Feed intake is a key factor affecting pig performance; thus, the objective of these studies was to assess a variety of factors that could potentially affect intake in pigs in different production stages. Studies were conducted to determine the effects of flavor and diet complexity, Appetein™ (an alternative protein source), and graded levels of salt on swine feed intake and feed preference. Two newly developed flavors were used in nursery pig diets. The use of the two flavors did not increase feed intake (P > 0.05). Nursery pigs actually showed a preference for the control diet. Complex diet formulation does increase feed intake (P < 0.03) in nursery pigs when diets are not over-formulated. When flavor was added to lactation diets sow feed intake did not change compared to the control. The flavor did not affect litter performance (P > 0.05). When Appetein™ was added to lactation diets at 0.5%, pig weight and litter weight were numerically greater for the sows fed Appetein™ but not significantly so. Appetein™ did not affect feed intake. When nursery pigs were fed graded levels of salt (0.1, 0.5, and 0.8%) feed intake increased (P < 0.01) as salt level increased. Nursery pigs also preferred (P < 0.05) 0.8% salt over other levels the first two weeks after weaning when given a choice among diets.

Heat resistant sporeforming psychrotrophic bacteria were isolated from raw milk samples from 59 Grade A farms in Oregon. Forty-nine of the 59 (83%) raw milk samples in this survey contained sporeforming psychrotrophic bacteria; isolates from twenty-four (40%) of the samples exhibited proteolytic properties. Populations of sporeforming psychrotrophic bacteria ranged from <10 to >10,000 CFU/mL for all samples. One hundred-two isolates were identified as Bacillus species. Twelve different Bacillus species were identified with B. licheniformis being the most predominate (18% of the samples) and B. laterosporus the least frequently isolated species, (2%). Fifty-eight percent of the bacilli isolates produced a bitter off-flavor and putrid odor, while 42% produced a fruity and/or rancid off-flavor when inoculated into sterile whole milk. Based on biochemical activity tests, 83% of the thermoduric isolates hydrolysed casein while 56% were proteolytic (in litmus milk), 57% demonstrated lipolytic activity and 31% produced acid in litmus milk. Forty-eight isolates that tested positive for proteolysis were evaluated quantitatively for activity, which ranged from 0.93 to 1.93 units (expressed as mM of alanine). Isolates of Bacillus cereus var. mycoides demonstrated significantly higher (p>0.05) proteolytic activity than other Bacillus species isolated. / Graduation date: 1988

The taste qualities of acidulants have not been studied in detail despite the fact that they are widely used by the food industry. Studies on characterizing the sensory properties of organic and inorganic acids are very limited. Reported studies are commonly on threshold, equi-sour and the time intensity values of sourness. A series of experiments were conducted to determine the sensory properties of selected acidulants by different sensory and multivariate methods. First, the technique of Free-Choice Profiling was applied in order to characterize the sensory profile of some selected acids (adipic, citric, fumaric, glucono-delta-lactone, hydrochloric, lactic, malic, phosphoric, quinic, succinic, tartaric, citric:fumaric, citric:malic and fumaric:malic) on a weight (0.08% w/v or v/v) basis. Results analyzed through Generalized Procrustes Analysis indicate that on a weight basis (w/v or v/v), acids differed in their flavor and taste dynamics. Likewise, acids were described differently by individual panelists. Second, the sourness power functions of the selected acidulants were generated from five molar concentrations by magnitude estimation involving 16 trained panelists. Equi-sour concentrations were determined by regressing the log of the rescaled response (sensory) on the log of the stimuli (physical). The calculated equi-sour levels ranged from 0.48 ml/L for HCl to 2.34 g/L for glucono-delta-lactone when citric add was set at 1.0 g/L. These theoretical equi-sourness were then tested by using an alternative sensory method, the directional difference from control test. Third, the sensory profile of the acidulants at their equi-sour levels was characterized using two sensory methods, free-choice profiling and the conventional descriptive analysis. The former was analyzed by Generalized Procrustes Analysis while the latter was analyzed by Principal Component Analysis. The two sensory methods gave similar patterns of information regarding the add samples. The similarities of several organic acids and their mixtures were very evident. Hydrochloric and phosphoric acids were astringent while succinic add was bitter and had a monosodium glutamate taste. It was concluded that adds had other sensory properties aside from sourness that must be considered in a given food application. / Graduation date: 1993

