Some properties of Streptococcus faecalis subsp. liquefaciens isolated from cheese with special reference to production of bitterness
✍ Scribed by Hegazi, Fakhreya Z.
- Book ID
- 102841423
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 546 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0027-769X
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✦ Synopsis
Streptococcus faecalis subsp. liquefaciens was examined for proteolysis and development of bitterness in sterile buffaloes' skim milk with and without some additives. Cell population and the pH of milk were the most important factors in the breakdown of casein and development of bitterness. Sodium chloride level, altering the final concentration of bacteria in milk, had a direct role in the production of bitter peptides.
Calcium ions up to 5 m M did not affect proteolysis whereas higher concentrations were inhibitory. Electrophoretic analysis of proteose-peptone formed in sterile skim milk with and without NaCl revealed the presence of 3 peptides, 2 of which were probably associated with bitterness.
S. faecalis subsp. liquefaciens produced acidity slowly, but was the most acid producer (I .25 % after 72 h) of the streptococci. However, milk coagulated enzymatically and the curd shrinkage was related to salt-dependent acidity.
Strains of the organism coagulated fresh citrated human plasma within 21 h a t 30 "C, but without any visible fibrinolysis. The strains also were all a-haemolytic with occasionally a very few b-haemolytic variants on sheep blood agar. On human blood agar, a weak alpha-reaction was given. pa3OM Ha 06pa30BaHHe rOpbKEiX I' IenTUAOB. klOHbI KWIbUHR LIO KOHUeHTpaU1111 5 MM He 113MeHRIOT IIpOTeO-JI113, B TO B P M R KaK 6onee BhICOKUe KOHI&HTpaUUU BbIllBJIRlOT TOpMO3RI4ee AelCTB11e. 3JIeKTpO($OPeTUYeC-KUg mulanu3 IIpOTeO3HbIX IIeIITOHOB, KOTOPbIe 0 6 p a 3 y m ~c ~ B CTepUnbHOM MOnOKe 6e3 nO6aBKU 11 C nO6aBKOg Y K K l l l aHulan113 IIpOTeO3HbIX IIeIITOHOB, KOTOPbIe 06pa3yIOTCa B CTePlUIbHOM MOnOKe 6e3 n o 6 a ~~u 11 C nO6aB-KOG NaCl, IIOKa3WI 3 IIeneTkiAa, 113 KOTOPbIX 2 BepOaTHO RBnRIOTCR TOPbKUMU. s. fuecuh subsp. /iqUefUCit??IS MeAJleHHO o6pa3ye~ KUCJIOTY, IIBJIReTCR, OnHaKO, CaMbIM CUJIbHbIM KUCJIOTO-06pa30BaTeneM (1,25% Wpe3 72 9) CTpenTOKOKKOB. 3H3HMaTUYeCKOe CBepTbIEaHHe MOnOKa 11 YCaAKa CryCTKa, OAHaKO, CB113aHbI C COJIe3aBBCUMbIM nOAK11CneHHeM. HO 6e3 KaKOrO-JI1160 ($116p€iHOn113a. b e LLlTaMMbI IlBJIllIOTCIl U-11MOJIUTHYeCKUM11, UHOrAa BCTPe' fZlEOTCX LUTaMMbi o p r a ~w ~a KoarynupymT caencp UmpaTHym n n a s ~y 9enoBeKa n p ~ 30 "C B Tereme 21 raca, ManowicneHHbIe p-reMonuTarecKae BapuaHm Ha arape c oeesbeii KpoBbm. Ha arape c qenoBeYecKoii Kpomm ~a6nmnanacb cna6aa u-pearsur.