Use of ultrafiltration and reverse osmosis to improve goats' milk yogurt

Acid and acetaldehyde production from yogurt starter was compared in goats' milk fortified by ultrafiltration (UF), reverse osmosis (RO) and addition of goats' milk powder. Starter activity was impaired when milk was concentrated by RO and aroma was poor in milk fortified by addition of dried milk, while yogurts made from milk concentrated by UF had good acidity and aroma. Threonine (0.1%) addition to unfortified milk and milk fortified by dried milk or UF produced yogurts with high levels of the aroma compound acetaldehyde.