<PAGE>   1
                                                                 EXHIBIT 10.31


GRATUITOUS LOAN AGREEMENT ENTERED INTO BY AND BETWEEN FRUTALAMO, S.A. DE C. V.
REPRESENTED HEREIN BY MR. FRANCISCO DOMENECH TARRAGO, ENGINEER, HEREINAFTER AND
FOR PURPOSES OF THIS AGREEMENT REFERRED TO AS "LENDER"; AND, "GISALAMO S.A. DE
C.V." REPRESENTED HEREIN BY MR. JOSE MA. MARTINEZ BROHEZ, ENGINEER, HEREINAFTER
AND FOR PURPOSES OF THIS AGREEMENT REFERRED TO AS "BORROWER"; PURSUANT TO THE
FOLLOWING PROVISIONS AND ARTICLES:

                                  DECLARATIONS

I.       WHEREAS MR. FRANCISCO DOMENECH TARRAGO, Engineer, as representative of
"LENDER" declares:

         a) That his principal is a Mexican company duly organized under the
laws of the nation [Mexico] and is duly authorized to enter into contracts and
assume such obligations, as attested to in public document number 16,471 dated
August 3, 1992, given under oath before LIC. ROGELIO MAGANA LUNA, Notary Public
No. 156 with jurisdiction in the Federal District and registered in the Public
Registry of Commerce under Commercial Page No. 162665, of the Book of Commerce,
on August 17, 1992.

         b) That his principal has as its primary business objective the
processing, bottling, commercialization and sale of citrus fruit for juice
extraction and manufacture of concentrate, as well as the performance of all
types of agreements permitted by Law.

         c) That in his capacity as Legal Representative of "LENDER", he has
sufficient legal authority to enter into this Agreement, the foregoing
agreement, and has been granted powers under the Actos de Administracion y
Dominio (Documents of Administration and Power) which have been conferred upon
him, which to this date have not been revoked or restricted, which are confirmed
in the public document cited in the foregoing paragraph a).

         d) That "LENDER" is the legitimate owner and has full possession of the
assets which comprise the juice extraction "PLANT" (land, buildings, and
equipment) which is equipped and ready for operation, including an evaporator
and residual water treatment plant (installation pending on these latter two
pieces of equipment), and holds all Permissions, Authorizations, and Licenses
required by the various Municipal, State and Federal Authorities for its
operation.

         e) That it is the "LENDER'S" desire to enter into this "GRATUITOUS LOAN
AGREEMENT" pursuant to the terms and conditions set forth hereunder.


                                       1
               [English translation of original Spanish document]
<PAGE>   2



II.      Mr. JOSE MA. MARTINEZ BROHEZ, ENGINEER, as "BORROWER'S" representative,
herein manifests:

         a) That his principal is a Mexican company duly organized under the
laws of the nation [Mexico] and being duly authorized to enter into contracts
and assume such obligations, as attested to in public document number 2,595
dated October 7, 1996, given under oath before LIC. BLANCA AMALIA CANO GARZA DE
BELLO, Notary Public No. 187 with jurisdiction in Cd. Victoria, Tam., with
pending registration in the Public Registry of Commerce.

         b) That his principal has as its primary objective the processing,
bottling, commercialization and sale of citrus fruit for juice extraction and
manufacture of concentrate, as well as the performance of all types of
agreements permitted by Law.

         c) That in his capacity as Legal Representative of "BORROWER", he has
sufficient legal authority to enter into this Agreement, the foregoing
agreement, and has been granted powers under the Actos de Administracion y
Dominio (Documents of Administration and Power) which have been conferred upon
him, which to this date have not been revoked or restricted, which are confirmed
in the public document cited in the foregoing paragraph a).

         d) That it is the "BORROWER'S" desire to enter into this "GRATUITOUS
LOAN AGREEMENT", pursuant to the terms and conditions set forth hereunder.

Both parties herein attest that this agreement is subscribed pursuant to Article
Nineteen of the "DEPOSIT, OPERATION, EXPLOITATION AND OPTION TO PURCHASE
AGREEMENT" executed October 30, 1997, between MR. FRANCISCO DOMENECH TARRAGO,
ENGINEER, LIC. FRANCISCO DOMENECH PERUSQUIA, by his own right and in his
capacity as representative of "FRUTALAMO, S.A. DE C.V." and "UNIMARK, GROUP
INC." represented by MR. RAFAEL VAQUERO BAZAN" which is attached to this
Agreement.

Pursuant to the aforementioned provisions made by the Parties, the same agree to
grant and submit to the following:

                                 A R T I C L E S

ARTICLE ONE: PURPOSE: "LENDER" GRANTS TO "BORROWER" a "GRATUITOUS LOAN" of the
assets mentioned in Provision 1, paragraph d) of this instrument, which are
equipped and ready for operation, including an evaporator and residual water
treatment plan (installation is pending on the latter two pieces of equipment).


