Equivalent Circuit Modeling of the Dielectric Loaded Microwave Biosensor

This article describes the modeling of biological tissues at microwave frequency using equivalent lumped elements. A microwave biosensor based on microstrip ring resonator (MRR), that has been utilized previously for meat quality evaluation is used for this purpose. For the first time, the ring-resonator loaded with the lossy and high permittivity dielectric material, such as; biological tissue, in a partial overlay configuration is analyzed. The equivalent circuit modeling of the structure is then performed to identify the effect of overlay thickness on the resonance frequency. Finally, the relationship of an overlay thickness with the corresponding RC values of the meat equivalent circuit is established. Simulated, calculated and measured results are then compared for validation. Results are well agreed while the observed discrepancy is in acceptable limit

Development, assessment and optimisation of meat systems for the aging consumer through processing and packaging modification

In response to the growing population of those aged over 65, it is essential we prepare for better quality of life not just increased life years. Sensory decline impacts, not just the way we perceive flavours, but the way we see food and the manner in which we handle food. The studies reported in this thesis examined the effects of sensory decline across a wide age cohort using different meat products. The thesis falls under two parts. Part 1 focused on the food aspect of sensory decline which assessed the impacts of texture modification, fat and salt-reduction, salt-substitution and flavour enhancement; all of which resulted in the development of the most enhanced product that incorporated aging consumer needs. Part 2 focussed on the decline in cognitive and physical ability which occurs as a result of the aging process in order to develop a more suitable, convenient and safe food package for the aging consumer. This thesis offers a design for establishing meal solutions for the elderly consumers based around meat products. Of all product attributes, texture was found to be a major determinant in establishing preferences in various age cohorts. It was found that softer foods which were easier to chew and swallow were favoured by older age cohorts. Flavour differences determined among varying age cohorts was also noted. Preferences for fat, fat-replacers, salt and salt-replacers were established. A consistent decreased perception for salt was noted in study participants aged 41-64 in three studies. The use of trained and consumer panels allowed for the development of the ‘ideal’ processed meat product which was then presented to older consumers in the elderly-friendly packaging formats which were highly accepted. Understanding the needs and requirements of the elderly consumers is paramount in encouraging independent, safe and healthy living of these individuals in our community. It is hoped that this study provides some evidence to educate and assist in this process

Effects of thawing method on palatability and thawing characteristics of beef loins

Master of ScienceDepartment of Animal Sciences and IndustryTravis G O'QuinnThe objective of this study was to investigate the effects of various thawing methods on beef palatability. USDA Choice paired beef strip loins (n = 15) were obtained from a Midwest commercial processing facility for palatability evaluation. Moreover, 6 USDA Low Choice strip loins for thawing characteristic data collection were collected. At day 11 of aging, the paired strip loins were portioned into 6 blocks, and fabricated into 2.5 cm steaks. Each block was then assigned one of six thawing methods, with each loin containing each thawing method. Thaw methods included the four USDA approved thawing methods: thawing in the refrigerator(2-3° C; 882 m), cold water (2-3° C; 637.5 m), microwave (50% power, 7 m), and cooking from frozen, as well as two methods commonly used by consumers: thawing in hot water (40° C; 10.3 m), and on the counter (19±1° C; 264 m). Within each block, steaks were assigned to one of four tests: consumer panel, trained