Changes in anti-nutrient, phytochemical, and micronutrient contents of different processed rubber (Hevea brasiliensis) seed meals

Rubber (Hevea brasiliensis) is a perennial plant crop grown in many parts of Africa, South East Asia, and South America, especially within the hot and humid climatic regions. Rubber seed, either as feed or food, is a useful raw material to produce edible oil and protein. Despite the huge quantity of rubber seeds produced in Nigeria and its potential as a protein source, rubber seeds still appear neglected and under-utilised as feed/food given its perception as inedible and toxic due to the high concentration of cyanogenic glycoside. Therefore, the quest for effective processing technique(s) that would enhance its food use application is very fitting. This current study was directed to determine the changes in anti-nutrient, phytochemical, and micronutrient contents of different processed rubber seed meals. Specifically, the rubber seeds underwent processing, which employed boiling and the combined action of boiling and fermentation methods that brought about three seed meal flour groups, i.e., raw (RRSM), boiled (BRSM), and fermented (FRSM) seed meals. These were subsequently analysed for anti-nutrient/phytochemical (oxalate, phytate, tannin, phenols, saponin, hydrogen cyanide (HCN), alkaloids, flavonoids, and trypsin inhibitors), and micronutrient (which involved minerals (magnesium, phosphorus, calcium, iron, zinc, potassium, sodium, manganese, lead, and selenium ) and vitamin (vitamin B1, B2, B3, C, E, and beta carotene)) contents. The results showed that the processing methods used to achieve the RRSM, BRSM, and FRSM, reduced the anti-nutrients (phytate, tannin, and oxalate) below the acceptable limits, and the HCN below the toxic levels. Importantly, the processing methods herein have not yet succeeded in removing HCN in the (processed) rubber seed meals, but can be seen to be heading toward the right direction. The FRSM obtained significantly lower (p < 0.05) anti-nutrient/phytochemical, but significantly higher (p < 0.05) mineral contents, compared with the other groups (RRSM and BRSM), except for flavonoids that obtained a 30% increase over the BRSM. Some mineral and vitamin contents could be lost in the BRSM compared to the others (RRSM and FRSM) in this study. Additionally, the FRSM obtained higher vitamin contents, after those of RRSM. Overall, the combined action of boiling and fermentation should be recommended for the proper utilisation of rubber seed as food/feed.

Automated summary

The study successfully reduced the anti-nutrient content in rubber seed meals and increased the mineral and vitamin content through processing methods. The combination of boiling and fermentation was recommended for the proper utilization of rubber seeds as food/feed.