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As a preliminary test for combining water cooking with vacuum cooling in soup of pork ham, three package treatments were designed to study the effect of cooking bag and netting on the quality of water cooked ham, i.e. ham cooked with a cooking bag and without a cooking bag (single netting and double netting). For treatments without a cooking bag, the results indicated that there was no significant superiority of ham cooked with double netting compared with ham cooked with single netting on the processing efficiency and quality characteristics. Although the hams cooked with a bag performed better in some chemical retentions and pigment, the water contents were significantly lower than those hams cooked in single netting (P0.05), and there was a higher shrinkage tendency compared with the hams cooked without a bag. For the processing characteristics and texture properties of pork ham, there were no significant differences observed among the treatments with and without a cooking bag in terms of the combined effect of cooking and cooling (P0.05). By considering the safety, convenience, cost, and the recovery effect on the quality changes of ham during vacuum cooling in soup, cooking with single netting is a better choice for future research.

Partial least squares regression (PLSR) was applied to understand the relationship between physical and chemical properties of pork leg ham with different cooling treatments, i.e., cold room, air blast and vacuum cooling. The results indicated that overall 69.8% variation of physical matrix was explained by chemical matrix. For the univariate analysis of physical attributes, the results showed that gumminess (88.1%) and hardness (86.5%) were best explained by chemical matrix, followed by springiness (78.7%), Warner-Bratzler Shear force (61.3%), and a* (60.0%). Graphical display of the regression coefficients indicated that different cooling treatments had different effects on the physical property of pork ham. Therefore, to predict the physical quality with chemical attributes, separate regression formulations should be adopted for different cooling methods. These findings have practical importance in attempts to predict physical properties from chemical components. In addition, they can also be used to control the physical properties by adjusting the components in the meat system.

A model has been developed for predicting the temporal temperature and mass of spherical solid foods during vacuum cooling. This paper discusses the effects of product thermophysical properties, convection heat transfer coefficient, latent heat of evaporation as well as vacuum environmental parameters that govern the heat and mass transfer of product. The temporal trends of total system pressure, product temperature such as surface temperature, centre temperature, mass-average temperature, the mass of product were predicted. This paper also compares the results of the computer algorithm with experimental results. The result demonstrates that the result of numerical simulation agrees well with the result of experiment.

The transient mass and heat transfer in cooked meat joints during vacuum cooling was analyzed by a validated mathematical model. The simulation indicated that a typical cooked meat joint can be vacuum cooled from an initial temperature of as high as 74³C to a final temperature of 10³C within 2 h, with 8% to 9% weight loss. Simulations also show that the effects of weights, sizes and shapes of meat joints on the cooling rate and percentage weight loss are negligible. The pore size has a significant effect on the pressure distribution within the meat joints. For commercial cooked meat joints with an average pore diameter over 1 mm, the effects of pore size on the cooling rate and weight loss are also negligible. However, the cooling rate, temperature distribution, and the percentage weight loss significantly depend on the porosity and pore distribution within the meat joints. A better performance of vacuum cooling for cooked meat joints, in terms of high cooling rate and low percentage weight loss, can be achieved if the porosity is large enough and the pores are distributed homogeneously within the meat joints.

End of Project Report Conventional cooling by air-blast or even by immersion in liquid is unlikely to achieve recommended cooling rates when dealing with joints weighing 5kg or more because meat has a low thermal conductivity. The objective was to investigate vacuum cooling as a technique for rapid chilling of cooked meat joints. In vacuum cooling, the food is enclosed in a chamber and reduction of the pressure to about 7 mbar causes evaporation of water from the surface of the food and from cavities in the food. The energy required to evaporate the water is extracted from the food, resulting in rapid chilling

In this study, four cooling methods, i.e., vacuum cooling, water immersion, air-blast and cold-room cooling were investigated to compare their effects on cooling efficiency and product quality. The overall mean results indicate that vacuum cooling is a very rapid and efficient means of cooling large cooked beef products. Vacuum cooling is over 800% quicker in terms of cooling times than the other cooling methods. However mass losses are higher (8-11%) than the other methods (2-3%). Sensory analysis indicated that overall acceptability of the samples was not affected by cooling treatment. Instrumental analysis showed that vacuum cooled samples had a tougher texture and a darker colour, but sensory panellists did not find vacuum cooled sample texture significantly different to others and the panellists preferred the darker colour of vacuum cooled samples.

