[Proteo-polysaccharidic turbidity in depectinized raspberry juice]

A revertible turbidity happens in the depectinized red raspberry juice under refrigeration. Its analysis is carried out: --Chemically: Total sugar determination by anthrone methol, galacturonic acid determination by carbazol, total nitrogen determination according to Berthelot's coloured reaction (automated analysis) -- Physically: Calcium, potassium and magnesium determinations by atomic absorption. -- Chromatographically: Sugar separation and determination by HPLC. M. W. determination of the different entites by GPC (gel Sephadex G 100). Pectic substances separation on DEAE-cellulose column. The turbidity ensues from an enhanced by cold and acidic pH flocculation process which occurs between the large nitrogeneous molecules (inactive and enzymic proteins mainly). M. W. (superior to 150.000) of the depectinizing preparation and rich in glucose and mannose polysaccharidiques (M. W. between the range from 1.000 to 10.000) accompanied by aldobiuronic units. The origin of the manno-glucan entity remains to be determined. It could be issued either a limit-substrate produced by the degradation of the raspberry pectic substances or an by Aspergillus niger excreted compound.