Hubbard Foods Limited of Auckland makes a variety of oats-based value-added products. In the preparation of a range of products at Hubbard Foods, technical staff has become aware of a bitterness problem that sporadically appears in toasted oats. Toasting involves dry heating to about 150°C resulting in the golden colour and flavour development necessary for range of products. Bitterness development has been described in the literature, but Hubbard staff is necessarily focussed on production issues, rather than on a sporadic problem seemingly outside the scope of production variables. The author of this thesis set out to identify the cause and suggest a remedy. Prior research with oats has shown that bitterness and associated off-flavours are linked to the accumulation of free fatty acids, their volatile oxidation products, and possibly amino acids and certain phenols. Oats are distinguished from related grains by their high relative fat content, about seven percent, and an associated very active lipase. The free fatty acids stem from the lipase activity that should be, but may not be, inactivated at source in Australia. This is achieved in the milling process by physical disruption and moist heating to a temperature at which the enzyme is denatured. However, residual lipase activity may adversely affect oats quality during time in storage and transit. A number of analytical methods for cereals were adapted to match the constraints of time and resources. These methods were for colour, moisture, peroxidase activity, p-anisidine, and fat and free fatty acids content, composition of fatty acids, total phenols, volatiles, and bitterness as perceived by an analytical sensory panel of four people. Determination of lipase activity is very expensive, so peroxidase activity is commercially used as an indicator. If the latter is inactive, the former will necessarily be also inactive. The designed methods were first applied to 17 oats lots passing through the Hubbard environment, where 14 were paired raw and toasted. The values of moisture, fat content, free fatty acids content and total phenols were within the normal limits expected for commercial lots of oats compared with the previous studies. Not much variation was observed among the 17 oats lots, with the exception of lot DWHE25. Lot DWHE25 was a faulty product, which had high moisture content, high free fatty acids content, and tasted very bitter. The results suggested that moisture content, free fatty acids and bitterness were usually correlated. In spite of the differences encountered and the clues provided by extremes, the data generated from Hubbard oats lots did not provide enough variation in quality to lead to a definitive chemical model of bitter flavour development. But perhaps crucially, it was found that most samples as received from Hubbard Foods were peroxidase-active which conflicted with the results reported on specification sheets prepared by the oats supplier. These specifications accompanied each lot delivered to Hubbard Foods. Therefore, the supplier’s method was examined and was found to be deficient in one critically important respect. Their method omitted the key reactant hydrogen peroxide. Therefore, it is possible that the lipase was active in many of the samples. Therefore, some experiments were conducted where raw oats, from Hubbard Foods and a supermarket, were treated with water additions and stored for a period to examine the effect of moisture content on the quality and flavour deterioration on subsequent storage. Water-treated oats were toasted to simulate a typical Hubbard process, yielding a total of 58 samples with carrying moisture contents. The data set was statistically analysed to identify the cause of bitterness and the means of its control. The free fatty acids content, volatile compounds particularly hexanal, and total phenols increased with moisture content and storage time. The correlations between chemical analysis and sensory test indicated that free fatty acids positively correlated with bitterness (r = 0.71), and hexanal was also positively correlated. Total phenols did not appear to correlate with bitterness. Oats lots with high peroxidase activity tended to have the poorest quality, strongly implicating residual lipase activity as the critical factor. There were no important interactions between water addition and toasting for most of the experiments. Therefore, it seems likely that the toasting procedures at Hubbard Foods are not responsible for bitterness formation. The cause(s) of bitterness is certainly at source, with a faulty peroxidase test strongly implicated.

