Futures thinking, or foresight, is increasingly recognised as a key element in science and environmental education. We integrated a futures thinking activity into an undergraduate general science course in Taiwan by using an online thinking and discussion tool that provides scaffolding questions to help students think systematically about future possibilities of the specific topic -- genetically modified (GM) food. As a course assignment, the enrolled students were asked to work on and write their responses to this online scaffolding tool over five weeks. The purpose of this study was to examine students' expressions of futures thinking on GM food as elicited through this assignment. We content analysed the written responses of 99 students who completed the online task. A particular emphasis of analysis was placed on examining students' thoughts and ideas about 'preferable' or 'desirable' futures of GM food. Nine themes emerged from the analysis and were found be organised into three categories using factor analysis. These results provided insight into characteristics of students' futures thinking and underlying perspectives, and can serve as a basis for future-focused curricular and instructional innovations.