Butter keeping quality and pallet physical stability during transport and storage are dependent on the temperature distribution through the product. Understanding these temperature changes are of vital importance for the dairy industry with regard to butter manufacture, storage and shipping. Three dimensional mathematical models of heat transfer were developed to predict thawing and freezing in butter products. These models require accurate thermophysical data as an input. Specific heat capacity and enthalpy of butter with different composition was measured using Differential Scanning Calorimetry. The specific heat capacity of butter differs for cooling and heating operations due to significant supercooling and delayed crystallization of the fat fraction of butter at temperatures well below the equilibrium phase change temperature during cooling. This reduces the heat capacity for cooling relative to that for heating. Thawing of individual blocks of butter was accurately predicted by the conduction only model (no mass transfer limitations) with equilibrium thermal properties giving accurate predictions when the butter was completely frozen before thawing. For partially frozen butter the conduction model with the measured temperature dependent specific heat capacity data for unfrozen butter including melting of some of the fat fraction gave accurate predictions. For freezing it was observed that water in the butter supercools many degrees below its initial freezing point before freezing due to its water in oil structure. Experiments suggested that during freezing release of latent heat observed as a temperature rebound is controlled as much by the rate of crystallisation of water in each of the water droplets as by the rate of heat transfer. A conduction only model including water crystallization kinetics based on the Avrami Model predicted freezing in butter successfully. Simple models with equilibrium thermal properties and nucleation only kinetics (based on homogenous nucleation theory) or the sensible heat only model (no release of latent heat) gave poor predictions. The models for individual blocks were extended to predict heat transfer in butter pallets. A butter pallet contains product, packaging material and the air entrapped between the packaging and butter cartons. Measurements were made for freezing and thawing of full and half pallets at a commercial storage facility and in the University laboratory. Thawing and freezing in wrapped tightly stacked pallets was predicted accurately by the conduction only model with effective thermal properties (incorporating butter, packaging and air) estimated by the parallel model. For unwrapped tightly stacked or loosely stacked pallets there is potential for air flow between the adjacent cartons of butter. An alternative approach was developed which consisted of modeling the pallet on block by block basis using effective heat transfer coefficients for each surface. Different heat transfer coefficients were used on different faces of the blocks depending on the location of the block in the pallet. This approach gave good predictions for both unwrapped tightly stacked and loosely stacked pallets using the estimated effective heat transfer coefficients from the measured data. Further experimental and/or modelling work is required in order to develop guidelines for estimating effective heat transfer coefficient values for internal block face for industrial scenarios.

