Both translations are correct, although "lieso" rather means "low-fat" or "fat-free", and "nugriebto" is "skimmed".

See the official page:
http://www3.lrs.lt/cgi-bin/preps2?Condition1=209810&Conditio...

and http://www.food.gov.uk/multimedia/pdfs/condensed.pdf
6.3.2. Sausasis nugriebtas pienas (nugriebto pieno milteliai, lieso pieno
milteliai) – dehidratuotas pienas, kuriame masės dalimis yra ne daugiau kaip
1,5 proc. riebalų [4, 19]
en – dried skim milk; DSM; skimmed milk powder; skimmilk powder; SMP; non
fat dried milk
fr – lait écrémé en poudre; poudre de lait écrémé; poudre de lait maigre; poudre
maigre

A am sure about my proposal because I had a similar question when translating EU legislation in the areas of dairy industry. Dairy specialists proposed (and insisted) on this variant ONLY (despite that there were many more alternatives).

Here are some useful references:
http://www.zum.lt/min/index.cfm?fuseaction=DisplayHTML&file=...

take a look at Item 5.2

Some useful info about thsi terminology also:

http://www.zum.lt/min/index.cfm?fuseaction=DisplayHTML&file=...

Hope it helps.

Regards
MariusV