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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Desenvolvimento de um produto dietetico funcional para idosos / Development of a functional dietetic product for the elderly

Ziegler, Fabiane La Flor 24 March 2006 (has links)
Orientador: Valdemiro Carlos Sgarbieri / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-05T21:56:49Z (GMT). No. of bitstreams: 1 Ziegler_FabianeLaFlor_M.pdf: 1806557 bytes, checksum: c7746abef0196b047e712da90766b294 (MD5) Previous issue date: 2006 / Resumo: O principal objetivo da presente pesquisa foi desenvolver um produto dietético funcional para idosos desnutridos. Para tal, realizou-se inicialmente a caracterização físico-química e nutricional das fontes protéicas: isolado protéico do soro de leite bovino (WPI) e hidrolisado de colágeno bovino (HCB), buscando-se adequar a proporção entre elas, bem como, avaliar algumas de suas propriedades físicas, composição, perfil de aminoácidos e propriedade nutricional. Posteriormente foi realizado o desenvolvimento do produto através de testes preliminares, caracterização físico-química, testes sensoriais e de vida de prateleira. Na 1ª etapa do trabalho observou-se que o componente de maior concentração foi a proteína para as duas amostras (~ 92%). A solubilidade foi elevada tanto do WPI como do HCB o que refletiu, conseqüentemente, na solubilidade da mistura dessas proteínas. O perfil de aminoácidos essenciais (EAE) do WPI atende às recomendações da Food and Agriculture Organization (FAO)/World Health Organization (WHO), no entanto o HCB apresenta deficiência em vários aminoácidos essenciais, particularmente em triptofano e aminoácidos sulfurados. Do ponto de vista nutritivo, os índices quociente de eficiência protéica (PER), utilização líquida da proteína (NPU), valor biológico aparente (VBa) e balanço de nitrogênio (BN), as misturas WPI:HCB (60:40 e 80:20) não diferiram estatisticamente entre si e do WPI (p > 0,05), sendo inferior (p < 0,05) à caseína comercial (CC) usada como referência. Em função dos resultados obtidos, optouse pela mistura 60% WPI: 40% HCB como componente protéico na formulação do produto dietético funcional, por razões econômicas. Nos testes preliminares avaliaram-se diferentes combinações e proporções entre os ingredientes para a obtenção da melhor formulação, principalmente em relação à solubilidade e ao aspecto sensorial. A escolha destes ingredientes, bem como a quantidade usada foi baseada em pesquisas na literatura a respeito do perfil nutricional de idosos e suas principais deficiências. Através da análise sensorial (testes de aceitação, ideal de doçura e intenção de compra) com idosos foram escolhidas as formulações sabor chocolate e sem adição de sabor dentre seis opções, as quais receberam médias de aceitação de 6,87 e 6,60, respectivamente, numa escala de nove pontos. Essas formulações apresentaram em torno de 12% de proteína e 80% de carboidratos com adição de inulina, frutooligossacarídeos (FOS), cálcio, zinco, magnésio, selênio e as vitaminas B1, B6, ácido fólico, B12, A, C e E. Com as formulações foi realizado estudo da vida útil do produto durante 30 dias de estocagem em temperatura ambiente e a 35 °C usando-se filme de polipropileno como material de embalagem. Realizaram-se análises de umidade, atividade de água (aw), isoterma de adsorção, taxa de permeabilidade ao vapor de água (TPVA), cor, avaliação sensorial e perda de vitaminas. O produto apresentou aw inicial abaixo de 0,3, valor característico de alimentos desidratados. As isotermas de adsorção foram utilizadas para determinação dos valores de aw crítica (0,5), umidade crítica (5,1%) e umidade inicial (~2,0%), os quais foram usados nos cálculos da estimativa da vida útil do produto. Observou-se pequena variação na cor (_E* = 0,4 para formulação sem saborizante e 0,6 para a formulação chocolate) durante os 30 dias de estocagem. A qualidade sensorial manteve-se satisfatória nas três avaliações (tempo zero, 15 e 30 dias), obtendo-se médias de aceitação