panel, Warner-Bratzler shear force, and lab assay. Steaks were aged a total of 21d prior to freezing. Loins designated for thawing characteristic data collection were fabricated into 2.5 cm steaks at 11 d of aging, assigned a random thawing treatment. Temperature probes were inserted, vacuum packaged, and frozen. End-point thawing temperature was targeted at 0°C for all steaks. For thawing characteristic steaks, temperature probes were connected to data loggers immediately upon removal from the freezer, Thaw rate, time, and temperature at times prior to thawing were all recorded from –6.67° C to 0° C. Data were analyzed as a completely randomized block design. Results from consumer panels indicate no differences (P > 0.05) among all thawing methods for consumer’s ratings for tenderness, juiciness, flavor, and overall liking. Similarly, there were no differences (P > 0.05) among thawing methods for percentage of steaks rated acceptable for tenderness, juiciness, flavor, and overall liking. Moreover, there were no differences (P > 0.05) in consumer perception of quality. In terms of myofibrillar tenderness in trained sensory panels, thawing in the refrigerator and cold water were more tender (P 0.05) for initial juiciness, sustained juiciness, connective tissue, Warner- Bratzler Shear Force, and slice shear force. In terms of objective quality measurements, thawing steaks in the microwave had lower (P < 0.05) a* and b* values than all other thawing methods, while cooking from frozen steaks had lower a* and b* values than thawing on the counter. Additionally, steaks thawing in the microwave had the highest (P < 0.05) cook loss, followed by cooking from frozen, with all other methods being similar. Similarly, steaks thawed in the microwave and in hot water had a higher (P < 0.05) thawing loss than thawing on the counter, in cold water, and in the refrigerator. Also, steaks thawed in the microwave had the highest (P < 0.05) total moisture loss, followed by hot water and cooking from frozen, then thawing in cold water, on the countertop, and in the refrigerator. Lastly, steaks cooked from frozen had a higher (P < 0.05) expressible moisture than thawing steaks on the counter, in colder water, or in the refrigerator. These results indicate thawing method had minimal differences on overall palatability, and objective quality measures. Although, increases in thawing loss should be considered when thawing large quantities of meat for potential overall economic loss. Therefore, consumers and food service establishments should use their preferred thaw method, taking food safety and time into consideration

Investigating the Strategies to Improve the Quality of Low-Fat Mozzarella and Cheddar Cheeses

Low-fat cheese faces great challenges associated with its texture being hard and rubbery, desirable flavors being missing, color being undesirably intense and translucent appearing, and melting being improper. In an effort of improving the quality of low-fat cheeses, several strategies have been tried to accomplish three major objectives, 1) improving the melting and baking properties of low-fat Mozzarella cheese, 2) improving the color of low-fat Cheddar cheese, and 3) investigating the feasibilities of enriching low-fat Cheddar cheese with dietary fibers. For objective 1, 4 batches of low-fat Mozzarella cheese with target fat of 6.0%, 4.5%, 3.0%, and 1.5% were made using a stirred curd method, comminuted in a bowl chopper and mixed with different levels of melted butter (0.0, 1.5, 3.0, and 4.5% (wt/wt), respectively) before pressing. This would made the cheese that had increased free oil, increased melting, and improved baking as the level of added butter increased. The added butterfat was present as free fat along the curd particle junctions as shown by laser scanning confocal microscopy while the fat droplets originating from the milk were distributed within the protein matrix of the cheese. In objective 2, consumer tests and flavor profile analysis were performed on 4 commercial brands of full-fat Cheddar cheese and 9 low-fat Cheddar cheeses manufactured at Utah State University with different colors. Low-fat cheeses were