Abstract This study aimed to evaluate the effect of the variability in ambient air conditions (temperature and relative humidity) and periods of exposure on the same batch of table grapes in the first stages of the fruit supply chain (harvesting, processing and storage prior to commercialization), in order to predict their dynamic shelf life. To estimate the shelf life we used a linear prediction model dependent on time and ambient air conditions (temperature and relative humidity). It was noted that during processing, there was considerable variations in ambient air conditions that grapes were exposed to, especially in harvesting stage. The ambient of following stages showed homogeneity in air conditions, but the residence time and the way of palletizing grapes affected their shelf life. We observed heterogeneity in the shelf life among different grape pallets and among boxes on a same pallet, with variations of up to 34 days. Thus, we ascertained a heterogeneity in the quality of table grapes from the same production batch, due to the variability in ambient air conditions and period of exposure, which should be considered in the logistics management of the dynamic shelf life of the product in the cold chain.
Abstract This work aimed to show heterogeneities in shelf life of table grapes from a same batch during road refrigerated transportation. The monitoring of temperature and relative humidity of air was done with a wireless sensor network strategically distributed among grapes boxes and pallets. The ambient conditions and time of exposure were associated with a linear predictive model of water loss in order to estimate fruits shelf life. Results showed that the loss of dynamic life of grapes varied according to the box position on different pallets within the refrigerated transport vehicle, due to differences in the conditions that fruits were exposed to. It was observed high heterogeneity in shelf life of the evaluated batch of grapes during transportation, with differences of 71 days between grape boxes. With that, one can conclude that these differences must be taken into account in the following stages of grapes cold chain.
Abstract Empirical models can be used to represent the recrystallization process in frozen food as a simple strategy (limited by the complexity of the process). Anyway, the empirical model has a better fit when used within the range of experimental values from which they were generated. In this work, an empirical mathematical model derived from the Arrhenius equation was proposed, since in previous publications it was shown that there is a direct relation between the growth of ice crystals and the temperature oscillations that occur during the storage of frozen products. Equivalent diameter data of ice crystals obtained from the storage of frozen Tilapia analyzed in the optical microscope was used as a database for the formulation of the empirical model. The developed model was acceptable to predict ice crystal growth during recrystallization in frozen Tilapia samples and had the advantage of being simple and robust enough to estimate this growth in the flotation range from -18 to -11 °C After the first 30 days of storage. The average equivalent diameter (Deq) values predicted by the model indicated that the model provides a satisfactory description of the growth of the crystals with R2 equal to 0.930.
ABSTRACT A comparative test of water heating between the hybrid system - solar collector with heat pump - and a system with conventional supplementary heating - with high electric power - was performed. For this, a small capacity heat pump was installed, which was later installed together with a solar heating system, composed of a 250 L thermal reservoir and three thermoplastic collector plates. Tests were carried out to evaluate the COP of the heat pump and the energy consumption of the solar heating system operating with the heat pump and with an electrical resistance of 3000 W. In the laboratory tests, the heat pump presented an average COP of 2.15. In the field tests, the energy consumption of the solar system with heat pump was 54.9% lower when compared to the tests in which electrical resistance was used as a source of supplementary heating.
Abstract Water loss is a critical problem affecting the quality of table grapes. Temperature and relative humidity (RH) are essential in this process. Although mathematical modelling can be applied to measure constant temperature and RH impacts, it is proved that variations in storage conditions are normally encountered in the cold chain. This study proposed a methodology to develop a weight loss model for table grapes and validate its predictions in non-constant conditions of a domestic refrigerator. Grapes were maintained under controlled conditions and the weight loss was measured to calibrate the model. The model described the water loss process adequately and the validation tests confirmed its predictive ability. Delayed cooling tests showed that estimated transpiration rates in subsequent continuous temperature treatment was not significantly influenced by prior exposure conditions, suggesting that this model may be useful to estimate the weight loss consequences of interruptions in the cold chain.
