Document:

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                                                                   Exhibit 10.54

                                 PROMISSORY NOTE

US$ 200,000.00                                                  January 24, 2003

                                    ARTICLE I
                               PAYMENT OBLIGATION

         FOR VALUE RECEIVED, the undersigned The UniMark Group, Inc., a Texas
corporation ("Maker"), unconditionally promises to pay to the order of M&M
Nominee, L.L.C., or its assigns ("Payee"), the sum of Two Hundred Thousand
Dollars (US $200,000.00), together with interest on the unpaid principal balance
from time to time outstanding at a rate per annum equal to ten percent (10%).
The principal of and accrued interest on this Note shall be due and payable in
lawful money of the United States on the earlier of (a) April 30, 2003, (b) a
Qualified Equity Financing (as hereinafter defined) or (c) upon demand following
the occurrence of an Event of Default (as defined in Article III) or as
otherwise provided in Article III hereof. Interest hereunder shall be calculated
on the basis of a year of 365 days and the actual number of days elapsed. As
used herein a "Qualified Equity Financing" shall mean the sale by Maker of (x)
equity securities of Maker or (y) debt securities which may be convertible into
equity securities of Maker or (z) any other securities convertible into or
exercisable for equity securities of Maker, in each case with net proceeds to
Maker in amount at least equal to the outstanding principal amount of this Note
and the outstanding principal amount of that certain Promissory Note dated
December 18, 2002 in the original principal amount of $100,000.00.

         Maker shall have the right to prepay the principal of this Note in full
or in part at any time and from time to time without premium or penalty,
provided, however, that accrued interest shall be due and payable
contemporaneously with such prepayment of principal.

                                   ARTICLE II
                                NEGATIVE COVENANT

         So long as any of the principal of and accrued interest of this Note is
outstanding, or until the Payee consents to the contrary and the Maker receives
prior written approval to the contrary from the Payee, Maker will not incur any
indebtedness senior or pari passu in right of payment to the prior payment in
full in cash of the outstanding principal of and accrued interest on the Note,
except for (a) indebtedness of the Maker owed on the date hereof and interest
accruing thereon or (b) to provide working capital necessary for the proper
conduct of the Maker's business or (c) to provide capital expenditure necessary
for the proper conduct of the Maker's business.

                                   ARTICLE III
                                EVENTS OF DEFAULT

         Any of the following shall constitute Events of Default ("Event(s) of
Default"):

         1.       default in making due and punctual payment of the principal of
                  the Note, or any interest accrued thereon, or any other amount
                  hereon, when and as such payment shall become due and payable,
                  whether at maturity or by acceleration or otherwise if such
                  payment is not made within five (5) days of written notice
                  received by Maker specifying such default; or

         2.       the failure by Maker to comply with the covenants set forth in
                  Article II of this Note; or

         3.       the sale by Maker of all or substantially all of its assets;
                  or

         4.       Maker shall admit in writing its inability to, or be generally
                  unable to, pay its debts as such debts become due; or

         5.       Maker shall (i) apply for or consent in writing to the
                  appointment of, or taking possession by, a receiver,
                  custodian, trustee or liquidator of itself or of all or a
                  substantial part of its

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                  property, (ii) make a general assignment for the benefit of
                  its creditors, (iii) file a petition seeking to take advantage
                  of any law relating to bankruptcy, insolvency, reorganization,
                  winding-up, or composition or adjustment of debts, (iv) fail
                  to controvert in a timely and appropriate manner, or acquiesce
                  in writing to, any petition filed against it in an involuntary
                  case under any law relating to bankruptcy, insolvency,
                  reorganization, winding-up, or composition or adjustment of
                  debts, or (v) take any action for the purpose of effecting any
                  of the foregoing; or

         6.       a proceeding or case shall be commenced, without the
                  application or consent of the Company, in any court of
                  competent jurisdiction, seeking (i) Maker's liquidation,
                  reorganization, dissolution, or winding-up, or the composition
                  or adjustment of its debts, (ii) the appointment of a trustee,
                  receiver, custodian, liquidator or the like of Maker or all or
                  any substantial part of its assets, or (iii) similar relief in
                  respect of Maker under any law relating to bankruptcy,
                  insolvency, reorganization, winding-up or composition or
                  adjustment of debts, and such proceeding or case shall
                  continue undismissed, or an order, judgment or decree
                  approving or ordering any of the foregoing shall be entered
                  and continued unstayed and in effect for a period of sixty
                  (60) days; or an order for relief against Maker shall be
                  entered in an involuntary case under any law relating to
                  bankruptcy, insolvency, reorganization, winding-up, or
                  composition or adjustment of debts.

