Free amino nitrogen concentration correlates to total yeast assimilable nitrogen concentration in apple juice

Abstract

Yeast assimilable nitrogen (YAN) is essential for yeast growth and metabolism during apple (Malus x domestica Borkh.) cider fermentation. YAN concentration and composition can impact cider fermentation kinetics and the formation of volatile aroma compounds by yeast. The YAN concentration and composition of apples grown in Virginia, USA over the course of two seasons was determined through analysis of both free amino nitrogen (FAN) and ammonium ion concentration. FAN was the largest fraction of YAN, with a mean value of 51 mg N L⁻¹ FAN compared to 9 mg N L⁻¹ ammonium. Observed YAN values ranged from nine to 249 mg N L⁻¹, with a mean value of 59 mg N L⁻¹. Ninety-four percent of all samples analyzed in this study contained <140 mg N L⁻¹ YAN, a concentration generally considered the minimum level needed in grape-based wines for yeast to fully utilize all of the fermentable sugars. FAN concentration was correlated with total YAN concentration, but ammonium concentration was not. Likewise, there was no correlation between FAN and ammonium concentration.

Yeast assimilable nitrogen (YAN), an important parameter in cider fermentation, was measured in two growing seasons in a range of apple cultivars grown in Virginia, USA and used in cider production. The concentration of free amino nitrogen was correlated with the total yeast assimilable nitrogen concentration, a finding that could streamline the process of total YAN determination for cider makers. The YAN concentration was not consistent from year to year, and on average, was below the minimum recommended value for successful fermentation.

http://ift.tt/2hlOX6Z