Contact Intensity II

Contact intensity between chocolate and filling, mould or cooling belt and its impact on fat bloom in pralines

Workgroup: Chocolate technology

Scientific Partners and Guidance:

  1. Fraunhofer Institut für Verfahrenstechnik und Verpackung IVV Freising, Isabell Rothkopf

Financing: IVLV e. V.
Duration: 2020

State of the art: Current investigations and the experience gained in the IVLV projects "Shelf life of chocolates" and "Contact intensity I" (2019) indicate that the later tendency of fat blooming correlates with the contact intensity between filling, praline shell and mould or cooling belt. Particularly in coated products fat bloom is a challenge for stability during shelf life. This product range includes pralines, bars and chocolate-coated pastries. For this reason, we want to focus our research on coated articles in 2020. We assume that the contact between the chocolate base and the cooling belt are core to the formation of fat bloom. When the cooled products are released from the belt, minimal roughness can occur on the chocolate base, which later promotes the crystallisation of the lipids, i.e. fat blooming starts. This phenomenon is already known from fingerprints on chocolate, which can be recognized in the form of fat bloom after storage.


  1. Development and establishment of models to simulate different contact intensities between chocolate and mould / cooling belt
  2. Investigation of the correlation between contact intensity and fat blooming
  3. Identification of the main influencing factors (e.g. solid fat content, stickiness of chocolate, material properties of the mould or belt, cooling temperature)

Approach: Flat chocolate bars will be stored on different materials (adhesion) and at different temperatures (solid fat content, measured by pulsed NMR) to vary the surface properties and intensity of the contact. The chocolate bars are filled, stored and examined for fat bloom (DigiEye – WI) as related to the storage time. On fresh products, gloss or loss of gloss serves as an indicator for fat blooming (DigiEye). The stickiness of the chocolate determines the surface properties of chocolate after removal from cooling belts. If crystallization is sufficient, the chocolate is easier to remove due to contraction processes. If crystallization is not optimal (too low temperature / too short cooling time), the chocolate remains slightly sticky and cannot be released from the cooling belt without surface damages. In this project the influence of solid fat content, polymorphic crystal form and temperature on the stickiness of dark chocolate will be investigated. A texture analyzer with an application for stickiness will be used as a measuring device.