Development and assessment of new sensor systems in food packaging applications

The use of optical sensor technology for non-invasive determination of key quality pack parameters improved package/product quality. This technology can be used for optimization of packaging processes, improvement of product shelf-life and maintenance of quality. In recent years, there has been a major focus on O2 and CO2 sensor development as these are key gases used in modified atmosphere packaging (MAP) of food. The first and second experimental chapters (chapter 2 and 3) describe the development of O2, pH and CO2 solid state sensors and its (potential) use for food packaging applications. A dual-analyte sensor for dissolved O2 and pH with one bi-functional reporter dye (meso-substituted Pd- or Ptporphyrin) embedded in plasticized PVC membrane was developed in chapter 2. The developed CO2 sensor in chapter 3 was comprised of a phosphorescent reporter dye Pt(II)- tetrakis(pentafluorophenyl) porphyrin (PtTFPP) and a colourimetric pH indicator α-naphtholphthalein (NP) incorporated in a plastic matrix together with a phase transfer agent tetraoctyl- or cetyltrimethylammonium hydroxide (TOA-OH or CTA-OH). The third experimental chapter, chapter 4, described the development of liquid O2 sensors for rapid microbiological determination which are important for improvement and assurance of food safety systems. This automated screening assay produced characteristic profiles with a sharp increase in fluorescence above the baseline level at a certain threshold time (TT) which can be correlated with their initial microbial load and was applied to various raw fish and horticultural samples. Chapter 5, the fourth experimental chapter, reported upon the successful application of developed O2 and CO2 sensors for quality assessment of MAP mushrooms during storage for 7 days at 4°C.

Development of food ingredients for modulation of glycemia

Starches are a source of digestible carbohydrate and are frequently used in formulated food products in the presence of other carbohydrates, proteins and fat. This thesis explored the effect of addition of neutral (Konjac glucomannan) or charged (milk proteins) polymers on the physical characteristics and digestion kinetics of waxy maize starch. The aim was to identify mechanisms to modulate the pasting properties and subsequent susceptibility to amylolytic digestion. Addition of αs- or β-caseinate protein fractions to waxy maize starch restricted granular swelling during gelatinisation, increasing granule integrity. It was shown that, while β-caseinate can adsorb to starch granules during pasting, αscaseinate can be absorbed into maize starch granules. The resultant effect was a reduction in granule size after heating, more intact granules and a subsequent decrease in starch digestion in vitro as determined by analysis of reducing sugars. The ability of αs-caseinate to reduce the level of amylolytic digestion was confirmed through in vivo pig (Teagasc, Moorepark) and human (University of Surrey, UK) trials. The scope of the thesis extended to the development of a new automated cell for attachment to a rheometer to measure digestion kinetics of starch-protein mixtures. In conclusion, the thesis offers new approaches to modulation of the physical characteristics of unmodified starch during gelatinisation and suggests that the type of protein and/or polysaccharide used in starch-based food systems may influence the ability of the food to modulate glycemia. This is an important consideration in the design of foods with positive health benefits.

Digital signal processing and artificial intelligence for the automated classification of food allergy

As a by-product of the ‘information revolution’ which is currently unfolding, lifetimes of man (and indeed computer) hours are being allocated for the automated and intelligent interpretation of data. This is particularly true in medical and clinical settings, where research into machine-assisted diagnosis of physiological conditions gains momentum daily. Of the conditions which have been addressed, however, automated classification of allergy has not been investigated, even though the numbers of allergic persons are rising, and undiagnosed allergies are most likely to elicit fatal consequences. On the basis of the observations of allergists who conduct oral food challenges (OFCs), activity-based analyses of allergy tests were performed. Algorithms were investigated and validated by a pilot study which verified that accelerometer-based inquiry of human movements is particularly well-suited for objective appraisal of activity. However, when these analyses were applied to OFCs, accelerometer-based investigations were found to provide very poor separation between allergic and non-allergic persons, and it was concluded that the avenues explored in this thesis are inadequate for the classification of allergy. Heart rate variability (HRV) analysis is known to provide very significant diagnostic information for many conditions. Owing to this, electrocardiograms (ECGs) were recorded during OFCs for the purpose of assessing the effect that allergy induces on HRV features. It was found that with appropriate analysis, excellent separation between allergic and nonallergic subjects can be obtained. These results were, however, obtained with manual QRS annotations, and these are not a viable methodology for real-time diagnostic applications. Even so, this was the first work which has categorically correlated changes in HRV features to the onset of allergic events, and manual annotations yield undeniable affirmation of this. Fostered by the successful results which were obtained with manual classifications, automatic QRS detection algorithms were investigated to facilitate the fully automated classification of allergy. The results which were obtained by this process are very promising. Most importantly, the work that is presented in this thesis did not obtain any false positive classifications. This is a most desirable result for OFC classification, as it allows complete confidence to be attributed to classifications of allergy. Furthermore, these results could be particularly advantageous in clinical settings, as machine-based classification can detect the onset of allergy which can allow for early termination of OFCs. Consequently, machine-based monitoring of OFCs has in this work been shown to possess the capacity to significantly and safely advance the current state of clinical art of allergy diagnosis