         If an Event of Default occurs under paragraphs 1, 2 or 3 above, then
and in any such case Payee may declare the outstanding principal amount of the
Note to be due and payable immediately, upon written notice to Maker and, upon
any such declaration, the outstanding principal amount of the Note, and the
interest accrued thereon, together with all costs of collection, including
reasonable attorneys' fees if collected by law or through an attorney at law (as
further set forth in Section IV(4) hereof), shall immediately become due and
payable. If an Event of Default occurs under paragraphs 4, 5 or 6 above, then
the outstanding principal of and all accrued and unpaid interest on this Note
shall automatically become immediately due and payable, without presentment,
demand, protest or other formalities or notice of any kind, all of which are
hereby expressly waived by Maker.

                                   ARTICLE IV
                                     GENERAL

1.       Notices. Any notice or demand given hereunder by the holder hereof must
         be in writing to be effective and shall be deemed to have been given
         and received (a) when actually delivered to the address of the party to
         be notified if delivered in person, or (b) if mailed, on the earlier of
         the date actually delivered to the address of the party to be notified
         or (whether ever so delivered or not) on the third Business Day
         (hereinafter defined) after it is enclosed in an envelope, addressed to
         the party to be notified, properly stamped, sealed, and deposited in
         the United States mail, certified mail, return receipt requested. As
         used herein, "Business Day" means every day other than a Saturday,
         Sunday, or legal holiday in Dallas, Texas or New York, New York.

2.       Renounciation. Maker hereby renounces to any presentation of this Note
         and to any notice or refusal, protest or notice of protest and to delay
         of grace.

3.       Waiver. This Note evidences the payment obligations of Maker to Payee.
         No failure on the part of Payee to exercise and no delay in exercising,
         and no course of dealing with respect to, any right, power, privilege
         or remedy under this Note shall operate as a waiver thereof, nor shall
         any single or partial exercise of any right, power, privilege or remedy
         under this Note 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.

4.       Expenses. Maker agrees to pay or reimburse Payee for (a) all reasonable
         out-of-pocket costs and expenses of Payee (including, without
         limitation, the reasonable fees and expenses of counsel to Payee), in
         connection with any amendment, supplement, modification or waiver of
         any of the

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         terms of this Note and (b) all reasonable costs and expenses of Payee
         (including the reasonable fees and expenses of counsel) in connection
         with any default or Event of Default and any enforcement or collection
         proceedings resulting therefrom. The obligations of Maker under this
         Section (IV)(4) shall survive the repayment of the principal amount of
         this Note.

5.       Amendments. This Note may amended or modified only by an instrument in
         writing duly executed by Maker and Payee. Any amendment or modification
         effected in accordance with this Section IV(5) shall be binding upon
         Maker and Payee.

6.       Successors and Assigns. This Note shall be binding upon, and inure to
         the benefit of, Maker and Payee and their respective successors and
         assigns. Maker may not assign its rights or obligations under this Note
         without the prior written consent of the Payee. Payee may assign or
         transfer this Note or any rights or obligations hereunder without the
         prior written consent of Maker.

7.       Headings. The section headings appearing herein are included solely for
         convenience of reference and are not intended to affect the
         interpretation of any provision of this Note.

8.       Severability. If one or more provisions of this Note are held to be
         unenforceable under applicable law, such provision(s) shall be excluded
         from this Note and the balance of this Note shall be interpreted as if
         such provision(s) were so excluded and shall otherwise be enforceable
         in accordance with its terms.

9.       Usury. Maker covenants (to the extent that it may lawfully do so) that
         it will not at any time insist upon, plead, or in any manner whatsoever
         claim or take the benefit or advantage of, any stay or extension law or
         any usury law or other law that would prohibit or forgive Maker from
         paying all or any portion of the principal of or interest on the Notes,
         wherever enacted, now or at any time hereafter in force, or which may
         affect the covenants or the performance of this Note.

10.      Governing Law; Consent to Jurisdiction; Waiver of Jury Trial. This
         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 PARTIES HERETO AGREE 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 PARTIES HERETO IRREVOCABLY SUBMIT TO THE EXCLUSIVE
         JURISDICTION OF SUCH COURTS AND IRREVOCABLY WAIVE 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.

         IN WITNESS WHEREOF, the undersigned have executed this Note as of the
date first above written.

MAKER:

THE UNIMARK GROUP, INC.

By  /s/ David E. Ziegler
    -----------------------
    David E. Ziegler
    Chief Financial Officer<PAGE>

                                                                   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
    ------------------------
    Emilio Castillo Olea
    Chief Executive Officer

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