16. Processing Technologies

Transcription

1 16. Processing Technologies What do you do with the produce that you can t sell? Or product that you wouldn t normally harvest because of weather damage, or the orders never eventuated, or because you only pick a certain part of the plant such as the fruit or root and leave the rest. This chapter is more about what you can do with the plant biomass on your farm that you have invested your resources into growing, and which at this point in time you haven t a market for. There are many things you can do with the whole of your crop of carrots, broccoli or corn. We re not talking about food waste as such i.e. food that s been harvested, prepared, maybe packaged and maybe sent to retailers and not sold. Or bought by consumers and not eaten. There have been a lot of studies recently looking at food waste and what to do about it. You can read some of the excellent reports on the opportunities here, and we will soon have a new CRC devoted especially to looking into this opportunity: People value fresh produce for what it is, and for what it does for them: Freshness, aroma Crunch, texture, fibre Flavour, sweetness Juiciness, water Colour, contrasts Nutrients: Vitamins, minerals, phytonutrients Protein, enzymes at s inside a ve What s inside a vegetable? Many components are easily destroyed by light, heat, oxygen Polysaccharides/sugars Inulin Pectin Proteins Oils/fats Food Acids Vitamins/Minerals/Phytonutrients Flavours & Colours Juices, purees, skins, dry material (pomace), fibre For all these reasons and more, food manufacturers add vegetables and products made from them to their: Bread and other bakery items, including crackers Crisps and other snack foods Ice-cream and other dairy products like yoghurt Dips and sauces Baby food Breakfast cereals Juices and smoothies any components 52

2 What are value-added vegetable products? So when you have produce left over after A grades have been sorted out for retail, wholesale or direct sales, you could consider: Making your produce available to companies who manufacture these types of foods Making these types of products yourself As a middle ground, look at what additional processing steps you can undertake to make saleable ingredients and/or products. Innovating via processing Processing may do one or several of these things: Reduce water content Reduce bacterial and other microbial load Break open cells and soften cell walls; increasing the surface area of the food Enable separation of liquids and solids Change colour, flavour and nutritional content (or bioavailability) These processes may change the requirements of the food for packaging, storage temperature and duration, and widen the foods the ingredient can now be used, or the occasions it could be eaten on. Here s a simple summary of some of the relevant technologies. For many of these steps, washing and peeling, slicing and cutting into smaller pieces may be required as a first step, prior to further processing. Drying removes the water in a food, reducing the water activity and preventing bacterial growth, and reducing the weight of foods. Heat and air movement (i.e. sun and wind) are both used for drying as well as modern techniques like Bed dryers, Fluidized bed dryers, Freeze Drying, Shelf dryers, Spray drying and Commercial food dehydrators and (simply) ovens. Once dried, vegetables can be milled to produce powders of various size grades which can easily be incorporated into other food products like bakery products. 53

3 Freeze Drying is becoming increasingly popular for producing crunchy fruit and vegetable snacks it retains the natural colour and nutrients, and quite a lot of the flavour and is also an excellent (if expensive) way of producing high quality vegetable powders. Freeze-drying works by freezing the material and then reducing the surrounding pressure (creating a vacuum) to allow the frozen water in the material to escape as a vapour. If a freezedried material is sealed to prevent the reabsorption of moisture, it may be stored at room temperature without refrigeration, and be protected against spoilage for many years. Packaging is the critical issue, and foil-lined bags or packs with very good seals are required. Freeze-dried foods have a puffed or aerated texture (a bit like a Crunchy bar), which makes for an interesting eating experience. Drying: It s not just about removing the water... Microwave-Vacuum drying produces similar results to freeze drying, but more quickly and at lower cost. Microwave heating generates heat deep within the food rather than just on the surface and when combined with the application of a vacuum, allows the moisture to be removed quickly with reduced risk of food degradation (loss of colour, flavour and nutrients) due to excessive heat. The technique has been used successfully for fruits and vegetables where the lower temperatures and faster drying times maintain a better quality, and when combined with an initial air drying stage, the vacuum application creates the puffed texture similar to that achieved with freeze drying Cooking: There are many ways to cook vegetables to create more stable and convenient products, and some of them warrant an explanation: Microwave Frying combines the techniques of conventional deep frying with heating via microwave to provide a cooking technique that for some foods can yield similar cooking qualities but with reduced fat uptake compared with conventional frying alone. Microwaves cook the part of the product not in direct contact with the hot oil, meaning that more a cooked effect is quicker, whilst still achieving the desired deep fried browning. The process has been demonstrated to be particularly good for frying donuts. 54

