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In this dissertation I present MRFM measurements of spin dynamics across the interfacebetween pure a diamond region and a region of densely implanted spins, which we call a `spinwire’. These measurements demonstrate that spin diffusion mediated by spin flip-flopscan be the dominant effect that determines the lifetime of spins in nanoscale volumes. Inparticular, the ability to measure nanoscale volumes illuminates the need to specify exactlywhat one means by `spin lifetime,’ which most commonly refers to T1, the ensemble spinlattice relaxation time. As the measured ensemble shrinks down to small numbers of spins,or even a single spin, the notion of spin lifetime most intuitively means the amount of timeit takes for a spin to flip from up to down. We show that on an individual-spin basis, thespin lifetime can be much less than T1.Although MRFM has reached a number of milestones, one significant capability whichhas not yet been accomplished is direct measurement of the transverse component of themagnetization. Such a capability would open MRFM to a wealth of techniques commonlyused for conventional NMR, which detects the transverse moment inductively. This capabilitywould require matching the nuclear Larmor precession frequency to the mechanicalresonance frequency, which is in the MHz regime for typical applied fields. While cantileverstypically have kHz frequencies, there are membrane mechanical resonators that have MHzfrequencies. To this end, we began MRFM studies using membranes. In this dissertationI demonstrate the first MRFM measurements of the longitudinal magnetization using amembrane resonator. I show that membranes have a number of advantages compared tocantilevers for MRFM applications, and are a promising candidate for transverse mechanicaldetection of magnetic resonance.Finally, I use the sensitive technique of cantilever magnetometry to study two-dimensionalvan der Waals materials. En route to measuring graphene, I measure de Haas van Alphenoscillations from 300 layers of graphite. These measurements demonstrate that cantilevermagnetometry is a powerful technique for interrogating the magnetism of 2D materials.

Australian underutilised fish species, such as silver warehou (Seriollela punctata) and eastern school whiting (Sillago flindersi) as well as fish by-products may be potent sources of bioactive peptides. These species and/or their by-products are often wasted due to their poor technological and textural properties, and not acceptable for consumption by the Australian consumers. Interestingly, these fish wastes possess important nutritional value and physiological benefits, owing to their high protein content. Technological processing and the presence of endogenous enzymes in the fish muscle have the potential to release the so-called bioactive peptides during storage or digestion in the gastrointestinal tract. In the new era of the field of food science and technology, the production of bioactive peptides released from fish wastes is becoming increasingly important to preserve the marine sustainable environment and develop essential functional food to maintain human health as well as preventing the risks of developing certain types of metabolic diseases, like obesity and/or metabolic syndrome. As a result, the main focus of this project was to investigate the controlled hydrolysis of fish muscle proteins from by-catch fish species as a means of producing bioactive peptides with beneficial physiological properties. Important in-vitro bioactivities investigated could be related to the prevention of obesity and associated health complications. They include i) angiotensin-converting enzyme (ACE – hypertension) inhibition, ii) trypsin inhibition (satiety-induced) and iii) anti-oxidative (oxidative stress and inflammation-related conditions) activity.