acima de 5 para os todos atributos. Mais de 65% dos provadores tiveram intenção de compra entre ¿certamente compraria¿ e ¿tenho dúvidas se compraria¿. Através desses resultados, constatouse uma maior preferência pela formulação chocolate. Verificou-se uma diminuição apreciável no teor das vitaminas B1, C, A e E ao final da estocagem. Através do ganho de peso das formulações estimou-se a vida de prateleira do produto, a qual foi de aproximadamente 4 meses. Dessa forma, recomenda-se o uso de embalagens com maior proteção, no caso de uma possível comercialização ou administração a idosos, evitando-se a degradação dos nutrientes mais sensíveis e conseqüente diminuição do valor nutricional do produto / Abstract: The main objective of the present investigation was the development of a functional dietetic product for undernourished elderly. First step was the chemical, physical and nutritional characterization of protein component, a mixture of whey protein isolate (WPI) and a bovine collagen hydrolysate (HCB) both materials containing around 92% protein and showing high solubility in water. The essential amino acid profile (EAE) of the WPI reaches all the requirements of the FAO/WHO reference standard, however the HCB is deficient in all essential amino acids, particularly in cysteine and tryptophan which is totally absent in collagen. The nutritional indices PER, NPU, VBa and nitrogen balance (NB) of the two mixtures WPI:HCB (60:40 and 80:20) respectively, did not show statistical difference (p > 0.05) among themselves and with the WPI. Nevertheless they were inferior (p < 0.05) to a commercial casein (CC) used as reference. The choice was for the mixture WPI:HCB (60:40) for economical reasons. The choice of ingredients, composition and concentrations in the formulation was based mainly in three criteria, i.e., solubility, sensorial aspects and nutritional deficiencies of elderly population, based on literature surveys. In sensorial tests (acceptance, ideal sweetness and buying attitude) conducted with an elderly group for six different formulations, the choice was for the formula dissolved in milk with chocolate flavor and the other with no flavouring added. The acceptance scoring was 6.87 and 6.60 respectively, for the two formulations using a 9 ¿ point scale. The two formulations contained around 12% protein and 80% carbohydrate in addition to inuline, frutooligosaccharides (FOS), calcium, zinc, magnesium, selenium and the vitamins B1, B6, folic acid, B12, vitamin A, C and E. A shelf life study was conducted with the two formulations during 30 days under the laboratory environmental conditions and at 35 °C. Humidity, water activity (aw), adsorption isotherm, water vapor permeability rate (WVPR), color, sensorial evaluation, mineral and vitamin analysis were performed. Water activity at time zero (T0) was below 0.3, characteristic of dehydrated powder. The adsorption isotherms were used for determination of the critical aw (0.5), critical moisture content of 5.1% and initial moisture of about 2.0%, which were used for the estimation of the product shelf life. A small color variation was observed (_E* 0.4 for the formulation without flavouring and 0.6 for the chocolate formula), during the 30 days of storage. Sensorial qualities were satisfactory for all three storage time (T0, T15 and T30), with an average acceptance score above 5. More than 65% of the panel demonstrated buying intention between ¿certainty of buying¿ and ¿doubt of buying¿. Higher preference was for the chocolate formula. Appreciable losses of the vitamins B1, C, A and E were detected during storage in both samples, independently of the storage condition. The shelf life estimated was of approximately 4 months for both formulations. It is recommended that a packaging material with more barrier to water vapor, light and oxygen must be used for product to minimize losses of the more unstable vitamins / Mestrado / Nutrição Experimental e Aplicada à Tecnologia de Alimentos / Mestre em Alimentos e Nutrição
32