4 Vacuum - Frying is a method where foods are deep fried under vacuum (or near vacuum conditions). The advantage of this process is that the frying occurs at lower temperatures than conventional deep frying (often around C, depending on the food) and that the fat content of the fried food is greatly reduced over conventionally fried foods. Due to the lower frying temperatures the foods generally retain higher nutrient levels and a more natural colour due to less browning. It is a suitable process for most foods that could normally be deep fried and is particularly popular for producing vegetable chips in some parts of Asia (and hopefully: one day in Australia!). Sous-Vide. The term sous-vide comes from the French for under vacuum and it is a method for gently cooking food. Despite appearances sous-vide is not boil in the bag! The food is normally vacuum packaged in a plastic pouch and is cooked in a water bath or steam chamber at a carefully controlled temperature (typically 55 to 60 C) for several hours. The aim is to cook the food evenly internally without overcooking the outside. The use of cooking temperatures below the boiling point of water allows vegetables to be cooked thoroughly whilst still maintaining a firm or crisp texture. Care must be taken when cooking sous-vide to ensure that botulism poisoning does not occur since Clostridium botulinum bacteria can grow in food in the absence of oxygen. Retorting: Involves packing food into a plastic pouch and sealing it. The pouch is then heated to C for several minutes under high pressure inside a retort or autoclave machine. The food inside is cooked in a similar way to pressure cooking. This process reliably kills all commonly occurring microorganisms (particularly Clostridium botulinum), preventing it from spoiling. The packaging process is very similar to canning, except that the package itself is flexible. The LoveBeets beetroot pack that we can see in most supermarkets in Australia these days is retorted. Aseptic Packaging: Involves sterilisation of food by quick exposure to ultra-high heat, then rapidly cooling to ambient temperature, and filling into sterilised containers that are then sealed in a commercially sterile environment. However, the assembled aseptic package is not further processed like retort products. Examples include milk, juices, soups, tofu, wines, liquid eggs, whipping cream, and teas. Pasteurisation: Involves heat processing a liquid or a food to kill pathogenic bacteria and make the food safe to eat. Pasteurised foods still require refrigeration. Pasteurisation can be achieved by heat, steam or irradiation with small amounts of gamma rays. Pasteurisation can affect the nutrient composition and flavour of foods. 55

5 Emerging Technology A new food processing technology microwave assisted thermal sterilisation (MATS) is being seriously investigated by the University of Tasmania and the Defence force, at the DSTO, Tasmania. This technology could create freshlike meals with good nutritional content, great flavour, texture and appearance; but potentially sterile, with long shelflife. The method involves placing prepared foods into a pack, and exposing to a microwave signal to induce dielectric heating within the packaged food, resulting in cooking much faster and with less damage to sensitive nutritional components than standard cooking methods like retorting. Preserving everything old is new again Pickling means preserving food in brine (salt solution) or marinating in vinegar (acetic acid) and in Asia, oil is used to preserve foods. At a concentration of 20%, salt kills and inhibits growth of microorganisms; acetic acid reduces the ph (increasing the acidity), slowing the rate of multiplication of bacteria and altering the flavour of the food. Chemical pickling may involve addition of sodium benzoate or EDTA to increase shelf life. Fermenting reduces the ph value (reducing food spoilage microbes, adding shelf-life and a tangy flavour) via in situ microbial activity (Lactobacillus spp), and sometimes by addition of lactic and acetic acids formed and by other microbial products. (e.g. ethanol, bacteriocins). This is used to produce kimchi, sauerkraut and many other traditional cultured foods (kefir, kombucha, tempeh.) which are increasingly seen in Australia. There are many groups springing up to provide information on fermentation, one such is High Pressure Processing (HPP) is a method that presses foods inside a vessel by exerting 70,000 pounds per square inch or more of pressure. This disables microorganisms and prevents spoilage but food retains its appearance, texture and flavour. HPP is also called cold pasteurisation, although the shelf-life for resultant products is in many cases not as long as pasteurisation, and the costs for both capital equipment and in-use are higher. The benefit of HPP over pasteurisation with heat (i.e C) is better flavour and colour, and nutritional content of the finished product with HPP. HPP is often used for smoothies and juices. Pulsed Electric Field Processing is a new method of preservation that uses brief pulses of strong electric field to process cells. This is still at an experimental stage; it inactivates microbes. One step (or more) further: Extraction (or biorefining as it is sometimes called) involves using more technical equipment to extract and purify specific components such as Water-soluble pigments and polysaccharides Fat-soluble pigments, vitamins and flavours Flavours and aromas Proteins and enzymes Fibre and pectin This is also a real opportunity for your produce, but involves significant investment in capital equipment as well as a different marketing focus and selling into a different business model. 56

6 Spinning cone extraction of flavours and aromas Other Resources: