Beiyi Shen | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Beiyi Shen. This seminar is open to the general public to attend.
Thesis Topic: The Saponin Composition of Common Canadian Pulses

MSc with Dr. Jonathan Curtis.

Seminar Abstract:

Pulses are high in nutritional value but are underutilized as foods due to their undesirable flavor attributes. These include bitterness, which may in part due to their saponin content.  In this research, a simple and rapid method using high-performance liquid chromatography-mass spectrometry (HPLC-MS) and requiring the minimum sample preparation was developed for the identification and quantification of saponins.  This was applied to 8 common Canadian pulses including 3 pea varieties, 4 faba bean varieties, pinto beans, black bean, kidney beans, chickpeas, and green and red lentils. The method was validated according to linearity, accuracy, detection limit, quantification limit, inter- and intra-day precision.

Saponin composition and content varies depending on the pulse type and variety. Four types of group B saponins including DDMP-conjugated soyasaponin bg and ag, and non- DDMP-conjugated soyasaponin Bb and Ba were identified in several pulse samples by HPLC-MS according to their relative retention times, and their molecular and fragment ions, as compared to standards and literature. All pulses tested contained soyasaponin Bb and bg with different amounts and percentile distribution. Amongst all 8 types of pulses, the total saponin content ranged from 30 to 8566 mg/g, where the lowest saponin content was found in faba bean variety Fabelle and the highest saponin content was found in black beans. Within the 3 pea varieties, the total saponin content varied from 550 to 2144 mg/g, and for the 4 faba bean varieties tested it varied between 30 and 388 mg/g. In all pulse samples, either soyasaponin Bb or bg was the predominant saponin type. Soyasaponin Ba and ag was only present in small amounts, except for black beans and pinto beans where 3145 and 1306 mg/g of ag was found, respectively.

The effects of pulse processing methods (sprouting, drying, baking and pressure cooking) on the saponin profile was investigated. Four cultivars of faba beans were germinated and subjected to a range of sprouting times (0, 48, 54, 60, and 72 h and drying times (0, 24, 36, 48, and 60 h). The saponin profiles of raw and sprouted faba bean seeds were measured, along with those found in baked faba bean flour-based crackers. Soyasaponin Bb and βg were the only two types of saponin found in the faba bean varieties studied. Soyasaponin Bb reaches the highest abundance after 54 h of sprouting in most cultivars, whereas the highest for βg was observed at 60 h in most cases, except for FB9-4 (54 h). A significant reduction of soyasaponin Bb was observed after 24 h of drying the sprouted seeds at 60°C. The total saponin content after 72 h of sprouting significantly increased in Snowdrop and Fabelle, decreased in FB9-4 and no change in Snowbird compared to unsprouted seeds. Prolonged drying times of up to 60 h significantly reduced the soyasaponin Bb content of 48 hours sprouted faba beans, whereas a slight increase was observed in the soyasaponin βg content in Snowdrop and Fabelle. Regardless of the sprouting condition, both baking and cooking of faba bean flour led to significant reductions in both total saponin and individual saponin content. In addition, the combination of sprouting and pressure cooking is more effective in reducing saponin content in faba bean comparing to pressure cooking alone.

The present research into the saponin profile of pulses and how this is changed by common food processing methods, contributes fundamental knowledge which may be beneficial in the utilization of pulses and pulse flour in food.