Efeitos da radiação gama na conservação e características físico-químicas de lichia (Litchi chinensis Sonn.) / Effects of gamma radiation in postharvest conservation and physicochemical characteristics of litchi fruits (Lichi chinensis Sonn.).

Diogo Marques 07 October 2015 (has links)
A lichia é uma fruta exótica de origem chinesa que cada vez mais tem ganhado espaço no mercado interno brasileiro, contudo problemas de pós-colheita existentes prejudicam a comercialização e a exportação de forma significativa. Diversos métodos são utilizados na tentativa de controlar estes problemas, um destes sendo a irradiação ionizante. Desta forma este trabalho tem como objetivo avaliar os efeitos de diferentes doses de radiação e de diferentes temperaturas nas características físico-químicas de frutos de lichia. Os frutos foram obtidos com produtores da região de Piracicaba e irradiados no Centro de Energia Nuclear na Agricultura em uma fonte de 60Co em um irradiador GammaCell 220 nas doses de 0 (testemunha), 0,5kGy, 1,0kGy e 2,0kGy com uma taxa de 0,259 kGy/h. Foram realizadas análises de pH, de cor da casca e da polpa, de teor aparente de sólidos solúveis, de acidez total e de teor de ácido ascórbico. Os resultados obtidos foram submetidos à análise de variância através de teste F a 95% de confiança e posteriormente a teste de Tukey a 5% de significância. As doses de irradiação apresentaram resultados variados dependendo da característica analisada, porém a dose de 1,0kGy apresentou os resultados mais favoráveis no geral. A redução da temperatura causou alterações desejáveis nos parâmetros estudados. Concluiu-se que os frutos de lichia armazenados a 8°C e irradiados a 1,0 kGy apresentaram melhoria significativa. / The lychee is a Chinese exotic fruit that has increasingly gained ground in the Brazilian domestic market, however existing post-harvest problems hinder the marketing and export significantly. Various methods are used in attempts to control these problems, one of these being ionizing irradiation. Thus this work aims to evaluate the effects of different radiation doses and different temperature on the physicochemical characteristics of litchi fruit. The fruits were obtained with producers of Piracicaba region and irradiated in the Center for Nuclear Energy in Agriculture into a source of 60Co in Gammacell 220 radiator at doses of 0 (control), 0.5kGy, 1.0kGy and 2.0kGy at a rate of 0,259kGy / hr. Were performed pH analyzes, color ratings, apparent soluble solids content measurement, total acidity and ascorbic acid content measurement. The obtained results were submitted to variance analysis by F test at 95% confidence and later to Tukey test at 5% significance. The irradiation doses showed varied results depending on the characteristic analyzed, but the dose of 1.0kGy presented the most favorable results in general. The temperature reduction caused desirable changes in the studied parameters. It was concluded that fruits stored at 8°C and irradiated at 1.0 KGy exhibited significant improvement in the physicochemical characteristics of the litchi fruits
33

Novas tecnologias e pre-tratamentos : tomate seco embalado a vacuo / New tecnologies and pre-treatments: vacumm packed dried tomato

