research+on+chip+cooking

September 20, 2009
Stuff on frying From the heart foundation website [] It is well documented that most of the oil uptake in French fries occurs once the fries have been removed from the frying medium. As a rule of thumb 20% of the fat uptake occurs during frying and 80% during cooling (Mellema, 2003; Gertz, 2005a). On this basis the management of the foods once removed from the frying medium has the most potential to minimise fat uptake. The mechanisms of fat uptake during the cooling phase were explored by Vitrac //et al// (2000), whilst other researchers have evaluated and quantified practises by which to minimise uptake (O’Connor //et al.//, 2000; Mehta & Swinburn, 2001; Morley-John //et al.//, 2002; O’Connor //et al.//, 2002b). The importance of adequate draining and shaking/banging of the fried product cannot be underestimated. Mellema (2003) identified that the review of Mehta and Swinburn (2001) remains an effective discussion of factors that can be controlled by the operator. Thus, these recommendations should continue to be promoted within food frying operations.

Frying Temperature: The generally referenced and recommended temperatures are 175 -190°C. Within this range temperature variation has little effect on oil uptake (O’Connor //et al.//, 2000; O’Connor //et al.//, 2002b). In light of recent research relating to the formation of acrylamide, 175 – 180°C is now recommended as the frying temperature range for the finish deep-frying of fries. Cultivar, potato solids /specific gravity: It is well documented that potatoes with a higher dry matter typically result in lower oil uptake, and that this can be related to variety (O’Connor //et al.//, 2001). Increased solids content through genetic modification or plant breeding to modify the starch content are continued areas of interest (Harvey, 2005; Lister, 2005). Optimisation of the ratio of amylopectin: amylose is also a potential area for further research (Gertz, 2005a).

Pre-treatments in processing: Pre-drying of fries prior to frying reduces the surface moisture content and subsequently the fat uptake (Krokida //et al.//, 2001b; Mehta & Swinburn, 2001; Mellema, 2003). Pre-drying is common practice within the French fry processing industry.

While results from a national survey (1998-99) of fast food outlets in New Zealand, found a negative association of chip total fat content and the amount of fatty acid C18:2 (linoleic acid) in the frying medium that was close to significance (Morley-John and Young, 2004), the general conclusion is that there is no significant effect on oil uptake by any of these factors.

In conclusion, no significant changes to techniques for either preparation, frying or post frying handling have been made in the past five years in relation to minimising oil uptake. Understanding of the mechanisms involved has improved significantly and it is expected that this should assist future developments. It is anticipated that on-going research will be focussed on the reduction of oil uptake, possibly with the development of practical and economic coatings for fries. In the mean-time best practise techniques post-frying should continue to be promoted.

(Adapted from the recommendations of (MacKay, 2000; Mehta & Swinburn, 2001) - Choose thick cut (≥ 12mm), wedges; not shoestring style - Choose straight-cut; not crinkle cut - Keep French fries free of surface water - Do not thaw frozen French fries before frying  - Home-made French fries, use low moisture potatoes (specific gravity ~1.1). - Cook French fries between 175 – 180°C - Have French fries in the vat for as little time as possible - Use a catering thermometer to regularly check that the vat thermostat is accurate - Use a temperature overload switch (195°C) to prevent overheating - Minimise the temperature drop in the vat: do not overload the French fry basket recommended volume ratio of French fries: fat is approximately 1:6 place baskets in alternate vats.
 * III. Recommendations – frying techniques**
 * French fries**
 * Temperature**

- Use a good quality, refined frying medium from a reliable supplier - Skim after each batch, filter daily (for some operations filtering by a professional company using filter aids is a viable alternative) - Keep the frying medium topped up with fresh frying medium - Change frying medium as required by turnover and physical indicators of the frying medium and French fries - Refresh frying medium before peak periods - Cover vats overnight and during quiet times - Clean vats thoroughly, ensure elements are free from build-up - Ensure vats are thoroughly rinsed and dried before refilling - Use a separate vat for French fries - Use as small a vat as practical - During quiet periods turn additional vats off or down - Salt French fries well away from the vat – ask customers if they want salt and always use iodised salt.
 * Frying medium**

- Do not overcook French fries – cook 3 – 4 minutes - Bang or shake the basket (at least twice) immediately after removing from vat; hang basket above the vat and drain for a minimum of 20 seconds.
 * Frying/Drainage Procedure**