Abstract In this work, a model of the process of freezing strawberries placed in boxes using forced air tunnel was studied. A strategy of operating condition modification in each stage of the process (pre-cooling, freezing step and sub-cooling) was applied, in a simulated process, regarding air temperature change. Time and energy consumption behaviors due to air temperature conditions in the tunnel were evaluated for each stage. Air temperature at different process stages affected both process times and system thermal demands. Operating conditions for each stage, which provided the best system global performance, were chosen, aiming energy consumption reduction without damaging product final quality, once each stage minimum requirements were taken into account. The strategy proposed produced an energy economy of 5.9%, comparing to the traditional process using constant temperatures, and it showed potential to be applied in different products and equipment with appropriate changes in the methodology.
Abstract The economy is currently driven by great competitiveness, demanding that the production and logistics sectors be agile, flexible and capable of action to solve difficulties. Logistics is of utmost importance to the operations of perishable food chains such as meats, fish, dairy, fruit and vegetable products, as well as for certain products in the pharmaceutical industry, such as vaccines, biomedicines and blood products that require the use of the cold chain due to their perishability. Temperature is the most important factor in the maintenance of quality and the shelf life of these products, cooling being one of the most widely used methods to slow the development of several factors that lead to product deterioration. Amongst the challenges for improving uncertainties related to the cold chain, is the mitigation of risks concerning its rupture. It is known there are inevitable variations in the storage conditions of the products during the stages of the cold chain, which cause changes in the shelf life of perishable foods. Both inside containers and in cold chambers there are temperature fluctuations around the ideal condition, and to this day, in most systems, monitoring of the temperature is measured by very few sensors. Although limited temperature monitoring technology is used to inhibit the risk of quality loss and improve food security, they are also used independently in the different logistics links of the cold chain. These challenges have driven efforts from some research groups in developed countries to improve the application of wireless sensor networks (WSN) and radio frequency identification (RFID), based on sensor devices. This paper addresses important aspects of the application of these new technologies that are able to detect the condition of these perishable products in real time during logistics operations, making it possible to avoid the loss of perishable products, improve their quality and reduce costs.
Resumo A economia, atualmente, é impulsionada pela alta competitividade, exigindo que os setores de produção e logística sejam ágeis, flexíveis e com capacidade de ação para a solução de dificuldades. A logística é de extrema importância para as operações das cadeias de alimentos perecíveis, como carnes, peixes, lácteos, frutas e produtos hortícolas, assim como para determinados produtos da indústria farmacêutica, como vacinas, biomedicamentos e hemoderivados, que necessitam do uso da cadeia do frio devido à sua perecibilidade. A temperatura é o fator mais importante para a conservação da qualidade e manutenção da vida útil destes produtos, sendo a refrigeração um dos métodos mais amplamente utilizados para retardar o desenvolvimento de vários fatores que conduzem à sua deterioração. Dentre os desafios para a melhoria de incertezas da cadeia do frio, há a mitigação de riscos de ruptura da mesma. Sabe-se que há variações inevitáveis das condições de conservação dos produtos durante as etapas da cadeia de frio, as quais causam alteração da vida útil de alimentos perecíveis. Seja no transporte ou nas câmaras frias de armazenagem, há flutuação de temperatura em torno da condição ideal, sendo que ainda hoje, na maioria dos sistemas, o monitoramento da temperatura é realizado por pouquíssimos sensores. Embora poucas tecnologias de monitoração de temperatura sejam utilizadas para inibir os riscos de perda de qualidade e obter a segurança alimentar, estas são utilizadas de forma independente, nos diferentes elos da cadeia logística do frio. Esses desafios têm impulsionado esforços de grupos de pesquisas de países desenvolvidos para o aperfeiçoamento de aplicações de rede de sensores sem fio (RSSF) e de identificação por radiofrequência (RFID), com base em dispositivos sensores. Este trabalho aborda aspectos importantes da aplicação destas novas tecnologias, que são capazes de detectar a condição destes produtos perecíveis em tempo real, durante as operações logísticas, possibilitando evitar a perda, melhorar a qualidade dos produtos perecíveis e reduzir os custos.
