Foam stability of leaves from anthocyanidin-accumulating Lc-alfalfa and relation to molecular structures detected by fourier-transformed infrared-vibration spectroscopy

Foam stability related to pasture bloat from alfalfa pastures might be reduced by introducing a gene that stimulates the accumulation of mono-/polymeric-anthocyanidin. The objective of this study was to determine the foam formation (at 0 min) and stability (at 150 min) from aqueous leaf extracts of three transgenic Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4), parental non-transgenic (NT) alfalfa and AC Grazeland (bloat-reduced cultivar) harvested at 07:00 or 18:00 h. Initial and final foam volumes at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min. At 18:00 h, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Spectroscopic vibration associated with carbohydrates increased initial foam volume and stability. More amide I relative to amide II, fewer a-helices relative to beta-sheets and leaf extract ethanol-film and protein content increased initial foam volume but did not stabilize it. Spectroscopic vibration associated with all carbohydrates other than structural carbohydrates was more important than vibration from protein structures for foam formation and stabilization. In conclusion, Lc-alfalfa accumulated anthocyanidin and had reduced foaming properties compared with parental NT alfalfa but AC Grazeland and RangLc4 had the lowest foaming properties.