National food consumption surveys: micronutrient intakes and the role of fortified foods in the diets of Irish pre-school children and adults

This research investigated the micronutrient intakes of Irish pre-school children (1-4 years) and adults (18-64 years) and the role that fortified foods (FFs) play in the diets of these population groups. Dietary intake data were collected as part of the National Pre-school Nutrition Survey (NPNS) (2010-2011) and the National Adult Nutrition Survey (NANS) (2008-2010) using 4-day food and beverage records. Nutrient intakes were estimated using WISP©, which encompasses McCance and Widdowson’s The Composition of Foods and the Irish Food Composition Database. A FF is one in which one or more micronutrients are added. Key dietary sources of micronutrients in NPNS and NANS were “milk”, “meat & meat products”, “breakfast cereals”, “fruit & fruit juices” and “breads”. In general, intakes of most micronutrients were adequate with the exception of iron (1 year old children and adult women) and vitamin D (in all population groups). Small proportions of the pre-school population had intakes which exceeded the upper level (UL) (zinc: 11%, folic acid: 5%, retinol: 4%, copper: 2%). Less than 2% of adults had intakes of iron, copper, zinc and vitamin B6 which exceeded the UL. FFs were consumed by 97% of pre-school children and 82% of adults, representing 17% and 9% of mean daily energy intake respectively. Relative to energy intake, FFs contributed substantially greater proportions to intakes of key micronutrients, such as iron and vitamin D. FFs were effective in reducing the prevalence of inadequate micronutrient intakes in these population groups, particularly for iron in women and 1 year old children. FFs made a significant contribution to folate intake in women of childbearing age (72µg). FFs contributed greater proportions of carbohydrate and lower proportions of fat to the diets of consumers. Voluntary addition of nutrients to foods did not contribute appreciably to intakes exceeding the UL in these population groups.

Nutraceutical and functional food bioactive peptides in beef

In recent years, the potential to positively modulate human health through dietary approaches has received considerable attention. Bioactive peptides which are released during the hydrolysis or fermentation of food proteins or following digestion may exert beneficial physiological effects in vivo. The aim of this work was to isolate, characterise and evaluate Angiotensin-І-converting enzyme (ACE-І) inhibitory, antimicrobial and antioxidant peptides from the bovine myofibrillar proteins actin and myosin. In order to generate these peptides, the myofibrillar proteins actin and myosin were hydrolysed with digestive enzymes pepsin, trypsin and α-chymotrypsin, or with the industrial thermolysin-like enzyme “Thermoase”, Amano Inc. It was found that each hydrolysate generated contained peptides which possessed ACE inhibitory, antioxidant and antimicrobial activity. The peptides responsible in part for the observed ACE inhibitory, antioxidant and antimicrobial activity of a number of hydrolysates were isolated using the method of RP-HPLC and the bioactive peptides contained within each active fraction was determined using either MALDI-TOF MS/MS or N-terminal peptide sequencing. During the course of this thesis six ACE inhibitory and five antimicrobial peptides were identified. It was determined that the reported antioxidant activity was a direct result of a number of peptides working in synergy with each other. The IC50 values of the six ACE inhibitory peptides ranged in values of 6.85 to 75.7 µM which compare favourably to values previously reported for other food derived ACE inhibitory peptides, particularly the well known milk peptides IPP and VPP, IC50 values of 5 and 9 µM respectively. All five antimicrobial peptides identified in this thesis displayed activity against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria innocua with MIC values ranging from 0.625 to10 mM. The activity of each antimicrobial peptide was strain specific. Furthermore the role and importance of charged amino acids to the activity of antimicrobial peptides was also determined. Generally the removal of charged amino acids from the sequence of antimicrobial peptides resulted in a loss of antimicrobial activity. In conclusion, this thesis revealed that a range of bioactive peptides exhibiting ACE inhibitory, antioxidant and antimicrobial activities were encrypted in bovine myofibrillar proteins that could be released using digestive and industrial enzymes. Finally enzymatic hydrolysates of muscle proteins could potentially be incorporated into functional foods; however, the potential health benefits would need to be proven in human clinical studies.

