title: The yogurt amino acid profile's variation during the shelf-life.
abstract: OBJECTIVE
  To analyze the yogurt amino acid profile starting from marketing through the whole shelf-life. The evaluation of the proteolytic activity of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, allows to deduce their vitality during the shelf-life period and within 45 days.
  
  
  METHODS
  Three types of full fats yogurts have been analyzed (a) natural white (b) sweet white and (c) whole fruit - in two stages: t0 (first day of shelf-life) and t1 (end of shelf-life). The proteins have been analyzed by the Kjeldahl method and the amino acid profile by HPLC.
  
  
  RESULTS
  In natural yogurt a significant increase of the amount of free amino acids has been observed during the period of shelf-life (97%). In the sweetened full fats and fruit yogurt, instead, there is a lower increase of respectively 33% and 39%
  
  
  CONCLUSIONS
  In whole milk natural yogurt, based on our data, the proteolytic activity seems to persist during the entire period of the shelf-life and this can be considered an index of bacterial survival, especially of Lactobacillus delbrueckii subsp. bulgaricus during the marketing process.
authors.affiliation: Departmentpt of Experimental Medicine, RU of Food Science and Human Nutrition, Sapienza University of Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Germani
authors.affiliation: Analysis srl., Frazione Pantalla, 06059 Todi (PG), Italy.
authors.forename: R
authors.initials: R
authors.lastname: Luneia
authors.affiliation: Departmentpt of Experimental Medicine, RU of Food Science and Human Nutrition, Sapienza University of Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Nigro
authors.affiliation: Departmentpt of Experimental Medicine, RU of Food Science and Human Nutrition, Sapienza University of Rome, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Vitiello
authors.affiliation: Departmentpt of Experimental Medicine, RU of Food Science and Human Nutrition, Sapienza University of Rome, Italy.
authors.forename: L M
authors.initials: LM
authors.lastname: Donini
authors.affiliation: Departmentpt of Experimental Medicine, RU of Food Science and Human Nutrition, Sapienza University of Rome, Italy.
authors.forename: V
authors.initials: V
authors.lastname: del Balzo
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D061353:Food Storage; D048668:Lactobacillus delbrueckii / Q000378:metabolism*; D048249:Streptococcus thermophilus / Q000378:metabolism*; D013997:Time Factors; D015014:Yogurt / Q000382:microbiology*
chemical_list: D000596:Amino Acids