Selection, Product Characteristics And Metabolite Spectrum Of A Common Starter Culture For Fufu And Usi Production

ABSTRACT

Fermented cassava products like fufu and usi (edible starch) are important staple foods in many African homes. Natural fermentation time is usually long resulting in slower acidification process and inconsistent nutritional composition of products which could be overcome with the use of starter culture. However, most available starter cultures are used for single food fermentation and are uneconomical. This necessitates the development of a starter culture for multiple related food products to reduce cost. Hence this study was designed to produce a common starter culture for the production of fufu and usi. 

Cassava varieties TME 30572, TME 4(2)1425 and TME 50395 were obtained from the International Institute of Tropical Agriculture, Ibadan and landraces from Bodija market. Fresh, peeled, chipped and grated cassava tubers were spontaneously fermented in the laboratory. Lactic Acid Bacteria (LAB) were isolated from the fermenting mash and identified phenotypically. Genotypically identified starters were selected based on screening for starch hydrolysis, linamarase and pectinase enzyme production, antimicrobial compound production and rate of acidification using standard methods. The starters were utilised singly and randomly combined to initiate fermentation for production of fufu and usi. Un-inoculated fermentation mash served as control. Rate of production of organic acids, various sugars, metabolic enzyme assays, nutritional and anti-nutritional content of the resulting mashes were monitored using standard procedures. Best starter was applied in the final production of fufu and usi. Shelf-life of the products were evaluated and compared with the control. Data were subjected to descriptive statistics and ANOVA technique at p=0.05.  

Ninety-eight LABs were identified as Lactobacillus plantarum (50.0%), L. acidilactici (12.2%), L. brevis (11.3%), L. fermentum (10.3%), L. delbrueckii (8.2%), L. mesenteroides (6.0%), and L. lactis (2.0%). Screened isolates did not hydrolyse starch but produced pectinase, linamarase alongside hydrogen peroxide, diacetyl and lactate with a rapid decrease in medium pH (6.5 - 3.6). Selected potential starters were genotypically identified as L. pentosus F2A (A), L. plantarum subsp. argentolarensis F2B (B), L. plantarum F2C (C), L. plantarum U2A (G) and L. paraplantarum U2C (I). The best starter combination CGI gave significant reduction in fermentation pH (7.1 - 3.7) and lactic acid ranged between 0.04mg/ mL and 6.9mg/mL. Sugars produced include xylose (3.2µg/mL), arabinose (1.4µg/mL), fructose (26.2µg/mL), glucose (30.3µg/mL) and sucrose (99.7g/mL). Enzyme assay revealed peak amylase (10.1U/mL) and pectinase (4.4U/mL) activities at 24 hours as well as linamarase (0.8U/mL) at 48 hours in fufu, whereas, in usi, highest linamarase (0.7U/mL) and pectinase (1.0U/mL) activities were recorded at 72hours with no amylase activity. The CGI-produced fufu and usi had significant reduction in phytate (0.3-0.1mg/g and 0.3-0.27mg/g), tannin (35.4-34.0mg/g and 35.4-32.3mg/g), cyanide (0.1-0.05mg/g and 0.1-0.0mg/g), and moisture (7.3%-5.1% and 7.3%-5.4%) content while total protein content increased (1.0-1.3% and 1.0-1.8%) respectively. Starter fermented fufu and usi had shelf-life of five days while control had three days.

The selected starter was able to ferment both fufu and usi to yield products with improved nutritional content, better shelf-life and reduced anti-nutritional composition. This could be employed in the production of indigenous fermented foods