<PAGE>   1
                                                              Exhibit 10.20
                      [FUISZ TECHNOLOGIES LTD LETTERHEAD]
                              RESIGNATION AGREEMENT

      THE PARTIES to this Resignation Agreement, Fuisz Technologies Ltd.
("FTL"), and Mr. Adrian Gerber ("Mr. Gerber") agree that the following sets
forth their complete agreement and understanding regarding the resignation of
Mr. Gerber on or about December 31, 1997.

      WHEREAS, the employment relationship between Mr. Gerber and FTL has been
terminated by this resignation of Mr. Gerber; and,

      WHEREAS, Mr. Gerber and FTL desire to settle fully and finally any and all
differences and issues between them which could arise out of this resignation or
otherwise;

      NOW THEREFORE, Mr. Gerber and FTL agree as follows:

      For and in consideration of execution of the Consulting Agreement attached
hereto (the "Consulting Agreement"), Mr. Gerber on his own behalf and on behalf
of his executors, agents, heirs, personal representatives, and assigns, and each
of them, hereby agrees to release and forever discharge FTL, its
representatives, agents, employees, subsidiaries, heirs, assigns, and
successors, and each of them, from any and all claims, actions, demands and
causes of action, known or unknown, in law or in equity, which have arisen or
may arise, which are based upon, or are in any way related to the hiring, the
employment or the resignation of employment of Mr. Gerber by FTL. Mr. Gerber
further covenants and agrees that he will not participate in, aid, institute or
maintain, or cause to be instituted or maintained, any suit in law or equity or
any other similar proceeding against FTL whether or not based directly or
indirectly upon any such claims, action, demands or causes of action. Such
causes of action include, but are not limited to, actions arising under Title
VII of the Civil Rights Act of 1964, the Age Discrimination in Employment Act,
the Americans With Disabilities Act, the Fair Labor Standards Act, the Employee
Retirement Income Security Act, the Consolidated Omnibus Budget Reconciliation
Act, the Fairfax County Human Relations Act, the Virginia Human Rights Act and
any causes of action based upon the public policy it sets forth, and any and all
actions in tort or contract. It is agreed and understood that the above
mentioned payments are not to be construed as an admission of any liability.

       Mr. Gerber, further in consideration of the payments to be made under the
Consulting Agreement, the agreement by FTL that the stock options granted to Mr.
Gerber through non-statutory option agreements shall be unaffected by this
resignation and for other good and valuable consideration, agrees to make no
statement, oral or written, either directly or indirectly, to any person or
other entity regarding Mr. Gerber's employment at FTL, the terms and conditions
of this Resignation Agreement, or the circumstances surrounding the termination
of the employment relationship between FTL and Mr. Gerber, nor to make any
statement or express any opinion to any person or other entity concerning or
relating to FTL or any of its employees, agents, officers or directors, or its
products, research and development, contracts, or any other business of FTL,
either directly or indirectly, or make any statement or opinion, directly or

<PAGE>   2
Resignation Agreement of Mr. Adrian Gerber
December 31, 1997
Page2



indirectly, to or concerning any customers or licensees of FTL, except that Mr.
Gerber may state that Mr. Gerber was employed by FTL, the dates of such
employment, his title and that he has resigned from his position at FTL as of
the date first set forth above, unless further disclosure is mandated by federal
or state law or by order of a court of competent jurisdiction. Additionally, Mr.
Gerber hereby reaffirms that he will remain subject to the provisions of the
Employee Confidentiality Agreement signed by Mr. Gerber and FTL including
without limitation the promises in paragraph 5 not to disclose Confidential
Information obtained during the course of Mr. Gerber's employment with FTL, and
in paragraph 6 not to engage in any activity or employment in which such
Confidential Information reasonably would be considered to be useful.

      For and in consideration of Mr. Gerber's agreement to the terms and
conditions hereof, FTL agrees to release and forever discharge Mr. Gerber from
any and all claims, actions, demands, and causes of action, in law or in equity,
which have arisen or may arise, which are based upon acts or omission by the Mr.
Gerber during the employment of Mr. Gerber by FTL. FTL further agrees to make no
statement, oral or written, either directly or indirectly, to any person or
other entity regarding Mr. Gerber's employment at FTL, the terms and conditions
of this Resignation Agreement, or the circumstances surrounding the termination
of the employment relationship between FTL and Mr. Gerber, except to state that
Mr. Gerber was employed by FTL, the dates of such employment, his title and that
he has resigned from his position at FTL as of the date first set forth above,
unless further disclosure is mandated by federal or state law or by order of a
court of competent jurisdiction. FTL hereby consents, pursuant to paragraph 6 of
the Employee Confidentiality Agreement dated February 5, 1996, to Mr. Gerber's
engagement in activities or employment in which Confidential Information would
reasonably be considered useful, provided that Mr. Gerber shall continue to be
fully bound by paragraph 5 thereof regarding preservation of the confidentiality
of all confidential information.

