FER-1000 Lecture Notes - Lecture 10: Gram-Positive Bacteria, Gram-Negative Bacteria, Hemocytometer
20 Mar 2017
School
Department
Course
Professor
Document Summary
In general we like to know yan (yeast assailable nitrogen) leading into fermentation. When we need nitrogen we can add diammonium phosphate (dap) and yeast autolysate: yeast material = amino nitrogen, vitamins, minerals. Ammonia ion specific probe: similar to ph probe, determines ion content based on activity on ions in solution. Ion specific probes can be purchased for any number of measurements: correlate electric potential produced through probe (ions passing through membrane) to concentration of that ion. Nopa: only amino acids that can be used directly. Fan: amount determined by formol titration (good estimate but no quantitative analysis) Yan: basically the nopa and ammonium test. Yeast need amino acids and ammonium for successful fermentation: ammonium naturally occurs in grapes but dap supply might still be necessary. Suggested nitrogen numbers differ a lot depending on sources (recommended minimum often around 150 pm prior to fermentation. Ammonium additions only visible for short time, rapid uptake by yeast (foaming) -> keeping records important!
