I want you to summarise this file which is 1000 words by letting it 500 words, so cut it down into this word count using the important info about the process
Microsoft Word - aaaaa.doc Freeze drying is one of the most popular processes used in the manufacturing of powdered substances as it is a method by which water is removed in order to obtain and preserve a perishable powdered product. The process of freeze drying contains three main stages and these include the freezing stage, then a primary drying phase (also known as sublimation) and finally a secondary drying phase (Adsorption) (Millrock, 2020). The ideal instant coffee would be the one that simulates the characteristics of freshly-brewed coffee but without the hassle and necessary additional equipment required. This includes a coffee powder which dissolves easily and does not clump, as well as the taste and aroma of freshly ground coffee. Manufacturers have used these requirements to attempt to develop instant coffee powder that is textured and sized to resemble granules associated with ground coffee rather than a fine powder. It was also found that in other drying methods the aroma of the coffee easily dissipated and therefore artificial aroma, through a step known as aromatization, was added to each jar (Advameg 2020). Fig#. Instant Freeze Dried Coffee - resembles granules of ground coffee (MyCuppa) The freeze drying method uses low operating temperatures and pressures to remove freewater from a liquid coffee solution. The use of such low operating temperatures increases the quality of the product and also allows it to be easily rehydrated. This means that the instant coffee produced by method of freeze drying will mix and blend easily again when introduced to water, which is ideal and a key component of producing instant coffee powder. The method also allows for preservation of the organoleptic (i.e.sensory) properties such as aroma, texture and taste. Which again forms some of the most desired properties of a high quality instant coffee product (Pisano, Fissore & Baressi 2013). The first step of this method is to dissolve the coffee extract in hot water, this creates a highly concentrated liquor that typically has around 15-30% coffee by mass (Fissore, 2015). This solution is then filtered to obtain the soluble coffee granules that will be dried in this process with any insoluble grains being discarded. The filtered liquid is then concentrated and cooled before entering the freeze dryer to around 40wt% and -5C. Next, the concentrated coffee “sludge” is loaded into the freeze dryer. This can be done in one of two ways depending on the capacity required for the process. In a batch configuration, the coffee is loaded onto trays that are then placed into a cabinet with a door that has various shelves that double as heat exchangers. Then a vacuum is pulled and cold liquid is pumped through the shelves to lower the temperature. A continuous process uses an airlock and a conveyor system to load the trays holding the coffee into a cylindrical dryer. The trays are either placed directly onto the heat exchanger shelves or between them as in batch plants. Fissore (2015) states that “a batch process is used for low capacities (generally ranging from 50-7,000kg of powder per day), while a continuous process is used for large capacities (generally ranging from 7,000-25,000kg of powder per day)”. Inside the dryer, a vacuum is pulled and cold liquid is pumped through the shelves to lower the temperature. The faster this sludge is cooled the smaller and lighter the final granules will be, whereas slower cooled coffee extract often produces darker and larger granules (Advameg 2020). The exact pressures and temperatures vary for different cabinet designs and coffee characteristics. However, they must coincide with those that are below the triple point of water (shown in figure #) to enable sublimation and is crucial to maintain the physical integrity of the coffee (Millrock 2020). Generally a temperature of approximately - 40⁰C and a pressure below 500Pa is used. The pressure is then held constant as the coffee is slowly heated, causing the water to cross the phase boundary from solid to gas, thus leaving the coffee granules and entering the surrounding air. This is considered the primary drying process. A secondary drying also occurs when the wet air is removed from the dryer, causing the pressure to lower further. This enables any remaining water and some impurities to be removed. Figure#:Phase Diagram of water highlighting the triple point and sublimation information (Phase diagram, 2020) As said by Pisano, Fissore and Baressi (2013), “the most critical step is primary drying, that accounts for about 45% of the total energy required by the process”. This primary drying step is responsible for removing the bulk of the water from the frozen coffee through a process called sublimation. The frozen ice crystals attached to frozen coffee under sublimation, which means they are converted from solid to gas without entering the liquid stage first. This removes a lot of the free water from the coffee. During this step organic solvents may also be removed. Sublimation occurs at cooler temperatures and lower pressures as shown by Figure # of the water phase diagram above. The frozen product is placed under vacuum to maintain low pressures and then heat energy is added causing the ice to sublime. The remaining water is removed through the secondary drying phase through which any water still bonded to the coffee must be desorbed. If conducted properly, all free water would have been removed through the sublimation stage earlier and therefore in this secondary drying phase the temperature can be increased without fear of damaging the integrity of the coffee. The rate of drying is dependent on the temperature of the product and a vacuum must continue to be used. This stage continues until the moisture content in the product, instant coffee powder is low enough to increase the shelf life of the product (Barley 2012). Millrock Technologies (2020) states that “proper freezing can reduce drying times by 30%,” which would be ideal when constructing a instant coffee production plant as it would involve the reduction of energy used to run the appropriate equipment thereby reducing the environmental impact of the plant itself. This can be achieved by optimising the process through an extensive experimental investigation or through mathematical modelling. The experimental investigation is typically carried out after the process has been built, while a mathematical modelling approach can be built into the design.