Two categories of functional food traits were researched: dietary minerals and antioxidants. The primary objectives were to (1) characterise diverse peanut phenotypes using established methods or developing and validating analytical methods if necessary; (2) estimate genotypic variation in the functional food trait; and (3) investigate the stability of the functional food trait through studies of genotype-by-environment (G × E) interaction. Essential mineral concentrations in kernels were analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ICP-mass spectrometry (ICP-MS) with the use of a dynamic reaction cell (DRC) after preparation of samples by microwave-assisted closed acid digestion. Antioxidant capacity was assessed using ABTS +, DPPH , Folin-Ciocalteu total phenolics, and ORAC assays adapted to a 96-well microplate format for high-throughput analysis. The phytochemical profile was quantitatively analysed by high performance liquid chromatography (HPLC) with the use of a photodiode array (PDA) detector, after ultrasound- and enzyme-assisted extraction and solid phase extraction to purify and concentrate the extracts. Genotypic variation for essential minerals and antioxidant capacity was estimated by analysis of 32 full-season maturity and 24 ultra-early maturity genotypes from the Australian Peanut Breeding Program (APBP). The studies established useful levels of variation of more than 10% relative standard deviation (RSD) among the genotypes in concentrations of most of the tested essential minerals, and of more than 20% RSD in antioxidant capacity, although only the ORAC assay distinguished statistically significant differences between genotypes. Studies of G × E interaction affecting the essential mineral and antioxidant capacity traits revealed that genotype, environment, and G × E interaction all significantly affected trait expression. The results confirmed that there was substantial genetic control of essential mineral concentrations and antioxidant capacity in peanut kernels, but that it will be important to characterise environmental interaction to enable plant/seed selection in the APBP and potentially manipulate the interaction through agronomic or postharvest management. The essential minerals data were used to develop approximately predictive calibrations for Ca, K, Mg, and P by near-infrared reflectance spectroscopy (NIRS) of sufficient accuracy to be useful as plant/seed selection tools in plant breeding. Techniques that enable high-throughput, non-destructive, time/cost-effective analysis of trait segregation are valuable due to the extremely large number of samples that are generated in breeding programs. Five peanut genotypes with diverse antioxidant capacity phenotypes were quantitatively profiled for p coumaric acid, salicylic acid, resveratrol, and daidzein. The co-eluting compounds, caffeic/vanillic acid and ferulic/sinapic acid, were quantified on caffeic acid equivalent and ferulic acid equivalent bases, respectively. The HPLC analysis established significant genotypic differences in phytochemical concentrations and also the importance of the bound (e.g., conjugated and matrix-embedded) fraction. Fractions of the HPLC eluate were evaluated by ORAC assay to evaluate relative contributions to antioxidant capacity, and allowed identification of a number of unknown compounds that made important contributions to antioxidant capacity. HPLC analysis of kernels subjected to various roasting treatments (150 °C, 0-70 min and 160 °C, 0-32.5 min) showed that ferulic/sinapic acid concentrations declined with roasting duration, but that most other tested analytes were relatively thermo-stable.

Oxidation limits the shelf life of many food products. Adding antioxidants to foods is the most common way to solve this problem. Reports on safety issues of synthetic food additives have raised consumer interest in "all natural" foods, without added antioxidants or with synthetic replaced with natural antioxidants. The natural antioxidants now in use are much more expensive and less potent than the synthetic antioxidants. Thus, effective and economical natural antioxidants are of great interest to researchers. Teng Cha is a type of herbal tea found in China that has reported high levels of antioxidants. Antioxidant activity of Teng Cha extract and its major component dihydromyricetin has been reported, but no studies have provided clear evidence for the antioxidant effectiveness of Tech Cha extracts. The goal of this study was to measure the antioxidant activity of Teng Cha extract and dihydromyricetin (DHM), a major component of Tech Cha extract. The DPPH assay was conducted and antioxidant activities of the crude extract and dihydromyricetin were evaluated in soybean oil based on the peroxide value, anisidine value, Totox value, headspace volatiles and headspace oxygen. Antioxidant effectiveness was also evaluated in a cooked beef model system. DHM was more potent than BHA in preventing soybean oil oxidation. The crude extract was not as effective as BHA and DHM, possibly because it contained transition metals. In cooked beef, DHM and the crude extract showed lower activity than BHA, possibly due to their low solubility. Overall, Teng Cha extract and DHM are potential natural food antioxidants for future applications.

The antioxidant properties of methanol extract, essential oil and authentic compounds relating to Limnophila aromatica Merr. essential oil components were investigated employing various established in vitro systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO) radical scavenging and inhibition of lipid peroxidation. The results indicated that methanol extract and essential oil of L. aromatica exhibited free radical scavenger, NO radical scavenger and antilipid peroxidation. The antioxidant activities of methanol extract were higher than essential oil. Eugenol showed antioxidant activity against the radical scavenging ability of DPPH. Eugenol and γ-terpinene also exhibited antilipid peroxidation whereas in the NO scavenging assay, the authentic compounds exhibited weak and no activity.

