CHARACTERIZATION OF HEAT RESISTANT MILK CHOCOLATES

Open Access
Author:
Dicolla, Carolina Bottignon
Graduate Program:
Food Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 03, 2008
Committee Members:
  • Ramaswamy C Anantheswaran, Thesis Advisor
  • B Douglas Brown, Thesis Advisor
Keywords:
  • confectionery
  • sensory analysis
  • textural analysis
  • heat resistant
  • chocolate
  • texture profile analysis
Abstract:
Conventionally heat resistance has been inferred as the fat phase melting point of the chocolate sample. The multitude of patents and literature proposing heat resistant chocolate samples, do not always change the melting point of the fat phase but instead induce heat resistance by affecting its structure. Hence heat resistance has to be measured as a multi-dimensional attribute. Although there are many methods of making heat resistant chocolate, there is no uniform method for measuring heat resistance. The overall goal of this research was to develop methods to characterize and differentiate the heat resistance of milk chocolate. A classification with different levels of heat resistance has also been proposed. One standard milk chocolate and six heat resistant milk chocolates were made, based on techniques published in patents and articles, to represent samples with a wide range of heat resistance. All samples were submitted to a descriptive sensory panel, which evaluated tactile attributes (firmness to touch, stickiness to fingers and snap) and oral attributes (abrasiveness, hardness with incisors, fracturability, cohesiveness of mass, time to melt, firmness with tongue, adhesiveness to teeth, number of particles, oily mouthcoating and chocolate messiness) related to the texture of milk chocolates at 24 °C (75 °F), 29 °C (85 °F), and 38 °C (100 °F). Instrumental techniques were used to measure physical and textural properties at these temperatures, which were correlated with the sensory results. Physical properties measured were particle size by laser diffraction, moisture content by Karl Fischer method, fat content by OICC method, thermal analysis measured by differential scanning calorimetry (DSC) and a melting collapse test using a dynamic mechanical analysis instrument. The parameters measured by the melting collapse test were onset of collapse, inflection point and % collapsed. Textural properties were measured using textural profile analysis (TPA) and a three point bending test (3PB). The instrumental parameters measured were: TPA hardness, TPA adhesiveness, TPA cohesiveness, TPA springiness, TPA resilience, TPA gumminess, TPA chewiness, 3PB hardness and 3PB work. An analysis of variance of the sensory results was performed. The main effects of sample, panelist and temperature and their interactions were considered in the model. The interaction between sample and panelist, was significant for five attributes: Stickiness to finger, cohesiveness of mass, adhesiveness to teeth, number of particles and oily mouthcoating. The interaction between sample and temperature was significant for eight attributes: Firmness to touch, stickiness to finger, snap, abrasiveness, hardness with incisors, fracturability, firmness with tongue and oily mouth coating. The interaction between panelist and temperature was significant for ten attributes: Firmness to touch, stickiness to finger, snap, hardness with incisors, fracturability, cohesiveness of mass, time to melt, firmness with tongue, number of particles, oily mouthcoating and chocolate messiness. An analysis of variance was also performed on the textural parameters measure by TPA and 3PB. The main effects of sample and temperature and their interactions were considered in the model. The interaction between sample and temperature was significant for seven parameters: TPA hardness, TPA adhesiveness, TPA cohesiveness, TPA resilience, TPA gumminess, 3PB hardness and 3PB work. The main effects were only taken into consideration for two attributes: TPA springiness and TPA chewiness. The main effect temperature was significant for both attributes, meaning that these parameters were affected by change in temperature. The main effect sample was only significant for TPA springiness. Linear correlations and principal component analysis were performed in order to explore the relationship between sensorial attributes and instrumental measurements. A method of ranking of heat resistance was proposed. When the samples were ranked at each temperature based on the sensory attributes and instrumental measurements, most of the heat resistant variants showed an improvement as compared to standard chocolate.