Effects of food formulation and thermal processing on flavones in celery and chamomile

Abstract

Flavones isolated from celery varied in their stability and susceptibility to deglycosylation during thermal processing at pH 3, 5, or 7. Apigenin 7-O-apiosylglucoside was converted to apigenin 7-O-glucoside when heated at pH 3 and 100°C. Apigenin 7-O-glucoside showed little conversion or degradation at any pH after 5h at 100°C. Apigenin, luteolin, and chrysoeriol were most stable at pH 3 but progressively degraded at pH 5 or 7. Chamomile and celery were used to test the effects of glycosidase-rich foods and thermal processing on the stability of flavone glycosides. Apigenin 7-O-glucoside in chamomile extract was readily converted to apigenin aglycone after combination with almond, flax seed, or chickpea flour. Apigenin 7-O-apiosylglucoside in celery leaves was resistant to conversion by β-glucosidase-rich ingredients, but was converted to apigenin 7-O-glucoside at pH 2.7 when processed at 100°C for 90min and could then be further deglycosylated when mixed with almond or flax seed. Thus, combinations of acid hydrolysis and glycosidase enzymes in almond and flax seed were most effective for developing a flavone-rich, high aglycone food ingredient from celery.

Fig. 1

Flavone aglycones and glycosides derived from celery.

Fig. 2

Deglycosylation and stability of flavone standards in aqueous solution at 100 °C for up to 300 min in pH 3, 5, or 7 ammonium acetate buffer. (A) apiin, (B) apigenin 7-O-glucoside, (C) apigenin, (D) luteolin, (E) chrysoeriol. Data are mean, n = 3. SD ≤ 10.8.

Fig. 3

Conversion of apigenin glycosides in chamomile extract to aglycone after incubation for 20 h at 37 °C alone (control) and combined 1:1 (w/w) with other food ingredients in 1.4 M, pH 5 sodium acetate buffer. Data are mean ± SD, n = 3. P < 0.001 versus control.

Fig. 4

Conversion of apigenin glycosides in lyophilised celery leaves to aglycone after incubation for 20 h at 37 °C alone (control) and combined 1:2 (w/w) with other food ingredients in 1.4 M, pH 5 sodium acetate buffer. Data are mean ± SD, n = 3.

Fig. 5

Conversion of apiin in celery to apigenin 7-O-glucoside and aglycone after acidification to pH 2.7 with phosphoric acid and thermal processing for 90 min at 100 °C. Data are mean ± SD, n = 3.

Fig. 6

Conversion of apigenin glycosides in celery to aglycone after incubation at pH 5 for 2 h at 50 °C alone (control) and combined with other food ingredients 1:1 or 5:1 (w/w). Data are mean ± SD, n = 3.