共查询到20条相似文献,搜索用时 15 毫秒
1.
B.H Ashby M.T Turczyn D.V Schlimme S.W Grant 《International Journal of Refrigeration》1985,8(5):283-288
Six commercially packaged frozen food products were subjected to simulated railway shock and vibration conditions and manual handling abuse at both cryogenic (?70°C) and non-cryogenic (?18°C) temperatures. The amount of package and food product damage under different temperatures and levels of abuse were determined. The effects of cryogenic temperatures upon sensory and various analytical quality attributes of the food products were examined. The test results indicated that frozen food can be shipped at cryogenic temperatures in railcars equipped with cushioned draft gears with minimal product or packaging damage, provided there is not excessive manhandling abuse. 相似文献
2.
I.M Mackie P Howgate A Craig W.M Laird A.H Ritchie 《International Journal of Refrigeration》1986,9(3)
Wide range testing is reported of customer acceptability of various fish products after varying periods of frozen storage at −18°C. Four products of cod, breaded fillets, glazed fillets, fillet fingers and minced fingers, were tested by trained assessors and by groups of students in Colleges of Home Economics after storage periods of up to one year. Some trends were apparent, but in general the acceptability to the consumers remained essentially unchanged even after 1 year at −18°C. 相似文献
3.
In this study, the freezing time and rate of 1 cm3 cauliflower floret samples were determined under different freezing conditions in an air blast freezer. Four different air temperatures (−20, −25, −30 and −35°C) and six different air velocities (70, 131, 189, 244, 280 and 293 m min−1) were applied in the freezer, and the freezing rate and time of cauliflower pieces were determined under each condition. The freezing time of cauliflower samples frozen with cold air at −20°C and 280 m min−1 was similar to that of samples frozen with cold air at −35°C and 70 m min−1. When the velocity of air was increased from 70 m min−1 to 293 m min−1, the freezing time was approximately halved. 相似文献
4.
Rainbow trout eggs (V/VI Maier scale maturity stage) stored at 2 and −25°C were studied for hardness, lipid components, peroxides and conjugated diene and triene groups. The egg resistance to crushing after seven days of cold storage decreased from 87.3 to 66.0 g. The concentrates of free fatty acids, peroxides, diene and triene groups showed no tendency to increase. Changes in sheath resistance to crushing during frozen storage were significant, the resistance dropping from 87.3 to 30.0 g after 12 months of storage at −25°C. The temperature of −25°C inhibited lipolytic enzymes. Egg lipids were not oxidized before the third month of storage. After four months of storage at −25°C (hardness 46.5 g), the eggs were salted to determine the extent of hardness changes under the influence of sodium chloride solution and thermal treatment. Egg sheath hardness assays showed salting to result in hardness increasing from 46.5 to 85.0 g. Pasteurization reduced egg hardness, but the extent of reduction was not proportional to the duration of thermal treatment. Hardness reduction (down to 50.0 g) in the rainbow trout eggs during frozen storage has no detrimental effects on the suitability of eggs for delicatessen product manufacture. 相似文献
5.
In 1984 international research took place which compared the transport conditions of quick-frozen foods in thin-wall vehicles and conventional vehicles. This work was done at the request of the group of experts of the UNECE/TRANS/GE.11 in Geneva, Switzerland. In the Netherlands measurements have been carried out on three road vehicles — one conventional and two thin-wall vehicles — in the test station and on the road. The road transport involved taking a commercial cargo of frozen fish from Holland to Italy during the summer (July). Later on an additional test was performed in the test station with a fourth thin-wall vehicle at an ambient temperature of 30°C. The results show, that in the conventional vehicle, equipped with a bulk head and a ceiling air duct, and working on a temperature setting of −25°C, a maximum product temperature of −18°C could be maintained. The maximum temperature difference in the cargo was 6 K. Thin-wall vehicles appeared to have a temperature difference of 12 K between air inlet temperature and warmest product temperature. The maximum product temperature could be held below −12, −15 or −20°C, depending on the air distribution and, in particular, on the cooling power of the thermal appliance. 相似文献
6.