      The parties agree and understand that no promises, covenants,
representations, understandings or warranties have been made by either of them
other than those expressly contained herein, and that this Resignation Agreement
constitutes the entire agreement between the parties and supersedes all prior
agreements and undertakings with respect thereto, whether written or oral, other
than the Employee Confidentiality Agreement, which shall remain in full force
and effect. The parties further agree to keep this Resignation Agreement and
each of its terms confidential.

      Mr. Gerber understands that he may take as many as twenty-one (21) days,
beginning December 23, 1997, to consider this Resignation Agreement prior to
executing it, that within seven (7) days after the execution of this Resignation
Agreement he may revoke the provisions of this Resignation Agreement that waive
and release any claims he may have under the Federal Age Discrimination in
Employment Act, and that he has consulted with legal counsel before entering
into this Resignation Agreement.



<PAGE>   3
Resignation Agreement of Mr. Adrian Gerber
December 31, 1997
Page3


      The parties hereby acknowledge that this Resignation Agreement and the
releases contained in this Resignation Agreement are entered into voluntarily
and that both parties understand the consequences of signing this Resignation
Agreement. The parties agree that either party will be entitled to seek
injunctive relief to prevent harm due to any breach or threatened breach by the
other of this Resignation Agreement, in addition to and without waiving any
other rights or remedies each may have in law or in equity.

      Should any of the provisions herein be determined to be invalid by a court
of competent jurisdiction, it is agreed that this shall not effect the
enforceability of the other provisions herein and the parties shall negotiate
the provision or provisions in good faith to effectuate its or their purpose and
to conform it or them to the law.

      It is further understood and agreed that if any fact with respect to any
matter covered by this Resignation Agreement is found to be other than the facts
now believed to be true by the parties, each expressly accepts and assumes the
risks of such possible differences and agrees that this Resignation Agreement
shall remain effective notwithstanding.

      This Resignation Agreement shall be governed by and construed in
accordance with the laws of the State of Virginia. The parties hereby agree to
the exclusive jurisdiction of Virginia with respect to any dispute, suit, action
or proceeding.

      IN WITNESS WHEREOF, the parties have executed this Agreement on
JANUARY 12, 1998


BY:  /s/ ADRIAN GERBER                          Witness:/s/ STEPHEN H. WILLARD
   -------------------                                  ----------------------



FUISZ TECHNOLOGIES LTD.


BY:/s/ KENNETH W. MCVEY                         Witness: /s/ STEPHEN H. WILLARD
   -------------------                                  -----------------------
      Kenneth W. McVey
Title:President & Chief Executive Officer

<PAGE>   4
                     [FUISZ TECHNOLOGIES LTD. LETTERHEAD]

                             FUISZ TECHNOLOGIES LTD.
                              CONSULTING AGREEMENT




Fuisz Technologies Ltd. ("Fuisz") wishes to retain the undersigned party ("Mr.
Gerber") to render consulting services ("Services") in a certain field
("Field"). Therefore, Fuisz and Mr. Gerber, intending to be legally bound, agree
that:

1.    Consultant is entering into this Agreement as an Individual.

2.    The Fuisz representative for receiving Services is Kenneth W. McVey or
      whomever Fuisz may designate.

3.    Services hereunder shall be provided directly by Mr. Gerber: General
      advice and consultation on business and technical issues as requested by
      Fuisz.

4.    Fuisz shall pay Mr. Gerber the sum of: (a) $150,000, payable to Mr. Gerber
      in 12 equal semi-monthly installments, the first installment of $12,500
      being payable on January 15, 1998, and each installment thereafter being
      payable on each subsequent 15th and final day of each month and ending
      June 30, 1998; (b) the continuation of Mr. Gerber's medical health care
      benefits under the applicable Plan of Fuisz up to and including June 30,
      1998; and (c) a car allowance of $450.00 per month payable at the end of
      each month up to and including June 30, 1998, as full consideration for
      Mr. Gerber's services hereunder and Mr. Gerber's agreement to the terms
      and conditions hereof. In addition, Fuisz shall reimburse Mr. Gerber upon
      presentation of appropriate receipts for reasonable out-of-pocket expenses
      incurred by Mr. Gerber at the prior request and approval of Fuisz in the
      performance of Mr. Gerber's services hereunder.

