Coffee, freeze-drying

Because products rich in desirable NPs command a high price, it becomes economic to build storage facilities that reduce NP loss and to invest in improved packaging—look at foil wrapped tea or vacumn wrapped coffee. Freeze drying, controlled atmosphere packaging and optimum harvesting also help deliver the best NP-rich products to the consumer. 

Fissore, D., Pisano, R Barresi, A.A., 2014. Applying quahty-by-design to develop a coffee freeze-drying process. J. Food Eng. 

Freeze Drying. Commercial freeze drying of instant coffee has been a common practice in the United States since the mid-1960s. The freeze-drying process provides the opportunity to minimize flavor degradation due to heat (34). 

Figure 2.3 illustrates a process in which the outer layer of a product is quickly frozen as a congealed crust. These CRUSToFREEZE plants have a capacity between 1500 and 5000 kg/h and require 0.5 to 0.8 kg LN2 pro kg of product, which has to be frozen totally on a conveyor belt. Figure 2.4 shows the product exit of the plant in Fig. 2.3. The freeze drying of coffee and tea extracts, fruit pulps or small pieces of meat require a multi- stage pretreatment. The granulated end product from coffee and tea extracts should have a defined grain size, a desired color, and a predetermined density. Fruit pulps should become granulated, with the appearance of fruit pieces, while meat pieces should not stick together like a small meat ball, but be recognized as single pieces when presented in a meal.

Fig. 2.55. Freeze drying plant, type CQC, as shown in Fig. 2.53. In this plant, two carriers are moved in parallel through the tunnel. The photograph shows the two heated shelves systems. The sliding gate valve is located in the large extension on the left side. In this plant approx. 5000 tonnes of freeze dried coffee granulate can be produced annually (photograph ALD Vacuum Technologies GmbH, D-63526 Erlensee).

Rolfgaard, J. Industrial freeze-drying for the food and coffee industry. Atlas Industries A/S, DK- 2750 Ballerup... 

The freeze drying of coffee extracts has been, and still is, the most frequent application of this process in the food industry. For economic reasons it is best to start with 40 % solid content in the extract. The final product is judged by the following criteria ... 

Fig. 4.6. Distribution of grain size as a function of bulk density of freeze dried coffee extract, which has been gassed with different pressures of C02 before freezing.

Downey and Dublin [4.22] used near-IR reflectance spectroscopy to identify the origin of the coffee beans, which have been used for the freeze dried extracts Pure Arabica, pure... 

The selected examples demonstrate that there is no ideal process for the freeze drying of fee extract. One must compromise in the various steps of the whole process, from bean iction. roasting, extraction, freezing, freeze drying and packing to achieve the desired ility and cost of the freeze dried coffee. 

Flink, J. M. The influence of freezing conditions on the properties of freeze dried coffee. International Course on Freeze-Drying and Advanced Food Technology, Burgenstock, Switzerland, 1973... 

Packets of instant coffee proudly proclaim that the product has been freeze-dried . In practice, beans of coffee are ground, boiled in water and filtered to remove the depleted grounds. This process yields conventional fresh coffee, as characterized by its usual colour and attractive smell. Finally, water is removed from the coffee solution to prepare granules of instant coffee. 

It is clear that decreasing the external pressure makes boiling easier. It is quite possible to remove the water from coffee at or near its freezing temperature - which explains the original name of freeze-drying. 

Freeze-desalination, 26 71 Freeze dryers, 9 135-136 Freeze drying, 9 93, 116 11 543 ceramics processing, 5 656g coffee, 7 262... 

Spray some drops of coffee into a vacuum chamber, and they, too, boil until they freeze. Even after they are frozen, the water molecules continue to evaporate into the vacuum until all that is left to be seen are little crystals of coffee solids. This is how freeze-dried coffee is made. The low temperature of this process tends to keep the chemical structure of the coffee solids from changing. When hot water is added, much of the original flavor of the coffee is retained. 

In contrast to the decaffeination of coffee, which is primarily executed with green coffee, black tea has to be extracted from the fermented aromatic material. Vitzthum and Hubert have described a procedure for the production of caffeine-free tea in the German patent application, 2127642 [11]. The decaffeination runs in multi-stages. First, the tea will be clarified of aroma by dried supercritical carbon dioxide at 250 bar and 50°C. After decaffeination with wet CO2 the moist leaf-material will be dried in vacuum at 50°C and finally re-aromatized with the aroma extract, removed in the first step. Therefore, the aroma-loaded supercritical CO2 of 300 bar and 40°C will be expanded into the extractor filled with decaffeinated tea. The procedure also suits the production of caffeine-free instant tea, in which the freeze-dried watery extract of decaffeinated tea will be impregnated with the aromas extracted before. 

Typical lengths of cycles for food stuffs are 5-10 hr, for bacterial pellets 2-20 hr, and for biological fluids 20-50 hr. A production unit with capacity of 500 L may have 75 kW for refrigeration and 50 kW for heating. Conditions for the preparation of freeze dried coffee are preparation of an extract with 20-25% solids, freezing at —25—43°C, sublimation at approx. 200Torr to a final final moisture content of 1-3%, total batch processing time of 6-8 hrs. 

Gosch and Montag (249) determined and compared the concentration of purines and pyrimidines in different coffees. The freeze-dried extract was dissolved in water, hydrolized with TFA/formic acid at 235°C, and applied to an RP18 SPE cartridge. The eluted sample (with methanol) was analyzed by HPLC on a LiChrosphere 100 RP-18. The mobile phase was a phosphate buffer containing A,A-dimethyloctylamine, and the detection was spectrophotometric at 269 nm. Adenine, guanine, hypoxanthine, xanthine, AMP, GMP, IMP, UMP, and uric acid levels were tabulated for arabica and robusta coffees from various sources. 

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