Novel ingredients from brewers' spent grain - bioactivity in cell culture model systems and bioactivity retention in fortified food products

Functional food ingredients, with scientifically proven and validated bioactive effects, present an effective means of inferring physiological health benefits to consumers to reduce the risk of certain diseases. The search for novel bioactive compounds for incorporation into functional foods is particularly active, with brewers’ spent grain (BSG, a brewing industry co-product) representing a unique source of potentially bioactive compounds. The DNA protective, antioxidant and immunomodulatory effects of phenolic extracts from both pale (P1 - P4) and black (B1 – B4) BSG were examined. Black BSG extracts significantly (P < 0.05) protected against DNA damage induced by hydrogen peroxide (H2O2) and extracts with the highest total phenolic content (TPC) protected against 3-morpholinosydnonimine hydrochloride (SIN-1)-induced oxidative DNA damage, measured by the comet assay. Cellular antioxidant activity assays were used to measured antioxidant potential in the U937 cell line. Extracts P1 – P3 and B2 - B4 demonstrated significant (P < 0.05) antioxidant activity, measured by the superoxide dismutase (SOD) activity, catalase (CAT) activity and gluatathione (GSH) content assays. Phenolic extracts P2 and P3 from pale BSG possess anti-inflammatory activity measured in concanavalin-A (conA) stimulated Jurkat T cells by an enzyme-linked immunosorbent assay (ELISA); significantly (P < 0.05) reducing production of interleukin-2 (IL-2), interleukin-4 (IL-4, P2 only), interleukin-10 (IL-10) and interferon-γ (IFN-γ). Black BSG phenolic extracts did not exhibit anti-inflammatory effects in vitro. Hydroxycinnamic acids (HA) have previously been shown to be the phenolic acids present at highest concentration in BSG; therefore the HA profile of the phenolic extracts used in this research, the original barley (before brewing) and whole BSG was characterised and quantified using high performance liquid chromatography (HPLC). The concentration of HA present in the samples was in the order of ferulic acid (FA) > p-coumaric acid (p-CA) derivatives > FA derivatives > p-CA > caffeic acid (CA) > CA derivatives. Results suggested that brewing and roasting decreased the HA content. Protein hydrolysates from BSG were also screened for their antioxidant and anti-inflammatory potential. A total of 34 BSG protein samples were tested. Initial analyses of samples A – J found the protein samples did not exert DNA protective effects (except hydrolysate H) or antioxidant effects by the comet and SOD assays, respectively. Samples D, E, F and J selectively reduced IFN-γ production (P < 0.05) in Jurkat T cells, measured using enzyme linked immunosorbent assay (ELISA). Further testing of hydrolysates K – W, including fractionated hydrolysates with molecular weight < 3, < 5 and > 5 kDa, found that higher molecular weight (> 5 kDa) and unfractionated hydrolysates demonstrate greatest anti-inflammatory effects, while fractionated hydrolysates were also shown to have antioxidant activity, by the SOD activity assay. A commercially available yogurt drink (Actimel) and snack-bar and chocolate-drink formulations were fortified with the most bioactive phenolic and protein samples – P2, B2, W, W < 3 kDa, W < 5 kDa, W > 5 kDa. All fortified foods were subjected to a simulated gastrointestinal in vitro digestion procedure and bioactivity retention in the digestates was determined using the comet and ELISA assays. Yogurt fortified with B2 digestate significantly (P < 0.05) protected against H2O2-induced DNA damage in Caco-2 cells. Greatest immunomodulatory activity was demonstrated by the snack-bar formulation, significantly (P < 0.05) reducing IFN-γ production in con-A stimulated Jurkat T cells. Hydrolysate W significantly (P < 0.05) increased the IFN-γ reducing capacity of the snack-bar. Addition of fractionated hydrolysate W < 3 kDa and W < 5 kDa to yogurt also reduced IL-2 production to a greater extent than the unfortified yogurt (P < 0.05).