A cadeia do frio é uma necessidade para a valorização da produção de frutas e hortaliças no Brasil. A fim de implantar uma cadeia do frio há que se considerar o resfriamento do produto. Este trabalho trata de uma técnica conhecida como resfriamento a vácuo que permite o tratamento de hortaliças visando reduzir suas perdas. Assim, foi realizada uma análise econômica de uma unidade de resfriamento a vácuo para alface. Analisou-se os custos fixos e operacionais envolvidos assim como procurou-se quantificar os benefícios derivados da adoção desta tecnologia considerando as perdas hoje existentes. Os resultados indicam uma boa viabilidade econômica (tempo de retorno inferior a 1 ano) para o projeto apesar do elevado investimento inicial. This paper presents an economic analyzes of a vacuum pre-cooling unit for lettuce in Brazil. The fixed and local operational costs were considered and the benefits derived from the investment were quantified considering the actual losses of horticultural products. The obtained results indicate a satisfactory period of return for the project (less than 1 year) although the investment is considered quite high.

Proving, baking and cooling are the stages of breadmaking that convert a fermenting dough into a stable product ready for consumption. There is evidence that leavened products were made in Egypt around 2000 BC and unleavened bread has been made since prehistoric times. The three operations, proving, baking and cooling have been essentially the same ever since, relying on the properties of the raw materials and the way they behave when heated to produce a staple product that is both nutritious and good to eat. How the process was discovered we shall never know in detail but the huge variety of leavened bread products eaten across the world today all rely on the same basic principles. Proving, or proofing, allows time under favourable conditions for the yeast and enzymes in the flour to be active. Then, during baking, the rate of heat transfer is increased so that the outside of the loaf dries to a crust and inside, the starch swells and the protein coagulates. Cooling reverses the direction of heat transfer and aims to produce loaves that are ready for wrapping, often with slicing as an intermediate operation. A typical timescale, with process conditions and their effect on loaf core temperature, is shown in Figure 5.1.

This chapter describes vacuum pumps, vacuum techniques, and air blowers. A vacuum pump is a compressor in which the inlet pressure is that of the chamber to be evacuated and the delivery pressure is that of the atmosphere. The characteristics of the vacuum circuit can considerably affect the behavior and efficiency of the pump and, when designing an installation, equal weight should be given to the system as to the pump. Vacuum technology includes all systems utilizing a pressure less than atmospheric, taken as 1.013 bar. The most common use of vacuum in industrial processes is to reduce the boiling point of water contained in a product. Vacuum cooling is closely allied to vacuum drying and is a simple mass transfer process which results in cooling of the product by the removal of a controlled quantity of moisture. Vacuum is usually measured in the unit torr which is equal to a pressure of 1 mm of mercury. The reason for preferring torr is that vacuum is most often measured by a barometer or a manometer which gives a direct reading of vacuum as a measurement of a liquid column.

The cooling condition has a significant effect on the morphology and optical properties of ZnO nanostructures. In this study, four types of nail-shaped nanostructures were prepared by thermal evaporation of Zn powders under different cooling conditions, including natural cooling, vacuum cooling, rapid cooling and vacuum & rapid cooling. XRD results suggest that our samples are highly crystallized wurtzite ZnO with preferable c-orientation. XPS indicated vacuum and/or rapid cooling could reduce the oxygen vacancies in the surface of ZnO samples. PL spectra showed that the intensity ratio of UV to green emission was increased under vacuum and/or rapid cooling conditions, which was in agreement with the XPS results. We can control the tip morphology of ZnO nanostructures and oxygen vacancies on the surface by adjusting cooling conditions for different applications.

Experimental investigations had been carried out to measure the evaporation coefficient of water from lettuce undergoing vacuum cooling, applying an evaporation boundary-layer model developed for the free surface of pure liquids. The value of evaporation coefficient for lettuce was found to be dependent on mass flux from the leaf surface, and about 4 times lower than that for the free surface of water. The effects of operating pressure to the coefficient were not appeared definitely under the experimental conditions.