Hubbard Foods Limited of Auckland makes a variety of oats-based value-added products. In the preparation of a range of products at Hubbard Foods, technical staff has become aware of a bitterness problem that sporadically appears in toasted oats. Toasting involves dry heating to about 150°C resulting in the golden colour and flavour development necessary for range of products. Bitterness development has been described in the literature, but Hubbard staff is necessarily focussed on production issues, rather than on a sporadic problem seemingly outside the scope of production variables. The author of this thesis set out to identify the cause and suggest a remedy. Prior research with oats has shown that bitterness and associated off-flavours are linked to the accumulation of free fatty acids, their volatile oxidation products, and possibly amino acids and certain phenols. Oats are distinguished from related grains by their high relative fat content, about seven percent, and an associated very active lipase. The free fatty acids stem from the lipase activity that should be, but may not be, inactivated at source in Australia. This is achieved in the milling process by physical disruption and moist heating to a temperature at which the enzyme is denatured. However, residual lipase activity may adversely affect oats quality during time in storage and transit. A number of analytical methods for cereals were adapted to match the constraints of time and resources. These methods were for colour, moisture, peroxidase activity, p-anisidine, and fat and free fatty acids content, composition of fatty acids, total phenols, volatiles, and bitterness as perceived by an analytical sensory panel of four people. Determination of lipase activity is very expensive, so peroxidase activity is commercially used as an indicator. If the latter is inactive, the former will necessarily be also inactive. The designed methods were first applied to 17 oats lots passing through the Hubbard environment, where 14 were paired raw and toasted. The values of moisture, fat content, free fatty acids content and total phenols were within the normal limits expected for commercial lots of oats compared with the previous studies. Not much variation was observed among the 17 oats lots, with the exception of lot DWHE25. Lot DWHE25 was a faulty product, which had high moisture content, high free fatty acids content, and tasted very bitter. The results suggested that moisture content, free fatty acids and bitterness were usually correlated. In spite of the differences encountered and the clues provided by extremes, the data generated from Hubbard oats lots did not provide enough variation in quality to lead to a definitive chemical model of bitter flavour development. But perhaps crucially, it was found that most samples as received from Hubbard Foods were peroxidase-active which conflicted with the results reported on specification sheets prepared by the oats supplier. These specifications accompanied each lot delivered to Hubbard Foods. Therefore, the supplier’s method was examined and was found to be deficient in one critically important respect. Their method omitted the key reactant hydrogen peroxide. Therefore, it is possible that the lipase was active in many of the samples. Therefore, some experiments were conducted where raw oats, from Hubbard Foods and a supermarket, were treated with water additions and stored for a period to examine the effect of moisture content on the quality and flavour deterioration on subsequent storage. Water-treated oats were toasted to simulate a typical Hubbard process, yielding a total of 58 samples with carrying moisture contents. The data set was statistically analysed to identify the cause of bitterness and the means of its control. The free fatty acids content, volatile compounds particularly hexanal, and total phenols increased with moisture content and storage time. The correlations between chemical analysis and sensory test indicated that free fatty acids positively correlated with bitterness (r = 0.71), and hexanal was also positively correlated. Total phenols did not appear to correlate with bitterness. Oats lots with high peroxidase activity tended to have the poorest quality, strongly implicating residual lipase activity as the critical factor. There were no important interactions between water addition and toasting for most of the experiments. Therefore, it seems likely that the toasting procedures at Hubbard Foods are not responsible for bitterness formation. The cause(s) of bitterness is certainly at source, with a faulty peroxidase test strongly implicated.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 123-137). Also available via the Internet.

