NOVELTY - A mixture comprises modified structure triglycerides and fatty acid-alkyl esters.    USE - Useful as fuels, combustibles, or fuel additives and/or combustible additives (claimed) for the propulsion of diesel engines and/or for burning in oil-operated boilers.    ADVANTAGE - At least 10% more biofuel is obtained from a unit amount of biomass. Glycerol is not obtained as side product that is the total energy content of the lipids is converted to engine fuel in biodiesel factories already in operation. Manufacturing of the fuels can be continued without reconstruction because of the smaller operation steps the energy requirement and working hour demand of the preparation decreases. There is no need for the application of special additives for the improvement of the physicochemical properties (turbidity point/pour point/viscosity) in case of triglycerides with high free fatty acid content (unrefined) as starting materials. The difficult two-step method (acid-catalyzed pre-esterification of the fatty acids, and base-catalyzed alcoholysis) can be omitted. Dewaxing of the crude vegetable oils can also be omitted at the preparation for fuel manufacturing, since in the transesterification reaction the waxes produce fatty acid methyl ester with methyl acetate and fatty alcohol acetates.    DETAILED DESCRIPTION - A mixture comprises modified structure triglycerides of formula ((CH)2-O-CO-R1)C(CH2-O-CO-R3)H-O-CO-R2 (I) and fatty acid-alkyl esters of R"-COO-Alk (II).    R1-R3=H or 1-28C alkyl, optionally incorporating at least one carbon-carbon double bond, with the limitation, at least 3%, but at most 97% of the R1-R3 groups present represent alkyl occurring in the triglycerides of biological origin optionally incorporating at least one carbon-carbon double bond, the remaining R1-R3 groups present represent hydrogen and/or 1-5C alkyl, optionally incorporating at least one carbon-carbon double bond, and the % values specified relate to the number of the R1-R3 groups;    R"=alkyl, optionally incorporating at least one carbon-carbon double bond, occurring in the triglycerides of biological origin, and optionally in the mono- and diglycerides and free fatty acids accompanying them, and this way covers the R1-R3 groups (I) originating from the triglycerides of biological origin; and    Alk=1-5C (preferably 2-5C) alkyl, optionally incorporating at least one carbon-carbon double bond, preferably Me, Et, propyl, acryl, or methacryl.    INDEPENDENT CLAIMS are included for:    (1) a fuel comprising modified triglycerides (I) and diesel oil, combustion oil, and/or known biodiesel as usual fuel component; and    (2) a method for the preparation of modified triglyceride (I) and optionally the fatty acid-alkyl esters comprising reacting a triglyceride of biological origin or mixture of triglycerides optionally comprising free fatty acids of formula R"-COOH and mono- and diglycerides of biological origin with carboxylic acid ester(s) of formula R'-COO-Alk-; adjusting the amount of carboxylic acid esters to 3-97% of the stoichiometric amount for the complete transesterification of triglycerides of biological origin and to the stoichiometric amount for the esterification of the mono- and diglycerides and the free fatty acids; optionally terminating the reaction; removing the fatty acids and alcohols optionally generated as side product by washing; and separating the fatty acid alkyl esters of formula R"-COO-Alk.    R'=H and/or 1-5C alkyl optionally incorporating at least one carbon-carbon double bond.