Energy use in a direct heat/vacuum cooling system was evaluated and compared to an indirect unit during start-up, sterilization, and milk processing. Product flow rates were 606-1325 L/hr. Process temperatures were 138 and 149°C. Energy for start-up was 1.7 to 2.9 x 105 kJ for the direct; 0.9 to 1.4 x 105 kJ, indirect. Energy for 30 min sterilization was 4.0 to 5.6 x 105 kJ for direct; 2.3 to 3.7 x 105 kJ, indirect. Product processing energy was 357.9-436.8 kJ/kg for indirect; 547.8-697.6 kJ/kg direct. Greater heat recovery potential and fewer pumps made the indirect system less energy intensive. Methods of energy conservation are suggested.

Pasteurized Valencia and Temple orange juices concentrated to 45°Brix by freeze concentration retained their fresh juice flavor. Direct steam infusion heating to inactivate enzymes allowed more rapid heating than indirect heating and successfully lowered juice peel oil during vacuum cooling. Except for considerable pulp reduction of feedstream juices, there were few differences from normal citrus juice recovery procedures for freeze concentration. Since the product retained most of the aroma constituents of fresh juice, careful handling and high quality feed juice prior to freeze concentration was much more important than for evaporation. Fresh juice freeze concentrated to 45°B, then pasteurized at temperatures of 80°, 97° and 111°C had reduced sucrose (up to 25%) as the temperature increased to 111°C.

Commercial-scale experiments carried out during the last five years have shown that the cooling time of a head of lettuce, wrapped in PVC film and packed in a carton, can vary from 25 to 65 min, depending on the design of the vacuum installation. Experiments were, therefore, carried out with a commercial four pallet vacuum cooler, provided in accordance with the requirements of the Agricultural Engineering Institute, with three vacuum pumps and two compressors. The influence of pumping speed, cooling unit capacity and initial temperature on the cooling time and on the final temperature of lettuce leaves and butts was investigated. The results were compared with the cooling rate obtained with other vacuum cooling installations. Design data are proposed.

In order to establish a long-term storage procedure for chestnuts, both precooling, by room cooling, pressure cooling and vacuum cooling, and cold-storage with polyethylene pouches were investigated. Results obtained were as follows:1. Vacuum cooling gave the fastest cooling rate, followed by pressure cooling and by room cooling. Vacuum cooling, however, gave rise to white spots on the shell of chestnuts which was considered to be an undesirable selling factor. Of the three precooling treatments mentioned above, pressure cooling was thought to be the best.2. The weight losses during cooling were 1.6% for pressure cooling and 2.8% for vacuum cooling. In the latter case, the loss was approximately equal to the result calculated from the temperature reduction, assuming that almost all of the latent heat of vaporization came from the product.3. The extent of mold growing on the shell or scar of the stored chestnuts increased with increasing storage temperature and storage period. Almost all of the chestnuts which were stored at 10°C for 4 months or at 5°C for 6 months were spoiled.4. To evaluate an elastic modulus of chestnut flesh, cylindrical specimens were cut out from chestnuts along with long and short axis parallel to the seed scar. In chestnuts stored at 1°C, elastic modulus of the long axis flesh changed with the storage period.5. The sucrose content of the chestnuts stored at 1, 5 and 10°C increased rapidly during the first month, particularly at 1°C. Conversely, the starch content of the chestnuts decreased during the above period.6. The LL size chestnuts were more suitable for storage than L size ones. Since both the respiration rate and the weight loss of these chestnuts were lower than in L size.7. The shelf life of the LL size chestnuts was 3 months at 1°C, 2 months at 5°C and 1 month at 10°C.

THREE systems for handling mechanically harvested lettuce were evaluated. Tumbling the lettuce into bins that served as shipping containers was the most effi-cient and the condition of the lettuce at destination was at least as good as when packed into conventional car-tons. However, the bins must be settled either by vibra-tion or vacuum cooling and because of variability in con-tent of lettuce, the bins could not be used as a unit of measure. Lettuce was packed into cartons more efficient-ly on the harvester than at a central location.

As the result of the crystallization of copper sulfate from waste liquor using commercial scale plant, it became clear that the application of the thermal history of solution was very effective to depress nucleation as expected previously. The optimum setup of crystallizer to recover copper sulfate as perfect as possible was decided by using a new double-stage vacuum cooling method. Im Ergebnis der Kristallisation von Kupfersulfat aus Ablaugen unter Verwendung einer Anlage mit handelsublichen Abmessungen wurde geklart, das die Ausnutzung der thermischen Vorgeschichte der Losung wie erwartet sehr wirksam war fur die Zuruckdrangung der Keimbildung. Das Optimum der Anlage des Kristallisators zur moglichst vollstandigen Ruckgewinnung des Kupfersulfats wurde erreicht bei Anwendung einer zweistufigen Vakuumkuhlmethode.