Shining light on food microbiology; applications of luciferase-tagged microorganisms in the food industry

Bioluminescence is the production of light by living organisms as a result of a number of enzyme catalysed reactions caused by enzymes termed luciferases. The lux genes responsible for the emission of light can be cloned from one bioluminescent microorganism into one that is not bioluminescent. The light emitted can be monitored and quantified and will provide information on the metabolic activity, quantity and location of cells in a particular environment, in real-time. The primary aim of this thesis was to investigate and identify several food industry related applications of lux-tagged microorganisms. The first aim was to monitor a lux-tagged Cronobacter sakazakii in reconstituted infant milk formula, in realtime. The second aim was to investigate a bioluminescent-based early warning system for starter culture disruption by bacteriophages and antibiotic residues. The third of this thesis was to examine the use of a bioluminescent-based assay to test the activity of bioengineered Nisin derivatives M21V and S29A against foodborne pathogens in laboratory media and selected foods.

Biomethane production from food waste and organic residues

Anaerobic digestion (AD) of biodegradable waste is an environmentally and economically sustainable solution which incorporates waste treatment and energy recovery. The organic fraction of municipal solid waste (OFMSW), which comprises mostly of food waste, is highly degradable under anaerobic conditions. Biogas produced from OFMSW, when upgraded to biomethane, is recognised as one of the most sustainable renewable biofuels and can also be one of the cheapest sources of biomethane if a gate fee is associated with the substrate. OFMSW is a complex and heterogeneous material which may have widely different characteristics depending on the source of origin and collection system used. The research presented in this thesis investigates the potential energy resource from a wide range of organic waste streams through field and laboratory research on real world samples. OFMSW samples collected from a range of sources generated methane yields ranging from 75 to 160 m3 per tonne. Higher methane yields are associated with source segregated food waste from commercial catering premises as opposed to domestic sources. The inclusion of garden waste reduces the specific methane yield from household organic waste. In continuous AD trials it was found that a conventional continuously stirred tank reactor (CSTR) gave the highest specific methane yields at a moderate organic loading rate of 2 kg volatile solids (VS) m-3 digester day-1 and a hydraulic retention time of 30 days. The average specific methane yield obtained at this loading rate in continuous digestion was 560 ± 29 L CH4 kg-1 VS which exceeded the biomethane potential test result by 5%. The low carbon to nitrogen ratio (C: N <14:1) associated with canteen food waste lead to increasing concentrations of volatile fatty acids in line with high concentrations of ammonia nitrogen at higher organic loading rates. At an organic loading rate of 4 kg VS m-3day-1 the specific methane yield dropped considerably (381 L CH4 kg-1 VS), the pH rose to 8.1 and free ammonia (NH3 ) concentrations reached toxicity levels towards the end of the trial (ca. 950 mg L-1). A novel two phase AD reactor configuration consisting of a series of sequentially fed leach bed reactors connected to an upflow anaerobic sludge blanket (UASB) demonstrated a high rate of organic matter decay but resulted in lower specific methane yields (384 L CH4 kg-1 VS) than the conventional CSTR system.

