Martin G. Scanlon1* | Helen H. Tai2
The Canadian potato industry enjoys an enviable position in the global food industry. This is especially true with respect to the value-added processing sector, where a Canadian-based manufacturer, McCain Foods, can boast that one in three French fries consumed globally emanates from a McCain’s plant1. Despite the position of potatoes as an economic powerhouse in the Canadian agricultural and manufacturing sectors, a number of pressures challenge the Canadian potato industry, demanding creative research and innovation solutions. In particular, the strong growth in frozen potato products that fuelled the growth of a sophisticated value-added industry in North America and Europe is now effectively curtailed on these continents2. Part of the reason is the perception that the relatively high carbohydrate and fat content of processed potatoes is contributing to the developed world’s prevalence of metabolic syndrome. Another challenge, in a manufacturing environment that is increasingly emissions-oriented, is that industries that consume large amounts of water and energy must be pro-active in altering manufacturing practices to reduce their environmental footprint. Nevertheless, innovations in the development of potato varieties and innovations in production and processing practices that target sustainability will ensure that this sector of Canadian agriculture maintains its position as a food industry leader. As will be apparent from this overview, variety development, a key priority within the national research strategy3, is a pivotal element in addressing many of these innovation targets.
Frozen Potato Products
The massive growth of the quick service restaurant (QSR) industry in the 1960s-80s was founded on a staple of high-quality French fries that could be prepared in a short time1,2. This in turn drove the growth of the manufacturing industry where frozen potato products were made to exacting food safety and food quality specifications. In attaining this, manufacturers successfully linked a number of different unit operations to ensure the delivery of a high volume of consistently made product4. Today, the processing industry utilizes over 60% of the potatoes produced in Canada5.
The three predominant French fry quality standards for the needs of the QSR industry are colour, texture and flavour. Few new varieties have met the standards for French fry processing, and so processing in North America is built around a small number of varieties. In addition, tubers need to be long and oblong shaped and have uniform size. In developing new varieties, traits for compatibility for industrial processing are also selected, including high dry matter (solids) and suitability for cold storage. Cold storage at 2 – 4 °C suppresses storage diseases and sprouting to allow for a year-round supply of potatoes for these capital-intensive manufacturing facilities. Unfortunately, potatoes respond to cold temperatures by converting starch to sugars in a process called cold-sweetening6. The resulting Maillard reaction of those sugars at the high temperatures of frying leads to undesirable darkened fry colour. Resistance to cold-sweetening is a key trait in the selection of potato varieties for both French fry and chipping markets.
The majority of potato breeding in Canada is carried out by Agriculture and Agri-food Canada (AAFC). Breeding activities are centered at the Potato Research Centre in Fredericton, NB and the breeding farm located at the Benton Ridge Substation. AAFC also breeds for varieties for western growing regions at Lethbridge, AB and the Vauxhall, AB substation. As well as developing varieties for French fry production, AAFC is also actively developing varieties for chipping and fresh market utilization. Developing varieties with disease resistance is of high interest and recent releases from AAFC have featured resistance to golden nematode, wart, common scab and late blight. A small number of private breeders are also active in Canada, forming the Canadian Private Potato Breeders’ Network. These private breeding programs target specific traits or markets including small potatoes, table potatoes, chipping and late blight resistance.
Within the frozen French fry manufacturing plant itself, continual improvements in process efficiency have occurred through improvements in the specific technologies for washing, peeling, slicing, blanching, drying, par-frying, freezing and packaging. Ongoing diversification of product offerings from the industry has led to the introduction of additional unit operations for batter application (to improve fry texture) or flavour enhancement (through electrostatic spray application). As mentioned above, the Maillard reaction impairs product colour, but it is also a food safety concern due to increased levels of acrylamide7. Therefore, there has been some modification of both unit operations and ingredients to address this concern. For example, vacuum frying has been investigated as a potential means of reducing acrylamide formation, with the additional advantage that it reduces oil uptake8.
One area of continuous innovation that continues to drive process efficiency and improved recovery in the industry is in sophisticated process control tools and manufacturing optimization software. Of note is the elimination of defects, driven primarily by the introduction of high-speed digital imaging technologies9. The ability to capture and process data at nanosecond timescales ensures that the deployment of near-infrared10 and hyperspectral imaging technologies11 will continue to drive process innovation.
Attaining a consistent optimal texture in frozen French fries for QSR requires removal of a large amount of water during manufacture. The energy costs associated solely with the latent heat of evaporation are considerable, and to this must be added the in-plant energy costs of heating water and oil and doing work to remove heat during the freezing operation. As a result, the potato processing industry is committed to strategies to harvest heat at various points during manufacturing and to capture waste solids so that they can be used for sustainable energy purposes such as biogas engines.
Water is a vital process aid for multiple operations during manufacturing. To reduce aqueous emissions from manufacturing plants and to reduce overall water consumption, various approaches have been employed. Examples include reusing the effluent of one operation in another operation whose water quality requirements are less critical, and devising creative separation technologies for removal of solids from water streams. For instance, using such approaches, Lamb Weston has formulated a 2020 objective of reducing their water usage per unit mass of finished product by 50%12. In achieving this, additional co-product streams (such as high quality ungelatinized starch) can be developed and these will also improve overall plant efficiency.
Although Atlantic and Prairie provinces predominate in the production of frozen potato products, Ontario is an important producer of potato chip (crisp) offerings. Chipping potato varieties need to produce round tubers with high dry matter that will fry to a light chip colour to meet standards for industrial processing. Chip potato breeding therefore involves selection of lines with low-reducing sugars and cold-sweetening resistance. There is also a research focus on storage practices that minimize the development of reducing sugars13. Novelty chips with pigmentation have also hit the market, including chips with red and purple colouring. The coloring is from naturally produced anthocyanin pigments that are also found in berries. Potatoes have genetic variation in colour, intensity and patterns of pigmentation. Recent products include chips with star patterns due to pigment deposition in vascular tissues of the potato tuber.
