The rheology of caramel was determined as a function of processing temperature and hydrocolloid additions. As the processing temperature increased the water content decreased and the caramel viscosity increased. X-ray diffraction showed that although crystalline fat was present, for the most part the sugars were in the amorphous state. The exception was the lowest water content caramel (7.9% water w.w.b.) which had been processed to a temperature of 122ºC. This had a small amount of crystalline fructose. Caramel rheology was assessed by rotational and capillary rheometry. Rotational rheometry gave information on the steady shear viscosity, the dynamic parameters (storage and loss moduli and related functions) and the creep compliance and recovery response. Capillary rheometry gave shear viscosities at high shear rates and an extensional viscosity. It was found that caramel without added hydrocolloids had behavior which was close to a Newtonian liquid. The only exception to this was the values obtained for the Trouton ratio which ranged from 10 to 40. This was considerably higher than the value of 3 for a Newtonian fluid and may reflect the difficulties in making measurements on these relatively low viscosity systems in the capillary rheometer. The viscosities obtained from steady shear, oscillation and creep were combined and three approaches were used to model the data as a function of measurement temperature and water content. An empirical statistical model using a second order polynomial, an Arrhenius fit and a Williams Landel Ferry (WLF) model. The former and the latter gave a good fit to the data although the constants used in the WLF model varied with the water content of the caramel. Arrhenius plots showed curvature particularly at low water contents. Incorporation of the hydrocolloids carrageenan and gellan gum into the caramel made the material non-Newtonian and elastic. For carrageenan incorporation in particular the Trouton ratio increased with carrageenan concentration reaching a value ~500 at a strain rate of 100s-1 for the caramel containing 0.2% carrageenan It was demonstrated that incorporation of carrageenan could be used to prevent cold flow in caramels processed at relatively high water contents. Glass transition temperatures were measured by differential scanning calorimetry and calculated from the temperature dependence of the shift factors used to superimpose the oscillatory rheological data. Generally there was agreement between the two approaches although for some gellan gum containing samples the rheological Tg was about 10ºC higher than the DSC value. Fragility calculated from the WLF constants for caramel was high as has been reported for sugars. The Tg for both caramel and sugar water mixtures calculated using the Couchman-Karastz equation in the water content of interest (9-15% w.w.b.) was some 30-40°C higher than measured. It is suggested that this disagreement could be related to the high fragility of the sugar water systems. Isoelectric point measurements using a streaming potential technique was shown to give information on the extent of the Maillard reaction and the presence of hydrocolloids.

ABSTRACT This project addressed two areas in the flavour industry – flavour reformulation required as a consequence of ingredient changes and flavour stability in solid food products. The aim of the flavour reformulation study was to evaluate both instrumental and modelling approaches to reformulate commercial flavourings for food products of different fat contents. A strawberry flavouring was chosen, which delivered an acceptable flavour in pectin jelly (0% fat) but did not perform so well in chewy candy (8% fat). Aroma release profiles in people eating these two sweets were measured by APCI-MS, the relative release differences for each flavour compound was determined and then used to reformulate the strawberry flavouring so its release in both sweets was similar. The sensory performance of candies confirmed a significant difference between the reformulated and original flavour (p < 0.05). The modelling approach was based on compound hydrophobicity (Log P) and the fat content of the food. This was used to estimate relative differences in flavour delivery for products with two varying fat contents. Flavourings were reformulated for yoghurt with reduce fat level, and the measured results showed good correlation with model’s prediction (r = 0.95). The aim of the flavour stability study was to explore the impact of product storage and flavour solvent in biscuits with vanilla flavouring. After eight weeks storage at 45 °C, up to 20% vanillin loss was measured, but sensory results suggested no difference in vanilla flavour perception. Texture analysis indicated that biscuits using triacetin (TA) as flavour solvent were more brittle than biscuits made with propylene glycol (PG). This was explained by X-ray CT analysis results which showed TA biscuits had larger pores than PG biscuits. Additionally, TA solvent provided higher vanillin stability during storage, so it should be a better choice than PG solvent used in flavourings for biscuits. IMPACT STATEMENT This research proved that it is feasible to apply laboratory-derived knowledge and adapt scientific techniques in a commercial context. It also demonstrated how the research findings can be transferred into the commercial field through two studies. The first study successfully illustrated two novel approaches to reformulate flavourings between food products of differing fat contents. Comparing with traditional trial and error process, this study demonstrated that instrumental and modelling approaches can be more effective ways for flavour reformulation in the flavour and food industry. The cost of flavour reformulation including the reformulation time and the cost in-use can therefore be reduced considerably. The results of this study have been presented to company’s major clients worldwide, and this has been applied commercially in a range of products including the successful reformulation of a £50 M (2010, brand value) soft drink into new formats (2011). The second study increased the understanding of the flavour stability within the stored food products. This ensured the flavour company to deliver high quality materials not only to their clients before food manufacturing, but also maintained its quality in the food products during storage for their end users. Comparing two flavour solvents – propylene glycol and triacetin, the results of this study suggested that triacetin is a better solvent as it offered better flavour stability in the stored biscuits. The findings can also be applied to reduce the cost in-use for vanilla flavouring in biscuit, which is especially beneficial for food and flavour company when high cost natural vanilla flavourings are required.