Physico-chemical properties and component interactions in high solids food systems

The present study aimed to investigate interactions of components in the high solids systems during storage. The systems included (i) lactose–maltodextrin (MD) with various dextrose equivalents at different mixing ratios, (ii) whey protein isolate (WPI)–oil [olive oil (OO) or sunflower oil (SO)] at 75:25 ratio, and (iii) WPI–oil– {glucose (G)–fructose (F) 1:1 syrup [70% (w/w) total solids]} at a component ratio of 45:15:40. Crystallization of lactose was delayed and increasingly inhibited with increasing MD contents and higher DE values (small molecular size or low molecular weight), although all systems showed similar glass transition temperatures at each aw. The water sorption isotherms of non-crystalline lactose and lactose–MD (0.11 to 0.76 aw) could be derived from the sum of sorbed water contents of individual amorphous components. The GAB equation was fitted to data of all non-crystalline systems. The protein–oil and protein–oil–sugar materials showed maximum protein oxidation and disulfide bonding at 2 weeks of storage at 20 and 40°C. The WPI–OO showed denaturation and preaggregation of proteins during storage at both temperatures. The presence of G–F in WPI–oil increased Tonset and Tpeak of protein aggregation, and oxidative damage of the protein during storage, especially in systems with a higher level of unsaturated fatty acids. Lipid oxidation and glycation products in the systems containing sugar promoted oxidation of proteins, increased changes in protein conformation and aggregation of proteins, and resulted in insolubility of solids or increased hydrophobicity concomitantly with hardening of structure, covalent crosslinking of proteins, and formation of stable polymerized solids, especially after storage at 40°C. We found protein hydration transitions preceding denaturation transitions in all high protein systems and also the glass transition of confined water in protein systems using dynamic mechanical analysis.

“Green preservatives” – combating fungi in the food industry by applying antifungal lactic acid bacteria

Fungal spoilage is the most common type of microbial spoilage in food leading to significant economical and health problems throughout the world. Fermentation by lactic acid bacteria (LAB) is one of the oldest and most economical methods of producing and preserving food. Thus, LAB can be seen as an interesting tool in the development of novel bio-preservatives for food industry. The overall objective of this study was to demonstrate, that LAB can be used as a natural way to improve the shelf-life and safety of a wide range of food products. In the first part of the thesis, 116 LAB isolates were screened for their antifungal activity against four Aspergillus and Penicillium spp. commonly found in food. Approximately 83% of them showed antifungal activity, but only 1% showed a broad range antifungal activity against all tested fungi. The second approach was to apply LAB antifungal strains in production of food products with extended shelf-life. L. reuteri R29 strain was identified as having strong antifungal activity in vitro, as well as in sourdough bread against Aspergillus niger, Fusarium culmorum and Penicillium expansum. The ability of the strain to produce bread of good quality was also determined using standard baking tests. Another strain, L. amylovorus DSM19280, was also identified as having strong antifungal activity in vitro and in vivo. The strain was used as an adjunct culture in a Cheddar cheese model system and demonstrated the inhibition of P. expansum. Significantly, its presence had no detectable negative impact on cheese quality as determined by analysis of moisture, salt, pH, and primary and secondary proteolysis. L. brevis PS1 a further strain identified during the screening as very antifungal, showed activity in vitro against common Fusarium spp. and was used in the production of a novel functional wortbased alcohol-free beverage. Challenge tests performed with F. culmorum confirmed the effectiveness of the antifungal strain in vivo. The shelf-life of the beverage was extended significantly when compared to not inoculated wort sample. A range of antifungal compounds were identified for the 4 LAB strains, namely L. reuteri ee1p, L. reuteri R29, L. brevis PS1 and L. amylovorous DSM20531. The identification of the compounds was based on liquid chromatography interfaced to the mass spectrometer and PDA detector

