Flour Food Safety White Paper
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FLOUR FOOD SAFETY By the Ardent Mills Food Safety Team Every year in the United States, one out the presence of Salmonella and E. coli Introduction of six Americans gets sick from foodborne in a variety of raw ingredients is well disease, resulting in approximately understood, many are unaware of the risks 128,000 hospitalizations and 3,000 deaths, of these microorganisms in one of the most according to the Center for Disease Control common ingredients of all: flour. (CDC, 2011). These surprising numbers are often the result of Salmonella and E. coli O157:H7, two microorganisms that have been the causative agents for foodborne outbreaks worldwide. Although Low-moisture foods and ingredients a validated kill step at the point of haven’t traditionally entered the production, such as baking or cooking, Foodborne discussion in terms of food safety, many other products may be at risk. primarily because these products don’t In 1952, an outbreak of Salmonella offer welcoming environments for Outbreaks Paratyphi B phage type 1 occurred in New microorganism growth. Yet, Salmonella South Wales, Australia, in which flour was has been implicated in several foodborne suspected, however, the microorganism outbreaks in low-moisture foods, including was not isolated from the flour (Dack, chocolate, powdered infant formula, raw 1961). almonds, toasted oat breakfast cereals, dry seasonings, paprika-seasoned potato In 2005, 25 people in the United States chips, infant cereals and peanut butter, were sickened with salmonellosis due according to the Grocery Manufacturers to cake batter ice cream. In this case, Association (GMA, 2004). a dry cake mix that was designed to be baked was added to a pasteurized sweet Flour, a low-moisture ingredient, has also cream base. Although flour was not the been associated with foodborne outbreaks. determined ingredient of contamination, While most flour-based products undergo the Food and Drug Administration (FDA) warned food manufacturers, retail and unbaked dough becoming ill. Thirty- Foodborne foodservice operators that Salmonella five patients were hospitalized, and ten is known to be present in flour and other developed life-threatening hemolytic- Outbreaks ingredients that might be listed on the dry uremic syndrome. (Neil et. al., 2011). Flour cake mix label. The FDA also commented suspected to be tainted with E. coli O157:H7 (continued) that dry cake mix should not be considered that was used in the cookie dough remains ready-to-eat (RTE) if it has not been the prime suspect for this foodborne illness processed to ensure it is safe to consume event. It should be noted that flour is without further cooking (FDA, 2005). typically purchased in very large quantities for commercial use in food products. If In 2008, flour traced back to the retail the flour contains pathogens, a single shelf was implicated in a Salmonella purchase can contaminate multiple lots outbreak in New Zealand. The evidence of finished product, which is a distinct was not conclusive, but the results of the possibility in the cookie dough incident. investigation indicated that individuals CDC investigators issued a report after the with the infection (especially children) outbreak that stated: “Foods containing were more likely to have eaten the raw flour should be considered as possible uncooked flour in homemade play dough, vehicles of infection of future outbreaks and raw cake and batter mixes. Sixty-six of STEC (Shiga toxin-producing E. coli) or cases of illness were reported, of which Salmonella infections. Food processors eight patients were hospitalized (Eglezos, should consider the use of pasteurized flour 2010). in ready-to-cook or ready-to-bake foods Salmonella is not the only pathogen that that are likely to be consumed without has been related to an outbreak caused cooking or baking, even though label by a product containing flour. In 2009, statements may warn against consuming prepackaged, ready-to-bake cookie dough uncooked product” (Neil et. al., 2011). was recalled due to E. coli O157:H7. The outbreak resulted in 77 consumers of The effects of flour milling and the mi- were analyzed for indicator microorgan- Microbiological crobiological quality of flour have been isms (aerobic bacteria, coliforms, E. coli, investigated both in the United States and yeast and mold) and Salmonella. In gener- Quality of Flour abroad to better understand the potential al, there were little differences in popula- food safety risks. Studies have shown that tions of aerobic bacteria, coliforms, yeast the milling process has little effect on the and mold across wheat types and season of microbiology of wheat flour other than milling. The overall average incidence of removing the outer bran of the wheat ker- E. coli and Salmonella was 12.8% (n=3,350) nel (Richter et al., 1993). Typically, the dry and 1.32% (n=3,040), respectively (Richter et milling process concentrates in excess of al., 1993). 