Browsing by Subject "amorfinen laktoosi"

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  • Maksimow, Christina (Helsingfors universitet, 2016)
    The milk component of milk chocolate is often milk powder. In spray-dried milk powder the physical state of lactose is usually amorphous. The physical state of lactose may affect the properties of milk chocolate, even chocolate bloom formation. Chocolate bloom is a problem of especially filled chocolate confectionary. It is caused by the fat migration of the oily filling to the surface of the chocolate coating due a liquid fat concentration difference. In this present study the aim was to study the physical state of lactose in milk chocolate and its effect on structure and chocolate bloom. Milk chocolate was produced with three different rations (0:100; 50:50; 100:0) of amorphous lactose to crystalline α-lactose monohydrate. The physical state of lactose was determined by using x-ray powder diffractometry and differential scanning calorimetry. The hardness and breakability of samples stored at room temperature (21 °C) were measured by a Texture Analyzer. The luminescence L* of color of the milk chocolates stored in room temperature and heat cycle (20 °C and 28 °C) was measured and analyzed by VeriVide DigiEye systems’ light cabinet and PC program. Fat migration was simulated by storing chocolate on a hazelnut-sugar-cocoa butter bed in room temperature and heat cycle. The physical state of the lactose was not stable during storing. α-lactose monohydrate crystals were found in the x-ray diffractograms during the storage period in samples which had in the beginning amorphous lactose. The molecules must have had the ability to move, either because the unpacked amorphous phase absorbed water from the environment which enabled the movement or the temperature fluctuation during non-stabilized room temperature or because of crystal seeds. The samples softened during the storing probably because of the presence of free fat due the addition of the milk fat separately to the chocolate system during manufacturing. No bloom developed on the surface of the samples. The samples did get a little bit lighter though. The chocolate filling model with a chocolate piece on top did not represent a real life situation. No bloom was observed probably due the lack of liquid fat and presence of free milk fat or the observation period was too short.