Summary The effects of direct steam injection heating on the development of heat-activated sulfur compounds in skimmilk were studied over a temperature and time range of 190 to 300 F and 2 to 150 sec. The heat activation of sulfhydryl groups, as measured by silver titration, followed a direct relationship to heating-temperatures in those samples held for 2 sec. At 20 and 150 sec, maximum responses to temperature were observed followed by a decrease, when vacuum cooling was used, as the temperature of heating increased. It was determined that much of the decrease in titration values above the critical treatment resulted from volatilization of sulfur compounds.

This paper describes some applications of finite difference models of heat and mass transfer developed at the Bristol Laboratory of the Institute of Food Research (IFR-BL). Successful prediction of temperature and mass changes of meat during chilled retail display, pressure cooking/vacuum cooling and cooking in convected air has required measurements of material properties, surface transfer coefficients and pilot scale tests to confirm the models. Further work is needed to analyse and model important structural changes affecting the mechanisms of weight loss and quality changes.

The chilled storage of horticultural produce has become one of the most significant factors in maintaining the food chain from the grower to the consumer. The days are long past when the problems of production could easily be separated from those of marketing and distribution. To ensure even marketing of the crop, a proportion of it must be stored under suitable conditions. The development of refrigeration has enabled storage problems to be overcome and today a variety of techniques is used to chill produce. These include basic airblast chilling, liquid nitrogen vapour chilling, hydrocooling, vacuum cooling, and modified-atmosphere storage. Their main application is to extend the storage-life of produce while it is being transported by rail, road or air for home-market use or during export transit operations. A particularly important aspect of storage is that of chilling such produce as vined peas, beans and apples prior to processing. It is important to remember that, as a result of storage, the produce may behave differently from the fresh material after processing. Operations such as peeling, blanching and heat processing may accentuate quality defects that would not otherwise be obvious until after the product was heated.

The cooling rate, weight loss and temperature distribution of large cooked meat joints during vacuum cooling are experimentally analyzed. For cooling cooked meat joints with a weight of more than 5 kg from an initial temperature of around 74C to a final temperature of 10C, the experimental results showed that the total cooling time for vacuum cooling was less than 2 h, compared with over 5 h, 7 h and 9 h for water immersion, air blast and slow air cooling, respectively. During vacuum cooling, meat weights had no significant effect on the cooling rate and the maximum temperature point was not always located in the geometrical center of meat body. Vacuum cooling of cooked meat resulted in a higher weight loss, which was as high as about 10-13% of the weight before cooling, in comparison with 6-7% for slow air and air blast cooling. However, the moisture loss of cooked meats during vacuum cooling can be reduced by manipulating the brine injection levels.

The objective of this research was to evaluate the effects of vacuum cooling and temperature on the quality and storage life of mung bean sprouts (Vigna radiata L. Wilczek). Sprouts in micro-perforated bags were either not precooled or vacuum cooled to 9, 6, or 3 °C, and stored for 7 days at 1, 3, or 6 °C. Vacuum-cooled bean sprouts lost more weight than sprouts not precooled, and the weight loss was greater when the sprouts were cooled to lower temperatures. However, the total loss never exceeded 5% and no apparent signs of shrivel were observed. Vacuum cooling resulted in greater product freshness after 4 days of storage, but the effect was nonsignificant after 7 days. Storage temperature had greater influence on bean sprout quality than did cooling temperature, with greater freshness and whiter hypocotyls at the lower temperatures. However, blackening of cotyledons increased as the storage temperature decreased. Vacuum cooling is used commercially in some areas to precool bean sprouts; the sprouts are washed with water at room temperature, packaged in waxed cardboard boxes contain- ing 13.5 kg of product, and then vacuum- cooled to ≈9 °C. However, little information exists in the literature on the benefits or the optimum cooling temperature. Therefore, the objective of this research was to evaluate the effects of vacuum cooling and temperature on the quality and storage life of fresh bean sprouts.