Food preservation using antifungal lactic acid bacteria

Fungal spoilage of food and feed prevails as a major problem for the food industry. The use antifungal-producing lactic acid bacteria (LAB) may represent a safer, natural alternative to the use of chemical preservatives in foods. A large scale screen was undertaken to identify a variety of LAB with antifungal properties from plant, animal and human sources. A total of 6,720 LAB colonies were isolated and screened for antifungal activity against the indicator Penicillium expansum. 94 broad-spectrum producers were identified through 16S rRNA sequencing with the majority of the population comprising Lactobacillus plantarum isolates. Six broad-spectrum isolates were consequently characterised. Pedicococcus pentosaceous 54 displayed potent anti-mould capabilities in pear, plum and grape models and may represent an ideal candidate for use in the beverage industry. Two antifungal Lb. plantarum isolates were assessed for their technological robustness and potential as biopreservatives in refrigerated foods. Lb. plantarum 16 and 62 displayed high levels of tolerance to freeze-drying, low temperature exposure and high salt concentrations. Both lactobacilli were introduced as supplements into orange juice to retard the growth of the spoilage yeast Rhodotorula mucilaginosa. Furthermore the isolates were applied as adjuncts in yoghurt production to successfully reduce yeast growth. Lb. plantarum 16 proved to be the optimal inhibitor of yeast growth in both food matrices. To date there is limited information available describing the mechanisms behind fungal inhibition by LAB. The effects of concentrated cell-free supernatant (cCFS), derived from Lb. plantarum 16, on the growth of two food-associated moulds was assessed microscopically. cCFS completely inhibited spore, germ tube and hyphal development. A transcriptomic approach was undertaken to determine the impact of antifungal activity on Aspergillus fumigatus Af293. A variety of genes, most notably those involved in cellular metabolism, were found to have their transcription modulated in response to cCFS which is indicative of global cellular shutdown. This study provides the first insights into the molecular targets of antifungal compounds produced by LAB. The genome sequence of the steep water isolate Lb. plantarum 16 was determined. The complete genome of Lb. plantarum16 consists of a single circular chromosome of 3,044,738 base pairs with an average G+C content of 44.74 % in addition to eight plasmids. The genome represents the smallest of this species to date while harbouring the largest plasmid complement. Some features of particular interest include the presence of two prophages, an interrupted plantaricin cluster and a chromosomal and plasmid encoded polysaccharide cluster. The sequence presented here provides a suitable platform for future studies elucidating the mechanisms governing antifungal production.

Assessment of dietary background exposure of the Irish adult population to dioxins and PCBs particularly taking into account additional exposure due to the 2008 Irish dioxin food contamination incident

Irish monitoring data on PCDD/Fs, DL-PCBs and Marker PCBs were collated and combined with Irish Adult Food Consumption Data, to estimate dietary background exposure of Irish adults to dioxins and PCBs. Furthermore, all available information on the 2008 Irish pork dioxin food contamination incident was collated and analysed with a view to evaluate any potential impact the incident may have had on general dioxin and PCB background exposure levels estimated for the adult population in Ireland. The average upperbound daily intake of Irish adults to dioxins Total WHO TEQ (2005) (PCDD/Fs & DLPCBs) from environmental background contamination, was estimated at 0.3 pg/kg bw/d and at the 95th percentile at 1 pg/kg bw/d. The average upperbound daily intake of Irish adults to the sum of 6 Marker PCBs from environmental background contamination ubiquitous in the environment was estimated at 1.6 ng/kg bw/d and at the 95th percentile at 6.8 ng/kg bw/d. Dietary background exposure estimates for both dioxins and PCBs indicate that the Irish adult population has exposures below the European average, a finding which is also supported by the levels detected in breast milk of Irish mothers. Exposure levels are below health based guidance values and/or Body Burdens associated with the TWI (for dioxins) or associated with a NOAEL (for PCBs). Given the current toxicological knowledge, based on biomarker data and estimated dietary exposure, general background exposure of the Irish adult population to dioxins and PCBs is of no human health concern. In 2008, a porcine fat sample taken as part of the national residues monitoring programme led to the detection of a major feed contamination incidence in the Republic of Ireland. The source of the contamination was traced back to the use of contaminated oil in a direct-drying feed operation system. Congener profiles in animal fat and feed samples showed a high level of consistency and pinpointed the likely source of fuel contamination to be a highly chlorinated commercial PCB mixture. To estimate additional exposure to dioxins and PCBs due to the contamination of pig and cattle herds, collection and a systematic review of all data associated with the contamination incident was conducted. A model was devised that took into account the proportion of contaminated product reaching the final consumer during the 90 day contamination incident window. For a 90 day period, the total additional exposure to Total TEQ (PCDD/F &DL-PCB) WHO (2005) amounted to 407 pg/kg bw/90d at the 95th percentile and 1911 pg/kg bw/90d at the 99th percentile. Exposure estimates derived for both dioxins and PCBs showed that the Body Burden of the general population remained largely unaffected by the contamination incident and approximately 10 % of the adult population in Ireland was exposed to elevated levels of dioxins and PCBs. Whilst people in this 10 % cohort experienced quite a significant additional load to the existing body burden, the estimated exposure values do not indicate approximation of body burdens associated with adverse health effects, based on current knowledge. The exposure period was also limited in time to approximately 3 months, following the FSAI recall of contaminated meat immediately on detection of the contamination. A follow up breast milk study on Irish first time mothers conducted in 2009/2010 did not show any increase in concentrations compared to the study conducted in 2002. The latter supports the conclusion that the majority of the Irish adult population was not affected by the contamination incident.

