All three treatment levels successfully inactivated all L. monocytogenes regardless of the inoculation levels, while 300 ppm was needed for inactivation of all Salmonella Thompson cells. When E. coli O157:H7 was inoculated at the high level, 300 ppm-h treatment did not inactivate all E. coli O157:H7. Results from Carter et al. showed that the sulfur treatment efficacy was determined by pathogen types. One significant drawback associated with gastric sulfur treatment is that this treatment is not environmentally friendly. Using sulfur dioxide treatments can release SO2 emissions into the atmosphere, which can easily partition due to it being a highly water-soluble gas . Craig states that this production of atmospheric SO2, such as from fumigation of produce, can cause many types of environmental damages, including acidification of water, injury to plants, and harmful sulfate particles accumulating in animals. Fumigation is the largest use of SO2 in the state of California and is showing a trend of increase for the future.Another method for applying sulfur is to soak fruits in solutions of sodium metabisulfite . To do so, sodium metabisulfite is first dissolved in cold water and then fruits are submerged in the solution and soaked for approximately 10 min . After that, fruits are drained and are ready to be dried . evaluated the antimicrobial effects of such treatments by using peaches inoculated with 7.81 log CFU/g of L. monocytogenes. Results showed that the reduction of L. monocytogenes was 1.13 log CFU/g greater when the peaches were exposed to 4.18% sodium metabisulfite prior to drying, compared to untreated peaches . The use of acids, in the form of ascorbic acid, citric acid, or lemon juice, is also a common pre-drying treatment for dried fruits . Application of these acids is very similar to application of sodium metabisulfite, tomato grow bags in which fresh fruits are soaked for approximately 10 min in a dilution of the acid in cold water. For every 1000 mL of cold water, recommended amounts of citric acid and ascorbic acid are 5 g and 34 g, respectively .

Lemon juice can be mixed with equal parts of water; 1,000 mL of solution is enough for approximately 10 L of fruit . DerricksonTharrington et al. evaluated the antimicrobial effect of these different acid pretreatments by using apple slices inoculated with 8 log CFU/g of E. coli O157:H7. Results showed that the reduction of E. coli, when compared to untreated apples slices was, 3.60, 3.60, or 4.00 log CFU/g greater when the apple slices were exposed to 1.7% citric acid, 2.8% ascorbic acid, or 50% lemon juice respectively .Another pre-treatment for dried produce is blanching. While vegetables are more commonly blanched, fruits can also be blanched. This pre-treatment is often used to prevent discoloration and oxidation . Blanching can be performed with steam or direct submersion in water. In both cases, water should be placed in a container and brought to a boil. For steam blanching, the water should be no more than 5 cm high, and the prepared fruit should be placed above the water in some sort of permeable container . For water blanching, there should be enough liquid to cover the fruit, which can be added directly. For both types of blanching, the container of water should be covered once the fruit is added and left to blanch for the time recommended for each specific fruit. Blanching often only lasts several min. Andress and Harrison propose blanching fruits such as apples for 3-5 min, while peaches should be blanched for 8 min. Once done, the fruit should be dropped in cold water to cool down, which stops the blanching process . Post-Drying treatments: A post-drying treatment that can be used on dried fruits includes ozone fumigation. Though commonly used in fresh produce postharvest, ozone fumigation can also be used to treat dried fruits. An ozone generator and a chamber to hold the dried fruits while applying the ozone are needed . Oztekin et al. looked at the effect of ozone fumigation on the microflora of dried figs. Aerobic mesophilic counts dropped from 2.57 to 1.59 log CFU/g on dried figs fumigated with 10 ppm ozone for 5 h . Coliform counts dropped from 1.46 to 0.00 log CFU/g .

Najafi and Khodaparast looked at the effect of ozone fumigationon the microbial populations on dates. Staphylococcus aureus counts dropped from 3.52 to 0.41 log CFU/g on dates fumigated with 5 ppm ozone for 45 min . Coliform counts dropped from 3.54 to 0.44 log CFU/g . Storage. Based on the survey results, most dried fruits are stored in bulk either under refrigerated or frozen storage. A wide variety of containers can be used for storage but all are usually airtight. One packaging technology used for dried fruits is modified atmosphere packaging . MAP works by replacing the air inside of the packaging of a final product with a mixture of gases that help preserve the quality and shelf life of the food . Passive MAP can be achieved by using a permeable packaging material that allows a certain percentage of different gasses to enter and leave the packaging . Randelovic et al. exposed packaged dried apricots to a modified atmosphere of 30% carbon dioxide, 60% nitrogen, and 10% oxygen, and monitored the quality of the peaches over 12 months. Across all types of packaging materials used , the dried apricots had less change from their original aw, moisture, and polyphenol content when packaged with MAP compared to normal atmospheric conditions . While there are limited studies on the impact of MAP on pathogens in dried fruits, MAP is often used to control foodborne pathogens . Oliveira et al. used passive MAP packaging on E. coli O157:H7 inoculated shredded lettuce. After 10 d of storage at 5 °C, the initial E. coli level of 4.48 log CFU/g dropped by 1 log CFU/g . Dried fruits can last up to a year in refrigeration depending on the fruit and processing .

One response in the survey stated that dried fruits can last indefinitely under frozen conditions. However, limited studies have evaluated impact of storage conditions on the behavior of pathogens and bacterial populations of dried fruits. Beuchat and Mann looked at the effect of storage temperature on the survival of Salmonella in dried cranberries and raisins. When stored at 4 °C, Salmonella inoculated on dried cranberries dropped from 6.87 to 1.8 log CFU/g and Salmonella inoculated on raisins dropped from 7.01 to 4.76 log CFU/g after 42 d . When stored at 25 °C, no Salmonella was detected on either of the dried fruits by the end of 42 d . Hyun et al. looked at the effect of storage temperature on the microbial populations of dried persimmons. With an initial mesophilic bacteria count of 4.60 ± 0.26 log CFU/g, dried persimmons stored for 70 d at 5 °C had an average of 3.18 ± 0.75 log CFU/g of total mesophilic bacteria, while dried persimmons stored at 25°C had an average count of 1.64 ± 1.50 log CFU/g . The initial coliform count was 1.92 ± 0.47 log CFU/g, and the average coliform count over the 70 d was 0.87 ± 0.48 log CFU/g at 5 °C and was 0.77 ± 0.58 log CFU/g at 25 °C . These studies suggest that the survival of bacteria is better at refrigerated temperatures compared to ambient temperatures. In summary, there are many drying or pre- and post-drying treatments can be applied during the preparation and storage of dried fruits. However, grow bags garden the efficacy of many of these methods have not been validated . For many processors, effectiveness of their techniques does not rely on agreed-upon values, but rather the know-how of the processors before them. Knowing when dried fruit is ready is often based on visual cues. Additional research is critically needed in order to bridge the knowledge gaps associated with the preparation and storage of dried fruits and address the concerns associated with the microbial safety of dried fruits. Foodborne pathogens of concern. According to the Centers for Disease Control and prevention , approximately 48 million people in the United States get sick from foodborne pathogens every year . Produce is the largest cause of foodborne illness in the US, and accounts for approximately 39 billion dollars in economic loss every year . Some of the top foodborne pathogens associate with fruits include Salmonella, Shiga toxin producing E. coli, and L. monocytogenes. Salmonella is estimated to lead to approximately 19,000 hospitalizations per year and E. coli O157:H7 is estimated to lead 2,100 hospitalizations per year; both pathogens are amongst the top five pathogens contributing to foodborne illness resulting in hospitalization . L. monocytogenes is estimated to lead to approximately 1,500 hospitalizations per year, and has a high mortality rate, causing an estimate of 255 deaths per year . Salmonella. Salmonella, a member of the family Enterobacteriaceae, is a gram-negative, non-spore-forming bacteria that can cause salmonellosis in humans and is one of the most common foodborne pathogens . While Salmonella can grow at temperatures ranging from 5.2 to 46.2 °C, the bacteria’s optimal growth temperature ranges from 34 to 40 °C . The optimal pH for growth of Salmonella is 6.5-7.5, while the overall pH range for growth is 3.7- 9.5 . Salmonella can grow in foods with a water activity of 0.94 or higher .

The reservoir of this bacteria is usually the gastrointestinal tract of animals, such as livestock . Contamination with fecal matter is what causes Salmonella to be found in so many other foods . While a few serotypes of the bacteria can cause typhoid fever, most disease-causing serotypes of Salmonella cause an infection in humans that is referred to as salmonellosis. Salmonella infects by attaching to and entering intestinal epithelial cells with the use of fimbriae and the injection of proteins via a type-three secretion system. Symptoms include diarrhea, fever, and abdominal cramps. Most people who get infected recover within a week with no need for hospitalization. However, the elderly, infants, and people with compromised immune systems have a greater chance for severe illness that may lead to rare chronic conditions or death . Salmonella is one of the leading causes of foodborne illness around the world. According to the CDC, Salmonella bacteria causes an estimated 1.35 million infections every year in the United States. Outbreaks in the past several years have come from a range of foods, including poultry, ground meats, fresh produce, nut butters, mushrooms, and grain-based snacks . Though the variety of foods linked to Salmonella outbreaks is wide, Salmonella is often associated with contaminated eggs and poultry. The association with eggs is due to an increase in illness from Salmonella Enteritidis in the USA during the 1980s to 1990s and the majority of outbreaks from this Enteritidis serotype were from undercooked eggs . The association of Salmonella with poultry, particularly chicken, is due to the high rate at which poultry tests positive for Salmonella. However, the serotypes of Salmonella most frequently isolated from poultry are not the same as the most frequently isolated from humans with salmonellosis .Salmonella has been associated with many low-moisture food outbreaks. As shown in Table 2, in 2001 a large outbreak of 168 cases of salmonellosis was linked to consumption of raw almonds . This multistate outbreak led to the realization that there is a need for reassessment of the safety associated with consumption of raw low-moisture foods . Salmonella is a particular concern in low-moisture foods because of its increased thermal resistance in dry conditions . The mechanisms by which Salmonella survives under dry conditions is not completely understood, but multiple mechanisms are believed to have an impact on its survival. One such mechanism is filamentation. It has been shown that in culture, Salmonella can filament if exposed to less than optimal growth conditions . However, filamentation has not been shown to occur in solid food matrices, so this mechanism does not explain increased survival of Salmonella in low-moisture foods . Osmoprotectants may help protect Salmonella from desiccation. These are compatible solutes that help maintain osmotic balance in the cell and prevent denaturation of proteins and lipids . Salmonella uses the transport systems ProP, ProP, and OsmU to bring osmoprotectants that it cannot make itself, such as glycine betaine, into the cell . Other mechanisms that may help to combat osmotic shock include outer membrane proteins , biofilm formation, fimbriae, and sigma factors .