McCullum Rebecca, Saifullah Md, Bowyer Michael, Vuong Quan
College of Engineering, Science and the Environment, University of Newcastle, 10 Chittaway Road, Ourimbah, NSW 2258, Australia.
Centre for Food Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Newnham, TAS 7248, Australia.
Foods. 2024 Jul 11;13(14):2185. doi: 10.3390/foods13142185.
The Illawarra plum (IP) is native to Australia and has been used as a bush food for centuries. With rich phytochemicals and natural pigments, IP has the potential to be an added ingredient to improve the physicochemical properties of food, including yoghurt. This study prepared dried IP powders through vacuum drying (VD) and freeze drying (FD), produced extracts from these dried powders, and fortified them into Greek-style set yoghurt. The changes in colour, pH, titratable acidity (TA), syneresis, total soluble solids (TS), and phytochemicals were measured throughout a chilled storage period of 28 days. The results showed that FD and FD extract could provide a stable, distinct pink colour to yoghurt. IP powders and their extracts improved TS content and, thus, the consistency of yoghurt. Compared to the control, VD, FD, and FD extract of IP did not significantly affect the level of acidity or syneresis after 28 days of chilled storage. Yoghurt fortified with FD and FD extract had the greatest level of phenolics, anthocyanins, and radical scavenging antioxidant activities. This study revealed that IP powders and their extracts can positively improve the physicochemical properties of Greek-style set yoghurt. FD powder is recommended over its extract to fortify this yoghurt, as it can be cost-effectively prepared by freeze drying and then grinding the fresh fruit into powder. Future studies are needed to evaluate other variables in yoghurt preparation, including the concentration of IP and strains of yoghurt culture. Further, the consumer perception of sensory quality and acceptability of yoghurt fortified with FD IP powder should be investigated.
伊拉瓦拉李子（IP）原产于澳大利亚，几个世纪以来一直被用作丛林食物。IP富含植物化学物质和天然色素，有潜力作为一种添加成分来改善食品的物理化学性质，包括酸奶。本研究通过真空干燥（VD）和冷冻干燥（FD）制备了IP干粉，从这些干粉中提取提取物，并将其强化到希腊式凝固酸奶中。在28天的冷藏期内，测量了酸奶的颜色、pH值、可滴定酸度（TA）、脱水收缩、总可溶性固形物（TS）和植物化学物质的变化。结果表明，FD和FD提取物可为酸奶提供稳定、独特的粉红色。IP干粉及其提取物提高了TS含量，从而改善了酸奶的稠度。与对照组相比，IP的VD、FD和FD提取物在冷藏28天后对酸度或脱水收缩水平没有显著影响。添加FD和FD提取物的酸奶中酚类、花青素和自由基清除抗氧化活性水平最高。本研究表明，IP干粉及其提取物可以积极改善希腊式凝固酸奶的物理化学性质。推荐使用FD干粉而非其提取物来强化这种酸奶，因为通过冷冻干燥然后将新鲜水果磨成粉末可以经济高效地制备。未来需要研究酸奶制备中的其他变量，包括IP的浓度和酸奶培养菌株。此外，还应调查消费者对添加FD IP干粉的酸奶的感官质量和可接受性的看法。