Use of oxygen sensors for the non destructive measurement of oxygen in packaged food and beverage products and its impact on product quality and shelf life

The principal objective of this thesis was to investigate the ability of reversible optical O2 sensors to be incorporated into food/beverage packaging systems to continuously monitor O2 levels in a non-destructive manner immediately postpackaging and over time. Residual levels of O2 present in packs can negatively affect product quality and subsequently, product shelf-life, especially for O2-sensitive foods/beverages. Therefore, the ability of O2 sensors to continuously monitor O2 levels present within food/beverage packages was considered commercially relevant in terms of identifying the consequences of residual O2 on product safety and quality over time. Research commenced with the development of a novel range of O2 sensors based on phosphorescent platinum and palladium octaethylporphyrin-ketones (OEPk) in nano-porous high density polyethylene (HDPE), polypropylene (PP) polytetrafluoroethylene (PTFE) polymer supports. Sensors were calibrated over a temperature range of -10°C to +40°C and deemed suitable for food and beverage packaging applications. This sensor technology was used and demonstrated itself effective in determining failures in packaging containment. This was clearly demonstrated in the packaging of cheese string products. The sensor technology was also assessed across a wide range of packaged products; beer, ready-to-eat salad products, bread and convenience-style, muscle-based processed food products. The O2 sensor technology performed extremely well within all packaging systems. The sensor technology adequately detected O2 levels in; beer bottles prior to and following pasteurisation, modified atmosphere (MA) packs of ready-to-eat salad packs as respiration progressed during product storage and MA packs of bread and convenience-style muscle-based products as mycological growth occurred in food packs over time in the presence and absence of ethanol emitters. The use of the technology, in conjunction with standard food quality assessment techniques, showed remarkable usefulness in determining the impact of actual levels of O2 on specific quality attributes. The O2 sensing probe was modified, miniaturised and automated to screen for the determination of total aerobic viable counts (TVC) in several fish species samples. The test showed good correlation with conventional TVC test (ISO:4833:2003), analytical performance and ruggedness with respect to variation of key assay parameters (probe concentration and pipetting volume). Overall, the respirometric fish TVC test was simple to use, possessed a dynamic microbial range (104-107 cfu/g sample), had an accuracy of +/- one log(cfu/g sample) and was rapid. Its ability to assess highly perishable products such as fish for total microbial growth in <12 hr demonstrates commercial potential.

The impact of saving and credit cooperatives on food security in the West Amhara Region of Ethiopia

In rural Ethiopia, among other things, lack of adequate financial service is considered as the basic problem to alleviate rural poverty and to solve the problem of food insecurity. Commercial banks are restricted to urban centres. Providing rural financial service through RUSACCO to the poor has been proposed as a tool for economic development and for achieving food security. Evidence from research in this regard has been so far scanty, especially in rural Ethiopia. The aims of this study are to analyze the determinants of membership, to identify socioeconomic and demographic factors that influence members’ participation in RUSACCOs and to quantify the impact of RUSACCOs on member households’ food security. The study was conducted in two purposely selected woredas in the Amhara region one from food insecure (Lay Gayint woreda) and the other from food secure (Dejen woreda). Six RUSACCOs were selected randomly from these two woredas. Both qualitative and quantitative data were collected. Key informant interviews, focus group discussions and survey techniques were used to collect primary data. Collected data was then analyzed using mixed methods depending on the nature of data. For quantitative data analysis appropriate statistical models were used. The study result reveals that the number of members in each RUSACCO is very small. However, the majority of non-member respondents are willing to join RUSACCO. Lack of information about the benefits of RUSACCO membership is the main problem why many rural poor do not join RUSACCOs. Members participate in different aspects of the cooperatives, starting from attending general assembly up to board membership. They also participate actively in saving and borrowing activities of RUSACCO. The majority of the respondents believe the RUSACCO is a vital instrument in combating food insecurity. The empirical findings indicate that gender, marital status, occupation, educational level, participation in local leadership and participation in other income generation means determine the decision of rural poor to join a RUSACCO or not. The amount of saving is determined by household head occupation, farming experience and income level. While age of household head, primary occupation, farming experience, date of membership, annual total consumption expenditure, amount of saving and participation in other income generation activities influence members’ amount of borrowing by RUSACCO members. Finally, the study confirms that RUSACCO participation improves household food security. RUSACCO membership has made positive impact on household total consumption expenditure and food expenditure.