Fresh Minimally-Processed Potato Products
Although health concerns may be slowing the consumption of chips and French fries, consumer convenience in food offerings is not a trend that is abating. Therefore, there has been significant growth in fresh ready to heat potato products. Some examples are cut frozen flavoured products and non-frozen items such as steam-in-the-package and refrigerated flavoured mashed potato products. Increased culinary interest in the potato is also driving growth in this sector. Often, market interest is variety specific due to specific flavour or appearance demands, and this is reflected in the outcomes of potato breeding programs. For example, in 2013, nine of the 14 selections released from AAFC were for the fresh market. Traits screened for the fresh market include boil and bake texture and flavour and flesh colour (ranging from white to yellow). Tuber appearance is important for the fresh market and breeders have to select for low tuber defects and uniform tuber size. Because of the importance of appearance, variety releases for the fresh market have included selections with red and purple skin and skin with splashes of pink around the eyes. Selections with small tuber size (also referred to as creamers) are also of interest for the fresh market. The fresh market for potatoes is now at 25% of the industry5. The growth of this sector has also driven research to tackle safety and quality concerns associated with these minimally-processed products14. There have also been innovations made in packaging technologies, particularly for those products that rely on modified atmospheres for shelf-life extension.
Tubers are the consumed part of the potato plant, but they are also used to clonally propagate the crop. These seed tubers can potentially carry diseases from the previous season. As such, the health and quality of the potato seed supply in Canada is monitored and regulated by a seed certification program to protect the industry. The Canadian Food Inspection Agency (CFIA) is responsible for the administration of the Seeds Act and Regulations and carries out inspections for the certification of seed quality. Potato seed growers are required to meet higher standards of production to maintain low levels of quarantined pests. Of particular concern to the Canadian seed growers in recent years are Potato Virus Y (PVY), potato wart, golden nematode and cyst nematode. Seed potato is sold at higher prices, which compensates for the costs of maintaining high standards for production on seed farms. In 2010, 15% of the potatoes produced in Canada were for the seed market with the exported seed potato having a value of $36 M from 18 countries5.
Maximizing Value from Canadian Potatoes
Although the direct production of food products from potatoes dominates the Canadian potato sector, the continual need to add value to Canadian agricultural resources has driven the development of alternative uses for potatoes. Given the high starch content of potatoes, there has been interest in the development of alternative food and non-food products from potato starch. Potatoes have two types of starch polymers: amylose and amylopectin. Altering the amount of each polymer in different potato varieties leads to different physiochemical properties of the starch15. Genetic modification has been used to produce a pure amylopectin potato, Amflora16 and a potato enriched in amylose17 that are specifically targeted for industrial use. Industrial applications for potato starch produced from these and other varieties have included thickeners, bioplastics, pharmaceutical fillers, binders, disintegrants and gelling agents18. Industrial starch production from raw potato occurs predominantly in Europe and China. In Canada, starch is produced mainly from recovered cuttings and filtrate from French fry and chip processors. The BioPotato Network has been active in adding more value to this important potato resource. This Canadian-based network, funded by the AAFC Agricultural Bioproducts Innovation Program from 2008-201119, developed starch modification processes for industrial applications ranging from resistant starches for the food and feed industries to bioplastics and pharmaceutical excipients. The BioPotato Network has also investigated the development of health bioactives and biopesticides from potatoes.
Coloured Flesh Potatoes
Anthocyanins, naturally-occurring pigments responsible for pink, red and purple pigmentation in plants, have been shown to prevent some human diseases20. Health benefits of anthocyanins are attributed to their anti-oxidant activities. Potato anthocyanins in particular have been associated with reducing growth of cancer cells21. The anti-oxidant capacity of pigmented flesh potatoes was as high as 35% of berries. The health benefits associated with anthocyanins have increased interest in breeding potato varieties with intensely red and purple pigmented flesh22. Pigmented flesh selections recently released by AAFC have targeted the French fry and table markets. Additional utilization of pigmented flesh potatoes include processing into dried granules and flakes that retain high levels of anthocyanins after processing23. Addition of dried pigmented potato granules and flakes to processed food products provides a way to enrich foods with beneficial anthocyanins.
Low GI Potatoes
Glycemic index (GI) is used to measure the rise in glucose level after consuming the food24. Health concerns for obesity, cardiovascular diseases and diabetes have increased demand for low glycemic index foods. Potatoes, like other carbohydrate-rich foods, tend to have high GI. Variation in GI has been found for different potato varieties and for different cooking methods25,26. Genotype by environment variation in the digestibility of potato starch has also been described27. The GI of potatoes can be reduced through breeding for potatoes with less digestible starch content so that niche varieties for low GI diets can be developed. AAFC has recently released one low GI selection.
Although Canada’s potato production and processing industries face some challenges, potatoes remain a strong component of Canada’s agriculture and value added manufacturing industries. Innovations that will ensure the sustainability of a valuable value-added potato sector are key to the industry’s future prosperity. These innovations will be required in plant breeding, agronomy, and in storage and manufacturing facilities. Marketing strategies that emphasize the nutritional quality, as well as the convenience of processed potato products, are also needed to ensure vitality for the industry. Because potatoes are a rich source of nutrients and carbohydrate polymers, the prospects for diversification of products in the potato industry are good.
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1Department of Food Science, University of Manitoba, Winnipeg, MB, Canada
2Agriculture and Agri-food Canada – Potato Research Centre, Fredericton, NB, Canada
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