Acid Production Of Maize Resistant Starch In The Simulated Fermentation In Vitro And Impacts Of Exogenous Lactic Acid Bacteria On Short-Chain Fatty Acid Production

Resistant starch (RS), known as enzyme-resistant starch or digestion-resistant starch, is defined as starch product that can resist enzyme hydrolysis and not be digested in the small intestine, but can be fermented in the large bowel by the microflora. Under the stimulated condition of the large intestines (anaerobic and37℃), water extract of healthy adult feces was used to ferment a maize resistant starch and a retrograded maize starch and a gelatinized maize starch, respectively. The content of four short chain fatty acids in the fermentation system was measured to investigate acid production. The impacts of added exogenous lactic acid bacteria on the RS fermentation system were studied, based on the amount of four short chain fatty acids produced in the fermentation system to reveal the effects the exogenous lactic acid bacteria on the acid production profiles. The main results are listed as below:(1) Gelatinized starch and retrograded maize and resistant starch were prepared by an autocla-ving-cooling treatment of high amylose maize starch. The content of RS resistant starch was29.4%(w/w) in the retrograded starch.(2) Under the stimulated conditions of the large intestines, water extract of health adult feces was used to ferment the gelatinized starch, retrograded starch and resistant starch for36h. The results showed that short chain fatty acids were detected in the fermentation system. The content of formic acid was the highest but other acids were lower in the fermentation system containing the gelatinized starch. The content of propionic and butyric acid increased slightly in fermentation system containing resistant starch and the retrograded starch.(3) When the adult fecal extracts and one culture of the selected exogenous lactic acid bacteria were mixed and fermented36h. The results demonstrated that total content of the short chain fatty acids or each of short chain fatty acids was very low in the fermentation product, especially propionic and butyric acid who were only determined after a fermentation of18h.(4) The adult feces extracts and exogenous lactic acid bacteria were used to ferment retrograded maize and resistant starch for different time. Analysis results showed that added L.fermentum, L.casei, L.rhamnosus, L. acidophilus and L. bulgaricus to fermentation system, the content of acetic acid increased significantly in fermentation production by twice; when E.faecalis, E.faecium, B.longum and B.infantis were added to fermentation system, the content of propionic acid and butyric acid increased significantly by four times.(5) Different volume exogenous of lactic acid bacteria were added to ferment retrograded maize, and analysis results showed that change of amount of lactic acid bacteria added did not affect the acid production; change of amount of lactic acid bacteria added affected the acid production and improved the quantity of the acid production rate.(6) Mixed bacteria with two strains of lactic acid bacteria were used to ferment resistant starch. Analysis results showed that after mixing two strains of lactic acid bacteria which did not impact on the content of acids, the content of short chain fatty acid in the fermentation products did not change; after mixing lactic acid bacteria with a strain producing acid and a strain without producing acid, the content of acid did not increase significantly compared with a mere strain of lactic acid bacteria producing acid; when two strains of lactic acid bacteria that produce acid were mixed, the content of acid increased significantly.