Camargo, Gisele Anne 06 January 2005 (has links)
Orientador: Roberto Herminio Moretti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-04T07:20:31Z (GMT). No. of bitstreams: 1 Camargo_GiseleAnne_D.pdf: 2325645 bytes, checksum: fa7c229e01b708eab93a1f58ce091081 (MD5) Previous issue date: 2005 / Resumo: A concentração osmótica e outros pré-tratamentos visam melhorar a qualidade do produto e otimizar o processo de secagem. Dentre estes tratamentos pode-se citar o uso de antioxidantes para evitar o escurecimento excessivo e manter as características nutricionais. A incorporação de concentrado de tomate com 18 a 36 oBrix, não é um método utilizado na fabricação de tomates secos, e foi um procedimento utilizado com o objetivo de melhorar a qualidade e aumentar o rendimento do processo de secagem. E ainda a utilização de ácidos fracos em soluções utilizadas em desidratação ou concentração osmótica representa uma alternativa de processamento brando. Os objetivos gerais desta pesquisa foram: avaliar e selecionar novas tecnologias e pré-tratamentos, visando melhorar a qualidade do produto final e também aumentar o rendimento e eficiência do processo de secagem de tomate para conserva; e definir e caracterizar a vida de prateleira do produto selecionado. Esta pesquisa definiu procedimentos que permitiram aumentar a eficiência e qualidade de um novo produto: tomates secos, embalados a vácuo com umidade intermediária e com segurança ao consumidor. Foi observado que a utilização de açúcares invertidos permitem maior perda de água e entrada de sólidos no tomate. O ácido ascórbico mostrou perda nos primeiros 30 minutos de pré-tratamento osmótico. O conteúdo de licopeno aumentou a disponibilidade nos primeiros 10 minutos com posterior decréscimo gradual. Os consumidores determinaram que o sabor é o fator mais importante na aceitação do produto e desaprovaram a aplicação de concentrado triplo de tomate como pré-tratamento à secagem. A aplicação de antioxidante (metabissulfito de sódio e ácido isoascórbico) anterior à secagem com ar forçado proporcionou maiores teores de ácido ascórbico e licopeno no produto final. A relação ¿Sólidos Solúveis/Acidez Total¿ escolhida pelo paladar dos consumidores foi de 23,8 a 26,65. A melhor eficiência do pré-tratamento osmótico (solução mista de sacarose e açúcares invertidos) foi obtida quando adicionado sal entre os valores de 5,05 a 7,45% e ácido cítrico entre os limites de 6,62 -7,25%. A preferência sensorial do consumidor foi para os produtos obtidos a partir de concentração osmótica em solução com 65º Brix, com a adição de 5,85% de NaCl e 6,00% de ácido cítrico. A qualidade microbiológica do tomate seco embalado a vácuo foi mantida durante o período avaliado de 180 dias para refrigerado e 90 dias em temperatura ambiente. A construção de isotermas permitiu observar que o armazenamento em umidade relativa superior a 50% proporciona a adsorção de água ao produto, alterando as características originais do tomate seco. Os tomates desidratados osmoticamente com açúcares invertidos, sal é ácido cítrico proporcionaram atividades de água entre 0,76 a 0,86. A reconstituição e reutilização do xarope foi um procedimento eficiente no processo produtivo / Abstract: Osmotic concentration and other pre-treatments aim to improve product quality and optimise the drying process. Amongst these treatments one can mention the use of antioxidants to avoid excessive browning and maintain the nutritional characteristics. The incorporation of tomato concentrate at 18 to 36°Brix is not a method currently used in the manufacture of dried tomatoes, but could be a suitable method for quality improvement as well as increasing the yield on drying, considering that it would add up to six times the amount of soluble solids naturally present in the tomato. And the use of weak acids in the solutions used for osmotic drying or concentration represents a mild processing alternative, resulting in a product with appropriate sensory characteristics for immediate consumption. The use of a combination of additives together with various types of sugar (sucrose, fructose and glucose), especially acidifiers, in addition to their antioxidant action, help to increase the rate of osmosis. The general objectives of this research were: to evaluate and select new technology and pre-treatments aiming at improving final product quality and process yield and efficiency in the drying of tomato, and also to define and characterise the shelf life of the selected product. This research defined procedures, which allowed for an increase in efficiency and quality of a new product: vacuum-packed dried tomato with intermediate moisture content, safe for consumption. The use of invert sugar was shown to increase the efficiency of the osmotic dehydration of tomatoes, and temperatures above 45°C failed to provide the desired quality. Ascorbic acid showed losses during the first 30 minutes of pre-treatment, and the lycopene showed an increase in availability during the first 10 minutes, followed by a gradual decrease. The consumers determined that flavour was the most important factor for product approval and disapproved the application of triple concentrated tomato paste. The application of antioxidant (sodium metabisulphite and isoascorbic acid) allowed for greater retention of the lycopene and ascorbic acid. The consumers preferred products with the ¿soluble solids/total acidity ratio¿ between 23.8 and 26.65. The salt concentration in the mixed syrup of sucrose and invert sugar was shown to be more efficient in the osmotic dehydration process between the values of 5.05 and 7.45%, with a citric acid concentration between 6.62 and 7.25%. The consumers chosen (sensory analysis) products obtained from pre-treatment: osmotic dehydration in 65°Brix syrups with the addition of 5.85% NaCl and 6.00% citric acid. The microbiological quality of the product, vacuum-packed dried tomato, was maintained during the periods evaluated of 180 days under refrigeration and 90 days at room temperature. The consumers considered values for the color parameter ¿L¿ above 38.37 as unacceptable, indicating this value as an instrumental colour limit (luminosity). The dried tomato adsorbed water in Relative Humidity to up 50%. The dried tomatoes osmotically dehydrated with invert sugar, salt and citric acid, provided values for water activity the 0.76 to 0.86. The syrup could be reused efficiently / Doutorado / Tecnologia de Alimentos / Doutor em Tecnologia de Alimentos
34