rated different (P \u3c 0.05) for their liking by a consumer panel even though they were all made the same way except for addition of color. The only difference in flavor detected by a trained panel was for a slight variation in bitterness. Using a combination of annatto and titanium dioxide produced a cheese that was rated the highest. Annatto when added singly produced a low-fat cheese that was rated the lowest. Moreover, commercial cheeses were also ranked significantly different for liking and buying preference. For objective 3, several trials were conducted to enrich low-fat cheese with inulin, pectin, polydextrose, or resistant-starch either by incorporating them into cheesemilk, mixing with 15-d aged cheese followed by repressing, or by formulating a W/O/W emulsion with inulin and incorporating the emulsion into the milk prior to cheesemaking. Adding fibers directly to milk resulted in less or no retention of fibers in cheese, whereas fibers added to comminuted cheeses were too crumbly. Adding fiber as a W/O/W emulsion improved fiber retention in the cheese and produced an improved texture of low-fat cheese

Characterization and modulation of technofunctional properties of pea proteins

Plant-derived ingredients for food formulation have gained increasing interest in recent years as animal products pose a higher burden on the environment. Among plant proteins, those from pea (Pisum sativum L.) are of particular interest because of their low allergenicity, low cost, high availability, and good reputation among consumers. However, the technofunctionality of pea proteins is often inferior to animal-derived proteins limiting a more widespread use in food products. These technofunctional properties include - among others - foaming, gelling, and binding of other ingredients and it depends on the food product, which functionality food scientists must utilize and optimize. Cost effective approaches to improve the technofunctionality of pea proteins are therefore desirable and would allow the industry to further implement the use of sustainable ingredients in foods. In line with these overall goals, the aim of the first section of this thesis was to characterize a commercial pea protein isolate and to modulate the physicochemical and technofunctional properties through homogenization for foaming application. The main goal of the second section was to mix pea proteins with pectin to obtain a suitable binder with desired properties for the application in meat alternatives. The mixing approach was based on previous research data that had shown that interacting protein-polysaccharide systems display a synergistic behaviour in terms of their functional properties. First section: Foams are two phase systems consisting of gas bubbles that are stabilized by surface-active ingredients such as proteins in the discontinuous, aqueous phase. The physico-chemical properties of proteins such as their solubility determines foaming performance. In Chapter I, a commercial pea protein isolate was fractionated into a water-soluble and a water-insoluble fraction for characterization. Although the two fractions were similar in protein composition, they showed distinct differences in physicochemical properties. For instance, the particle size of soluble pea proteins was around 40-50 µm at acidic pH (3-5), while no measurable particles were detected at neutral The insoluble pea proteins were large at pH 3 and 7 (> 80 µm) and ca. 40-50 µm close to their isoelectric point at pH 5. The results suggest that commercial pea protein isolates consisted of several fractions with differences in their physico-chemical properties. The yield of the water-insoluble fraction was higher and therefore used in Chapter II, where experimental results illustrated that dispersions of insoluble pea protein aggregates (5% w/w, pH 7) could be disrupted from 180 ± 40 µm (control) to 0.2 ± 0.0 µmm upon homogenization at pressures &#8805; 125 MPa. This was attributed to a cleavage of intermolecular interactions such as disulphide bonds, hydrogen bonds, and hydrophobic interactions. The decrease in insoluble pea protein aggregate size was accompanied by an increase in