Strawberries were frozen at different air velocities in an air blast freezer at −30°C. The freezing time was taken as the time required to lower the temperature at the geometric centre of the samples to −10°C. The freezing times measured in the experiments were compared with the values calculated using Plank's equation. The freezing times calculated by Plank's equation were fround to be higher than those found experimentally at any given air velocity. Freezing time decreased with increasing air velocity. This is attributed to the increase in heat transfer coefficient at increased air velocities. 相似文献
7.
Application of hydrocarbon mixtures enables the creation of simple, reliable and durable refrigerating and cryogenic Joule–Thomson micro coolers for the temperature range of −73 to −183 °C. The temperature, thermal, power and hydraulic performances of a series of prototypes are presented. The results of tests demonstrate that small, single stage, sealed, lubricated compressors can be applied to these purposes. The start up and steady operation hydraulic performance of those machines are quite similar to the performance of domestic refrigerators. The last, together with the fact that in the studied micro coolers the lubricated compressors are used at temperatures down to −183 °C, ensures a large resource of operation. That is just the reason that holds out a hope for prospects in a broad field of applications for the studied prototypes, despite their lower power performances in contrast to gas micro coolers. 相似文献
8.
C. James I. Lejay N. Tortosa X. Aizpurua S.J. James 《International Journal of Refrigeration》2005,28(6):253
Accurate data on the initial freezing point of cured meat is required to predict freezing rates or identify optimal slicing temperatures. However, little data was found in the literature. Experiments were therefore carried out using the ‘Karlsruhe test substance’ (‘Tylose’) with varying salt concentrations as a cured meat substitute. Initial freezing points were −1.4, −3.1, −4.1, −5.2 and −6.3 °C at salt contents of 0.5, 2, 3, 4 and 5 kg salt/100 kg sample, respectively. These values were within ±0.5 °C of published values for cured pork and within ±0.9 °C of theoretical predictions. Modifying the salt content of Tylose is therefore a simple way of determining the initial freezing point of cured lean meats, and Tylose modified in this way can be used to simulate the freezing of cured meat. 相似文献
9.
V.R. Tarnawski D.J. Cleland S. Corasaniti F. Gori R.H. Mascheroni 《International Journal of Refrigeration》2005,28(6):425
Thermal conductivity models of frozen soils were analyzed and compared with similar models developed for frozen foods. In total, eight thermal conductivity models and 54 model versions were tested against experimental data of 13 meat products in the temperature range from 0 to −40 °C. The model by deVries, with water+ice (wi) as the continuous phase, showed overall the best predictions. The use of wi leads generally to improved predictions in comparison to ice; water as the continuous phase is beneficial only to deVries model, mostly from −1 to −20 °C; fat is advantageous only to meats with high fat content. The results of this work suggest that the more sophisticated way of estimating the thermal conductivity for a disperse phase in the deVries model might be more appropriate than the use of basic multi-phase models (geometric mean, parallel, and series). Overall, relatively small differences in predictions were observed between the best model versions by deVries, Levy, Mascheroni, Maxwell or Gori as applied to frozen meats with low content of fat. These differences could also be generated by uncertainty in meat composition, temperature dependence of thermal conductivity of ice, measurement errors, and limitation of predictive models. 相似文献
10.
Alain Le-Bail Nicolas Chapleau Marie Anton-De Lamballerie Marc Vignolle 《International Journal of Refrigeration》2008,31(5):816-821
The freezing process is widely used in the food industry. In the 70s, French regulation authorities have created in collaboration with the food industry the concept of «surgélation» process with the objective of improving the image of high quality frozen foods. The process of “surgélation” which could be translated as “super freezing” corresponds to a freezing process for which a final temperature of −18 °C must be reached “as fast as possible”. This concept was proposed in opposition to a conventionally “freezing” process for which no specific freezing rate is expected and the final storage temperature can be of −12 °C only. The objective of this work is to propose a methodology to evaluate the mean amount of frozen ice in a complex food as a function of temperature and to deduce a target temperature that must be considered as the temperature for which the food may be considered as “frozen”. Based on the definition proposed by the IIF-IIR red book, this target temperature has been defined as the temperature for which 80% of the freezable water is frozen. A case study is proposed with a model food made of two constituents. 相似文献
11.