Combined boiling and irradiation treatment on the shelf life and safety of Ready-to-eat bovine tripe

Parry-Hanson, Angela Araba Bondzewaa 04 April 2007 (has links)
Please read the abstract in the 00front part of this document / Dissertation (MSc (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted
35

SENSORY ANALYSIS OF EQUINE FEED PRODUCTS

Francis, Jesse 01 May 2020 (has links)
Three experiments were conducted to investigate factors that may influence horse and consumer preference of equine feed products. The first experiment was a two-phase study designed to investigate the impact of oil-based palatants on horse preference when topically applied to a pelleted diet. In Phase One, treatment diets containing six palatants (banana, anise, apple, peppermint, spearmint, and orange) were compared to a control diet (corn oil) in a paired preference test. Phase Two then compared three palatants (anise, apple, and peppermint) to each other. Preference testing was comprised of a 15 second olfaction period followed by a 3 minute consumption period and first diet sniffed, first diet consumed, first action, aversive behaviors, excessive salivation, amount consumed, and number of chews were recorded. Results from Phase One revealed that orange negatively impacted palatability indicated by less consumption when compared to the control (P = 0.02), though there was no impact on chews per gram. No difference between control and treatment diets for first sniff or first consumed was observed when analyzed individually in either Phase One or Two, though there was a moderate positive correlation (ф = 0.39, P = 0.04) between olfaction and consumption during the peppermint and anise comparison. Consumption as the first action was consistent across all trials (P < 0.05). Anise was preferred over apple and peppermint as indicated by higher total consumption (P < 0.05) in Phase Two. The second experiment was designed to compare horse and consumer preferences of two horse treats products. Horses were presented with two different treat products in a paired preference test comprised of separate olfaction and consumption periods. Additionally, consumers evaluated the two different horse treat products separately for purchase intent as well as consumer preference using a Hedonic ranking scale of the sensory attributes. Consumer data were analyzed by comparing 1) the preferences of horse owning participants to non-horse owning participants, and 2) horse owning participants preference for the two different treat products. No difference was observed for first product sniffed, consumed, or finished during the horse preference test. However, moderate positive correlations were observed between first product sniffed and consumed (P = 0.01, ф = 0.40) as well as first product consumed and finished (P < 0.01, ф = 0.48). Consumer testing revealed lower ratings for Product A in size (P = 0.01), texture (P = 0.02), and purchase intent (P = 0.02) from horses owners when compared to non-horse owners. Horse owners rated Product A lower in appearance (P < 0.01), texture (P < 0.01), size (P < 0.01), and purchase intent (P < 0.01) than Product B.The third project investigated the influence of packaging on shelf life stability and horse preference of treats. Three packaging treatments (control, poly, and paper) were examined at five time points over a 12-month period. Treatments were analyzed for moisture, water activity, mold, yeast, pH, and volatile organic acids. Horse preference testing evaluated first treatment sniffed, consumed, and finished as well as number of treats consumed. Moisture content and water activity increased in all treatments (P < 0.01) from month 0 to month 12, with paper packaging providing a greater fluctuation and containing visible mold at month 12 (P < 0.01). No difference was observed for first treatment sniffed, consumed, or finished during preference testing. However a trend (P = 0.09) for the period*treatment interaction was observed for number of treats consumed, with a poly increasing while paper decreased. These data indicate that 1) palatants and packaging material influence horse preference of feed products, and 2) both horse and consumer testing should be considered during product development to maximize acceptance.
36

Correlation of SPME-GC-MS Volatile Compounds with Descriptive Sensory Odor Analysis of Whole Wheat and Quinoa Flours in Accelerated Storage