Thesis (B.S.)--Butler University, 2009. / Includes bibliographical references.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: ~-Glucosidases constitute a major group of biologically important enzymes that catalyze the hydrolysis of glycosidic linkages in ~-glucosides, as well as in glycosides that contain only carbohydrate residues, e.g. cellobiose. These enzymes occur in all living kingdoms and perform a variety of functions in organisms ranging from bacteria to highly evolved mammals. Three different types of ~-glucosidases are found in humans, each with its own function: glucocerebrosidase (a deficiency causes Gaucher disease), lactase-phlorizin hydrolase (a deficiency results in lactose intolerance) and cytosolic ~-glucosidase (responsible for the hydrolysis of ~- glucosides ingested with foods of plant and animal origin). In plants, the functions of ~-glucosidases include pigment metabolism, biomass conversion and cyanogenesis, a function it shares with insect ~-glucosidases. Microbial ~-glucosidases, as part of the cellulase enzyme system that is responsible for the hydrolysis of cellobiose and short-chain oligosaccharides into glucose, playa role in the conversion of cellulosic biomass to liquid fuel. These microbial ~-glucosidases also playa very important role in the enhancement of fruit and wine aromas through the liberation of monoterpenols. Monoterpenols play an invaluable role in the flavor and aroma of grapes and wine, and are present as free, volatile and odorous molecules, as well as flavorless, non-volatile glycosidic complexes. These complexes most often occur as 6-0-~-Dxvlopyranosyl- B-Dcqlucopyranosides, 6-0-~-D-glucopyranosyl-~-D-glucopyranosides, 6-0-a-L-arabinofuranosyl-~-D-glucopyranosides, 6-0-a-L-rhamnopyranosyl-~-Dglucopyranosides, or 6-0-~-D-apiofuranosyl-~-D-glucopyranosides of mainly linalool, geraniol, nerol, a-terpineol and hotrienol. Two mechanisms exist for the release of monoterpenes from glycosidically bound non-volatile precursors: acid hydrolysis and enzymatic hydrolysis. As high temperature acid hydrolysis causes a rearrangement of the monoterpene aglycones, the focus has shifted towards the more efficient enzymatic hydrolysis that does not result in modifications of the intrinsic aromatic character of the wine. The endogenous ~-glucosidases of grapes (Vitis vinifera), as well as of the wine yeast Saccharomyces cerevisiae, exhibit very low activity towards the glycoside precursors, and thus the focus has increasingly fallen on the addition of exogenous ~-glucosidases to enhance wine flavor. Fungal, bacterial and some yeast ~- glucosidases have been indicated as effective aroma liberators, but these enzymes are not always suitable for use under the harsh conditions that prevail during winemaking (i.e. low pH, low temperatures, and high ethanol and glucose concentrations). The limited enzyme activities of the abovementioned microorganisms have resulted in a search among non-Saccharomyces yeasts for ~- glucosidases that can withstand these conditions. The ~-glucosidase activities of 20 wine-associated non-Saccharomyces yeasts were quantified, characterized and assessed to determine the efficiency with which they could liberate monoterpenols from their terpenyl-glycosides. The Debaryomyces pseudopolymorphus l3-glucosidase from intracellular crude cell extracts exhibited the most suitable combination of properties in terms of functionality at wine pH, resistance to wine-associated inhibitory compounds (glucose, ethanol and sulfur dioxide), high substrate affinity and large aglycone-substrate recognition. This yeast strain was also used, in conjunction with S. cerevisiae VIN13, for the small-scale fermentation of Chardonnay juice. The results indicated that the l3-glucosidase of D. pseudopolymorphus had definite potential as a wine aroma-enhancing enzyme, as the concentrations of free terpenols (nerol, geraniol and citronellol) were significantly increased during fermentation. Future experimental work would include an in-depth study of the kinetic characteristics of the l3-glucosidases (both cytosolic and cell-associated) exhibiting the highest terpenol-liberating activity under winemaking conditions. The next step would then be the cloning and expression of the most efficient l3-glucosidase gene in a commercial wine yeast. Such a recombinant wine yeast would release grapederived aroma compounds from their non-volatile precursors during single culture fermentations, thereby increasing the sensorial quality of wine. / AFRIKAANSE OPSOMMING: I3-Glukosidases vorm deel van 'n groot groep biologies belangrike ensieme wat die hidrolise van glikosidiese bindings binne l3-glukosiede,sowel as binne glikosiede wat slegs uit koolhidraatresidue bestaan, soos bv. sellobiose, kataliseer. Hierdie ensieme kom in alle koningkryke van lewende organismes voor en verrig 'n wye verskeidenheid funksies binne organismes wat wissel van bakterieë tot hoogs ontwikkelde soogdiere. Drie verskillende tipes l3-glukosidases,elk met sy eie funksie, kom in mense voor: glukoserebrosidase ('n gebrek hieraan lei tot Gaucher-siekte), laktaseflorizinhidrolase ('n gebrek hieraan gee aanleiding tot laktose-intoleransie) en sitosol l3-glukosidase (verantwoordelik vir die hidrolise van l3-glukosiede wat saam