This thesis explores the effects of different cooking techniques on the antioxidant activity in collard greens. Chapter 1 is a literature review covering the topics of antioxidants, nutrition, cooking techniques and the effect of thermal treatment on antioxidants. Chapter 2 is a research manuscript evaluating collard greens from a local South Carolina farm exposed to seven different thermal treatments along with an untreated raw group. The thermal treatments utilized were sautŽ, both long and short simmer, the sautŽ treatment applied to both a long and short simmer treated group and the reserved cooking water from both a long and short simmer treatment group. After treatment, the total phenolic content (TPC) expressed in gallic acid equivalents/sample concentration (GAE/conc.) , 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferrous ion chelating (FIC) antioxidant assays were performed on all treatment groups. The sautŽ treated group showed the highest TPC (8.2858 GAE/conc.) followed by the raw group (8.0361) and the short simmer + sautŽ group (7.6227). The raw group showed the highest DPPH activity (7.7952 % inhibition/conc.) followed by the sautŽ group (7.5877) and the short simmer + sautŽ group (7.4753). In both of these assays the addition of a sautŽ treatment to either short or long simmered treatment increased the antioxidant activity of samples compared to just the short or long simmer treatment alone. Additionally both TPC and DPPH assays showed greater antioxidant activity in the cooking water reserved from a long simmer treatment compared to the reserved cooking water of a short simmer treatment suggesting significant (p≤0.05) leeching of antioxidants from collard greens into the water related to the duration of aquathermal treatment. Similar trends were not found in the results of the FIC chelating assay where both long and short simmer treatment groups showed the highest chelating abilities and the reserved cooking water from both treatments showed the lowest chelating abilities. This suggests that chelators contained in collard greens are not water soluble and therefore not negatively affected by aquathermal treatments.

Borage (Borago officinalis L.) water extracts were prepared from raw stems and leaves and from cooked (boiled and steamed) stems. Antioxidant activity (AA) was determined by ABTS and DPPH after their respective calibration with Trolox as standard and expressing results of both assays as µg Trolox/g fresh plant. Also total phenolic compounds (TPC) were determined for each extract. Values for DPPH and ABTS in leaf extracts were similar and approximately 3.5 fold the values obtained for stem extracts. The high antioxidant activity of leaf extracts might be attributed to the high amount of phenolic compounds (2.36 mg GAE/g fresh plant for leaves and 0.57 mg GAE/g fresh plant for stems). Boiling significantly decreased antioxidant activity (51-52 % decrease) and total phenolic compounds (67 % decrease). Steaming caused no significant effect on the antioxidant activity values, whereas total phenolic compounds showed approximately half of the decrease found for boiling (35 %). Borage water extracts, and particularly, those of their by-products (leaves) showed great antioxidant activity, that could potentially be used for different applications in food industry.

Antioxidant research is an important topic in the medical field as well as in the food industry. Recent research with important bioactive compounds in many plant and food materials, including peanuts and peanut plants has received much attention. The research presented here is the first step in identifying known, or novel, bioactive compounds from peanut plants that may provide the basis for value added products for the peanut industry. The objective of this work was to identify an extract of peanut plant tissues that has substantial antioxidant activity. Peanut plants were collected from a NC research farm on two separate dates. Plants were separated into various tissues, dried, and extracted with organic solvents. The solvents used were hexane, methylene chloride, acetone, and methanol. Antioxidant activity of the extracts was tested using the oxidative stability index (OSI), inhibition of the free radical action in the Oxygen Radical Absorbance Capacity (ORAC) and free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH•) compared with those of synthetic antioxidants. The highest antioxidant activities in the DPPH and ORAC analyses were found in the leaves and roots of the peanut plant. Extract activity increased with increasing polarity of solvents except for the methanol extract of the roots. Root extracts had higher antioxidant activity than nodules found on the roots. The methanol extracts from 500mg of leaves had an OSI value comparable with 10mg of BHT. The results among leaf extract antioxidant activity on sampling dates were variable. The results of this research suggest that there is extractable antioxidant activity in peanut plant tissues. Future isolation and identification of the specific compounds may lead to value added products along with new or novel bioactive compounds for use in the food or pharmaceutical industries.

The antioxidant properties of methanol extract, essential oil and authentic compounds relating to Limnophila aromatica Merr. essential oil components were investigated employing various established in vitro systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO) radical scavenging and inhibition of lipid peroxidation. The results indicated that methanol extract and essential oil of L. aromatica exhibited free radical scavenger, NO radical scavenger and antilipid peroxidation. The antioxidant activities of methanol extract were higher than essential oil. Eugenol showed antioxidant activity against the radical scavenging ability of DPPH. Eugenol and γ-terpinene also exhibited antilipid peroxidation whereas in the NO scavenging assay, the authentic compounds exhibited weak and no activity.