1995 Volume 40 Issue 4 Pages 410-419
A 60-week long storage experiment was conducted to determine carotenoid stability on freeze-dried alfalfa (c.v. Natsuwakaba) leaf extract treated with various antioxidants during herbage processing. The antioxidants used were ethoxyquin (ETX), sodium metabisulfite (MBS), butylated hydroxyanisole (BHA), ascorbic acid (AA), α-tocopherol (AT) and tea leaf extract (TLE). Each leaf extract was divided into six portions and allocated into 2 clear and 4 amber coloured glass jars. One clear and 2 amber jars were flushed with nitrogen gas while ordinary air head space prevailed in the other three jars. The amber jars were kept under two storage shemes ; (a) 12-h constant lighting provided by 16 pieces of 40W fluorescent lamps with temperature controlled at 28℃ and (b) in a freezer (-18℃) without exposure to light. The clear jars were kept only under storage scheme (a). Low temperature protected the xanthophylls regardless of treatments of antioxidants but did not protect effectively β-carotene without ETX under long-term storage. At 28℃, both β-carotene and xanthophylls were degraded but the rate was far reduced by treating with ETX and keeping in amber coloured jars. With these treatments, about two-thirds of the values at 6-week storage were recovered after 60 weeks. Nitrogen gas flushing had no significant effect. Butylated hydroxyanisole, MBS and TLE could be alternative antioxidants but only for short-term storage. α-Tocopherol and AA did not prevent the decomposition of carotenoid at all. The study showed that addition of ETX during herbage processing and storing the leaf extract at low temperature (-18℃) gave the best protection for carotenoids. The best protein yield was also obtained in ETX treated leaf extract.