Chilled foods are stored for periods of between a few hours and many days in domestic refrigerators. However, there are little published data on the temperature performance of domestic refrigerators within the home. A survey has been taken in 252 households in the UK and some of the results are presented in this paper. The refrigerators investigated in the survey were found to have an overall mean temperature of approximately 6°C, which ranged from 11.4 to −0.9°C. Temperature ranges over the whole refrigerator varied from 4.5 to 30.5°C with 3.7% of the total being warmer than 20°C. On average 29.9% of refrigerators operated below 5°C and 66.7% operated below 7°C. Few refrigerators (7.3%) ran, on average, above 9°C. No refrigerator characteristic (apart from type) could be related to temperatures or temperature distribution in the refrigerators investigated. 相似文献
12.
Influence of mist-chilling on post-harvest quality of fresh strawberries Cv. Mara des Bois and Gariguette 总被引:1,自引:0,他引:1
The aim of this study was to assess the impact of mist-chilling on high-grade strawberry post-harvest quality (Cultivars “Gariguette” and “Mara des Bois”). Strawberries were chilled at 2 °C using three processes: air blast chilling at 0.3 m s−1 or 1 m s−1 and mist-chilling at 1 m s−1. After chilling, fruits were submitted to different distribution chains characterised by different handling conditions and storage temperatures (2 °C or 7 °C) and by a 12 h retailing step at 20 °C. Strawberry quality was assessed by measuring 7 parameters: weight loss, commercial loss, firmness, sugar content, acidity, colour and sensory quality. Compared to air-chilling, mist-chilling did not reduce chilling time but it reduced weight loss by 20–40%. Mist-chilling had no detrimental effect on commercial loss defined as the percentage of fruit more than 1/3 of surface affected. It did not induce any major changes on strawberry quality. Temperature fluctuations undergone during cold storage and retailing had a detrimental effect on weight loss. The beneficial effect of packaging on weight loss was confirmed. 相似文献
13.
Stone fruits require rapid cooling within a few hours of harvest. High temperature and cooling delays can speed fruit deterioration from several causes. Flesh softening is most rapid at temperatures between ≈4 and 38°C, where ethylene sensitivity is greatest. Water loss is related to exposure time and the magnitude of water vapour pressure difference between fruit and environment. Internal breakdown, a low temperature injury problem, is aggravated in California by high temperature delays before cooling. Fruit rot organisms spread most rapidly at warm harvest temperatures and are slowed or stopped at near 0°C. When packing is delayed, then cooling before packing is essential. Because injury susceptibility is least at intermediate temperatures (5–20°C), fruit may be cooled to 5–10°C for next day packing, but should be cooled to near 0°C for longer delays. Regardless of prior cooling, the warming that will occur during packing makes essential final cooling to near 0°C following packing. Methyl bromide fumigation, if needed for quarantine treatment, should occur before cooling because warm fruit is less injured and fumigant doses are lower at warmer temperatures. 相似文献
14.
Strawberry pulp packed in bulk in containers of various shapes and of large sizes (10–2001) was frozen in a tunnel at −35°C. Time-temperature curves and freezing times for heat transfer in one, two and three dimensions were obtained. Experimental freezing times were compared with predicted values given by approximate methods based on two different equations for the calculation of freezing times in slabs, which in turn used three different methods for the calculation of shape factors. The predicted results obtained in this work confirmed that both the simplified prediction methods of freezing times and the shape factors used were sufficiently accurate for the design of freezing equipments for these types of product and working conditions. 相似文献
15.
Nasser Hamdami Jean-Yves Monteau Alain Le Bail 《International Journal of Refrigeration》2003,26(7):809-816
The modelling of heat transfer within materials with high porosity is complicated by evaporation-condensation phenomena. The aim of this work is to develop a model for apparent thermal conductivity in these products. The effective thermal conductivity of a porous food model (sponge) having 0–60% moisture contents and 0.59–0.94 porosity was measured by a line-source heat probe system in the range −35 to 25 °C. Two predictive models of the effective thermal conductivity of porous food were developed (Krischer and Maxwell models). The effective thermal conductivity predicted by Krischer model were in good agreement with the experimental data. Also, it was shown that the model including the effect of evaporation-condensation phenomena in addition to heat conduction was useful to predict the effective thermal conductivity of sponges. 相似文献
16.
