Gould Joanne, Garcia-Garcia Guillermo, Wolf Bettina
Division of Food Sciences, School of Biosciences, The University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
Centre for SMART, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK.
Materials (Basel). 2016 Sep 21;9(9):791. doi: 10.3390/ma9090791.
In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component imparting emulsifying ability. The waste coffee particles readily stabilised o/w emulsions and following hydrothermal treatment adapted from the bioenergy field they also stabilised w/o emulsions. The hydrothermal treatment relocated the lignin component of the cell walls within the coffee particles onto the particle surface thereby increasing the surface hydrophobicity of the particles as demonstrated by an emulsion assay. Emulsion droplet sizes were comparable to those found in processed foods in the case of hydrophilic waste coffee particles stabilizing o/w emulsions. These emulsions were stable against coalescence for at least 12 weeks, flocculated but stable against coalescence in shear and stable to pasteurisation conditions (10 min at 80 °C). Emulsion droplet size was also insensitive to pH of the aqueous phase during preparation (pH 3-pH 9). Stable against coalescence, the water droplets in w/o emulsions prepared with hydrothermally treated waste coffee particles were considerably larger and microscopic examination showed evidence of arrested coalescence indicative of particle jamming at the surface of the emulsion droplets. Refinement of the hydrothermal treatment and broadening out to other lignin-rich plant or plant based food waste material are promising routes to bring closer the development of commercially relevant lignin based food Pickering particles applicable to emulsion based processed foods ranging from fat continuous spreads and fillings to salad dressings.
在本文中，我们展示了废弃颗粒作为水包油（o/w）和油包水（w/o）乳液乳化剂的功能及功能化。由于其天然含有高含量的木质素（一种具有乳化能力的化学成分），研磨咖啡渣被选为候选废料。废弃咖啡颗粒能轻易稳定o/w乳液，并且在借鉴生物能源领域的水热处理后，它们也能稳定w/o乳液。水热处理将咖啡颗粒细胞壁中的木质素成分转移到颗粒表面，从而增加了颗粒的表面疏水性，这通过乳液测定得以证明。对于亲水性废弃咖啡颗粒稳定o/w乳液的情况，乳液滴尺寸与加工食品中的相当。这些乳液至少12周内抗聚结稳定，在剪切力作用下会絮凝但抗聚结稳定，并且对巴氏杀菌条件（80℃下10分钟）稳定。在制备过程中，乳液滴尺寸对水相的pH值（pH 3 - pH 9）也不敏感。用经水热处理的废弃咖啡颗粒制备的w/o乳液中的水滴抗聚结稳定，尺寸要大得多，显微镜检查显示有聚结受阻的迹象，表明颗粒在乳液滴表面发生了堵塞。优化水热处理并扩展到其他富含木质素的植物或植物基食品废料，有望推动适用于从脂肪连续涂抹酱和馅料到沙拉酱等乳液基加工食品的商业相关木质素基食品皮克林颗粒的开发。
