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Subject: search.filters.subject.Extraction (Chemistry)

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    Deodorisation of protein hydrolysate and extraction of proteins from Hoki (Macruronus novaezelandiae) skin : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Albany, New Zealand
    (Massey University, 2018) Sharim, Nur Syazwana
    The present study had two main objectives. The first objective was to identify a suitable deodorisation treatment for pre-prepared Hoki skin protein hydrolysate (HSPH) and the second objective was to investigated suitable pre-treatment and extraction processes for collagen and gelatine from Hoki (Macruronus novaezelandiae) skin which resulted in low odour extracts. The off-odour in HSPH post-deodorisation treatments and in the Hoki collagen and gelatine post-extraction processes were assessed by determining the total volatile base nitrogen (TVB-N) and trimethylamine (TMA) concentrations. The sensory technique of flash profiling was employed to determine the odour attributes in all HSPH, gelatine and collagen samples after treatment and extraction processes. In addition to the respective off-odour assessments, the extracted collagen and gelatine were evaluated in terms of total protein content (g protein/100g dry sample), moisture content (w/w%), and yield (w/w% of dry sample). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was conducted to determine the molecular weight (kDa) of extracted collagen and gelatine. Amino acid profile analysis was performed to identify the extracted samples. In the first part of this study, dried green tea leaves (GT), powdered tea polyphenol (TP) and dried olive leaves (OL) investigated for deodorisation of HSPH. Using an orthogonal design, three factors (concentration, temperature and time) and three corresponding levels were used in the design. The two most suitable deodorisation treatments for pre-prepared HSPH were 1) deodorant: powdered tea polyphenol; concentration: 0.04 g/ml hydrolysate; temperature: 50˚C; time: 20 min, and 2) deodorant: powdered tea polyphenol; concentration: 0.04 g/ml hydrolysate; temperature: 80˚C; time: 60 min. For a more economical solution, GT was determined to be a possible alternative deodorant to TP by manipulating the total phenolic content prior to deodorisation. For a secondary deodorisation treatment, preliminary results on strong acid hydrogen form ion exchange resin (Dowex G-26) reduced the TMA concentration in partially deodorised HSPH sample significantly (p-value<0.05) from 3.4±0.1 deodorisation to 0.8±0.1 mg of nitrogen/100g wet sample. In the second part of this study, Hoki skins were pre-treated using 0.2 M NaOH solution (1:6 w/v) for 60 min at 18±2oC and then extraction with distilled water (1:10 w/v) for 60 minutes at 50±2˚C. This treatment produced gelatine product with the highest protein content (41.3±0.9 g of protein/100g dry sample) and reduced off-odour based on TMA content (0.9±0.1 mg of nitrogen/ 100 g wet sample). However, a lower gelatine yield recovery of 61.0±1.7 % was determined in this gelatine sample. SDS-PAGE and amino acid profile tests concluded that all pre-treatment and extraction processes successfully extracted gelatine samples as the final product. In contrast, collagen samples were not confirmed as pure collagen in this study. The current findings for both objectives of this study has shown that pre-treating the raw material using acid or alkali prior to subsequent processes is more efficient in reducing the off-odour in the final products rather than employing deodorisation processes as a subsequent countermeasure after hydrolysis and extraction.
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    Use of headspace solid-phase microextraction for the analysis and characterisation of volatile compounds in rumen contents : a thesis presented in partial fulfillment of the requirements for the degree of Masterate of Science in Chemistry at Massey University
    (Massey University, 2005) Lu, Shengyi
    Volatile fatty acids (VFAs), alkyl phenols and indolic compounds are produced by rumen microbes during the fermentation of forages in ruminants. In this study, ruminal fluid obtained from sheep was examined by headspace solid-phase microextraction (SPME) sampling followed by GC-MS analysis. This technique provides a non-invasive, clean and selective method to characterize the volatiles in ruminal fluid from an in vitro fermentation system. The factors which can influence the extraction efficiency were studied and include the SPME fibre, sample volume, pH of sample matrix (rumen fluid) and extraction time by the fibre in the headspace. The optimum experimental conditions for the analytes in question included: polyacrylate fibre to perform the headspace SPME above 20 mL of rumen fluid in a 68 mL vial for 5 min, followed by immediate GC-MS analysis. The pH of the rumen fluid sample greatly influenced VFA extraction efficiency. Quantitative analysis of p-cresol, m-cresol, indole and skatolc with SPME were compared with steam distillation simultaneous extraction. This comparison showed that the HS-SPME method was semi-quantitative. The optimum in vitro system (16 mL of rumen fluid and 4 mL of artificial saliva in a 68 mL vial incubated at 39°C) was utilised to study production of indole, skatolc and p-cresol from the anaerobic fermentation of tryptophan and tyrosine. Spirulina is an abundant source of dietary protein. Therefore, ¹³C labelled spirulina was used to study the metabolism of protein and formation of analytes derived from ruminal metabolism of protein. A series of labelled end products, including toluene, acetic acid, propanoic acid, iso-butyric acid, n-butyric acid, iso-valeric acid, n-valeric acid, p-cresol, indole, skatole, dimethyldisulfide and dimethyltrisulfide were detected by GC-MS. This result indicates that these compounds are the products of ruminal metabolism of spirulina. When applied to the in vitro rumen system the headspace SPME technique provides a fast approach to study metabolism of target compounds and allows the researcher to follow proposed pathways with labelled substrate.