5.    This Agreement shall be effective beginning as of the date hereof and
      ending on June 30, 1998, provided, however, that Mr. Gerber's obligations
      under paragraphs 6, 7 and 9 shall terminate five (5) years following the
      latter date.

6.    Mr. Gerber shall exercise due care to prevent the unauthorized disclosure
      of Confidential Information. Confidential Information shall include all
      information concerning Fuisz and the Field disclosed to Mr. Gerber or
      developed as a result of Mr. Gerber's services under this Agreement,
      except any portion thereof which: (a) is known to Mr. Gerber before
      receipt thereof under this Agreement, as evidenced by Mr. Gerber's written
      record and not subject to any other Confidentiality Agreement with Fuisz;
      or (b) is disclosed or provided to Mr. Gerber after receipt



<PAGE>   5


      thereof under this agreement by a third party who has a right to make such
      disclosure; or (c) is or becomes part of the public domain through no
      fault of Mr. Gerber. Further, Mr. Gerber shall not use Confidential
      Information for any purpose other than that indicated in this Agreement
      without the prior written approval of Fuisz.

7.    Mr. Gerber shall not disclose the existence of this Agreement or use the
      name of Fuisz in any publicity or advertising without the prior written
      approval of Fuisz.

8.    At the request of Fuisz, Mr. Gerber shall make written reports and consult
      with Fuisz personnel at the facilities of Fuisz or at other mutually
      agreed locations, at mutually agreed times.

9.    Any information (whether copyrightable, patentable or not), reports, data,
      designs, software, screen displays, computer-readable media, manuals and
      other work of any kind, made or developed by Mr. Gerber in the course or
      as a result of services performed by Mr. Gerber under this Agreement or
      which are derived, directly or indirectly, from information provided to
      Mr. Gerber by Fuisz hereunder, are affirmatively acknowledged by Mr.
      Gerber as Work Made for Hire, and such Work Made for Hire shall be
      promptly disclosed to Fuisz, shall be the sole property of Fuisz, and
      shall be free from any claim or retention of rights thereto by Mr. Gerber.
      Mr. Gerber shall derive no interest in or to such Work Made for Hire, and
      shall upon the request and expense of Fuisz, execute such documents and
      take such other actions as Fuisz deems necessary or appropriate to obtain
      patents or copyrights and to register same with appropriate governmental
      authorities, in the name of Fuisz, covering any of the foregoing. In the
      event that a judicial body determines that any of the foregoing are not
      Work Made for Hire, Mr. Gerber shall assign any and all copyright thereto
      to Fuisz.

10.   Mr. Gerber warrants and represents that the terms of this Agreement are
      not inconsistent with other contractual obligations Mr. Gerber may have,
      or with the policies of any institution with which Mr. Gerber is
      associated, including, but not limited to, policies regarding the
      administration of grants and funded research.

11.   Mr. Gerber shall not disclose to Fuisz any information which is
      proprietary to a third party.

12.   Mr. Gerber's status under this Agreement is that of an independent
      contractor. Mr. Gerber shall not be deemed an employee or agent of Fuisz
      for any purpose whatsoever, and Mr. Gerber shall have no authority to bind
      or act on behalf of Fuisz except as otherwise expressly stated herein. Mr.
      Gerber shall be responsible for, and agrees to comply with, all
      obligations under federal, state and local laws for the payment of income
      and self-employment taxes, penalties, fines and/or assessments resulting
      from any payments to Mr. Gerber by Fuisz under this Agreement.



<PAGE>   6

13.   This Agreement constitutes the entire understanding of the parties hereto
      with respect to the matters herein contained.

14.   All additions or modifications to this agreement must be made in writing
      and executed by both parties.

15.   This Agreement shall be deemed to have been made and performed in the
      Commonwealth of Virginia, and shall be governed by, construed and enforced
      in accordance with the laws of the Commonwealth of Virginia, without
      reference to its choice of law or conflict of laws provisions.

FUISZ TECHNOLOGIES LTD.                   ADRIAN GERBER

By:  /S/ KENNETH W. MCVEY                 11335 SENECA VIEW WAY
    ------------------------------        -----------------------------------
        Kenneth W. McVey
Title:  President & CEO                   GREAT FALLS VA 22066
                                          -----------------------------------
                                          Address

Date JANUARY 12, 1998                     /s/ ADRIAN M. GERBER
    -------------------------------       -----------------------------------
                                          Signature

                                          /s/ ADRIAN M. GERBER
                                          --------------------------------
                                          Printed Name


                                          --------------------------------
                                          Title
                                                JAN. 12, 1998
                                          --------------------------------
                                          Date
                                                ###-##-####
                                          --------------------------------
                                          Social Security Number
                                          (Provide only if Consultant is
                                          contracting as an individual)