This research aimed to extract sap from residues after harvest of hot pepper, onion and sweet potato using EM fermentation extraction and hot water extraction method, and to produce safe and high-quality agricultural products for consumer with reducing agricultural management cost and developing environment-friendly agricultural materials. This research also scientifically verified the applicability of extracted sap on the production of safe and high-quality agricultural product. Chemical composition, total polyphenol and total flavonoid content of extracted sap from residues after harvest of hot pepper, onion and sweet potato were investigated in Chapter 1. Radical scavenging activity using DPPH and cytotoxicity of extracted sap using MTT assay are also looked into. In Chapter 2, by analyzing antibacterial activity of extracted sap from residues after harvest of hot pepper, onion and sweet potato, not only the function as plant food but the applicability as natural pesticide is also considered. Therefore, antimicrobial property of the extracted sap was inquired using food-hazardous bacteria, crop-hazardous bacteria and crop-hazardous eumycetes. In Chapter 3, on-site applicability of plant extract was evaluated by investigating the effect of extracted sap from residues after harvest of hot pepper, onion and sweet potato on germination and growth of hot pepper seed as well as the quality of hot pepper fruit. The results obtained are summarized as follows ;
Chapter 1. The Analysis of Biological Activity of Extracted Sap from Residues after Harvest of Hot Pepper, Onion and Sweet Potato
1. Regarding the pH of extracted sap, fermented extract was acidic with pH 3.05-3.50 regardless of the plant type. For hot water extract, Cheongyang pepper, Nokkwang pepper, onion and sweet potato indicated pH of 7.51, 7.55, 4.93, and 6.38, respectively. Fermented extract of Nokkwang pepper showed the highest level of nitrogen component with 0.11% while fermented extract of onion exhibited the highest level of phosphoric acid component with 0.05%. The level of potassium component was the highest with 0.28% among the hot water extracts of sweet potato. Hot water extract of sweet potato showed the highest calcium component of 0.052%, while hot water extract of Nokkwang pepper showed the highest magnesium component of 0.067%. Zinc component was found only in fermented extract of sweet potato with 0.0013%. Manganese component was the highest with the value of 0.0004% in hot water extract of sweet potato when boron component was the highest in hot water extract of Nokkwang pepper and onion with 0.0024%. Hot water extract of sweet potato showed 0.0036% of iron component, which was the highest value among others. Also, silicon component was the highest in hot water extract of sweet potato with 0.0114%. The highest organic component was found in the fermented extract of Nokkwang pepper with 1.21%, and molybdenum and copper component was not found at all.
2. Hot water extracted sap of sweet potato showed the highest content of total polyphenols and flavonoids with 60.5±2.7 and 50.7±2.7 mg/g, respectively. In the comparative analysis of radical scavenging activity using DPPH, fermented extract of Nokkwang pepper displayed the highest antioxidant activity with 55.6 ㎍/mL. On the other hand, in the comparative analysis of radical scavenging activity using ABTS, hot water extracted sap of sweet potato showed the highest antioxidant activity with IC50 value of 99.0 ㎍/mL.
3. As a result of comparative analysis of cytotoxicity of sap extracted from residues after harvest of hot pepper, onion and sweet potato using MTT assay, the range of cell viability of all extracts was 76.9~106.6%, indicating no or little toxicity.
Chapter 2. Antibacterial Activity of Sap Extracted from Residues after Harvest
of Hot Pepper, Onion and Sweet Potato
1. No clear zone was produced against 6 different food-hazardous microorganism in undiluted and 1/2-, 1/3-diluted sap of hot water extract from residues after harvest of hot pepper, onion and sweet potato, indicating there was no antibacterial property. In undiluted and 1/2-, 1/3-diluted sap of fermented extract, Nokkwang pepper showed the strongest antimicrobial activity against 6 different food-hazardous microorganisms.
