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                                                                   Exhibit 10.55

                               GUARANTY AGREEMENT

         In consideration of certain financial accommodations made by of M&M
Nominee, L.L.C., or its assigns (hereinafter referred to as "Lender"), to The
UniMark Group, Inc., a Texas corporation (hereinafter referred to as
"Borrower"), the undersigned, Industrias Citricolas de Montemorelos, S.A. de
C.V. (hereinafter referred to as "Guarantor"), hereby unconditionally and
irrevocably guarantees the payment in full of, and promises to pay to Lender, on
demand, all obligations of Borrower to Lender pursuant to that certain
Promissory Note, dated as of even date herewith, made by Borrower in the
original principal amount of $200,000.00 (the "Promissory Note").

         Guarantor hereby waives, to the fullest extent permitted by law, notice
of acceptance of this guaranty and all other notices in connection herewith or
in connection with the indebtedness or obligations guaranteed hereby, including,
without limitation, notice of default, notice of intent to accelerate, notice of
acceleration and notice of non-payment, and further waives diligence,
presentment, protest, and suit on the part of Lender in the collection of any
indebtedness or obligation hereby guaranteed, and agrees that this is a guaranty
of payment and that Lender shall not be required first to endeavor to collect
from Borrower any indebtedness or obligation hereby guaranteed, to collect from
any other guarantor of any such indebtedness or obligation (an "Other
Guarantor") or to foreclose, proceed against, or exhaust any collateral or
security for any indebtedness or obligation hereby guaranteed, before requiring
Guarantor to pay the full amount of the liability hereby created. Suit may be
brought and maintained against the undersigned Guarantor at the election of
Lender, without joinder of Borrower or any Other Guarantor as parties thereto.
If any sum due Lender by Guarantor hereunder is placed in the hands of an
attorney for collection, or is collected through probate, bankruptcy, or other
court proceeding, then the undersigned Guarantor promises to pay the Lender's
reasonable attorneys' fees in such matter. In addition, the Guarantor agrees
that the Lender shall be under no obligation to marshal any assets or property
of the Borrower in order to protect the interest of the Guarantor with respect
to any claims, by subrogation or otherwise, for reimbursement after payment by
the Guarantor to the Lender hereunder.

         This guaranty is absolute and continuing and shall continue to apply
without regard to the form or amount of indebtedness or obligation guaranteed
that Borrower may create, renew, extend, or alter, in whole or in part, without
notice to Guarantor.

         Guarantor hereby represents and warrants that the execution and
delivery of this guarantee and the performance of the terms hereof will not
cause Guarantor to be in default under any agreement or instrument to which it
is a party or by which it is bound..

         Lender may surrender, release, exchange, or alter any collateral or
security for any indebtedness or obligation hereby guaranteed or may release or
compromise the obligations of any Other Guarantor without affecting the
liability of Guarantor under this Guaranty Agreement, and this guaranty shall
continue, in full force and effect, notwithstanding any legal disability of
Borrower to incur any indebtedness or obligation incurred to Lender.

         The undersigned Guarantor acknowledges that this Guaranty Agreement is
operative and binding as to the undersigned without reference to whether it is
signed by any other person or persons, including but not limited to, any Other
Guarantor, and without reference to whether it is signed by any other person
under any legal disability to sign the same; and that the liability hereunder of
the undersigned shall be cumulative of and in addition to any other liability or
obligation to Lender, whether the same is incurred through the execution of a
similar guaranty agreement, through endorsement, or otherwise.

         This Guaranty Agreement shall be binding upon, and inure to the benefit
of, Lender and Borrower and their respective successors and permitted assigns.
Lender may assign or transfer this Guaranty Agreement or its rights hereunder,
in whole or in part, without the prior consent of Borrower, and upon any such
assignment, all of the terms and provisions of this Guaranty Agreement shall
inure to the benefit of such assignee, to the extent

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so assigned. Guarantor may not assign or transfer this Guaranty Agreement or its
rights hereunder without the prior written consent of Lender.

         The Guarantor acknowledges and agrees that the proceeds of the loan
made pursuant to the Promissory Note have been and/or will be advanced to them
by the Borrower and that Guarantor has received value from the Promissory Note.
Lender is relying and is entitled to rely upon each and all of the provisions of
this Guaranty Agreement, and accordingly, if any provision or provisions of this
instrument should be held to be invalid or ineffective, then all other
provisions shall continue in full force and effect notwithstanding and the
balance of this Guaranty Agreement shall be interpreted as if such provision(s)
were so excluded and shall otherwise be enforceable in accordance with its
terms.

         This writing is intended by the parties as a final expression of this
Guaranty Agreement and is also intended as complete and exclusive statement of
the terms of that agreement. No course of dealing, course of performance, or
trade usage, and no parol evidence of any nature, shall be used to supplement or
modify any terms or provisions hereof. There are not any conditions to the full
effectiveness of this Guaranty Agreement.

         Guarantor represents and warrants to Lender that this Guaranty
Agreement has been duly and validly executed and delivered by Guarantor and
constitutes Guarantor's legal, valid and binding obligation, enforceable against
Guarantor in accordance with its terms. The Guarantor covenants with the Lender
that the Guarantor will not incur any lien on, or otherwise pledge or encumber
any of its assets without Lender's prior written approval.

         No failure on the part of Borrower to exercise and no delay in
exercising, and no course of dealing with respect to, any right, power,
privilege or remedy under this Guaranty Agreement shall operate as a waiver
thereof, nor shall any single or partial exercise of any right, power, privilege
or remedy under this Guaranty Agreement preclude any other or further exercise
thereof or the exercise of any other right, power, privilege or remedy. The
remedies provided herein are cumulative and not exclusive of any remedies
provided by law.

            This Guaranty Agreement shall be governed by and construed in
accordance with the laws of the State of Delaware applicable to contracts to be
performed in such state. THE GUARANTOR AGREES THAT VENUE IN ANY AND ALL ACTIONS
AND PROCEEDINGS RELATED TO THE SUBJECT MATTER OF THIS AGREEMENT SHALL BE IN THE
STATE AND FEDERAL COURTS IN AND FOR WILMINGTON COUNTY, DELAWARE, WHICH COURTS
SHALL HAVE EXCLUSIVE JURISDICTION FOR SUCH PURPOSE, AND THE GUARANTOR
IRREVOCABLY SUBMITS TO THE EXCLUSIVE JURISDICTION OF SUCH COURTS AND IRREVOCABLY
WAIVES THE DEFENSE OF AN INCONVENIENT FORUM TO THE MAINTENANCE OF ANY SUCH
ACTION OR PROCEEDING. SERVICE OF PROCESS MAY BE MADE IN ANY MANNER RECOGNIZED BY
SUCH COURTS. EACH OF THE PARTIES HERETO IRREVOCABLY WAIVES ITS RIGHT TO A JURY
TRIAL WITH RESPECT TO ANY ACTION OR CLAIM ARISING OUT OF ANY DISPUTE IN
CONNECTION WITH THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY.

WITNESS MY HAND, this 24th day of January, 2003.

INDUSTRIAS CITRICOLAS de MONTEMORELOS, S.A. DE C.V.

By: /s/ Emilio Castillo Olea
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    Emilio Castillo Olea
    Chief Executive Officer