Abstract The estimated world population growth of 9 billion people by 2050 provides a major challenge for the next few years, considering the current problems regarding the lack of food safety and provision of healthy food in a world in which most people live in urban areas. The importance of diet in health is unquestionable, and as time goes by, so the consumer is becoming more aware that health is directly related to a balanced and safe diet. Post-harvest technologies for fruits and vegetables, whose metabolisms are still active, have the goal of maintaining the quality by way of the appearance, texture, taste, nutritional value and food safety, and also to reduce qualitative and quantitative losses between harvest and consumption. The combination of technologies such as rapid cooling, refrigeration, and the use of active and passive modified atmospheres applied post-harvest, must be combined with adequate temperature management for each product throughout the whole distribution chain. Thus, according to the temperature history from harvest to the retail locations, the shelf life estimate becomes a highly dynamic variable. Radio Frequency Identification (RFID) technologies with sensors, can revolutionize the transportation and handling of perishable products through accurate and continuous readings of the conditions of the conservation environment during the logistics, interpreted by mathematical models that estimate the remaining shelf life. This review describes how technology, by way of sensor-integrated RFID chips and associated with the use of mathematical modelling, can be incorporated into the management of Distribution Centres, shifting the emphasis from the classic FIFO (First In, First Out) to a FEFO (First Expired, First Out) strategy. Thus, better knowledge of the shelf life of the products may lead to reduced losses in addition to improving product conservation.
Resumo A estimativa do crescimento populacional mundial de nove bilhões de pessoas, em 2050, estabelece um grande desafio para os próximos anos, considerando os problemas atuais de insegurança alimentar e o fornecimento de alimentos saudáveis, num mundo, predominantemente, de pessoas vivendo em regiões urbanas. A importância da dieta na saúde é indiscutível, sendo que, a cada dia que passa, o consumidor está mais consciente de que a saúde está diretamente relacionada a uma dieta balanceada e segura. As tecnologias aplicadas na pós-colheita de frutas e hortaliças que continuam com seu metabolismo ativo buscam manter a qualidade através dos parâmetros aparência, textura, sabor, valor nutritivo e segurança alimentar, bem como reduzir perdas qualitativas e quantitativas entre a colheita e o consumo. A combinação de tecnologias, como resfriamento rápido, refrigeração e utilização de embalagens com atmosferas modificadas ativas e passivas, aplicadas na pós-colheita, precisa estar aliada a uma adequada gestão de temperatura para cada produto, em toda a cadeia de distribuição. Assim, conforme o histórico de temperatura desde a colheita até os locais de vendas no varejo, a estimativa da vida útil torna-se uma variável altamente dinâmica. Tecnologias de RFID (Radio Frequency Identification - Identificação por Rádio Frequência) integradas a sensores podem revolucionar o transporte e o manuseio de produtos perecíveis, por meio de leituras precisas e contínuas das condições do ambiente de conservação durante a logística, interpretadas por modelos matemáticos que estimam a vida útil restante. Esta revisão descreve como a tecnologia, por meio de chips RFID integrados a sensores e associados ao uso de modelamentos matemáticos, pode ser incorporada na gestão de Centros de Distribuição, alterando a ênfase, a partir do clássico FIFO (First In, First Out - Primeiro a Entrar, Primeiro a Sair), para uma estratégia de FEFO (First Expired, First Out - Primeiro Expirado, Primeiro a Sair). Desta maneira, com o melhor conhecimento da vida útil dos produtos, espera-se menor perda, além de melhor conservação dos produtos.
Abstract The degenerative effect of temperature fluctuations during storage time is a critical condition that needs to be quantitatively characterized in products where drip losses are appreciable. In this work, real storage conditions were reproduced using freezers modified to cause 3 levels of temperature fluctuation (± 0, ± 3, ± 5; ± 7) during storage of Tilapia (Oreochromis sp), at temperature of –18 °C. The fast frozen tilapia muscle (freezing cabinet) was chosen to quantify the growth of ice crystals according to temperature fluctuations. The identification of crystals in the optical microscope as well as histological treatments and measurements using specific software has shown that the growth of ice crystals in the first days of storage follows an asymptote, whose final value is conditioned only by the level of temperature fluctuations regardless of initial diameter, which begins storage. It has also been found that the growth of crystals formed during rapid freezing rapidly develops according to temperature fluctuations to which the product has been subjected. This work also identified statistically significant differences in the equivalent diameter of crystals formed at the four proposed levels of temperature fluctuation with significance level of p < 0.05.