met voedsel van plant en dier oorsprong ingeneem word). Die funksies van 13- glukosidase binne plante sluit in pigmentmetabolisme, biomassa-omsetting en sianogenese, wat ook 'n funksie van insek l3-glukosidases is. Mikrobiese 13- glukosidases, as deel van die sellulase-ensiemsisteem wat verantwoordelik vir die hidrolise van sellobiose en kortketting-oligosakkariede na glukose is, speel 'n rol in die omsetting van sellulosebiomassa na brandstof. Hierdie mikrobiese 13- glukosidases speelook 'n baie belangrike rol in die verbetering van vrugte- en wynaroma deur die vrystelling van monoterpenole. Monoterpenole speel 'n belangrike rol in die geur en aroma van druiwe en wyn, en kom voor as vry, vlugtige en aromatiese molekules, asook geurlose, nie-vlugtige glikosidies-gebonde komplekse. Hierdie komplekse is meestal in die vorm van 6-0- I3-D-xilopiranosiel-I3-D-glukopiranosiede, 6-0-a-L-arabinofuranosiel-I3-D-glukopiranosiede, 6-0-I3-D-glukopiranosiel-I3-D-glukopiranosiede, 6-0-a-L-ramnopiranosiel- I3-D-glukopiranosiede,of 6-0-I3-D-apiofuranosiel-I3-D-glukopiranosiedevan hoofsaaklik linalool, geraniol, nerol, a-terpineol en hotrienol. Monoterpenole kan op een van twee maniere van hul suikermolekules vrygestel word: suurhidrolise of ensimatiese hidrolise. Die hoë temperature waarby suurhidrolise plaasvind veroorsaak 'n herrangskikking van die monoterpeen aglikone, en die fokus het gevolglik verskuif na die meer effektiewe ensimatiese hidrolise wat nie verandering van die intrinsieke aromatiese karakter van die wyn tot gevolg het nie. Die endogene l3-glukosidases van druiwe (Vitis vinifera) en die wyngis Saccharomyces cere visiae , toon baie lae aktiwiteit ten opsigte van die aromatiese voorlopers, en dus word daar toenemend op die toevoeging van eksogene 13- glukosidases tot die wyn gefokus om meer geur vry te stel. Daar is bevind dat 13- glukosidases van fungiese, bakteriële en gis oorsprong effektiewe aromavrystelIers is, maar hierdie ensieme is nie altyd gepas vir gebruik in wyn nie, aangesien dit 'n omgewing is met 'n lae pH, lae temperatuur, en hoë etanol- en glukosekonsentrasies. Die beperkte ensiemaktiwitiet van bogenoemde mikroorganismes het gelei tot 'n soeke onder nie-Saccharomyces giste na l3-glukosidases wat in die wynomgewing kan funksioneer. Die ~-glukosidase-aktiwiteit van twintig wyn geassosieerde nie-Saccharomyces giste is gekwantifiseer en gekarakteriseer om te bepaal tot watter mate dit monoterpenole van hul terpeniel glikosiede kan vrystel. Die intrasellulêre ~- glukosidase teenwoordig in the selekstrak van Debaryomyces pseudopolymorphus, het die belowendste resultate getoon ten opsigte van funksionaliteit by wyn se pH, weerstand teen wyn geassosieerde inhibeerders (glukose, etanol en swaweidioksied), hoë substraataffiniteit en breë aglikoon-substraat herkenning. Hierdie gisras is ook in kombinasie met S. cerevisiae VIN13 gebruik vir die kleinskaalse fermentasie van Chardonnay sap. Die resultate het getoon dat die ~- glukosidase van D. pseudopolymorphus wel potensiaal het om wynaroma te verhoog, aangesien die konsentrasie van ongebonde terpenole (nerol, geraniol en citronellol) aansienlik tydens fermentasie toegeneem het. Toekomstige eksperimentele werk sluit in, onder meer, In in-diepte studie van die kinetiese eienskappe van die ~-glukosidases (beide sitesolies en sel-geassosieerd) wat die meeste terpenole onder wynrnaakkondisies vry stel, asook die klonering en uitdrukking van die enkele ~-glukosidasegeen met die hoogste aktiwiteit, in In kommersiële wyngis. Só In rekombinante wyngis sal die vrystelling van druifgebaseerde aromakomponente van hul nie-vlugtige, geurlose voorlopers tydens enkel-kultuur fermentasies teweeg bring.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21564号 / 理博第4471号 / 新制||理||1642(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 市川 温子, 教授 鶴 剛, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Flavonoid and limonoid glycosides influence taste properties as well as marketability of Citrus fruit and products, particularly grapefruit. In this work, nine grapefruit putative natural product glucosyltransferases (PGTs) were resolved by either using degenerate primers against the semiconserved PSPG box motif, SMART-RACE RT-PCR, and primer walking to full-length coding regions; screening a directionally cloned young grapefruit leaf EST library; designing primers against sequences from other Citrus species; or identifying PGTs from Citrus contigs in the harvEST database. The PGT proteins associated with the identified full-length coding regions were recombinantly expressed in Escherichia coli and/or Pichia pastoris and then tested for activity with a suite of substrates including flavonoid, simple phenolic, coumarin, and/or limonoid compounds. A number of these compounds were eliminated from the predicted and/or potential substrate pool for the identified PGTs. Enzyme activity was detected in some instances with quercetin and catechol glucosyltransferase activities having been identified.