solubility from 23 ± 1% to &#8805; 80% that may be beneficial for its technofunctionality. Consequently, homogenization was applied to the same material at pH 3 and 5 with the aim of investigating its foaming performance in Chapter III. In general, unhomogenized dispersions of pea protein aggregates (5% w/w, pH 3 or 5) did not foam at both tested pH values due to large pea protein aggregates with low solubility and surface activity. At pH 3, the dissociation of pea protein aggregates into smaller, more soluble, and more surface-active proteins was responsible for a high foam capacity (FC = 360-520%) with medium foam stability as measured by drainage (FS = 19-30 min). Only a limited particle size reduction upon homogenization was observed at pH 5, which was close to the isoelectric point of the pea proteins. Nevertheless, the still large aggregates consisted of re-aggregated smaller protein particles that were able to form a smaller amount of rather stable foams with thick interfacial films (FC = 213-246%, FS = 32-42 min). Overall, homogenization of insoluble pea protein aggregates was shown to change its physicochemical properties thereby benefitting technofunctional properties such as foaming. Second section: Another technofunctionality of interest is binding of different structural elements in e.g., meat alternatives. For this, the binder must be i.) sticky to glue heterogeneous components together and ii.) able to readily solidify upon further processing thereby ensuring a coherent bulk matrix. In Chapter IV, the influence of pH (3.50, 4.75, 6.00) and biopolymer concentration (17.5-50.0% w/w) on the stickiness of a pea protein isolate apple pectin mixture (mixing ratio r = 6:1) was investigated. It was found that biopolymer concentrations of 17.5-20.0% w/w led to low stickiness due to a lack of cohesive forces (WoA = 0.29-0.51 mJ). At high biopolymer concentrations of 40-50% w/w, the biopolymer mixtures were also not sticky because of adhesion being limited (WoA = 0.02-0.05 mJ). There was a good balance of adhesion and cohesion that facilitated a high stickiness (WoA = 0.48-0.65 mJ) at intermediate concentrations of 25-30% w/w, which was also indicated by a viscoelastic behavior (G &#8776; G). At those concentrations, the mixtures at pH 6 were stickier due to increased swelling of the pea proteins. The importance of viscoelasticity for stickiness of biopolymer mixtures was confirmed in Chapter V, where pea protein isolate and apple pectin (25% w/w, pH 6) were mixed in different ratios r. Mixtures of pea protein and apple pectin and particularly the sample with r = 2:1 possessed high stickiness due to the development of a multiphase morphology that allowed for a good balance of adhesion and cohesion with distinct frequency dependency. Pea protein alone (r = 1:0, c = 25% w/w) had an elastic but soft texture with low stickiness due to limited viscous properties, whereas a sample solely consisting of apple pectin (r = 0:1, c = 25% w/w) was also not sticky because of its high cohesion and stiffness. The results of Chapter VI revealed that pea protein homogenization prior to mixing with apple pectin led to smaller protein particles in the blend that contributed to a higher cohesive strength. Interestingly, vacuum-dried pea proteins resulted in a higher network strength as this drying method prevented reaggregation of small protein particles to a higher extent as compared to freeze-drying. Overall, the mixture with homogenized and vacuum-dried pea proteins was nearly twice as sticky as the mixture with untreated pea proteins. In Chapter VII, sticky mixtures of different pea protein preparations (soluble, homogenized and unhomogenized pea proteins) and pectin (25% w/w, pH 6, r = 2:1) were tested for their ability to solidify upon different treatments, namely heating as well as the addition of transglutaminase, laccase, calcium, and combinations thereof. Calcium was found to facilitate crosslinking of pectin chains and thus induced solidification of the mixtures. For instance, the consistency coefficient K increased from 2800 ± 1000 Pasn for pea protein isolate apple pectin mixtures to around 19000 Pasn when calcium was