Perhaps you should try some spelling variations:
yeast extract » plant extract, het extract
malt extracts » plant extracts, cell extracts, also extracts
meat extract » meat extracts, death extract, meal extracts
melt extract » malt extract, melt extracted, cell extract

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((((meat extract) OR (yeast extract))) OR (((melt extract) OR (malt extracts)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((meat extract) OR (yeast extract))) or (((melt extract) or (malt extracts))))".
• Adding a wildcard symbol may retrieve word variants: ((((meat extract) OR (yeast extract))) or (((melt extract) or (malt extracts))))*.