90% of aerobic bacteria present on wheat A microbiological survey of milled cereal into the bran and germ fractions (Sperber grains was also conducted (mostly from et al., 2007). Flours with lower bran or ash 2003 to 2005) using routine data from content typically have the greatest reduc- North American dry-milling operations tion in microbial populations. (Sperber et al., 2007). For wheat flour, the Over the 1997-98 and 1998-99 wheat average levels of microbiological popula- seasons, raw wheat, in-process wheat tions were: aerobic bacteria at 4.41 log flour and finished wheat flour in Australia CFU/g, coliform bacteria at 3.64 log CFU/g were analyzed for various microbiological (Petrifilm method), E. coli at 0.84 log populations (Berghofer et al., 2003). E. coli CFU/g (Petrifilm method), mold at 2.58 log was not recovered in raw wheat; however, CFU/g, and yeast at 1.79 log CFU/g. Lev- tempered wheat was contaminated at 14% els of coliform bacteria and E. coli were and finished wheat flour was contami- lower when MPN methods were reported. nated at 1%. The level of E. coli in finished Salmonella was present in 0.14% of wheat wheat flour was 9 MPN/g. flour (n=4,358). In 1989, a total of 4,796 flour samples from various wheat types and seasons of milling There are two popular misconceptions indeed other areas in the lot may contain Misconceptions regarding flour and food safety risks. The pathogens. first is that pathogens such as Salmonella Accordingly, when testing for pathogens, are not of importance in low-moisture About Flour the probability of acceptance based on ingredients simply because these incidence rate is important. For a lot ingredients do not support the growth where 5% of the samples are contaminated, Food Safety of the microorganism. On the contrary, analyzing one sample will yield a 95% chance Salmonella does not need to grow to cause that you are accepting a contaminated lot. illness; in some instances infection has Testing 300 samples would give a less than occurred from consuming low-moisture 0.5% chance of accepting a contaminated lot products contaminated with less than 1 cfu/g (Table 1). The challenge is that testing to this depending on the host, the product, and magnitude is not realistic because it’s cost- the Salmonella strain (GMA, 2004). It’s also prohibitive. important to note that flour may be added to environments that are more receptive to growth, such as batters and mixes. Table. 1 The second misconception is that sample For lots with =.05 For lots with =.01 testing is a reliable means to assure (5% of samples are (1% of samples are contaminated) contaminated) food safety. Microbiological testing of a production lot of a food product does Probability Probability Probability Probability not guarantee the whole of the lot to be of of of of Acceptance Rejection Acceptance Rejection pathogen free. Production lots are usually n of lot of lot of lot of lot very large, so only a fraction of a lot can 1 0.95 0.05 0.99 0.01 be tested. Pathogens generally are not 5 0.77 0.23 0.95 0.05 15 0.46 0.54 0.86 0.14 homogeneously distributed throughout the 30 0.21 0.79 0.74 0.26 lot; they tend to clump together in groups. 60 0.05 0.95 0.55 0.45 Therefore, a sample that is tested for the 300 <.005 >.995 0.05 0.95 pathogen can return a negative result, when Probabilities of Acceptance of Lots Containing Indicated Proportions of Defective Sample Units. Since microbiological testing does not brownie/cake mixes and ready-to-cook Risk Mitigation: guarantee a safe food product in all meals. The SafeGuard Treatment and ® applications, it is important to understand Delivery System can also produce flakes, SafeGuard how to mitigate the risk of pathogen whole kernels/seeds and custom grain contamination in flour for use in ready-to- blends for RTE products. cook or ready-to-eat foods. Flour and For manufacturers, it’s also important Ardent Mills has developed a solution to consider how flour shipments will for flour: SafeGuard® Flour and the be received: in bag or bulk. Bagged SafeGuard SafeGuard Treatment and Delivery System. SafeGuard flour is treated in the bag SafeGuard’s lethality treatment maintains then shipped. Ardent Mills has also made Treatment and flour’s natural flavor, color, absorption, SafeGuard flour available in bulk, a first appearance and gluten functionality while for the industry. In designing the bulk achieving up to a 5-log validated pathogen SafeGuard Treatment & Delivery System, Delivery System Ardent Mills took a holistic approach reduction. Although treated flour options and considered all aspects of delivering have existed for some time, the effects on SafeGuard flour products to the customer.