added. Heat treatment and transglutaminase did not lead to solidification indicating that pectin made up the continuous phase. Furthermore, laccase led to the highest degree of solidification when sugar beet pectin was used (K > 30000 Pasn) due to ferulic acid and pea protein tyrosine crosslinking. Consequently, the sticky mixture of pea protein and sugar beet pectin (25% w/w, pH 6, r = 2:1) with the addition of laccase for solidification was identified as the most suitable binder for a bacon type meat analogue, which was the object of the study carried out in Chapter VIII. This binder had the highest binding strength (W = 2.0-4.3 mJ) between textured protein, fat mimic, and both layers at 25 °C due to the introduction of covalent bonds by laccase within the binder and between the binder and the adherends. A control sample without laccase addition had lower binding properties (W = 0.7-1.0 mJ) and the binding strength of a methylcellulose hydrogel (6% w/w) serving as benchmark was only higher between two fat mimics at 70 °C (W = 1.8 ± 1.1 mJ) due to increased hydrophobic forces. Finally, the pea protein sugar beet pectin binder (22.5% w/w, pH 6, r = 2:1) was tested in burger patty type meat analogues to glue textured vegetable protein and fat particles together (Chapter IX). The binder system did not influence the hardness of the burger patties suggesting that this property was governed by the structural elements and not the binder. However, the cohesiveness as determined by sensory analysis was found to be superior when the pea protein sugar beet pectin binder was used (-0.7 ± 0.2) as compared to the methylcellulose benchmark (-2.9 ± 0.3). This was attributed to the sticky character of the biopolymer mixture that enabled improved binding of the different structural elements. Overall, this novel binder based on plant-derived ingredients was shown to be applicable in different meat alternatives. Last, Chapter X reviewed the functionality and binding mechanism of currently used binders in foods and showed that stickiness, hardening/solidification, and water holding capacity are of great importance. In many food products, the binder transitions from a sticky food glue to a solid matrix triggered by different process operations that depend on the characteristics of the applied binder. From the presented results, it can be concluded that pea proteins are useful functional ingredients in various application scenarios. The desired technofunctionality can be improved through different process operations such as fractionation, homogenization, or mixing with other plant-derived ingredients. For this, knowledge regarding structure-function relationship and other influential factors is needed. In some cases such as in binders process operations must be well orchestrated to induce structural transitions and therefore changes in functionality at the desired time during manufacturing. Overall, the results of this thesis contributed to a better understanding for a more widespread use of pea proteins to promote a more sustainable food system. The appended graphical abstract summarizes the key steps undertaken in this thesis to come to this conclusion.Pflanzliche Inhaltsstoffe für die Herstellung von Lebensmitteln haben in den letzten Jahren zunehmend an Bedeutung gewonnen, da tierische Produkte eine größere Belastung für die Umwelt darstellen. Unter den pflanzlichen Proteinen sind diejenigen aus Erbsen (Pisum sativum L.) wegen ihrer geringen Allergenität, ihrer niedrigen Kosten, ihrer hohen Verfügbarkeit und ihrer Wertschätzung seitens der Verbraucher von besonderem Interesse. Die Technofunktionalität von Erbsenproteinen ist jedoch häufig schlechter als die von tierischen Proteinen, was eine breitere Verwendung in Lebensmitteln einschränkt. Zu diesen technofunktionellen Eigenschaften gehören unter anderem Schäumen, Gelieren und Binden anderer Zutaten, und es hängt vom Produkt ab, welche Funktionen Lebensmittelwissenschaftler nutzen und optimieren müssen. Kostengünstige Ansätze zur Verbesserung der Technofunktionalität von Erbsenproteinen sind daher wünschenswert und würden es der Industrie ermöglichen, die Verwendung nachhaltiger