Effect of ultrasound-accelerated debittering method on total alkaloid and total carotenoid content of lupin seeds (Lupinus albus L.) and storage stability of thermally treated lupin flours

Lupin (Lupinus albus L.) is a protein- and fiber-rich legume which has numerous health benefits. It also contains toxic quinolizidine alkaloids which must be removed for safe consumption (total alkaloid content < 0.02 g/100 g). This study aimed to develop novel lupin debittering method using ultrasound application at different temperatures (25-65 degrees C) and durations (10, 15, 20 and 25 min-every 4 h) as an alternative to traditional debittering method (including a boiling stage in water for 75 min followed by soaking for 144 h). The impacts of debittering methods on the total alkaloid content, total color difference ( increment E) and total carotenoid content of lupin were determined. In addition, it was to investigate the effects of different stabilization (dry roasting and microwave) and packaging (kraft and vacuum) methods on the color, acidity and peroxide values of debittered lupin flours by traditional and ultrasound-accelerated (25 degrees C-25 min-every 4 h) methods during 6 months to improve storage stability. The seeds were accepted as debittered when their total alkaloid contents were less than 0.02 g/100 g. The shortest debittering time (60 h) was obtained with ultrasound application at 25 degrees C for 25 min every 4 h. Moreover, all ultrasound applications elicited shorter debittering times (60-84 h) than traditional method (144 h). The increment E value of traditionally debittered lupin seeds (2.42) was lower than ultrasound-treated seeds (4.67-6.97). As the ultrasonication time increased from 10 to 25 min at 25 degrees C and 65 degrees C, total carotenoid content of debittered seeds decreased from 4.85 to 4.62 mu g/g and 4.63 to 4.19 mu g/g, respectively. Dry roasting method showed higher a* and lower peroxide values in both kraft and vacuum packaged samples compared to microwave heating. The acidity of the samples increased from 0.006 to 0.019% (kraft) and 0.021% (vacuum) after 6 months of storage. At the end of 6 months of storage time, acidity and peroxide values of lupin flours packaged with kraft bags were lower than vacuum-packed counterparts. The results showed that the ultrasound-accelerated debittering method seems to be effective in reducing the alkaloid content of lupin seeds with lower process time and water consumption. It also revealed that kraft bags are more suitable for longer storage stability than vacuum bags for the storage of stabilized lupin flour.

Automated summary

This study aimed to develop a new method for debittering lupin. The results showed that ultrasound-accelerated debittering method had shorter processing time and lower alkaloid content in lupin, while also improving storage stability.