Abstract In this work, an experimental unit of a vacuum spray dryer was built. This prototype attempted to combine the advantages of freeze-drying (drying at low temperatures due to vacuum) and spray drying (increase of surface area aiming the improvement of heat transfer efficiency). Maltodextrin solutions were dried in the vacuum operated equipment and in conventional spray dryer. The vacuum spray dryer system allowed obtaining powder at low temperatures due to the lowering of pressure conditions (2-5 kPa) inside the drying chamber. The products obtained in the two systems were characterized and compared for particle size distribution, moisture content, water activity, bulk density and solubility in water. The processes yields were also evaluated and compared. The vacuum spray dryer system allowed the production of larger, more soluble and less dense particles than those obtained in the conventional configuration of the equipment, resulting in drier and, therefore, with lower water activity particles. Thus, the use of the vacuum spray dryer as a drying technique may be an alternative for the production of powder rich in thermosensitive compounds.
The search for efficient and accessible cooling systems has increased worldwide. This study aims to build and evaluate an evaporative cooling system using a water driven ejector, allowing it to be installed in places with plenty of water. The system was investigated varying the flow rate and temperature of the circulating water, temperature of the replacement water, and coefficient of performance. The best vacuum obtained was 8.5 kPa at nominal operating conditions of 4.1 ± 0.1 m³/h and 5 ± 0.5 ºC for the circulating water reaching the temperature of 9.7 ± 0.5 ºC. The pulse-like disturbance generated by replacing the cooling water at different periods of times did not result in significant affect vacuum destabilization and the temperature rise in the cooling tank. The coefficient of performance of the system at the highest thermal power of 92.27 W was 0.077, which was underestimated due to possible problems related to pump efficiency. The system evaluated under the conditions proposed can be very efficient for cooling fluids at higher temperatures, and it can be complementary to main refrigeration systems.
The objective of this work was to monitor the operational conditions of the transport of chilled and frozen foods during delivery within cities and to evaluate the impact of the door openings on the alteration of the internal temperature of the refrigerated environment. Several temperature and pressure sensors were used in a refrigerated container with two compartments and they were installed in the refrigeration system unit and on the internal and external surfaces of the container. After the monitoring tests, it was verified that door openings during deliveries resulted in a disturbance that raised the internal temperature of the refrigerated container above values recommended for adequate conservation of the products transported. Moreover, increasing the number of door openings promoted a cumulative effect on the internal temperature, mainly in the chilled food compartment of the container. It was concluded that the refrigeration system unit presented serious limitations with regard to the maintenance of the container's internal temperature during the actual distribution routine, since it does not possess enough instantaneous capacity to restore the temperature set-point between deliveries.
O objetivo deste trabalho foi monitorar as condições operacionais do transporte frigorificado urbano de alimentos resfriados e congelados durante as entregas dos produtos e avaliar a influência das aberturas das portas da câmara nas alterações das temperaturas internas do ambiente frigorificado. Instrumentou-se uma câmara frigorífica bipartida do tipo ¾ com sensores de temperatura e pressão, que foram instalados em pontos específicos no sistema de refrigeração e nas superfícies internas e externas da câmara do caminhão. Após as monitorações, foi verificado que as aberturas de portas no momento das entregas resultaram na elevação da temperatura interna da câmara acima dos valores recomendados para a conservação adequada dos produtos transportados, além de que o aumento no número de aberturas de porta provocou um efeito acumulativo de aumento da temperatura interna, principalmente no compartimento de resfriados. Concluiu-se que o sistema de refrigeração utilizado pela frota de caminhões da empresa que produziu os alimentos transportados apresenta limitações quanto à manutenção da temperatura interna da câmara durante a rotina real de distribuição, pois não possui capacidade instantânea suficiente para retomar a temperatura adequada entre as entregas.
The objective of this work is to build an experimental portable forced-air freezing tunnel which creates a low or high pressure region surrounding the product. Comparative studies with air exhausting and blowing were conducted. The tunnel was built and placed inside a freezing product storage chamber, and the objective was to improve the air circulation and the thermal distribution between the product and cold air for a sample batch left inside the chamber. A heat transfer analysis comparing the process and the air distribution around the product was performed. The air evacuation process reduced up to 14% of the freezing time in relation to the blowing system and 10% in relation to the mixed system.
Este trabalho propôs a montagem experimental de um túnel portátil de congelamento por ar forçado composto por um ventilador que produz uma região de alta ou baixa pressão em um palete com produto, onde se pode avaliar o processo com a utilização de insuflação, exaustão de ar e uma combinação mista destes dois processos. O equipamento foi alocado no interior de uma câmara de estocagem de produtos congelados, buscando-se melhorar a distribuição do ar, potencializando-se a troca térmica entre o ar e o produto. Durante o congelamento, foram comparados os processos e analisada a transferência de calor entre o ar de resfriamento e o produto em diferentes posições e camadas do palete, bem como a distribuição do ar de resfriamento em circulação ao redor do produto. O processo de exaustão apresentou uma redução de 14% do tempo para o congelamento em relação à insuflação e 10% em relação ao misto.
Freezing of poultry cuts in continuous convective air blast tunnels is normally performed with the products protected by Low Density Polyethylene (LDPE) as a primary packaging and using Corrugated Cardboard Boxes (CCB) as secondary packaging. The objective of this work was to investigate the influence of these secondary packaging on the freezing of poultry cuts in continuous convective air blast tunnels. The study was performed by replacing CCB with Perforated Metal Boxes (PMB) in order to remove the packaging thermal resistance. The assays, performed in a industrial plant, demonstrated that CCB used commercially for meat freezing have a high heat transfer resistance. Their replacement with PMB can lead to shorter freezing times and spatially homogeneous freezing. Reductions of up to 45% in the freezing times were observed using PMB. The plateau of the temperature curve, related to the freezing time of free water, was significantly reduced using PMB, which is accepted to lead to better product quality after thawing. As the products were protected by the LDPE films as primary packaging, their appearance were not affected. The results presented in this work indicate that replacing CBB with PMB can be an excellent alternative to reduce freezing time and improve freezing homogeneity in industrial air blast tunnels, which could also be applied to other products.
O congelamento de cortes de frango em túneis convectivos é normalmente realizado com o produto envolto por filmes de polietileno de baixa densidade (PEBD, embalagem primária) e acondicionado em caixas de papelão (CP, embalagem secundária). O objetivo deste trabalho foi avaliar o efeito da embalagem secundária no congelamento dos cortes de frango. Para isso, compararam-se as curvas de congelamento do produto processado acondicionado em caixas metálicas perfuradas (CMP), que praticamente eliminam a resistência térmica da embalagem secundária, com as curvas de congelamento do produto nas CP. Os ensaios, realizados em uma planta industrial de processamento de aves, indicaram que as CP possuem uma grande resistência térmica e que a substituição delas por PMB pode resultar em maior homogeneidade espacial do processo de congelamento e em tempos de processo 45% inferiores. A duração do patamar de temperaturas que caracteriza a etapa de solidificação foi sensivelmente reduzida, o que favorece a obtenção de produtos congelados de melhor qualidade. A aparência dos produtos congelados em CMP não foi afetada, devido à proteção oferecida pelo PEBD. Assim, a substituição das caixas de papelão por caixas metálicas perfuradas pode ser uma excelente alternativa para reduzir o tempo de congelamento e melhorar sua homogeneidade espacial em túneis industriais.
The rheological behavior of invert liquid sucrose with two different percentages of inversion (59.68% and 89.88%) was studied from 17°C to 65°C using a concentric cylinders rheometer. The results showed that the invert liquid sugar exhibits Newtonian behavior within the range of temperature tested. The effect of temperature on viscosity of invert sugar was expressed by the Arrhenius relationship and the fitted models presented correlation coefficients (R²) greater than 0.99. The activation energies calculated for both samples, 59.68% and 89.88% of inversion, were respectively 70.5kJ.mol-1 and 86.5kJ.mol-1.
O comportamento reológico do açúcar líquido invertido com inversão de 59,68% e 89,88% foi estudado experimentalmente nas temperaturas de 17°C a 65°C, utilizando um reômetro rotacional de cilindros concêntricos. Os resultados mostraram que o açúcar líquido invertido apresenta comportamento Newtoniano na faixa de temperatura estudada. O efeito da temperatura na viscosidade foi expresso por relações do tipo Arrhenius, cujos coeficientes de correlação foram superiores a 0,99 e as energias de ativação apresentaram valores de 70,5kJ.mol-1 e 86,5kJ.mol-1 para as soluções com inversão de 59,68% e 89,88%, respectivamente.