2. There was no antibacterial activity in undiluted sap extracted with hot water and 1/2-, 1/3-diluted sap from residues after harvest of hot pepper, onion and sweet potato for Erwinia carotovora subsp., Xanthomonas campestris, Clavibacter michiganensis subsp. michiganensis, and Pseudomonas sp. Antibacterial activity was identified for Clavibacter michiganensis subsp. michiganensis only in undiluted sap of Cheongyang and Nokkwang pepper, extracted with hot water. Undiluted and 1/2-, 1/3-diluted sap of fermented extract of hot pepper, onion and sweet potato showed strong antibacterial property against Xanthomonas campestris and Pseudomonas sp. with the fermented extract of Cheongyang and Nokkwang pepper.
3. As a result of investigating the activity of antifugal activity of sap extracted from residues after harvest of hot pepper, onion and sweet potato, 7.1±0.9 mm of clear zone was produced against Rhizoctonia solani AG-1(IA) Kuhn in Cheongyang pepper fermented extract. 8.3±0.6 mm of clear zone was produced in Nokkwang pepper fermented extract.
Chapter 3. The Effect of Sap Extracted from Residues after Harvest of Hot Pepper, Onion and Sweet Potato on Hot Pepper Growth
1. As a result of analyzing the effect of sap extracted from residues after harvest of hot pepper, onion and sweet potato on the germination of pepper seed, the seed was not sprouted in undiluted and 1/2-, 1/3-diluted sap of fermented extract of hot pepper, onion and sweet potato. In undiluted sap treatment plot of hot water extract, hot water extract of onion showed 84% of germination rate while hot water extract of Cheongyang pepper showed 94% and 97% of germination percent in 1/2- and 1/3-diluted sap treatment, respectively.
2. In the investigation of the effect of the sap extracted from residues after harvest of hot pepper, onion and sweet potato on the growth of hot pepper, length of main stem and stem diameter showed no significant difference in all treatment plot including untreated plot. Undiluted sap of fermented extract and 150 times diluted treatment plot exhibited shorter plant height compared to the untreated (water), control (EM), and hot water extract treatment groups. Especially, as extracted sap was being diluted, growth of first plant height, main stem length and stem diameter increased. Pepper fruit also showed activated growth with diluted concentrations of extracted sap. Yield was the highest in the fermented extract of Nokkwang pepper in undiluted plot with 770 g/plant, while hot water extract of Nokkwang pepper also showed the highest yield in 150 times diluted plot with 900 g/plant.
3. With regard to the effect of the sap extracted from residues after harvest of hot pepper, onion and sweet potato on the property of hot pepper, springiness and cohesiveness showed similar values for all plots of extracted sap. Hardness and gumminess were the highest in undiluted plot of hot water extract of sweet potato with the value of 35.5 and 27.5, respectively. Chewiness was the highest in undiluted group of fermented extract of sweet potato with the value of 23.2. In ASTA values, undiluted and 150 times diluted plot in hot water extract of onion indicated the highest value with 78.0 and 76.3, respectively. The pH of pepper fruit was in the range of 5.42-7.07, and hot water extract of sweet potato in undiluted plot showed the highest value with 7.07. Sugar content was in the range of 0.20-0.47 °Brix, and the fermented extract of sweet potato in 150 times diluted plot showed the highest value of 0.47 °Brix. Total acidity was distributed in the range of 0.19-0.71, while hot water extract of Cheognyang pepper of undiluted plot showed the highest value of 0.71.
4. Finally, the effect of sap extracted from residues after harvest of hot pepper, onion and sweet potato on photosynthesis, chlorophyll content of hot pepper leaf was measured. The value was in the range of 80.0-84.7 mg/L, relatively similar results among the various samples. From the result of measuring chlorophyll component of pepper fruit, which is the quality indicator of color and gloss of pepper, the distribution range was 14.7-30.1 mg/L. The chlorophyll content was the highest in undiluted plot of hot-water extract of Cheongyang pepper with the value of 30.1 mg/L. Total polyphenol content of pepper fruit was in the range of 130.1-248.0 mg/g, while hot water extract of onion in 150 times diluted plot showed the highest value of 248.0 mg/g.