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    Headspace analysis of natural yoghurt using headspace solid phase microextraction : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Food Technology at Massey University (Turitea Campus), Palmerston North, New Zealand
    (Massey University, 2001) Sivalingam-Reid, Geedha
    The Solid Phase Microextraction (SPME) method was originally developed to extract volatile and semivolatile compounds from wastewater samples but has since been applied to flavour compounds in foods and beverages. Research using the HS-SPME in related areas such as cheese and skim milk powder has been carried out but, to date, no work has been done on yoghurt flavours. The main objective of this study was to devise a methodology for the Headspace Solid Phase Microextraction (HS-SPME) technique to investigate and quantify six flavour analytes in natural, set yoghurts made from recombined milk. The relevant literature was reviewed and from it, a research proposal for this work on yoghurts was drawn. The first step in analysing and quantifying the yoghurt volatiles was to set up a working methodology for the HS-SPME method. The 100 μm polydimethylsiloxane (PDMS) fibre was chosen along with 20 minutes being the optimum fibre adsorption time. General equipment, materials and methods used throughout this thesis are also detailed. The external standard (ES) method was used to calibrate the GC and quantify the analyte concentrations in this study. The internal standard (IS) method was not used as a quantitative tool in this study. Once the HS-SPME methodology had been set up for the analysis of yoghurts, the classical Static Headspace (SH) method was compared with the HS-SPME method for extraction efficiency. The results suggested that the two methods were complementary in that the SH method extracted the more volatile compounds (acetaldehyde, acetone and 2-butanone) whereas, the HS-SPME method extracted the semi- to non-volatile compounds (ethanol, diacetyl and acetoin) more readily. However, the HS-SPME was found to be the more sensitive and effective method of the two techniques tested. The next step in the thesis was to investigate the presence of the six analytes in milk and cultured yoghurt. The effects of the sample matrix, fat levels and incubation on the volatile concentrations were also examined. The results suggested that the six analytes were inherently present in milks but at low concentrations. No conclusive effects were found for the sample matrix, fat levels and incubation. However, it was evident that fermentation of the milks using bacterial starter cultures resulted in a large increase in some of the volatiles being investigated. Following this, the effects of fat levels, storage time and storage temperature on the six volatiles in yoghurts were examined. The results indicated that significant fat level effects were only seen for diacetyl and acetoin, while temperature effects were only observed for ethanol. In both trials, only general trends for the analytes concentrations were drawn because the data varied from day to day. The results suggested that most of the compounds decreased with time except for diacetyl, which seemed to increase. The final part of this study looked at applying the devised HS-SPME methodology to a series of commercial yoghurts as a preliminary trial, with a view to investigating a potential application for the HS-SPME method. Fourteen commercial yoghurts were analysed and the six analytes quantified. The data obtained was analysed using Principle Component Analysis (PCA), which divided the yoghurts into groups based on their analyte concentrations. From these groupings, eight yoghurts were selected and fresh samples were analysed using HS-SPME and PCA. This was carried out parallel with an untrained consumer panel, which had to distinguish differences between the yoghurts in a series of triangle tests by smelling the headspace on opening the yoghurt containers. The conclusions drawn were that, unlike the HS-SPME method with PCA, the average consumer could not differentiate the yoghurts based on smell alone. PCA also showed that the HS-SPME results obtained were fairly reproducible. In conclusion, the HS-SPME method was shown to be a useful analytical technique, which can be used to analyse and quantify flavour compounds in natural, set yoghurts. This area of investigation has a lot of scope, with the results from this study providing a basis or starting point for further investigations in this area. Future studies may lead to potential applications for the HS-SPME method, one of which may be quality control where correlation of sensory data with HS-SPME analytical data is required.