Page 82 - New additives and ingredients in the formulation of aquafeeds

Nevertheless, the expected biological advantages obtained by the inclusion
of enzyme extracts obtained from fish viscera (reduction of the fish
production cycle or increase of the food conversion efficiency) are not good
enough to counteract the high increase in feed cost derived from their
inclusion.
There are still many questions regarding real cost of production of enzyme
extracts at industrial scale. The scaling up study has been developed as
detailed as possible, but a massive production would probably decrease the
costs calculated here. In this sense, perhaps the main factor to consider
should be the substitution of the highly expensive stabilization of final
product by freeze-drying by alternative procedures like (J Sineiro 2012, pers.
comm., 20th of March):
Vacuumdrying at low temperature; the final product is not a freeze-dried but
an aggregated powder with low moisture. Equipment for this processing is
routinely used in food industry.
The use of cold acetone for precipitation of the enzymes before the second
centrifugation would allow to obtain a semi solid material not requiring
further freeze drying and hence reducing production cost. The product
could be dried using cyclonic dryers operating at low temperature and not
complete vacuum (J A Vázquez 2012, pers. comm., 27th of March).
Ultrafiltration followed by stabilization by adsorption in chitin or chitosan. In
this case the adsorbent is a cheap product with a not great purity, what also
implies a price reduction compared to the initial procedure.
Ultrafiltration and further freezing in liquid phase. In this case, the suitability
of using a liquid additive by feed producers should need to be assessed.
Microencapsulation in cyclodextrin. It is routinely used in the elaboration of
pharmaceutical/cosmetics, although it is also quite expensive.
Although at a first glance the high production cost enzyme extracts fromfish
viscera may be discouraging, some additional points should be considered
in a future prospect, i.e.; the biological evaluation using a different species
or the combination of extracts obtained from different sources which can
provide an enrichment in both protease and lipase activities.
80 Use of purified extracts from fish viscera as an enzyme additive in feeds for juvenile marine fish