Call number: LD2668 .T4 1985 B55 / Master of Science

Call number: LD2668 .T4 1985 Y37 / Master of Science

Background: In Sweden and Europe adults fail to reach the recommendations for fruit and vegetable intake. Additionally in Sweden, young adults have the worst overall diets. Frozen vegetables have shown to take less time to cook, are less expensive and might be healthier than fresh vegetables.  Aim: The aim of this study was to explore by interviews how 18-30-year-old individuals experience eating microwaved frozen vegetables. Method: This study was a focus group interview with an intervention. The study recruited 13 individuals who microwaved frozen vegetables for a week. Three virtual focus group interviews were conducted.  Results: Five categories were found which described how the participants perceived eating frozen vegetables. 1) The idea of eating frozen vegetables, 2) The attributes of frozen vegetables, 3) Prefer other/different, 4) The microwave oven routine as a whole, and 5) Vegetables in relation to meals. Many enjoyed eating microwaved frozen vegetables although other vegetables and cooking methods were preferred. The advantages and disadvantages discussed by the participants resulted in four categories. 1) The cooking, 2) At the dinner table, 3) Experiences of frozen vegetables as a product, and 4) The importance of cost.  Many advantages were found in category one and three, but an overall downside was the lack of variation. Conclusion: It is important when designing methods to increase individuals vegetable intake that the method is simple, not time-consuming, flexible and have variation. The microwave oven fulfils most of these criteria, however it might not be for everyday use and individuals who enjoy cooking. / Bakgrund: Vuxna i Sverige och Europa når inte upp till rekommendationerna för frukt och grönsaksintag. Dessutom har unga vuxna den sämsta övergripande kosten i Sverige. Frysta grönsaker har visat sig ta mindre tid att tillaga, är inte lika dyra och kan vara hälsosammare än färska grönsaker.  Syfte: Syftet med denna studie är att undersöka via intervjuer hur 18-30 åriga individer upplever att äta mikrovågsuppvärmda frysta grönsaker.  Metod: Den här studien är fokusgruppstudie med en intervention. Studien rekryterade 13 individer som mikrovågsugns värmde frysta grönsaker i en vecka. Sedan utfördes tre virtuella fokusgrupper.  Resultat: Fem kategorier hittades som beskriver hur deltagarna upplevde att äta frysta grönsaker. 1) Föreställningen av att äta frysta grönsaker, 2) Frysta grönsakers egenskaper, 3) Föredrar annat, 4) Mikrovågsugnrutinen som helhet, och 5) Grönsaker i relation till måltider. Många av deltagarna tyckte det var trevligt att äta mikrovågsugnsuppvärmda frysta grönsaker även om dem föredrog andra grönsaker och tillagningsmetoder. Fördelarna och nackdelarna deltagarna diskuterade resulterade i fyra kategorier. 1) Matlagningen, 2) Vid matbordet, 3) Erfarenheter av frysta grönsaker som produkt, och 4) Vikten av kostnad. Många fördelar hittades i kategori ett och tre men en gemensam nackdel som deltagarna upplevde var en avsaknad av variation.  Slutsats: Det är viktigt vid design av metoder som ska öka individers grönsaksintag att metoden är lätt, icke tids konsumerade, flexibel och har variation. Mikrovågsugns rutinen uppfyller de flesta av kriterierna, men den kanske inte är till för daglig användning och för individer som gillar att laga mat.

CNPq / Mudanças nos hábitos alimentares, nas políticas de segurança alimentar e nos estilos de vida da população tem modificado os padrões de projeto das embalagens dos alimentos. Estas mudanças são visíveis especialmente nas funções das embalagens que precisam dar conta da diversidade de oferta de alimentos congelados preparados, denominados alimentos preparados. No contexto do desenvolvimento de embalagens, questiona-se a necessidade de aprofundar a pesquisa nas funções das embalagens para essas categorias de produtos, identificando parâmetros que atendam suas especificidades. E ainda, considerando o cenário produtivo, a análise daquelas já disponíveis no mercado. Para mapear o contexto de projeto de produto, esta investigação busca delimitar as principais funções e características exigidas das embalagens de alimentos congelados preparados, bem como os métodos e práticas de projeto e o cenário de regulamentação dos órgãos normatizadores de segurança alimentar dos alimentos embalados. Como resultado dessa investigação foi elaborado um manual de referência para profissionais envolvidos na estratégia e projeto para o segmento - designers industriais e projetistas de embalagens - de modo a integrar ações, normas e métodos de projeto de produto. Uma amostragem desses perfis profissionais esteve envolvida na pesquisa com usuários e avaliação do manual e os resultados apontaram a necessidade de interlocução entre as áreas (de projeto/alimentos), reforçando a carência de materiais de referência que reúnam, de forma objetiva e sistemática, mecanismos de apoio aos responsáveis pelas análises e validações de embalagens para alimentos preparados congelados. / Changes in eating habits, the food security policies and people's lifestyles have modified food packages of design standards. These changes are visible especially in the functions of the packages that need to account for the diversity of supply of prepared frozen foods, prepared foods called. In the development of packaging, we question the need for further research into the functions of packaging for these product categories, identifying parameters that meet their specific requirements. Further, considering the manufacturing scenario, the analysis those already available on the market. To map the product design context, this research seeks to define the main functions and characteristics required of prepared frozen food packaging, as well as the methods and design practices and regulatory setting of the standard-setting bodies for food safety of packaged food. As a result of this investigation has produced a reference manual for professionals involved in strategy and design to the segment - industrial designers and packaging designers - to integrate actions, standards and product design methods. A sampling of these professional profiles has been involved in research with users and manual evaluation and the results showed the need for dialogue between the areas (design / food), reinforcing the lack of reference materials, comprising an objective and systematic way, mechanisms support those responsible for analysis and packaging validations for frozen prepared foods.