Zutaten in Lebensmitteln weiter zu beschleunigen. Basierend auf diesen übergeordneten Absichten bestand das Ziel des ersten Abschnitts dieser Arbeit darin, ein kommerzielles Erbsenproteinisolat zu charakterisieren und die physikochemischen und technofunktionellen Eigenschaften durch Homogenisierung für die Anwendung als Schaumbildner zu modulieren. Das Hauptziel des zweiten Abschnitts bestand darin, Erbsenproteine mit Pektin zu mischen, um ein geeignetes Bindemittel mit den gewünschten Eigenschaften für die Anwendung in Fleischalternativen zu erhalten. Der Mischungsansatz basierte auf früheren Forschungsdaten, die zeigten, dass interagierende Protein-Polysaccharid-Systeme eine Synergie in Bezug auf ihre funktionellen Eigenschaften aufweisen. Erster Abschnitt: Schäume sind Zweiphasensysteme, die aus Gasblasen bestehen und durch oberflächenaktive Bestandteile wie Proteine in der diskontinuierlichen, wässrigen Phase stabilisiert werden. Die physikochemischen Eigenschaften der Proteine, wie ihre Löslichkeit, bestimmen die Schaumbildung. In Kapitel I wurde ein kommerzielles Erbsenproteinisolat zur Charakterisierung in eine wasserlösliche und eine wasserunlösliche Fraktion auftrennt. Obwohl die beiden Fraktionen eine ähnliche Proteinzusammensetzung aufwiesen, zeigten sie deutliche Unterschiede in ihren physikochemischen Eigenschaften. So betrug die Partikelgröße der löslichen Erbsenproteine bei saurem pH-Wert (3-5) etwa 40-50 µm, während bei neutralem pH-Wert keine messbaren Partikel festgestellt wurden. Die unlöslichen Erbsenproteine waren hingegen bei pH 3 und 7 groß (> 80 µm) und lagen bei pH 5 (in der Nähe ihres isoelektrischen Punktes) bei ca. 40-50 µm. Die Ergebnisse deuten darauf hin, dass handelsübliche Erbsenproteinisolate aus mehreren Fraktionen bestehen, die sich in ihren physikochemischen Eigenschaften unterscheiden. Die Ausbeute der wasserunlöslichen Fraktion war höher und wurde daher in Kapitel II verwendet. Die experimentellen Ergebnisse zeigten, dass Dispersionen von unlöslichen Erbsenproteinaggregaten (5% w/w, pH 7) durch Homogenisierung bei einem Druck von &#8805; 125 MPa von 180 ± 40 µm (Kontrolle) auf 0,2 ± 0,0 µm zerkleinert werden konnten. Dies wurde auf eine Spaltung der intermolekularen Wechselwirkungen wie Disulfidbindungen, Wasserstoffbrücken und hydrophobe Wechselwirkungen zurückgeführt. Die Verringerung der Größe der unlöslichen Erbsenproteinaggregate ging mit einem Anstieg der Löslichkeit von 23 ± 1% auf &#8805; 80% einher, was wiederum für die Technofunktionalität von Vorteil sein könnte. Folglich wurde das gleiche Material bei einem pH-Wert von 3 und 5 homogenisiert, um die Schaumkapazität und Schaumstabilität in Kapitel III zu untersuchen. Im Allgemeinen schäumten unhomogenisierte Dispersionen von Erbsenproteinaggregaten (5% w/w, pH 3 oder 5) bei beiden getesteten pH-Werten nicht, was auf große Erbsenproteinaggregate mit geringer Löslichkeit und Oberflächenaktivität zurückzuführen ist. Bei pH 3 war die Dissoziation der Erbsenproteinaggregate in kleinere, besser lösliche und oberflächenaktivere Proteine verantwortlich für eine hohe Schaumkapazität (360-520%) mit mittlerer Schaumstabilität (= 19-30 min), die mittels Drainage gemessen wurde. Bei pH 5, der nahe dem isoelektrischen Punkt der Erbsenproteine lag, wurde nur eine begrenzte Verringerung der Partikelgröße bei der Homogenisierung beobachtet. Dennoch bestanden die immer noch großen Aggregate aus reaggregierten kleineren Proteinpartikeln, die eine kleinere Menge recht stabile Schäume mit dicken Grenzflächenfilmen bildeten (Schaumkapazität = 213-246%, Schaumstabilität = 32-42 min). Insgesamt hat sich gezeigt, dass die Homogenisierung von unlöslichen Erbsenproteinaggregaten deren physikochemische Eigenschaften verändert und dadurch technofunktionelle Eigenschaften wie das Schäumen begünstigt wurden. Zweiter Abschnitt: Eine weitere Technofunktionalität von Interesse ist die Bindung verschiedener Strukturelemente, z. B. in Fleischalternativen. Dazu muss das Bindemittel i.) klebrig sein, um heterogene Komponente zusammenzukleben, und ii.) in der Lage sein, sich bei der Weiterverarbeitung leicht zu verfestigen, um dadurch eine kohärente