Turner, Sarah Snow 01 June 2017 (has links)
The acceptability of whole grain flours during storage varies widely, as does the estimated shelf life of such flours, in part because acceptability is typically determined using subjective human sensory testing. Research is needed to establish more objective measures of acceptability. This study correlated the quantitative results of a descriptive odor sensory panel with volatile compounds determined by solid-phase microextraction-gas chromatograph-mass spectrometry (SPME-GC-MS). Whole wheat flour and quinoa flour were held at 40°C for up to 24 weeks to accelerate changes occurring during storage. Samples were collected every 4 weeks and placed in frozen storage. Thawed samples were then evaluated using SPME-GC-MS and descriptive sensory odor analysis. Significant correlations were found between 1-hexanol, 2-pentylfuran, phenol, hexanoic acid, and hexanal volatiles of whole wheat flour and the odor descriptor cardboard/stale. This indicates that SPME-GC-MS can be used as a less expensive, less time-consuming, more precise method to determine the acceptability of whole wheat flour during storage. Significant correlations were not present in the quinoa flour data, suggesting that SPME-GC-MS may not be preferable to human sensory odor analysis in determining acceptability of stored quinoa flour.
37

Refrigerated and Frozen Shelf-Life of Fresh Pork Sausage after the Addition of Antioxidants

Pham-Mondala, Alessandra Julian 07 May 2016 (has links)
Fresh pork sausages were prepared from prerigor meat with synthetic antioxidants and combinations of Rosemary (R: 1500, 2000, 2500 ppm) and Green tea (G: 100, 200, 300 ppm) extracts. Experimental controls contained synthetic antioxidants only. A randomized complete block design with a factorial arrangement involving ten treatment combinations, three frozen storage periods (0.5, 3, 6 mos) and four retail display times (0, 7, 14, 21 d) was utilized. Secondary lipid oxidation products were reduced (P < 0.05) in treatments with higher amounts of R compared with the control across all frozen storage periods. Higher concentrations of both plant extracts led to increased (P < 0.05)CIE a* (redness) andCIE b* (yellowness) and decreased (P < 0.05) CIE L* (lightness) up to 6 mos of storage. Higher concentrations of R enhanced chroma and delayed discoloration throughout 14 d of retail display after 3 and 6 mos of storage. Combinations of R2500+G100 inhibited (P < 0.05) microbial growth compared with the control throughout retail display. Higher levels of R and G showed higher (P < 0.05) concentrations of spice-derived terpenes alpha-pinene, camphene, and isopulegol up to 3 mos of storage. Incorporation of R resulted in lower (P < 0.05) concentrations of lipid or microbial degradation products 2,4-decadienal, 2-butanone, and methanethiol following 3 mos of storage. Higher levels of G showed lower (P < 0.05) concentrations for 3-methyl-1-butanol and methyl isovalerate after 6 mos of storage. Natural plant extract addition led to higher (P < 0.05) consumer acceptability scores and were liked by >80% of the respondents across all frozen storage periods. The control displayed spoilage and detectable rancidity by day 7 following 6 mos of storage. Pork, nutmeg, ginger, and spice complex aromas were higher (P < 0.05) in sausages with increased concentrations of R following 0.5 and 3 mos of storage. Caramelized aroma followed a similar trend for treatments with a higher G content. Ginger, copper-herbal, rancid, offlavor and off-odor descriptors which were lower (P < 0.05) in sausages containing increased G concentrations. The use of R2500+G300 improved quality over time when the product was stored frozen for 6 mos.
38

Impact of Sodium Lactate and Acetic Acid Derivatives on the Quality of Fresh Italian Pork Sausage Links