Shifts in the New Zealand market for deep-fat frying have occurred over the past five years. Results from a national survey conducted in 1998-99 (Morley-John & Young, 2004) indicated that 82% of the frying fats for foodservice and industrial use were tallow or tallow-based blends. In 2005, industry representatives have stated that whilst tallow still remains the most common foodservice and industrial fat, there has been a marked increase in the use and interest in vegetable fats and oils. The replacement of tallow with palm olein is the most predominant trend. This allows claims as to the use of ‘vegetable oil’, and ‘cholesterol-free’, but unfortunately does not address the key issue of saturated fat consumption. Neither palm, nor cottonseed oils meet the Heart Foundation’s recommendation for frying mediums. The market for the high monounsaturated oils (such as Sunola™ and Liquid Gold™) remains relatively small, however there is increasing consumer interest and demand and companies marketing these oils are supporting growth with the use-of-point of sale materials
 * 1.1** **Frying mediums in New Zealand**

The market remains divided into distinct market groupings: – fast food chains such as McDonald’s Restaurants (NZ) Ltd., KFC, Burger King ; – independent operators. In general, the fast food chains are very conscious of consumer pressure for more healthy food and will typically specify or have their own proprietary fat blend manufactured. Amongst the independents there is a small group who are very health and quality focussed and who will buy quality frying mediums with good nutritional properties. Confidential industry sources, consistently agree that by far the largest group of independents are those that purchase purely on price, with performance (long-life) a secondary factor (Anon, 2005b). This group almost certainly will purchase the lowest priced product – typically tallow.

French fry manufacturers also reported significant changes in the types of frying mediums used in manufacture. Although tallow remains popular and is used to make most foodservice fries, customer demand, particularly from the fast food chains and export customer, has resulted in a change to vegetable frying mediums where required. According to confidential New Zealand industry sources, French fries manufactured for foodservice markets in Asia are most often manufactured using palm or palm-based frying mediums. This is consumer driven as in most Asian countries the flavour of beef tallow is not preferred, even if it is only used at the par-fry stage (Anon, 2005b).
 * 1.2** **Frying mediums used in the manufacture of French fries**

Typically the French fry manufacturers have on-site facilities to allow storage of multiple frying medium types (tank farms) and they process according to customer requirements. In addition to tallow, vegetable frying mediums now regularly used as the frying medium in the manufacture of French fries include: – sunflower and sunflower blends, – canola and canola blends, – palm olein and palm olein blends, – cottonseed and cottonseed blends The proportions used differ between manufacturers, according to their customer base.

In early 2004 //Consumer// randomly tested the fat content of French fries bought at outlets (chains and independents) in an Auckland suburb (Allan, 2004b). Results were varied and the use of vegetable oils did not necessarily relate to a low ratio of saturated to unsaturated fats. Unspecified vegetable blends were used at six of the 12 (50%) outlets surveyed, beef or beef-based blends at four of the 12 (33%) including McDonald’s Restaurants (NZ) Ltd. at that time, with the remaining two outlets specifying palm oil. In the survey portion size varied from 98g (Burger King) to 370g (Independent). This is consistent with the patterns of serving size discussed by MacKay (2000). The total fat content on a percentage basis also varied significantly from 4.5% (Pizza Haven) to 16.9% (McDonalds). Fat content and serving size were not correlated, however in the worst example (an Independent using a vegetable blend) a massive 55g of fat was present in the single serving size. The findings of this survey suggest a large variation in the fat delivery (quality, nutritional value and quantity) from commercial French fry operators still exists.
 * Fast Food Outlets**