Matrix zu gewährleisten. In Kapitel IV wurde der Einfluss des pH-Wertes (3,50, 4,75, 6,00) und der Biopolymerkonzentration (17,5-50,0% w/w) auf die Klebrigkeit einer Mischung aus Erbsenproteinisolat und Apfelpektin (Mischungsverhältnis r = 6:1) untersucht. Es wurde festgestellt, dass Biopolymerkonzentrationen von 17,5-20,0% w/w zu einer geringen Klebrigkeit aufgrund geringer Kohäsion (Adhäsionsarbeit 0,29-0,51 mJ) führten. Bei hohen Biopolymerkonzentrationen von 40-50% w/w waren die Biopolymermischungen ebenfalls nicht klebrig, da die Adhäsion gering war (Adhäsionsarbeit 0,02-0,05 mJ). Bei mittleren Konzentrationen von 25-30% w/w herrschte ein gutes Gleichgewicht zwischen Adhäsion und Kohäsion, wodurch eine hohe Klebrigkeit (Adhäsionsarbeit 0,48-0,65 mJ) ermöglichte wurde, was sich auch im viskoelastischen Verhalten (G &#8776; G) widergespiegelte. Bei mittleren Konzentrationen waren die Mischungen bei pH 6 klebriger, was auf eine verstärkte Quellung der Erbsenproteine zurückzuführen war. Die Bedeutung der Viskoelastizität für die Klebrigkeit von Biopolymermischungen wurde in Kapitel V bestätigt, indem Erbsenproteinisolat und Apfelpektin (25% w/w, pH 6) in verschiedenen Mischverhältnissen r gemischt wurden. Mischungen aus Erbsenprotein und Apfelpektin und insbesondere die Probe mit r = 2:1 besaßen eine hohe Klebrigkeit aufgrund der Entwicklung eines Mehrphasensystems, das ein gutes Gleichgewicht von Adhäsion und Kohäsion mit deutlicher Frequenzabhängigkeit ermöglichte. Erbsenprotein allein (r = 1:0, c = 25% w/w) hatte eine elastische, aber weiche Textur mit geringer Klebrigkeit aufgrund begrenzter viskoser Eigenschaften, während eine Probe, die nur aus Apfelpektin bestand (r = 0:1, c = 25% w/w), aufgrund ihrer hohen Kohäsion und Steifigkeit ebenfalls nicht klebrig war. Die Ergebnisse von Kapitel VI zeigten, dass die Homogenisierung von Erbsenprotein vor dem Mischen mit Apfelpektin zu kleineren Proteinpartikeln in der Mischung führte, die zu einer höheren Kohäsion beitrugen. Interessanterweise führten vakuumgetrocknete Erbsenproteine zu einer höheren Netzwerkfestigkeit, da diese Trocknungsmethode im Vergleich zur Gefriertrocknung die Reaggregation kleiner Proteinpartikel eher verhinderte. Insgesamt war die Mischung mit homogenisierten und vakuumgetrockneten Erbsenproteinen fast doppelt so klebrig wie die Mischung mit unbehandelten Erbsenproteinen. In Kapitel VII wurden klebrige Mischungen aus verschiedenen Erbsenproteinpräparaten (lösliche, homogenisierte und nicht homogenisierte Erbsenproteine) und Pektin (25% w/w, pH 6, r = 2:1) auf ihre Verfestigungsfähigkeit durch verschiedenen Behandlungen, nämlich Erhitzen sowie Zugabe von Transglutaminase, Laccase, Calcium und Kombinationen daraus, geprüft. Es wurde festgestellt, dass Calcium die Vernetzung der Pektinketten fördert und so die Verfestigung der Mischungen bewirkt. So stieg beispielsweise der Konsistenzkoeffizient K bei Mischungen aus Erbsenproteinisolat und Apfelpektin von 2800 ± 1000 Pasn auf etwa 19000 Pasn, wenn Calcium zugesetzt wurde. Wärmebehandlung und Transglutaminase führten nicht zu einer Verfestigung, was darauf hindeutet, dass das Pektin die kontinuierliche Phase bildet. Darüber hinaus führte Laccase zum höchsten Verfestigungsgrad, wenn Zuckerrübenpektin verwendet wurde (K > 30000 Pasn), was auf die Vernetzung von Ferulasäure und Erbsenprotein-Tyrosin zurückzuführen ist. Folglich wurde die klebrige Mischung aus Erbsenprotein und Zuckerrübenpektin (25% w/w, pH 6, r = 2:1) mit dem Zusatz von Laccase zur Verfestigung als das am besten geeignete Bindemittel für ein bacon-ähnliches Fleischersatzprodukt ermittelt und in Kapitel VIII untersucht. Dieses Bindemittel wies bei 25 °C die höchste Bindungsstärke (Arbeit 2,0-4,3 mJ) zwischen texturierten Protein- und Fettimitatschichten sowie Schichten des gleichen Materials auf, was auf die Bildung kovalenter Bindungen durch Laccase innerhalb des Bindemittels und zwischen dem Bindemittel und den Adhärenten zurückzuführen ist. Eine Kontrollprobe ohne Laccase-Zusatz hatte geringere Bindungseigenschaften (Arbeit 0,7-1,0 mJ), und die Bindungsstärke eines Methylcellulose-Hydrogels (6% w/w), das als Referenz diente, war