Microwave Extraction Of Beet Pulp Dietary Fiber And Its Structural Characteristics

Beet pulp is a by-product generated in the process of beet sugar, which riched incellulose, hemicelluloses, pectin and other functional dietary fiber. This kind of dietary fiberis considered to be not easily digested by the human body, but it’s the nutrient with specialphysiological function. This paper takes the beet pulp as the research object, the microwaveextraction technology of pectin polysaccharides were studied to optimize the process and thestructure of extraction products were studied; Made comparative study of pecticpolysaccharides extraction with hydrochloric acid assisted by microwave, and analyzed thestructure and function of pectin extracted with the organic acid assisted by microwave.Continued to extracted alkali soluble polysaccharide from the sugar beet residue which haveextracted pectin with alkali method assited by microwave, and its structure was analyzed.Through the research, this thesis had drawn the following conclusion:The study on the process of beet pectin extracted with microwave. The optimumconditions of microwave-induced extraction for pectin yield was obtained as follows:extraction temperature of70℃, pH1.5, time of3min and water-material ratio of1:20, and itspectin yield reached15.03%. Neutral sugar, the degree of deacetylation and protein extractedwith microwave were21.95%,25.31%and9.94%respectively, which were much higher thanthe traditional thermal acid method (pH1.5/80℃/1h/SLR1:20). Microwave method madegreater degradation on Arabia sugar structure and molecular structure than the traditionalthermal acid method, which was the main reason leading to the sharply decreases ofmolecular weight (Mw), which ranged from123.7-197.1kg mol-1.The composition and function study of pectin extracted by organic acid assisted withmicrowave (MAO) from SBP. At the same condition(pH1.5/70℃/3min), MAO were higherthan what was extracted by hydrochloric acid with microwave(MAH) in pectin yield, Mw,protein content and acetyl content, but its content of GalA and ash were much lowercompared with MAH. Compared with the pectin extracted by conventional hot acid method(HEP-pH1.5/80℃/1h), the types of monosaccharide composition in pectin extracted by hotacid assisted with microwave (MEP-pH1.5/80℃/3min) did not have any change. Besides, thecontent of GalA, protein, acetyl and the polydispersity coefficient(PDI) in MEP were much higher than HEP, but the ratio of (Gal+Ara)/Rha was lower, which showed that themicrowave heating method had prompted the backbone and side chain of pectin degradation.According to the preceding analysis, the method of pectin extracted by oxalate acid assistedwith microwave(pH1.5/70℃/3min) was choosed for higher extraction rate, lower ash contentand stronger advantages in emulsifying activity/stability than other.The structure and function research of alkali soluble polysaccharide (ASP) extractedby microwave from the depectinized sugar beet pulp (DSBP). The extraction of ASP fromDSBP was carried out under different conditions using a full two–state experimental designfor three extraction parameters (time, temperature and NaOH%). The yield rate of the ASPvaried from11.8%to19.16%, GalA content was38.05-48.80%, arabia sugar content was14.55-20.71%, ferulic acid content was0.10-0.29%, the protein content was1.98-6.24%, andthe Mw ranged widely from39.44-146kDa. The ASP extracted as the condition E2(14min/80℃/0.45%NaOH) was easier to form emulsion for its higher Molecular weight,lower surface tension than others. Microwave extraction did not change its monosaccharidecomposition and structure types in the parameter range identificatted through the method ofFT-IR and AFM (atomic force microscopy). Compared with the traditional alkali extractionof ASP(1h/2℃/10%NaOH), the extraction method of microwave assisted alkali (14min/80℃/0.45%NaOH) was more efficient and environmentally.This study could lay a theoretical foundation for the establishment of the microwaveextraction technology in polysaccharide. It could expand the application of microwave in foodindustry, and enlarge the use of pectin polysaccharides in the field of medicine. This newtechnology has important significance in protecting environment for making full use of sugarbeet pulp, citrus, apple pomace and other waste of resources in China.