A method for production of food quality starch from potato starch-containing sludge, wherein the potato starch-containing sludge comprises starch milk including non-hydrolyzed starch or hydrolyzed and non-hydrolyzed starch, waste water, potato pulp or fibers, and fruit juice, the method comprising: a) moving the potato starch-containing sludge through a first cross-flow filtration unit wherein the potato starch-containing sludge is separated into a first permeate stream comprising the starch milk, waste water, and fruit juice and a first retentate stream comprising the remaining potato pulp or fibers, wherein said potato pulp or fibers are collected for further use; b) moving the first permeate stream through a second cross-flow filtration unit wherein the first permeate stream is separated into a second permeate stream comprising waste water and fruit juice and a second retentate stream comprising starch milk; and c) moving the starch milk through a third cross-flow filtration unit, wherein the starch milk is concentrated and dewatered and wherein the removed water is directed into a third permeate stream and the starch is collected in a third retentate stream, wherein the starch content is at least 20%, wherein the dewatering step is conducted at a temperature not higher than 35°C, in order to avoid gelatinization which destructs the granular structure of starch, and wherein the cross-flow filtration units comprise a porous filter element across a surface of which the liquid medium to be filtered is flowed in a tangential flow fashion. the method comprising: a) moving the potato starch-containing sludge through a first cross-flow filtration unit wherein the potato starch-containing sludge is separated into a first permeate stream comprising the starch milk, waste water, and fruit juice and a first retentate stream comprising the remaining potato pulp or fibers, wherein said potato pulp or fibers are collected for further use; b) moving the first permeate stream through a second cross-flow filtration unit wherein the first permeate stream is separated into a second permeate stream comprising waste water and fruit juice and a second retentate stream comprising starch milk; and c) moving the starch milk through a third cross-flow filtration unit, wherein the starch milk is concentrated and dewatered and wherein the removed water is directed into a third permeate stream and the starch is collected in a third retentate stream, wherein the starch content is at least 20%, a) moving the potato starch-containing sludge through a first cross-flow filtration unit wherein the potato starch-containing sludge is separated into a first permeate stream comprising the starch milk, waste water, and fruit juice and a first retentate stream comprising the remaining potato pulp or fibers, wherein said potato pulp or fibers are collected for further use; b) moving the first permeate stream through a second cross-flow filtration unit wherein the first permeate stream is separated into a second permeate stream comprising waste water and fruit juice and a second retentate stream comprising starch milk; and c) moving the starch milk through a third cross-flow filtration unit, wherein the starch milk is concentrated and dewatered and wherein the removed water is directed into a third permeate stream and the starch is collected in a third retentate stream, wherein the starch content is at least 20%, wherein the dewatering step is conducted at a temperature not higher than 35°C, in order to avoid gelatinization which destructs the granular structure of starch, and wherein the cross-flow filtration units comprise a porous filter element across a surface of which the liquid medium to be filtered is flowed in a tangential flow fashion.