                                       2
               [English translation of original Spanish document]
<PAGE>   3

ARTICLE TWO: UTILIZATION: ""BORROWER" shall utilize the Industrial Facility
(Land, Buildings and Equipment) for the exploitation of its Commercial Purpose,
that being the processing, packaging, commercialization and sale of citrus fruit
for juice extraction and production of concentrate.

ARTICLE THREE: TERM: The term of this Agreement shall be from October 30, 1996
to October 30, 1999.

ARTICLE FOUR: PAYMENT OF SERVICES: "BORROWER" shall bear the expenses of water,
electricity and phone utilities.

ARTICLE FIVE: MAINTENANCE COSTS AND INSURANCE PAYMENT: ""BORROWER" shall pay all
costs incurred for maintenance required for the proper functioning of the
Industrial Plant. Furthermore, "BORROWER" shall bear the expense of premiums for
fire and liability insurance which it shall be required to obtain; and the
beneficiary of said insurance shall be "FRUTALAMO, S.A. DE C.V."

ARTICLE SIX: INDEMNIFICATION OF WORKERS: Inasmuch as "LENDER" currently employs
thirty-seven workers, it shall indemnify them in order to terminate the
contractual relationship no later than November 30 of the current year.
Furthermore, and if it so desires, "BORROWER" shall have the option to rehire
said personnel, thereby freeing "LENDER" from all employer-employee
responsibility which may arise with said employees or with any other employee
which may be hired, and all obligations and risks associated with those
contracted employees shall be born by "BORROWER".

ARTICLE SEVEN: PERMISSIONS AND AUTHORIZATIONS: "LENDER" promises "BORROWER" to
maintain all Permissions, Authorizations, and Licenses which, as of this date,
have been granted by the various Municipal, State and Federal Authorities, and
furthermore shall obtain Land Use Permits from pertinent Municipal and State
authorities as well as those permits required for the Concession of Water Wells
and Residual Water Discharge provided that these are not significantly altered.

ARTICLE EIGHT: EXPORT QUOTA TO THE UNITED STATES: "LENDER", during the term of
this "GRATUITOUS LOAN AGREEMENT", assigns to "BORROWER" its assigned volume of
quota for Orange Juice (Fresh and Concentrate).

ARTICLE NINE: ASSIGNMENT: Both "LENDER" and "BORROWER" are in agreement to
prohibit the partial or total assignment or transfer of the rights and
obligations acquired herein in this "GRATUITOUS LOAN AGREEMENT"; the foregoing,
without prior written consent of the other party.

ARTICLE TEN: AMENDMENTS TO AGREEMENT: In the event that amendments to this "LOAN
AGREEMENT" are required, both "LENDER" and "BORROWER" shall be required to carry
out the respective Amendment Agreement, which must be signed by the parties as
well as two witnesses, in order to incorporate said Amendment as an integral
part of this Agreement.


                                       3
               [English translation of original Spanish document]
<PAGE>   4


ARTICLE ELEVEN: INTEGRATION: Both "LENDER" and "BORROWER" herein declare that
this Agreement is real, just and equitable, and is free of error, fraud,
violence, ignorance, inexperience, unlawful enrichment, and injury which could
nullify same; therefore, the parties convene that this is the sole document
executed by both parties, and replaces any verbal or written agreement executed
prior to this date.

At the termination of this Agreement, "BORROWER" shall deliver to "LENDER" the
goods delivered in this "GRATUITOUS LOAN AGREEMENT," in the same condition in
which they were received, excepting normal wear and tear.

ARTICLE TWELVE:  ADDRESSES:  The parties hereunder indicate their addresses:

              "LENDER"                                "BORROWER"
       Rafael Rebollar No. 67,              Carrera Torres Poniente No. 226
     Col. San Miguel Chapultepec               Cd. Victoria, Tamaulipas
      Mexico, Distrito Federal                        C.P. 87000
             C.P. 11850

ARTICLE THIRTEEN: JURISDICTION AND APPLICABLE LAW: The parties convene and
expressly agree to abide by the jurisdiction of the Courts of Cd. Victoria,
Tam., as well as the applicable laws of the State of Tamaulipas, and the
foregoing shall be applied to the interpretation and fulfillment of this
"GRATUITOUS LOAN AGREEMENT", and hereby renounce any other jurisdiction which
might apply, by reason of their present or future residence.

The parties, having read this Agreement and being duly informed of the scope of
the same, do hereby execute the same in duplicate in the presence of two
witnesses in the City of Cd. Victoria, Tam., on the 17th day of the month of
December, 1996.

              "LENDER"                                 "BORROWER"

             (Signature)                              (Signature)
   FOR "FRUTALALMO, S.A. DE C.V."             FOR "GISALAMO, S.A. DE C.V."
         FRANCISCO DOMENECH                        JOSE MA. MARTINEZ
          TARRAGO, ENGINEER                         BROHEZ, ENGINEER


                                       4
               [English translation of original Spanish document]