SQUID detected low-field NMR for the evaluation of internal fruit quality

[摘要] ENGLISH ABSTRACT: Assessing the quality of fruit has become vitally important for farmers andgrowers. With retailers placing ever stricter requirements on fresh produce,growers have to spend a greater amount of time and effort sorting and gradingtheir harvest. Increasingly, vendors are placing requirements not only onexternal factors like colour, and firmness, but on internal quality factors suchas sugar content and acidity, because, although consumers buy fruit based ontheir external appearances, the taste of the fruit is what determines whetherthe consumer will buy again. Different techniques exist that probe the internalquality of fruit non-destructively. The technique most widely used todayis Near Infrared Spectroscopy. This technique is powerful, but has certainlimitations such as poor reliability and the need for constant recalibration.This thesis suggests an alternative method for evaluating internal fruit qualitybased on low-field nuclear magnetic resonance detected by superconductingquantum interference devices. It introduces the theory of SQUIDs and NMR,and evaluates the use of SQUID detected NMR spectroscopy as a methodfor determining the internal quality of fruit. The fabrication techniques andprocesses are explained in detail and a design for a SQUID detected NMRspectrometer is given. Relevant simulations and simulation results are also given. No working SQUID could be fabricated and, as such, no working NMRspectrometer was demonstrated. This thesis serves as a reference work forfuture research.

[发布机构] Stellenbosch University