Novel structured emulsions for delivering of food flavours

Flavour release from food is determined by the binding of flavours to other food ingredients and the partition of flavour molecules among different phases. Food emulsions are used as delivery systems for food flavours, and tailored structuring in emulsions provides novel means to better control flavour release. The current study investigated four structured oil-in-water emulsions with structuring in the oil phase, oil-water interface, and water phase. Oil phase structuring was achieved by the formation of monoglyceride (MG) liquid crystals in the oil droplets (MG structured emulsions). Structured interface was created by the adsorption of a whey protein isolate (WPI)-pectin double layer at the interface (multilayer emulsion). Water phase structured emulsions referred to emulsion filled protein gels (EFP gels), where emulsion droplets were embedded in WPI gel network, and emulsions with maltodextrins (MDs) of different dextrose-equivalent (DE) values. Flavour compounds with different physicochemical properties were added into the emulsions, and flavour release (release rate, headspace concentration and air-emulsion partition coefficient) was described by GC headspace analysis. Emulsion structures, including crystalline structure, particle size, emulsion stability, rheology, texture, and microstructures, were characterized using differential scanning calorimetry and X-ray diffraction, light scattering, multisample analytical centrifuge, rheometry, texture analysis, and confocal laser scanning microscopy, respectively. In MG structured emulsions, MG self-assembled into liquid crystalline structures and stable β-form crystals were formed after 3 days of storage at 25 °C. The inclusion of MG crystals allowed tween 20 stabilized emulsions to present viscoelastic properties, and it made WPI stabilized emulsions more sensitive to the change of pH and NaCl concentrations. Flavour compounds in MG structured emulsions had lower initial headspace concentration and air-emulsion partition coefficients than those in unstructured emulsions. Flavour release can be modulated by changing MG content, oil content and oil type. WPI-pectin multilayer emulsions were stable at pH 5.0, 4.0, and 3.0, but they presented extensive creaming when subjected to salt solutions with NaCl ≥ 150 mM and mixed with artificial salivas. Increase of pH from 5.0 to 7.0 resulted in higher headspace concentration but unchanged release rate, and increase of NaCl concentration led to increased headspace concentration and release rate. The study also showed that salivas could trigger higher release of hydrophobic flavours and lower release of hydrophilic flavours. In EFP gels, increases in protein content and oil content contributed to gels with higher storage modulus and force at breaking. Flavour compounds had significantly reduced release rates and air-emulsion partition coefficients in the gels than the corresponding ungelled emulsions, and the reduction was in line with the increase of protein content. Gels with stronger gel network but lower oil content were prepared, and lower or unaffected release rates of the flavours were observed. In emulsions containing maltodextrins, water was frozen at a much lower temperature, and emulsion stability was greatly improved when subjected to freeze-thawing. Among different MDs, MD DE 6 offered the emulsion the highest stability. Flavours had lower air-emulsion partition coefficients in the emulsions with MDs than those in the emulsion without MD. Moreover, the involvement of MDs in the emulsions allowed most flavours had similar release profiles before and after freeze-thaw treatment. The present study provided information about different structured emulsions as delivery systems for flavour compounds, and on how food structure can be designed to modulate flavour release, which could be helpful in the development of functional foods with improved flavour profile.