Few publications on oil bodies or oleosomes seem concerned about their quality (chemical and physical) ex-vivo. This work attempts to identify the main factors (processing and pre-processing) that affect the quality/integrity of sunflower seed oil bodies recovered through a wet-milling process. The physical state of seeds during wet milling had a significant impact on the quality of the oil body suspension. Pre-soaking for 6 hours before wet milling and multiple washing with alkaline buffer (0.1M sodium bicarbonate) was performed to isolate high quality oil body suspensions. It was evident from different physical measurements such as particle size, ζ-potential and light microscopy that pre-soaking had a positive influence on the quality of oil body suspensions with no significant signs of aggregation or coalescence. It was also observed that the resultant washed oil body suspensions were highly surface charged (-28.4 ± 1.2 mV) indicating very stable suspension phase behavior. Washing oil bodies not only removes non-integral, extraneous proteins (derived from the seed matrix) but enriches the lipid content including Tocopherol (α-tocopherol: 491.6 mg/kg of washed oil bodies compared with 252.6 mg/kg crude oil bodies). Changes in the composition of oil bodies after washing have been observed before, but this research also monitored the size of oil bodies after washing, and our results indicate that certain factors can shift the distribution of droplet size. It is believed that any change in average size of droplets indicate the presence of disrupted oil bodies whose surface chemistry has changed enough to compromise their integrity on washing. The retention of droplet size on washing may, therefore, be diagnostic for the recovery of intact oil bodies. An assessment of the integrity of oil bodies recovered from sunflower seeds after accelerated aging (5 months) was carried out. Free fatty acid was more pronounced in oil rather than oil bodies, this could be due to the elimination of some of the free acid bound to oil body during washing. Although some minor variation was observed during seed aging, however, the oil bodies remained stable in the final suspension. The results indicate that oil body membrane was extremely robust under extreme conditions and the integrity of oil bodies was preserved. In addition, oil bodies obtained in this study were resistant to oxidation due to the presence of naturally occurring antioxidants (including vitamin E) associated with them. The results indicate that the physical barrier of surface membrane protein (oelosin) protect oil bodies against pro-oxidants.

Beer, as manufactured, is not at chemical equilibrium and undergoes complex chemical reactions during storage which can lead to undesirable changes in the sensory characteristics of beer. Since beer contains more than 600 volatile compounds, beer flavour change is a complex field of research and the dependable prediction of shelf life remains a top research priority. Chapter 1 places the work described in this thesis into this context. Chapters 2 and 3 provide details of the experimental methods used and their development, respectively, to evaluate flavour stability. The methods used and developed include: (i) the determination of one of the major antioxidants present in beer, sulphur dioxide (SO2), via distillation; (ii) a solid phase micro extraction (SPME)-GC-MS method with on fibre derivatization as a reliable detection method for aldehydes related to off flavours perceived in aged beer; (iii) measurement of the oxidative stability using electron paramagnetic resonance (EPR) spectroscopy. Chapter 4 describes oxidative stability measurements via EPR spectroscopy for three different lager-style beer qualities pre- and post-filtration. The trial included a large scale Kieselguhr frame filter, and two pilot-scale membrane filtration system. The results illustrate how EPR spectroscopy is sensitive to metal ion pick-up from traditional filter media and oxidative stability measures were evaluated versus oxygen pick up during filtration and sulphur dioxide content of the beer samples. The effect of a brewhouse addition of gallotannins on the flavour stability of a lager-style beer was investigated in Chapter 5. Pilot scale (16 hl) and large scale production line (1500 hl) experiments with gallotannins additions in the Brewhouse were performed. The effects of the different additions were monitored at key points of the production process and through to the final beer. Despite showing significant improvements in the pilot scale wort samples, the results for the related packed beer samples did not show clear flavour stability improvements. For the production-scale trials, only a very limited effect of improved flavour stability could be observed. In Chapter 6 a factorial experimental design was adopted to probe the interactions between seven factors known to impact on beer flavour stability. Chemical additions were made to a bright beer prior to bottling, to vary the following factors: total in pack oxygen, SO2, total iron, iso-α-acid and α-acid content, (+)-catechin and glutathione. Increased SO2 concentrations had the largest impact across the entire design space, resulting in reduced radical formation, staling aldehyde concentrations and improved sensory scores. The impacts of increased TIPO levels were rather limited. In contrast, a significant impact regarding the oxidative stability could be observed for increasing Fe concentration, highlighting the significance of pro-oxidative effects of transition metals.

