Institute of Pharmaceutical Science, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
Food Funct. 2018 Sep 19;9(9):4621-4634. doi: 10.1039/c8fo00729b.
Recrystallisation occurs frequently in confectionery. More information on sucrose re-crystallisation will aid our understanding of popular foods like chocolate. However, progress has been limited due the lack of a robust method for the production of amorphous sucrose, with known purity. Poor control has led to the glass transition temperatures (Tg's) for amorphous sucrose varying between 48-78 °C in the literature. Our objective was to investigate the recrystallization of sucrose in the presence of lactose, NaCl and water. The purity of sucrose was confirmed by ion chromatography, polarimetry and differential scanning calorimetry. Amorphous sucrose was prepared by freeze-drying 10% w/v aqueous solutions. Fisher (99.7%) and Silver Spoon (98.4%) sucrose samples melted at 186 ± 0.6 °C & 189 ± 0.3 °C respectively. For the Fisher sample the absence of invert sugars and low mineral content allowed the observation of a small endotherm (≈ 150 °C). The Tg of amorphous sucrose was 58.3 ± 1.1 °C with a recrystallization enthalpy (ΔHcrys) of 72.8 ± 6.0 J g-1. NaCl reduced both the Tg (54.8 ± 1.8 °C) and the ΔHcrys (35.7 ± 3.8 J g-1) without affecting the onset temperature of sucrose's re-crystallization (Tcrys, 129.5 ± 6.9 °C), suggesting that a proportion of the sample remained amorphous. The presence of water (1.6 ± 0.07%) inside the hermetically sealed pans caused an earlier onset of Tg (52.3 ± 1.3 °C) and Tcrys (85.1 ± 4.0 °C), as well as lowering ΔHcrys (45.2 ± 2.4 J g-1) compared to samples contained in pin-holed pans (where evaporation was possible). The presence of lactose inhibited the crystallization of sucrose completely. On the basis of this study, it is apparent that sucrose crystallization is highly dependent on the presence of other common food ingredients within the matrix.
重结晶在糖果制造中经常发生。更多关于蔗糖再结晶的信息将有助于我们理解巧克力等流行食品。然而，由于缺乏生产具有已知纯度的非晶态蔗糖的稳健方法，进展一直受到限制。由于对非晶态蔗糖的玻璃化转变温度（Tg）控制不佳，文献报道中其范围在 48-78°C 之间。我们的目标是研究蔗糖在乳糖、NaCl 和水存在下的重结晶。通过离子色谱、偏振光法和差示扫描量热法确认蔗糖的纯度。通过冷冻干燥 10%w/v 水溶液制备非晶态蔗糖。Fisher（99.7%）和 Silver Spoon（98.4%）蔗糖样品分别在 186±0.6°C 和 189±0.3°C 下熔化。对于 Fisher 样品，由于没有转化糖和低矿物质含量，观察到一个小的吸热峰（≈150°C）。非晶态蔗糖的 Tg 为 58.3±1.1°C，重结晶焓（ΔHcrys）为 72.8±6.0J g-1。NaCl 降低了 Tg（54.8±1.8°C）和ΔHcrys（35.7±3.8 J g-1），而不影响蔗糖重结晶的起始温度（Tcrys，129.5±6.9°C），这表明样品的一部分仍保持非晶态。密封盘内水的存在（1.6±0.07%）导致 Tg（52.3±1.3°C）和 Tcrys（85.1±4.0°C）的起始更早，并降低了ΔHcrys（45.2±2.4 J g-1），与包含在针孔盘（可能蒸发）中的样品相比。乳糖的存在完全抑制了蔗糖的结晶。基于这项研究，显然蔗糖结晶高度依赖于基质中其他常见食品成分的存在。
