzymatic hydrolysis process which reduces the amount of polysaccharides and increases the reducing sugar and dissolved solids present in the material [18]. As sugar is consumed during fermentation, the released CO2 gas reacts with water vapor to form carbonic acids which increases acidity [19].

There was decreasing in pH value for both samples during fermentation, where the highest decrease occurred in the first 6 days. Figure 2 shows that the pH value of sample A was higher than sample B at the beginning of the process, but from day 6 to the end of the process the pH value of sample A became lower than sample B. Generally this pH is decreased due to yeasts that synthesize sugars into alcohol and then by acetate bacteria reformed into organic acids, such as acetic acid and gluconate acid, which decrease in the pH of the fermentation medium [20]. Therefore, besides the total sugar content and pH value, LAB fermentation will also produce acidic and alcohol contents in the product. For LAB, the microflora includes several species of Lactobacillus, Pediococcus, and O. oeni. Generally, a higher pH increases microbial diversity during alcoholic fermentation [17].

The alcohol content in the fermentation is affected by many factors, such as initial fermentation time, acidity, sugar content, and yeast inoculation. Generally, alcohol content increases initially to a maximum, and then decreases. The best condition of fermentation beverage product is also when the alcohol content is not too high.

In the present research, the alcohol content peaked at day 3 and then tended to reduce (Fig.3). This was possible because in the first 3 days, fermentation proceeds quickly and the sugar is rapidly converted into alcohol due to the high concentration of sugar. Therefore, there was also a fairly high decline of sugar concentration from ±20oBrix to ±12oBrix by the 3rd day (Fig. 1).

After initially increasing during fermentation, the alcohol content decreases probably because the resulting alcohol stimulates the growth of Acetobacter xylinum that produce acetic acid aerobically using the alcohol as the nutrient [20]. Figure 3 shows a decrease in alcohol value for both samples during fermentation however other changes occurred between day 12 and day 15.

The slight increase at day 12 to day 15 actually did not only occur in alcohol content, but also on sugar content (Fig. 1) and pH value (Fig.2). It was estimated to be caused by a decrease in temperature in the fermentation room which had occurred from day 3 to day 12 when the temperature only reached 33oC (Table 1). Temperature is one of the important factors in fermentation. Higher fermentation temperatures are

www.mutagens.co.in 6277 Journal of Global Biosciences Vol. 8(6), 2019 pp. 6271-6280 ISSN 2320-1355 known to accelerate the process. Higher temperatures and sufficient nutrient content can stimulate bacterial growth and activity in fermented products [21]. Afoakwa et al. (2011) also reported that probably because of volatile acid evaporation, including acetic acid, in the product, sometimes there is an increasing of pH value during fermentation [22].

CONCLUSION

The general results revealed that spaghetti squash can be used as an ingredient for fermented beverages. The characteristics, such as sugar content, pH value, and alcohol content of a product during the process are in accordance with the fermentation product condition. In this study also shows the whole spaghetti squash produced better fermentation products from lactic acid bacterial (LAB) fermentation with Yinkin fermented powder than seedless fruit.

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