| African locust, called Parkia biglobosa in Latin, is a kind of leguminous tree, its seed is apopular food condiment in Guinea and other West African countries, which is rich in proteinand starch. For nutritional purposes, starch in foods may be classified into three typesaccording to in vitro digestibility: rapidly digestible starch (RDS), slowly digestible starch(SDS), and resistant starch (RS), and there were RS1-4based on the process. More and moreresearches were focused on the modified digestibility of starch to be lowly digestible duringthe processing, its potential health benefit is satiety, stable glucose metabolism, diabetesmanagement, and mental performance, which will be benefical to human body for fightingcertain diseases serious (obesity, cardiovascular disease, diabetes, and cancer). In this study,the digestibility and applpication of starch from Parkia biglobosa bean were studied.Firstly, different solvents were used to extract the starch from the beans, including0.5%NaOH,1.5%Na2S2O5and water, and the highest yield of starch (32.86%) could be obtainedwhen5folds of water to flour is used, while protein content of the starch obtained was low(0.12%). In vitro digestibility analysis by Englyst method showed that their RDS, SDS, RScontents were11.56%-9.08%,52.29%-50.26%and24.56%-23.12%respectively bythe above different solvent extraction.To understand the formation of digestibility of Parkia starch, it was prehydrolyzed by α-amylase and amyloglucosidase at different prehydrolysis time before modification. Theresuidal of different prehydrolysis time were analyzed by X-ray, SEM and DSC, it showedthat the layered structure of crystalline and amorphous regions is likely the fundamentalstructural basis for their slow digestion property and the amorphous region was moresusceptible to digestion than the crystalline regions.And then the Parkia starch was modified by different methods were studied, includingphycial and chemical method. To produce RS, the Parkia starch was treated by heat-moisturetreatment, a physical modification. The Parkia starch was subjected to different heat-moisturetreatment (HMT) at different moisture contents (15%,20%,25%, and30%) at110oC for16h. The result showed that compared with native starch, the RS content of HMT starchesincreased significantly (P <0.05), the RS content could be the highest of31.96%when themoisture content was20%. To produce RS, the Parkia starch was modified by chemicalmodification; the effect of pyrodextrinization (PD) and cross-linking (CL) treatment on in vitro formation and digestibility of RS were used. The yield of RS with30.43%and30.69%respectively were obtained by pyrodextrinization (PD) and cross-linking (CL) respectively.Based on the above three modified method, all the RS content could be higher. However, theAfrican locust bean was rich in protein; if only use the starch compent, it is regret. So,following the sweet bean paste production which is normally made of pea in China, the beanpaste production is processed. The effect of cooking process conditions (bean/water ratio,soaking and cooking) on the Parkia starch digestibility was studied. The results exhibited thatwhen the bean mixed with water as1:4(W/V), soaked for12h, and then cooked at110°C,the sweet bean paste production with higher level RS content was obtained, and thedigestibility of Parkia starch was13.23%,44.33%and27.11%of RDS, SDS and RS,respectively. X-ray, DSC analysis showed that amylose is the molecular basis of RS, andamylopectin plays a key role in the structure of SDS and is the main constituent of SDS.And the physical methos of modification RS is more safe, convient, and very near to thehome preparation, the main procedure of the sweet bean paste production, the soakingprocedure was used to produce Parkia flour but not starch, because of its higher potein, ashand fiber with more valuable to human. The bean was treated by soaking at28°C for12h indistilled water (pH=5.3), citric acid solution (0.1%pH=2.6) and sodium bicarbonatesolution (0.07%, pH=8.4), cooking temperature (90°C) for3h and then placed in arefrigerator4°C for72h. The Parkia flour with high RS content (17.51%) was obtained, andthen it is applied to bread production by replacement of wheat flour with0,5%,10%,15%,20%,30%and40%. Processing, proximate composition, digestibility of starch in bread andsensory quality were evaluated. The RS content was1.67%in wheat bread and7.74%-8.68%in Parkia bread baked at200°C for45min, while3.61%in wheat bread and7.72%-10.54%in Parkia bread baked at130°C for90min. Color of the bread was remarkablyaffected by addition of different levels of Parkia flour. Sensory evaluation results indicatedthat bread with5%-15%Parkia flour were rated the most acceptable and there was nosignificant difference in their acceptabilityOur result showed that Parkia flour with high RS could be used in bread to change itsdigestibility, which will be valuable for the human with metabolic disease. |
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