The bitterness of beer remains one of its most important flavour attribute. However, complexity surrounding bitterness perception alone represents a significant challenge in its understanding, in addition to other factors relating to production processes and raw materials used in making beer. The aim of this research was to better understand beer bitterness in terms of its intensity and quality, and how hopping technology (e.g. quantity and time of hop addition during the brewing process), hop aroma and variety may effect perceived bitterness intensity and quality. This project combined both analytical and sensorial analysis, and used statistical techniques to identify the key compounds driving bitterness perception. Analytical techniques were employed to quantify bitterness-contributing compounds and analytical bitterness units in beers alongside descriptive analysis of perceived sensory bitterness. Perceived sensory bitterness (both qualitative and quantitative) was assessed using a purpose developed list of well-defined bitterness attributes, to aid the characterisation of bitterness quality in beers. The impact of cross-modal flavour interactions on the perception of beer bitterness intensity and qualities was also investigated at varying analytical bitterness levels. Lastly, the effect of hop variety, and how this significant raw material affects perceived bitterness quality was also investigated using three distinctively different hop varieties (Hersbrucker, East Kent Goldings and Zeus). Results revealed a significant impact of the analytical profiles of beers, derived from the type of hop products and hopping technology adopted in beer production, on the perceived bitterness quality of beer. In general, beers high in hop acid compounds and polyphenols were, as expected, perceived to be higher in bitterness intensity. The results further showed that bitterness intensity also played a role in the perception of bitterness quality i.e. whether the beer was ‘harsh’, ‘lingering’ or ‘round’. However, beers high in these compounds were not always of ‘negative’ bitterness quality, and correspondingly lower amounts of these compounds did not always result in ‘positive’ bitterness qualities in beer. Results on the impact of cross-modal flavour interactions showed that hop aroma plays a crucial role in beer bitterness perception, and can modify the perception of bitterness intensity and quality as well as temporal profiles of bitterness in beer depending on analytical bitterness levels. The investigation into the impact of hop variety on perceived bitterness quality revealed hop-derived bitterness profiles relating to individual hop varieties, and further suggests that careful selection of the hop variety used for brewing is important for controlling perceived bitterness quality. This research provides a comprehensive interdisciplinary approach to understanding perceived beer bitterness and its associated qualities, with findings suggesting that besides bitterness intensity, the quality and overall impression of bitterness as perceived by consumers are significantly influenced by raw materials, production processes and other factors such as aroma which might be overlooked by brewers - but are likely to be significant for consumer preference and the success of a brand.

Very High Gravity fermentations are an increasingly attractive proposition within the brewing industry as a means of energy saving and optimising process efficiency. However, the use of very high gravity ( > 20°P) wort is associated with a range of biological stress factors. Ethanoic and osmotic stresses have been widely analysed along with oxidative stress in relation to propagation and early stage fermentation. The aim of this research was to investigate the impact of wort gravity on oxidative stress, and understand how this affects the plasma membrane at VHG. Finally the effect altered ergosterol content was analysed. The characteristics of Saccharomyces pastorianus strains were assessed for their ability to withstand the increased pressures of VHG (22°P) fermentations. VHG fermentations showed increase ethanol production at the expense of fermentation length, and increased ethanol production during VHG fermentations was offset by an increase in fermentation length. All fermentations were observed to accumulate ROS and increased antioxidant levels, with levels being furtherelevated in the VHG environment. Further analysis of S. pastorianus strains indicated that the levels of oxidative stress observed in fermentation had a negative effect on membrane fluidity and increased damage of the plasma membrane was observed. Analysis of ergosterol enriched yeast indicated that although fermentation rate was increased, a trade off with alcohol and biomass production was observed. Furthermore in response to oxidative stress, ergosterol enriched yeast showed reduced tolerance, decreased membrane fluidity and increased membrane damage. This work will give further insight into the response of lager yeast to oxidative stress present during VHG fermentations.

In 1978, Stanislaus County took a proactive approach to food processing byproduct waste and established the Food Processing Byproduct Use Program. It allows processors to transport byproduct to local producers, where it serves as an alternative input. There is concern that the program negatively impacts local groundwater. The Regional Water Quality Control Board proposed that the County institute water monitoring which would increase program expenses. In response to this proposal, participants investigated the impact of the cost increase and some have concluded that this increase would preclude their continued involvement. They believe the program has allowed them to maintain their competitiveness and has kept them from relocating. This study investigates the economic impact of the food processors leaving the region due to a modification of the current program. Four economic impacts were studied—output, value-added, taxes, and employment. A sensitivity analysis was run to establish a range of possible value and the analysis yielded significantly higher results. It was estimated that program modification would result in significant fiscal and employment effects for Stanislaus and San Joaquin Counties. This study determined that both Stanislaus and San Joaquin Counties have a vested interest in ensuring that the program remains viable for processors.