nur zwischen zwei Fettimitatschichten bei 70 °C höher (Arbeit 1,8 ± 1,1 mJ), was auf erhöhte hydrophobe Kräfte zurückzuführen ist. Schließlich wurde das Bindemittel aus Erbsenprotein und Zuckerrübenpektin (22,5% w/w, pH 6, r = 2:1) in Fleischersatzprodukten vom Typ Burger-Patty getestet, um texturiertes pflanzliches Protein und Fettpartikel zusammenzukleben (Kapitel IX). Das Bindemittelsystem hatte keinen Einfluss auf die Härte der Burger-Patties, was darauf hindeutet, dass diese Eigenschaft von den Strukturelementen und nicht vom Bindemittel bestimmt wird. Die sensorische Analyse ergab jedoch, dass die Kohäsion bei Verwendung des Bindemittels aus Erbsenprotein und Zuckerrübenpektin besser war (-0,7 ± 0,2) als bei Verwendung von Methylcellulose (-2,9 ± 0,3). Dies wurde auf den klebrigen Charakter der Biopolymermischung zurückgeführt, der eine bessere Bindung der verschiedenen Strukturelemente ermöglichte. Insgesamt konnte gezeigt werden, dass dieses neuartige Bindemittel auf Basis pflanzlicher Inhaltsstoffe in verschiedenen Fleischalternativen eingesetzt werden kann. Schließlich wurde in Kapitel X die Funktionalität und der Bindungsmechanismus von derzeit in Lebensmitteln verwendeten Bindemittel aufgezeigt und resümiert, dass Klebrigkeit, Aushärtung/Verfestigung und Wasserhaltevermögen von großer Bedeutung sind. In vielen Lebensmitteln geht das Bindemittel von einem klebrigen Lebensmittelkleber zu einer festen Matrix über, was durch verschiedene Prozessschritte ausgelöst wird, die von den Eigenschaften des verwendeten Bindemittels abhängen. Aus den vorgestellten Ergebnissen lässt sich schließen, dass Erbsenproteine nützliche funktionelle Inhaltsstoffe in verschiedenen Anwendungsszenarien sind. Die gewünschte Technofunktionalität kann durch verschiedene Prozessschritte wie Fraktionierung, Homogenisierung oder durch Mischen mit anderen pflanzlichen Inhaltsstoffen verbessert werden. Hierfür sind Kenntnisse über die Struktur-Funktions-Beziehung und andere Einflussfaktoren erforderlich. In einigen Fällen - wie z. B. bei Bindemitteln - müssen die Prozessabläufe gu

The effect of electrical processing on mass transfer and mechanical properties of food materials

In this research work, the effect caused by electrical processing on mass transfer in food materials was studied by designing and performing experiments that allowed the visualisation of: the effect of moderate electrical fields (MEF $\leq$1000V cm$^{-1}$) on mass transfer in cellular materials; the effect of MEF on mass transfer of solutes to polymer networks; and the effect of MEF and pulsed electrical fields (PEF) on mechanical properties of polymer networks. MEF treatment was performed with continuous alternating current (50Hz frequency) at electrical fields up to 1400V m$^{-1}$ using a jacket system processing cell to maintain constant temperatures. PEF treatment was performed with a pulse generator at Lund University, Sweden. Extraction of betanin from beetroot was monitored online and measured by spectrophotometry. Mass transfer of rhodamine6G into gel networks (alginate, albumin and gelatine) was measured by image analysis. Effective diffusion coefficients (D$_{eff}$) for mass transfer of betanin and rhodamine6G were estimated, assuming Fickian diffusion was valid. Mechanical properties of alginate and gellan gum treated with MEF and PEF were studied. Compression force of gel samples was measured with texture analysis. Results showed that the application of MEF and thermal treatment had an enhancing effect on the extraction of betanin from beetroot. The orientation of the beetroot slab also appeared to have an enhancing effect on extraction when the slab was placed perpendicular to the electrical field. The application of MEF had a decreasing effect on mass transfer of rhodamine6G to gel networks set with ions. Mass transfer decreased as electrical field increased. This effect was influenced by electrical conductivities of the gel and rhodamine6G solution. No significant effect of MEF was observed on gelatin or albumin. MEF and PEF had an increasing effect on compression force of polymer networks

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids