Display Cabinet Research Articles

Pink discolouration defect in commercial cheese: a review

Development of a pink color defect is an intermittent but persistent defect in a wide range of ripened cheese varieties (Swiss, Cheddar, Grana, and Italian types) which may or may not contain an added colorant, e.g., annatto. Pink discoloration results in downgrading or rejection of a product with consequential economic loss to producers. Pink discolorations can manifest in a number of ways, e.g., patches at the surface or within the cheese block, or as a uniform pink border occurring below the surface of cheese blocks. Little consensus exists as to what the discolorations and their underlying causes are. This review seeks to provide an overview and interpretation of the underlying factors associated with the defect for both research and commercial audiences. In cheeses without added colorant, pink discoloration has been associated with: certain strains of thermophilic lactobacilli and propionic acid bacteria, Maillard reactions, and microbial pigments (e.g., carotenoids and phenolic compounds), which may be responsible for development of pink-brown or dark brown discoloration. In cheeses with added colorant (usually annatto), the development of pink discoloration has been associated with: alteration of annatto colorant due to factors such as varying pH levels within the cheese matrix (particularly < pH 5.4), oxidation of bixin in storage under high intensity fluorescent lights in display cabinets, presence of oxygen, variations in redox potential, interactions between nitrates and annatto present in plastic surface coating and also due to interactions between colorants, and the use of high heat treatment during processed cheese manufacture.

OCCURANCE OF HISTAMINE IN FISH PRODUCTS ON MARKET

Histamine fish poisoning is quite common and occur in consequence of microbial decarboxylase whose activity begin early in the post-mortem but are triggered in consequence of abuse in the shelf life of fish products. In this study forty-eight samples of tuna, mackerel, anchovies, sardines, fresh or processed were sampled from fish shops and supermarkets in the City of Bologna in the period from January to July 2010. Concentration of histamine was assessed using ELISA quantitative test and presence of psicrotrophic histamine forming bacteria was searched using a modified Niven agar medium which allow detection of suspect colonies that were confirmed by PCR for detecting the presence of the histidine decarboxylase genes in their DNA. The positive colonies were then identified on the basis of their morphology, Gram reaction and biochemical characteristics with API20E. The differential capability of the Niven agar was found to be low and approximately one fifth of the suspect colonies were confirmed by the PCR test, which however included both strong and weak histamine producing strains. The presence of Morganella morganii was associated with concentration of histamine 460 mg∙kg-1 above the allowed limit in a sample of tuna sampled from a fish shop. The same bacterium was found in samples of Atlantic horse mackerel (Trachurus trachurus). High histamine concentration (between 258 and &gt; 300 mg∙kg-1) were observed in salted European pilchard and European anchovy (228 mg∙kg-1) sold loose in supermarkets. Because temperature abuse could occur when Tuna (fresh/defrozen) are hold on chopping board to sell fresh cuts and during shelf life of salted pilchard and pickled anchovies held in opened cans in chilled display cabinets for extended period, which might results in very high histamine concentration, controls on time and temperature at the retail, in addition to those done during the harvest and processing are needed. The studies aiming at quantitatively assess the prevalence and number of histamine producing bacteria in fish products that were not involved in histamine poisoning cases and/or do not show high level of histamine are rather complex , requiring many tests for confirming the histamine forming ability of the suspect isolated strains and further studies are needed to develop techniques for enumerating the histamine producing bacteria.

La copia y la reconstrucción: un recurso visual en las exposiciones de historia del arte moderno desde los años 60 del siglo XX

This paper analyses the fact that most of the works pertaining to the so-called “Historical Avant-garde” -as well as to some of the Neo-Avant-garde- from the first half of 20th century have been gradually rebuilt since the 1960s to fill the gaps in some temporary exhibitions, and in many museums. We mean those works that were created with an ephemeral or plain temporary intention; we refer to others that articulated a critical discourse against the compulsive hoarding of museums, as well as to the greater part of works with an environment-like, interactive or conceptual nature which were produced during the 1960s and the 1970s.These copies are not usually destroyed; they end up, almost without exception, in the vaults of museums and collections. And, in the foreseeable future, they are to be employed not only to support a museographical discourse, but also to be loaned for temporary projects of third parties. The paradox lies within the fact that museums tend to use the same set of formalities for preservation that they apply to original works, cancelling then most of the educational values that those copies had in origin. Locked up inside every manner of display cabinet, these materials are protected from the hand and, therefore, sadly absent from the experience of viewers.

Quality Retention and Shelf-life Extension in Mediterranean Cucumbers Coated with a Pectin-based Film

&lt;p&gt;Edible coating is a simple and inexpensive concept for extending post-harvest life of fruits and vegetables. In this study, cucumbers were coated with different pectin-based emulsions to preserve the fruit quality and extend the post harvest shelf life. The formulations consisted of pectin, beeswax, sorbitol, water, and an emulsifying agent. By monitoring the physiological and quality parameters, the coating effects on the storability of cucumber fruits at 23°C and 40% RH (display cabinet), and 12°C and 85% RH (cold room) were determined. The parameters included weight loss, respiration rate, firmness, color, soluble solids and chlorophyll content. The coating markedly reduced weight loss and respiration rate at both temperatures. In addition, the coating reduced loss of firmness, color, chlorophyll and total soluble solids, and extended the storage life of cucumber fruits at both storage conditions.&lt;/p&gt;

Experimental study of heat transfer and air flow in a refrigerated display cabinet

The heat transfer and air flow in a vertical open refrigerated display cabinet loaded with packages of test product was studied in order to analyse unsteady state phenomena. The product and air temperatures in the curtain were measured using tiny thermocouples, air velocity using a hot wire anemometer and PIV (Particle Image Velocimetry). A comparison between the air velocities measured by these two methods shows a good agreement at the internal side of the air curtain. However, these two methods give quite different result at the external side of the air curtain which can be explained by the complex air flow in this region. The temporal variation of the air temperature inside the air curtain is due partly to the “on/off” compressor cycle and partly to the introduction of ambient air via vortices. The latter phenomena contribute to the rapid velocity fluctuations which are greatest in the mixing layer of the air curtain. The product position in the cabinet is a determining factor of its temperature.The convective and radiative heat flux between the products located at the front of the display cabinet and the air was also measured. Near the air supply and return ducts, the convective heat transfer coefficient was higher than between these two positions because of the high instability of air flow near the inlet and return ducts. The radiative exchange is more significant at the top of the display cabinet than at the bottom.

Performance and conditions of use of refrigerated display cabinets among producer/vendors of foodstuffs

The current study concerns the temperature of foodstuffs on sale in refrigerated display cabinets in bakeries, pork butcher's/delicatessens and cheese/dairy shops. The authors propose a single criterion to estimate whether storage conditions are satisfactory: foodstuffs must remain at temperatures below or equal to 7 °C to avoid any hazardous bacterial growth. Applying this criterion, 70% of time–temperature profiles are unsatisfactory.Of the main factors responsible for these excess temperatures, the authors distinguished factors related to the refrigerated display itself from factors related to professional practices. The equipment must be properly designed, used and maintained in order to keep foodstuff temperatures within a range geared to food safety needs.

Combined deterministic and stochastic approaches for modeling the evolution of food products along the cold chain. Part I: Methodology

Many deterministic models have been developed to describe heat transfer in the cold chain and to predict the thermal and microbial evolution of food products. However, different product items will have different evolutions because of the variability of logistic supply chain, equipment design and operating conditions, etc.The objective of this study is to propose a general methodology to predict the evolution of food products and its variability along a cold chain. This evolution is characterized by state variables such as temperature, water content, microbial load, etc. The methodology, presented in part I, is based on deterministic models for equipment and on stochastic laws for different sources of randomness. A Monte-Carlo algorithm is proposed for solving the model equations. The approach will be applied for the three last links of the cold chain: display cabinet, shopping basket and domestic refrigerator in part II of this study.

Combined deterministic and stochastic approaches for modelling the evolution of food products along the cold chain. Part II: A case study

The aim of the Part II is to apply the methodology combining deterministic and stochastic approaches to describe the evolution of food products along the cold chain. The proposed methodology, presented in Part I, takes into account different sources of variability (logistics, thermal conditions, consumer behaviour…) and uses deterministic models for equipment and product evolution. First, the data structure of a case study involving the three final links of the cold chain (display cabinet, shopping basket and domestic refrigerator) is presented. Then, the simulation results are analysed in order to highlight the potentialities of the modelling approach. These results are compared with survey data to validate the model. This part also underlines the sources of variability which exert the greatest influence on the microbial load development: the residence time of the product inside the refrigerator and the thermostat setting of the refrigerator.

Detailed CFD Modelling of Open Refrigerated Display Cabinets

A comprehensive and detailed computational fluid dynamics (CFDs) modelling of air flow and heat transfer in an open refrigerated display cabinet (ORDC) is performed in this study. The physical-mathematical model considers the flow through the internal ducts, across fans and evaporator, and includes the thermal response of food products. The air humidity effect and thermal radiation heat transfer between surfaces are taken into account. Experimental tests were performed to characterize the phenomena near physical extremities and to validate the numerical predictions of air temperature, relative humidity, and velocity. Numerical and experimental results comparison reveals the predictive capabilities of the computational model for the optimized conception and development of this type of equipments. Numerical predictions are used to propose geometrical and functional parametric studies that improve thermal performance of the ORDC and consequently food safety.

CFD Parametric Studies for Global Performance Improvement of Open Refrigerated Display Cabinets

A detailed CFD modelling of an open refrigerated display cabinet has been formulated in a previous study. Some modifications are introduced in order to perform parametric studies dealing with low-cost geometrical and functional characteristics for improvement of the global performance and energy efficiency. The parametric studies are devoted to the analysis of the thermal response and behaviour inside the food conservation space influenced by (1) air flow rate through the evaporator heat exchanger; (2) air curtain behaviour; (3) hole dimensions and distribution of the back panel; (4) discharge and return grilles angles; and (5) flow deflectors inside the internal duct. The analysis of the numerical predictions from the parametric studies allows the development of an optimized model for the conception of an open refrigerated display cabinet with a more adequate configuration. The numerical predictions of the optimized model show lower product temperature and reduced electrical energy consumption, allowing the improvement of the food safety and the energy rationalization of the refrigeration equipment.

Temperature prediction in a refrigerated display cabinet : deterministic and stochastic approaches

The product temperature in the refrigerated display cabinets is very variable and it influences directly the safety and quality of the food products. This variability is due to the type of display cabinet (vertical, horizontal), the position of the product inside the equipment, the fluctuation of the ambient air temperature in the supermarkets (day/night, opening hours, seasons, air conditioning etc.) and the surrounding condition of the display cabinet (in front of another refrigerated display cabinet or in front of grocery products) etc. This study proposes a thermal model to predict the load temperature in an open vertical display cabinet in function of two random parameters: ambient temperature in the supermarket and radiation temperature of the surrounding walls. The knowledge of the probability density of these parameters, from field measurements or expert knowledge, allows predicting the variability of the product temperatures inside the display cabinet.

The impact of geometric structure and flow arrangement on the performance of CO 2 evaporators in multi-deck medium temperature display cabinets

The CO 2 refrigerant is widely applied in retail refrigeration systems to replace HFC fluids such as R404A, but its system performance requires further improvement. One feasible method would be to pinpoint the matching components of the system, in particular its evaporator coils. This paper focuses on the potential optimization of the CO 2 evaporator design in an existing multi-deck medium temperature display cabinet charged previously with R404A refrigerant. To achieve this target, a display cabinet model with an integrated CFD and detailed evaporator sub models was utilized. This model could readily imitate the actual cabinet performance under varied operating conditions and component designs. Various design options of the CO 2 cabinet evaporator were considered and their impacts on the cabinet performances were predicted by the integrated model. Ultimately, the optimized designs of CO 2 cabinet evaporator coil geometries and refrigerant side operating parameters have been attained.

The importance of chill rate when characterising colour change of lamb meat during retail display

An experiment was conducted to compare the effect of two chilling rates (Con and Fast) on colour change of lamb meat during simulated retail display. Measurements were made on 3 muscles; LD ( m. longisimuss dorsi), SM ( m semimembranosus) and ST ( m. semitendinous). Meat samples from 32 Merino crossbred lambs were vacuum packed and stored for 5 days at 2 °C, then cut and overwrapped in polyvinyl chloride film on black polystyrene trays, stored in a display cabinet at 4 °C with lights on and measured twice daily for 4 days, using a Hunterlab minilab 45/20 L D65, aperture 10°. Sarcomere length was shorter, shear force higher and colour change greater in meat from the Fast treatment compared to the Con treatment. Colour differences between treatments were likely due to oxygenation (bloom) as well as oxidation effects. Chill rate is important when characterising colour change during display and should be considered in measurement protocols.

Heat transfer modelling in a refrigerated display cabinet: The influence of operating conditions

The product temperature in refrigerated display cabinets is very variable and directly influences the safety and quality of food products. This variability is due to the type of display cabinet (vertical, horizontal), the position of the product inside the cabinet, fluctuations in the ambient temperature in supermarkets (day/night, opening hours, seasons, air conditioning, etc.) and the surrounding conditions of the display cabinet (in front of another refrigerated display cabinet or in front of grocery products, etc.).This study proposes a heat transfer model to predict the load temperature in an open vertical display cabinet. Heat transfer by conduction, convection and radiation was taken into account in the model. Four load positions were considered: top/front, top/rear, bottom/front and bottom/rear where the product temperatures are significantly different. The model was validated by comparing predicted values with experimental ones. Then it was used to predict the influence of various parameters such as the ambient temperature in the supermarket, the radiation temperature of the surrounding walls and the internal/external infiltration rates. Through integration of quality and microbiological predictive models, this approach can be used as a numerical tool for quality and sanitary evaluation of products displayed in display cabinets. The developed model will be further used in the modelling of the cold chain, which comprises several types of refrigeration equipment.

Development of a stability model for a vertical single band recirculated air curtain sealing a refrigerated cavity

Recirculating cold air curtains are used to seal the open front of all multi-deck refrigerated display cabinets commonly used in food retail. Infiltration through the air curtain has been estimated to be the source of between 78 and 81% of the total heat gain to the cabinet. More efficient air curtains would not only save energy but would enable more precise temperature control of the produce within the display cabinet, better preserving food quality. Curtain thickness, length, discharge temperature and velocity all influence the efficiency of the air curtain and design optimisation has until recently been largely empirical or has used complex CFD models. The aim of this study was to generate a design guide which would enable cabinet designers with limited fluid flow expertise to rapidly identify the most efficient air curtain design to seal any given cavity from fundamental measurements without any need for intensive computation.

A Method of Self-Adaptive Controlling Temperature Fluctuation of Display Cabinet in Dynamic Ice-Storage System

Dynamic ice storage system has advantages of energy-saving by using electricity price difference of the different period. Food in display cabinet requires small temperature fluctuation to prolong preservation time. Considering the questions of energy consumption and unable to adopt the traditional method of halting and running compressor to control center temperature fluctuation in display cabinet, the paper provides dynamic ice storage system to cool display cabinet. When the wind speed keeps in suitable space, according to environment temperature, humidity and wind change, self-adaptive adjusting cooling water pump flow can maintain the center temperature within a certain range, and reduce center temperature fluctuations in display cabinet by controlling inverter frequency using PLC. Experiments prove that when environment temperature change range is 20°C to 32°C, and relative humidity is 40% to 90%, if not adopting PLC control pump flow, the temperature difference is 2.5°C, on the contrary, temperature difference is 1.3°C.

급기제트 조건에 따른 냉동용 전시케이스의 성능

Vertical open display cabinets are widely used in shopping mall, supermarkets, retail stores. Maintaining the temperature of foods in the display cabinet is vitally important to retailers to ensure optimal food quality and safety. The purpose of this study is to reduce the infiltration of air and heat loss from ambient space to display cabinet. The three-dimensional Computational Fluid Dynamics(CFD) simulation is used for the analysis of air flow patterns and temperature distribution in refrigerated display cabinets. Under several operating conditions which vary both the inner and outer jet velocities in the range from 0.3 to 1.1 m/s, simulations were carried out. This paper presents a performance of display cabinets with single jet and double jet. The energy consumption due to thermal entrainment ratio is plotted with varying Re. It was found that the double jet system is better than single jet system in terms of temperature distribution and energy saving.

Powder spray guns

This work presents an experimental and numerical analysis of the flow distribution in the cooling duct of a commercial refrigerated display cabinet. The analysis is carried out on a channel mock-up, in which the air is forced through the evaporator by two fans. A steady-state isothermal numerical analysis of the flow distribution is performed with the commercial code ANSYS-CFX and the k-epsilon method is used to model the turbulence. The numerical results are compared with the 3D air velocity fields, taken on three planes placed at different heights inside the duct, by the stereoscopic Particle Image Velocimetry (PIV) technique. Once validated, the model allows a better comprehension of the flow mal-distribution source and its effect on the velocity field at evaporator exit.

Public Law and The Executive

The contemporary public law jurisprudence of the High Court has transformed the basis of judicial review of executive action, removed traditional restraints on the scope of executive power, reinforced the separation of powers, and transformed the federal compact by identifying new constitutional limits on State institutions. The High Court has, over the last two decades, emphasised the constitutional dimension of a number of terms found in the Constitution by characterising them as “constitutional expressions”. These expressions have been imbued with substantive force by identifying a bundle of essential characteristics of each such expression, being characteristics that Parliament cannot alter. The impact of this new approach on executive power has been the emergence of a constitutional foundation for Commonwealth and State administrative law, a renewed focus on the constitutional foundation of executive authority, and the extension of the separation of powers doctrine to State institutions. This development is of profound significance for the entire range of interaction between the judiciary and executive government.

Experimental analysis of the thermal entrainment factor of air curtains in vertical open display cabinets for different ambient air conditions

Abstract The vertical open refrigerated display cabinets suffer alterations of their thermal performance and energy efficiency due to variations of ambient air conditions. The air curtain provides an aerothermodynamics insulation effect that can be evaluated by the thermal entrainment factor calculation as an engineering approximation or by the calculus of all sensible and latent thermal loads. This study presents the variation of heat transfer rate and thermal entrainment factor obtained through experimental tests carried out for different ambient air conditions, varying air temperature, relative humidity, velocity and its direction relatively to the display cabinet frontal opening. The thermal entrainment factor are analysed and compared with the total sensible and latent heats results for the experimental tests. From an engineering point of view, it is concluded that thermal entrainment factor cannot be used indiscriminately, although its use is suitable to design better cabinet under the same climate class condition.