A stable low-fat water-in-oil emulsion was satisfactorily prepared from milk-fat under laboratory condition. The best product contained 40 per cent fat, 56.8-57.3 per cent water, 0.8 per cent sodium carboxymethyl cellulose, 0.7-1.2 per cent milk solids-non-fat, and 1.2 percent salt. The spread was prepared equally well from butter or high test cream. When the product was made from cream (containing 74 per cent milk-fat) it was necessary to convert most of the globular fat to free fat prior to forming an emulsion. Globular fat in cream was successfully changed to free fat by homogenization at 2500 pounds per square inch or by storing the cream at 5 centigrade for 24 hours. tHe free fat was shock cooled from 41 to 18 centigrade in a swept-surface heat exchanger to give a smooth velvety texture to the milk-fat. The solidified milk-fat was warmed to 22-24 centigrade and emulsified with water containing sodium carboxymethyl cellulose 7HF (manufactured by Hercules Incorporated) and salt. Color and flavoring were added during emulsification.

During the past two decades several novel spoilage micro-organisms have emerged. Raw materials and products have been contaminated in increasing numbers of spoilage incidents causing widespread problems within the juice and beverage industry. This study investigates two such spoilage micro-organisms, A licyclobacillus acidoterrestris and Propionibacterium cyclohexanicum, both isolated from pasteurised contaminated fruit juice. A variety of media were tested to determine which supported optimal growth of A. acidoterrestris with Orange Serum Agar providing consistently high plate counts. The presence of A. acidoterrestris in raw materials and shelf stable products was monitored and the effects on its growth and survival of temperature, headspace and movement of containers during storage were investigated. The survival of P. cyclohexanicum after pasteurisation was assessed and growth determined at a variety of temperatures. The survival of each bacterium was investigated in different fruit juices, when challenged by the preservatives sodium benzoate and potassium sorbate and the bacteriocin nisin and when grown in the same juice container and co-cultured on the same solid medium. 17% of samples tested were contaminated by A. acidoterrestris; however P. cyclohexanicum was not isolated from any sample. P. cyclohexanicum survived 10 minutes at temperatures of 4°C to 95°C and grew in orange, tomato and pineapple juice while A. acidoterrestris grew in all juices tested. A. acidoterrestris was inhibited by sodium benzoate (500ppm), potassium sorbate (500ppm) and nisin (51U/ml). P. cyclohexanicum, although not inhibited by nisin (1000IU/ml), was susceptible to sodium benzoate (500ppm) and potassium sorbate (l000ppm). I-Ieadspace, movement of containers and storage temperatures affected detection rates of A. acjdoterrestrjs. Co-cultures demonstrated that if found within the same enviromnent, both bacilli can survive and cause spoilage. A. acidoterrestris is a world wide contaminant within the soft drinks industry and, considering the results of these studies P. cyclohexanicum with its heat resistance and tolerance to nisin may also emerge as a major spoilage microorganism

In the brewing industry it is standard practice to propagate a pure yeast culture and inoculate (pitch) it into the fermentation vessel. Once fermentation is complete, yeast is recovered and reused in subsequent fermentations (known as serial repitching) until a decline in performance occurs or the required number of successive fermentations has been conducted. Propagation is currently required to initiate the entire process again, which requires additional equipment, energy, water inputs and time. It has long been proposed that Active Dried Yeast (ADY) offers an alternative method of yeast supply. Adoption of this innovation by the brewing industry has been low because of perceived issues with the fermentation performance of ADY, the availability of strains and hygiene concerns. In the current study the fermentation performance of ADY has been assessed with respect to viability, genomic stability, membrane integrity, yeast growth, attenuation, uptake of wort nutrients and aspects of flavour development. ADY requires rehydration before use and it has been demonstrated that viability is impaired in these slurries, though the extent of viability loss was dependent on strain and rehydration conditions. The source of cell death is unclear. Mitochondrial and genomic DNA integrity was assessed using a variety of techniques and shown to be unaffected by dehydration and rehydration. In contrast membrane integrity was affected. Changes in membrane fluidity, sterol content and fitness to perform could be detected in ADY. Performance of ADY in fermentation was also impaired. A lag in cell growth, attenuation and sugar and amino acid uptake were noted. Diacetyl formation occurred more rapidly and end fermentation diacetyl levels were higher for ADY. These differences were not maintained during serial repitching. It is proposed that ADY could be utilised to replace freshly propagated yeast, but direct addition to fermenters would require an improvement of performance during the first fermentation.