Note: Descriptions are shown in the official language in which they were submitted.
- 2087621
This invention relates to the production of livestock
feed and more particularly to converting potato waste to a
nutritious livestock feed through the growth of yeasts using
potato waste as a growth medium.
Persons engaged in raising and marketing livestock are
continually searching for a high-quality economical
livestock feed since the cost of feed represents a
substantial portion of the cost of bringing an animal to
market. The most cost effective feeds result from the
conversion of a potential waste product to a feed product.
Potato waste from plants processing sweet potatoes or
producing potato flakes, granules, french fries or potato
chips is a waste product which is too poor in quality to use
effectively as animal feed and which is often merely
discarded as a slurry. In addition, because such slurries
can degrade water quality, the disposal of slurries of
potato waste is an expensive matter, subject to federal and
state regulations.
What is need, therefore, is an economical method of
converting potato waste having only minimal food value into
a nutritious livestock feed.
Mense U.S. Patent No. 2,738,274 discloses a process for
preparing livestock feed by inoculating a substrate with a
culture and growing a strain of bacteria on it. The
substrate is various finely divided, steamed and cooled
- 2087621
vegetable materials, including potatoes. The Mense patent
does not disclose or suggest the use of yeast as an
inoculant.
Lines U.S. patent No. 4,144,132 discloses the
production of single-cell protein by using potato processing
waste as a growth medium for the yeasts Endomycopsis
fibuliger and Candida utilis. However, the yeasts fail to
utilize all the starch in the potato waste and cease growing
before all the carbohydrates in the potato waste are
converted to proteins.
Muller et al. U.S. Patent No. 4,046,789 discloses a
process for separating barkery-type waste products into
reusable sugar, starch, protein and fat components by
solvent extraction of the fat components and the addition of
a starch-hydrolyzing enzyme and a yeast of the Saccharomyces
or Candida type to the starch-containing residue. Kanter
U.S. Patent No. 4,894,244 discloses a process utilizing an
amyloglucosidase and Candida utilis to produce a product
suitable for human consumption. However, each of theæe
process is intended to produce a human food product, and
therefore is conducted under conditions designed to limit
any impurities which would render the product unsuitable for
human food. Neither of the processes is economically
feasible in a process for the production of livestock feed.
The present invention overcomes the foregoing drawbacks
~ 2087621
of the prior art by providing an economical and efficient
method of making livestock feed from potato waste. Potato
waste is comminuted into particles and the particles are
heated. The particles are then cooled to a cooling
temperature lower than that temperature at which a starch-
hydrolyzing enzyme is added to the particles. The particles
are further cooled to a cooling temperature lower than that
temperature at which a fermenting yeast is inactivated and a
fermenting yeast is added to the particles. The particles,
with added enzyme and yeast, are then divided into two
portions. The yeast Saccharomycopsis fibuliger is added to
the second portion, and the yeasts present in the portions
are grown. The first and second portions are recombined to
a batch in which the yeasts that are present are grown. The
batch is dried to form livestock feed.
The starch-hydrolyzing enzyme aids in the conversion of
the starch present in the potato waste to sugars which the
fermenting yeasts utilize during their growth. The yeast
Saccharomycopsis fibuliger is able to directly utilize
starch during its growth. The particular combination of
yeasts and enzymes added to the potato waste thereby insures
that all carbohydrate present in the potato waste will be
used to support the growth of the yeasts. In the process,
the yeasts convert a low protein, high carbohydrate waste to
a high protein, low carbohydrate livestock feed.
-- 4 --
20874~1
It is therefore a principle object of the present
invention to provide a method of converting a potato waste
to a nutritious feed by utilizing an enzyme and a
combination of yeasts, which enables essentially all the
starch and sugar in the waste to support the growth of the
yeast.
The foregoing and other objectives, features, and
advantages of the invention will be more readily understood
upon consideration of the following detailed description of
the invention.
According to the present invention potato waste is
converted by yeasts to a nutritious livestock feed. The
potato waste, from plants processing sweet potatoes,
producing potato flakes, granules, french fries or potato
chips, may include the waste slurry from steam or abrasive
peelers, potato trimmings from inspection tables, improperly
blanched potatoes, finished potato product from cold storage
which is damaged due to dehydration or grade problems, and
undersized potatoes from storage that do not meet fresh pack
or processing standards. The potato waste is ground,
chopped, riced or otherwise comminuted to form particles,
each particle preferably having no dimension greater than
1/16th inch, before being placed in a holding tank.
The potato particles are preferably heated by injecting
super heated steam through an enclosed auger as the
"- 2087621
particles are transferred from the holding tank to a first
fermentation tank that is equipped with heating and cooling
coils and a stirrer. The particles are preferably heated to
a temperature of at least 100 C to ensure that each cell in
S each potato particle is heated or cooked.
Water is added to the heated particles in the first
fermentation tank to form a slurry which is about 80 wt%
water. The particles are cooled to a temperature below the
temperature at which a starch-hydrolyzing enzyme such as
amylase is inactivated, preferably to between 55 to 60 C.
An amylase such as an amyloglucosidase is then added to the
cooled slurry. A suitable commercially available
amyoglucosidase is sold under the name "Diazyme L-200" and
available from Solvay Enzymes, Inc. of Elkhart, Indiana.
The amyloglucosidase is preferably added to the particles in
an amount approximating 0.25 wt%. The heating and cooling
coils of the fermentation tank maintain the selected
temperature of the slurry while the starch-hydrolyzing
enzyme contacts the particles for 1-2 hours.
The temperature of the particles in the fermentation
tank is reduced to a cooling temperature lower than that
temperature at which a fermenting yeast is inactivated, and
a fermenting yeast is added to the fermentation tank. The
fermenting yeast is a yeast capable of using a sugar such as
glucose for its own growth and producing protein. A yeast
2087621
such as Saccharomyces cerevisiae is acceptable, producing
- protein and B-complex vitamins during its growth. When
Saccharomyces cerevusuae is the fermenting yeast the
preferred cooling temperature is 25 to 30C.
About half the slurry with added enzyme and yeast is
transferred to a second fermentation tank, which is also
equipped with heating and cooling coils and a stirrer,
thereby forming a second portion, the first portion
comprising that remaining in the first fermentation tank. A
second fermenting yeast such as Candida utilis is added to
the first portion and the yeast Saccharomycopsis fibuliger
is added to the second portion. The fermenting yeasts are
added to the particles in an amount approximating 2.0 wt%.
The fermenting yeasts are available from W. Yeast of Mt.
Hood, Oregon. It should be noted that the addition of the
fermenting yeasts Candida utilis and Saccharomyces
cerevisiae could be reversed from the preferred order
specified above. The two portions are mixed or stirred
under aerobic conditions at the selected temperatures for
about two hours.
The two portions are then recombined into one batch and
the batch is maintained under aerobic conditions for a
minimum of about 48 hours. Excess water is removed from the
batch, for example, by a centrifuge. The excess water is
recovered and returned to a holding tank, whre additional
~_ 2û87621
nutrients such as phosphorus may be added, for reuse in the
production of the next batch of livestock feed. The
livestock feed may be dried, for example, in a cyclone
drier, and shaped into pellets or cubes, as desired.
The terms and expressions which have been employed in
the foregoing specification are used therein as terms of
description and not of limitation, and there is no
intention, in the use of such terms and expressions, of
excluding equivalents of the features shown and described or
portions thereof, it being recognized that the scope of the
invention is defined and limited only by the claims which
follow.
