Title page for ETD etd-04152010-105532


Type of Document Dissertation
Author Buck, Vinodini
URN etd-04152010-105532
Title Rheological Properties of Peanut Paste and Characterization of Fat Bloom Formation in Peanut-Chocolate Confectionery
Degree PhD
Department Food Science and Technology
Advisory Committee
Advisor Name Title
O'Keefe, Sean F. Committee Chair
Davis, Richey M. Committee Member
Duncan, Susan E. Committee Member
Zhou, Kequan Kevin Committee Member
Keywords
  • chocolate
  • sensory tests
  • squeeze flow rheology
  • peanuts
  • triacylglycerols
  • fat bloom
Date of Defense 2010-04-12
Availability unrestricted
Abstract
Fat bloom in chocolates is the gray-white discoloration and dullness that can occur

on the surface of the confectionery. Fat bloom is a common quality defect that can result

from temperature fluctuations during storage. Chocolates candies with peanuts or other nut

fillings are more prone to fat bloom compared to plain chocolates, due to a release of

incompatible nut oils into the chocolate matrix. The overall goal of this study was to

determine if differences in triacylglycerol (TAG) composition and rheological properties of

high, medium, and normal oleic peanuts influence fat bloom formation. All three peanut

varieties showed high concentrations of triolein. Normal oleic peanuts had a slightly

higher trilinolein than high and medium oleic peanuts, which contained trilinolein in trace

amounts. Peanut pastes from the three peanut varieties all had a minimum apparent yield

stress, and all pastes showed varying degrees of shear thinning. The apparent yield stress

of high and normal oleic pastes was higher than the apparent yield stress of medium oleic

paste. The absolute value of the flow index behavior was 1 for the high oleic peanut paste,

suggesting friction in the experimental apparatus, even with use of Teflon plates. The

peanut chocolate candies took around 45 days for significant dulling of the chocolates with

temperature cycling between 26-29 °C approximately every 26 hours. Optical microscopy

scans showed differences in glossiness and surface textural attributes of the unbloomed and

bloomed peanut chocolate confectionery. Consumer evaluation showed some differences

in the glossiness and significant differences in surface texture of unbloomed and bloomed

chocolates. A majority (62%) of the survey respondents had seen whitish discoloration in

chocolates and 40% of the respondents thought this is because the chocolate had grown old.

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