Wheat and wheat products represent a major food staple consumed around the world. Asian noodles account for the end-use of at least twelve percent of all wheat produced globally. Whereas there has been extensive research into the role and significance of enzymes in the utilisation of wheat flour in bread-making, less is known of their role in Asian noodles. Accordingly, this study has been based on the hypothesis that some enzymes will have a significant impact on the quality characteristics of at least some styles of Asian noodle products. Five enzymes were selected for study: á-amylase, lipase, lipoxygenase, peroxidase and ascorbic acid oxidase. The focus has been on the processing of white salted and yellow alkaline styles of Asian noodles and the role of the enzymes in relation to the quality attributes of these products has been systematically investigated. The quality aspects encompass colour and colour stability, texture, cooking properties as well as structural characteristics of the products. As a part of the preliminary phases of the investigation, procedures for analysis and assessment of flours and noodles have been evaluated. In particular, for the textural properties of noodles, results were obtained with the TA-XT2 Texture Analyser using both a flat cylinder probe, to measure noodle hardness, and also a cutting blade measuring noodle firmness. In addition, various approaches were trialled for sample preparation and presentation in the use of scanning electron microscopy for the investigation of noodle structure. In order to measure the activity of the enzymes in flours and noodle products, assay procedures were set up and validated. These were then used for the analysis of a series of commercial flours and the levels of activity in each of the flours was relatively low indicating that they had been milled from wheat which had not been subjected to preharvest sprouting. á-Amylase was measured using the Ceralpha method and two different sources of exogenous á-amylase (bacterial and barley) were added to noodle formulations. In preliminary experiments various levels of á-amylase incorporation were compared and Abstract viii the impact on texture measured. Both sources of á-amylase resulted in softer noodle products. Adverse effects of the preparations on colour were observed in fresh noodles, although the differences were less obvious when noodles were cooked or dried immediately after preparation. Cooking losses were higher in noodles incorporating amylase, particularly the bacterial preparation. These impacts were reflected in changes in the appearance of starch granules in scanning electron micrographs of the noodles. Three different lipase preparations were studied and their incorporation had only minor effects on texture of noodles. Addition of wheat germ lipase resulted in slightly softer noodles, fungal lipase caused slightly harder noodles, while addition of porcine pancreas lipase gave harder noodles in the raw state and softer noodles after cooking. Similarly variable results were observed when colour and colour stability were evaluated, and there were no adverse effects upon cooking quality of Asian noodles. Two different preparations of horseradish peroxidase were investigated and both resulted in adverse effects on colour including at all stages of storage. One of the preparations resulted in softer noodles when texture was measured using the cylinder method and in firmer noodles when the blade attachment was applied. Neither the surface appearance of noodles nor the cooking properties were altered by the addition of peroxidase to the formulations. Different levels of addition of ascorbic acid oxidase from Cucurbita species showed only minor effects on characteristics for both styles of noodles. Incorporation of this enzyme resulted in lower lightness values but there was little effect on yellowness. Discolouration of noodle sheets was faster and more obvious at 25°C and compared to the storage of noodles at 4°C. The cooking qualities of noodles did not change upon addition of the oxidase. Activity of the enzyme lipoxygenase was measured spectrophotometrically using linoleic acid as substrate. Upon addition to the noodle formulations the enzyme preparation from soy bean resulted in slightly harder and firmer noodles. Colour and colour stability were not enhanced by the addition of lipoxygenase and significantly higher yellowness values were measured in some samples. This enzyme did not adversely impact upon the cooking or structural properties of either style of noodles. Abstract ix Some of the enzymes studied here demonstrated undesirable impacts on one or another aspect of noodle quality, particularly producing darkening or soft textural characteristics. Enzymes that might usefully be considered at lower levels of addition are ascorbic acid oxidase, porcine pancreas lipase and lipoxygenase. These three had no negative effects upon texture, structure or cooking quality of noodles. Visually the colour properties were not adversely impacted and instrumental assessment indicated brighter noodle sheet colours. At lower levels of addition, these three enzymes provide enhancement of noodle quality. On the other hand peroxidase, the two amylases and lipases affected the colour and colour stability of noodles. It was observed that the amylase preparations did result in pronounced softening of noodles. However, the data indicate that the adverse impact attributed to this enzyme when flour from sprouted wheat is used in noodle processing, are probably due to enzyme activities other than a- amylase.

Fortification of instant Asian noodles with folic acid has the potential to enhance dietary folate intakes. Recent studies show folate deficiency is prevalent in many countries. Furthermore, this vitamin is unstable upon exposure to light, air, heat and extreme conditions of acidity and alkalinity. Internationally, folate in foods has traditionally been analysed by a microbiological assay, however, due to the extensive time required for sample preparation and analysis, alternative procedures for analysis require consideration. The aims of the current study have been to investigate the stability of added folic acid in fortified instant fried noodles by analytical methods of capillary electrophoresis and reversed-phase HPLC. Additionally, procedures for the microencapsulation of folic acid by spray drying have been evaluated along with their significance in increasing the stability of the vitamin during processing and boiling of instant noodles. Optimisation of capillary electrophoretic conditions showed that the maximum response of folic acid relative to an internal standard was achieved using various concentrations of phosphate and borate. Analytical parameters including the effects of pH, voltage and temperature were studied along with enzymatic treatments for liberation of folic acid from the noodle matrix based. Higher recoveries were obtained using the enzymes however these exceeded 100% due to sample matrix interference. Standard addition or internal calibration were both effective in correcting for matrix interferences. Comparative investigations with reversed-phase HPLC confirmed the results obtained with the capillary electrophoresis. Using either a phosphate based buffer in conjunction with an ion-pairing agent at alkaline pH or an acidic mobile phase, the results attained were in good agreement as folic acid exhibited excellent stability under typical processing conditions. Various food approved hydrocolloids were evaluated for encapsulation of folic acid by spray drying. Incorporation of the microcapsules into formulations of instant fried noodles showed that after boiling the folic acid was chemically degraded to some extent and leaching also occurred. The microcapsules exhibited similar properties regardless of the binding agent used, with losses still occurring during the boiling stage. In order to enhance the structural integrity of the spray dried microcapsules, CaCl2 was used as a cross-linking agent for capsules prepared using alginate or pectin binding agents. Considerable increases in retention of core material were observed as the network exhibited a reduction in swelling and hydration, and subsequently a decrease in the release of folic acid. In summary, capillary electrophoresis and reversed-phase HPLC provided excellent separation and good quantitatation of added folic acid in instant Asian noodles. Excellent resolution was obtained between the sample matrix interference of instant noodles and the analysed vitamin. Folic acid displayed high stability throughout the processing of instant noodles whereas there was consistent evidence that unencapsulated folic acid was degraded during boiling. Microencapsulation of folic acid with combinations of alginate and pectin as the binding agents, proved to be effective in maintaining folic acid stability when calcium treatment was performed after spray drying. These findings provide an effective way to retain folic acid used in fortifying Asian instant noodles.