Crist, Courtney Alissa 11 August 2012 (has links)
Sodium lactate and acetic acid derivatives were evaluated for their impact on fresh Italian pork sausage links using commercial pork trimmings. Treatments included: 2.5% acetic acid (48.5%) –sodium lactate mixture (51.5%) (V), 2.5% sodium lactate (60% solids) (S), control –0.02% BHA/BHT (B) and negative control –seasoning only (C). Analysis over storage included total plate count (TPC), oxidative rancidity (TBARS), sensory analysis (descriptive and consumer), cooking loss, pH, and color. The S and V treatments had lower TPC (P<0.05) from days 5 through 14 when compared to B and C. TBARS values increased (P<0.05) for treatments C, S, and V while B was did not change (P>0.05) over time. While CIE a* surface values for redness generally decreased over time for all treatments, treatment B maintained more redness over the storage period. Of consumers tested, 85.6% rated all treatments between like slightly and like very much.
39

Food Shelf Life: Estimation and Experimental Design

Larsen, Ross Allen Andrew 15 May 2006 (has links) (PDF)
Shelf life is a parameter of the lifetime distribution of a food product, usually the time until a specified proportion (1-50%) of the product has spoiled according to taste. The data used to estimate shelf life typically come from a planned experiment with sampled food items observed at specified times. The observation times are usually selected adaptively using ‘staggered sampling.’ Ad-hoc methods based on linear regression have been recommended to estimate shelf life. However, other methods based on maximizing a likelihood (MLE) have been proposed, studied, and used. Both methods assume the Weibull distribution. The observed lifetimes in shelf life studies are censored, a fact that the ad-hoc methods largely ignore. One purpose of this project is to compare the statistical properties of the ad-hoc estimators and the maximum likelihood estimator. The simulation study showed that the MLE methods have higher coverage than the regression methods, better asymptotic properties in regards to bias, and have lower median squared errors (mese) values, especially when shelf life is defined by smaller percentiles. Thus, they should be used in practice. A genetic algorithm (Hamada et al. 2001) was used to find near-optimal sampling designs. This was successfully programmed for general shelf life estimation. The genetic algorithm generally produced designs that had much smaller median squared errors than the staggered design that is used commonly in practice. These designs were radically different than the standard designs. Thus, the genetic algorithm may be used to plan studies in the future that have good estimation properties.
40

Acceptability and Shelf-Life of Fresh and Pasteurized Crab Meat Stored Under Different Environmental Conditions

Tyler, Carla Gutierrez 02 April 2009 (has links)
Crab meat is important to the economy of coastal Virginia. The objectives of this study were to complete a shelf-life study on two different packaging styles of fresh crab meat and to test the inhibition capabilities of Carnobacterium piscicola against the pathogen, Listeria monocytogenes. In a shelf-life study, a 12 ounce food grade polyethylene traditional snap-lid container of fresh crab meat was compared to an 8 ounce SimpleStep® trays with Cryovac™ film of equally fresh crab meat sealed with 10,000 cc/m2/24hr oxygen transmission rate (OTR) film. Eleven g samples were used for the microbial shelf-life study conducted at 4°C for 12 days. Aerobic plate counts of crab meat indicated microbial growth from the SimpleStep® trays with Cryovac™ film in 10,000 cc/m2/24hr OTR versus the polyethylene snap-lid was not significant (P>0.05). In objective two, 25 g samples of fresh and pasteurized blue crab (Callinectes sapidus) meat were inoculated with 0.1ml of each, C. piscicola and L. monocytogenes. Three different concentrations of the inoculation levels were studied on select days at both 4°C and 10°C. Microbial spoilage was defined as 107 CFU/g. In fresh crab meat, at both 4°C and 10°C, crab meat spoilage occurred at 7 days or less. In the pasteurized crab meat, at 4°C and 10°C, spoilage did not occur prior to 26 days, and studies were terminated at 28 days of storage. The growth of the two organisms in fresh crab meat was found to be significant for the differing concentration levels and sampling days (P<0.05). The growth of the two organisms in pasteurized crab meat was significant for different concentration levels, sampling days and temperature (P<0.05). In both fresh and pasteurized crab meat, regardless of the inoculation ratios, the L. monocytogenes and C.piscicola followed similar growth trends, but L. monocytogenes was higher in the 2:2 CFU/g concentration and lower at the 6:2 CFU/g concentration level. Although C. piscicola did not completely inhibit L. monocytogenes growth at any concentration ratio, some inhibition was observed. / Master of Science

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