Colour changes and chlorophyll degradation of frozen green beans (Phaseolus vulgaris, L., variety bencanta) were studied during 250 days of storage at −7, −15 and −30 °C. Chlorophyll a and b losses and colour Hunter a and b co-ordinates and total colour difference (TCDH) changes were successfully described by first order and reversible first order models, respectively. The temperature effect was described by the Arrhenius law. Disagreement between the colour co-ordinates and chlorophyll content was obtained. Therefore, chlorophyll content is not a good colour index of frozen green beans. The results emphasise that colour is a more important parameter to assess frozen green beans visual quality. 相似文献
17.
Gab-Soo Do Yasuyuki Sagara Mizuho Tabata Ken-ichi Kudoh Toshiro Higuchi 《International Journal of Refrigeration》2004,27(2):184-190
A novel technique has been developed for measuring the three-dimensional (3-D) structure and distribution of ice crystals formed in frozen beef by using a micro-slicer image processing system (MSIPS). The system has functions to reconstruct the 3-D image based on the image data of exposed cross-sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1 μm and to display the internal structure as well as an arbitrary cross-section of the sample choosing observation angles. The size and distribution of ice crystals can be determined from the 2-D quantitative information, such as the periphery and area of the crystals. The effects of freezing conditions on the morphology and distribution of the ice crystals were demonstrated quantitatively from the observations of raw beef stained by fluorescent indicator. For the samples frozen at −15 °C, the network structure of ice crystals were observed mainly at intercellular space, having approximately 100 μm in cross-sectional size, while that prepared at −120 °C showed the spherical crystals of 10–20 μm in diameter within the cells. The 3-D image of the sample demonstrated that the growth of ice columns was restricted by the intrinsic structure of muscle fibers. The proposed method provided a new tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals. 相似文献
18.
Interactions among cooling, fungicide and postharvest ripening temperature on peaches 总被引:1,自引:0,他引:1
J. Pablo Fernndez-Trujillo Antonio Cano Francisco Arts 《International Journal of Refrigeration》2000,23(6)
Peach fruit (Prunus persica L. cv. ‘Miraflores’) harvested at the firm-ripe stage, treated or not with 2 g l−1 iprodione, were cooled or not at 1°C and ripened at 15 or 20°C and 95% RH for 10 days. During ripening, weight loss, fungal development and changes in quality parameters (firmness, soluble solids content, titratable acidity, pH and ground and flesh color), and carbon dioxide and ethylene production were monitored. Cooling alone or combined with iprodione avoided Rhizopus nigricans decay during ripening at either ripening temperatures. A skin damage not previously reported on fungicide treated peach was observed at 20°C. Cooled fruit ripened at 15°C showed an anomalous respiration rate and ethylene production after the climacteric peak, a loss of firmness and a drop in titratable acidity after 7 days of storage, and reduced endo-polygalacturonase activity in presence of continuous pectinmethylesterase activity during the first week. Cooling before ripening at 20°C led to the best flavor without excessive total losses. These results helped in the optimization of warming cycles during cold storage used to avoid chilling injuries development on peaches. 相似文献
19.
Frozen food can undergo temperature rise essentially during handling processes which are the weakest links of the cold chain: delivery, loading or unloading operations and temporary storage where pallets are generally handled in an ambience above 0°C. In this study, the temperature rise in a pallet is investigated numerically and experimentally. A three-dimensional finite-volume heat transfer model is developed using Phoenics Computational Fluid Dynamics (CFD) software. Food temperature within the pallet is predicted as a function of time of exposure, ambient conditions, product initial temperature, palletization and thermal characteristics of products and packaging. The experiments are carried out with packaged frozen fish pallets placed on a closed or open dock. The temperatures are recorded, at different levels in pallets over 25- to 85-min periods. The model shows good agreement with experimental results. 相似文献
20.
In 1993 legislation is being enacted throughout the European Community (EC) that will require the maximum temperature of pork carcasses to be below 7°C before cutting or transportation. Results from a survey of UK abattoirs are summarized to highlight the problems and inadequacies of current commercial chilling systems. Design data are presented for conventional pork-chilling systems, which detail the effects of air temperature, air velocity and carcass weight on chilling times. Four novel or modified chilling systems are discussed: ultra-rapid chilling with air at −30°C; immersion chilling in brine at 0°C; ice-bank chilling in humid air at 2°C; and spray chilling in two stages, at 10°C for 2 h followed by 4°C for 21 h. The potential of such systems for the acceleration of chilling rates and for substantial weight savings is identified. 相似文献