A 1996 survey of 241 take-away food outlets in New South Wales found that only 10% followed best practice chip cooking and 50% failed to follow any one of the three key tips. shoestrings. thermostat and thermometer of 16°C. Forty-six percent relied on the thermostat for the right temperature to fry and 33% considered the fat hot enough by experience. Seventy-eight percent turned off the dial to lower the temperature during slack periods. In 17% of cases it was found that the shortening had deteriorated beyond what is recommended for cooking (food oil sensor reading above 4) 16 A random survey of 150 takeaway outlets throughout New Zealand was conducted during 1998/199916. This involved 27 chain outlets (eg McDonald’s, Burger King, KFC, pizza) and 123 independent fish and chip shops. Over one third of operators did not have English as a first language, particularly independent operators. Mandarin or Cantonese was the most common first language after English. The majority of participants had learned their deep-frying techniques through on-the-job training. This was mainly a formal training process for chain operators (89%) and an informal process for independent operators (92%). Most operators felt they could influence the health of their customers through reducing the fat content of the foods they cooked. The major barrier to achieving this was lack of knowledge about healthier cooking practices, with cost and customer preference less of a barrier. The key draft results of the analysis follow. content of chips from chain outlets was significantly higher than those from independent outlets (12.9% versus 11.2%), possibly due to the use of thinner chips and/or crinkle cut chips by chain outlets. Multivariate analysis showed that four factors explained 24% of the variance in fat content – chip size, fat temperature, serving size, crinkle cut. Every 1mm increase in chip size was associated with 0.18 percent point decrease in fat content. Every 1% increase in fat temperature was associated with 0.04 decrease in percent points in fat content. Using crinkle cut chips adds 1.3 percent points of fat content. The national survey found 16 the average scoop of chips was 300g and the average fat content was 11.5% giving 35g fat per scoop. ESR estimated that the total fat content consumed with the average meal of fish and chips when fried in animal fat is 48g and in plant oils is 41g14. The Heart Foundation17 states there is 95g fat in a meal of 2 pieces of battered fish with chips while a Consumer test8 found 136g fat in a meal of 2 fish and a large scoop of chips. The estimated trans fatty acid content of potato chips fried in beef dripping is 5.6g/100g fatty acids which is a lower percentage than butter or margarine18. Long thin fries have consumer appeal and are identified with McDonald’s. Research groups have shown that KFC chips are very popular, perhaps the most popular type of chip and this could be because of the size and the sprinkled flavour.
 * 2.0 Current Practices in New Zealand**
 * • Surveys indicate many operators are not cooking food at the correct temperature.
 * • The fat content of chips varies with a general level of 10-15% fat and 16% for
 * • There is a growth of quick-service restaurants at the expense of independent takeaways.Auckland Healthcare completed a survey of 24 fish and chip shops in Auckland to investigate the uptake of fat and cooking methods. The fat content of regular-sized chips varied from 6.4% to 16.3%. Crinkle-cut chips of the same size were higher in fat. Thirteen percent of chips were cooked within the survey recommended temperature range of 180-185°C. Many takeaway bar operators (75%) did not know the correct temperature to cook chips, with 58% considering the optimum temperature to be 160-180°C. In 54% of takeaway bars the thermostats were incorrectly calibrated with the mean temperature difference between the
 * 2.1.2** **National Survey of Takeaway Outlets**
 * //Fat content chips//**
 * • The mean fat content of chips was 11.5% with a range of 5-20%.
 * • Chain outlets used significantly more best-practice operating techniques which tend to reduce the fat content of chips and the quality of the frying fat. Despite this, the fat
 * //Cooking Temperature & Post-cooking Techniques//**
 * • The mean frying temperature used was 182ºC ranging from 136ºC -233ºC.
 * • Sixteen percent of operators fried within the recommended temperature range of 180- 185ºC. In 37% of chains and 43% of independent outlets, the stated optimal cooking temperature was between 175ºC and 190ºC.
 * • In most independent outlets there was a considerable deviation between the thermostat dial setting and the actual cooking temperature, with only 29% of the independent outlets having a temperature deviation of less than 5%. Chains had a much smaller temperature deviation.
 * • Temperature was negatively associated with fat content in the multivariate analysis, with chips cooked at a lower temperature having a higher fat content.
 * • Fifty-six percent of operators used appropriate post-cooking techniques (bang or shake, drain for 20+ seconds) to reduce the fat content of chips.
 * //Care of Fat//**
 * • Compared to chain outlets, fat used in independent outlets was older, filtered less often and discarded less frequently.
 * • Chains were bigger operators and could therefore afford to operate vats that were used for cooking chips exclusively, while independents also cooked other food in the vats.
 * • The mean fat age of 6.3 days for independents indicates they did not meet the general recommendation that fat older than 5 days should be discarded.
 * • As a measure of fat degradation, a free fatty acid value above 2.5% was recorded by 54% of the outlets, and 5% of outlets had a polar compound value >25%.
 * • Observation of darkening fat colour was considered by operators as the most important indication of deteriorated fat, with more chains using various calibrated colour tests.
 * • Most operators skimmed the fat, and chain outlets filtered at least once per day. Forty seven percent of independent operators filtered only every 1-2 weeks or not at all.
 * • Seventy-one percent of operators covered fryers when the outlet was shut.
 * • Seventy-six percent of independent operators reduced the fat temperature during quiet times.
 * • Almost all outlets cleaned vats regularly, but only 60% used cleaning agents or detergents and only 3% rinsed with an acid solution (eg vinegar).
 * //Chips//**
 * • Chains used significantly more frozen products (92% of chains) than independents (40%). Thirty-six percent of independents used chilled chips and 24% used home-made chips.
 * • Chain outlets were more likely to use 10mm or 7mm wide chips (79%, 41% respectively) than independents who generally used 13mm chips (63% of those using commercial chips). The mean width of home-made chips was 15.6mm.
 * • Most operators used straight-cut chips.
 * • There was no significant difference between frozen and chilled chips, nor between the cooking of chips from frozen/chilled/room temperature with respect to fat content.
 * • Twenty-six percent of independents pre-fried chips (most were home-made chips).
 * //2.2 Fat content of chips//**