Efficacy of ATP Monitoring for Measuring Organic Matter on Postharvest Food Contact Surfaces.

ABSTRACT: The Food Safety Modernization Act, specifically the Produce Safety Rule, requires growers to clean and sanitize food contact surfaces to protect against produce contamination. An ATP monitoring device is a potential sanitation tool to monitor the efficacy of an on-farm cleaning and sanitation program that could help growers meet regulatory expectations mandated by the Produce Safety Rule. This ATP monitoring device uses bioluminescence to detect all ATP (found in bacteria and produce matter cells) from a swabbed surface. Because little work has been done to test the efficacy of these tools under postharvest conditions, the present study evaluated ATP measurement for postharvest food contact surface cleanliness evaluation. Concentrations of leafy greens (spinach, romaine, and red cabbage, with or without Listeria innocua) were used as organic matter applied to stainless steel, high-density polyethylene plastic, and bamboo wood coupons to represent postharvest food contact surfaces. The ATP levels on the coupons were then measured by using swabs and an ATP monitoring device. Results showed that the concentration of L. innocua and leafy greens on a food contact surface had a highly significant effect on the ATP monitoring device reading (P < 0.0001). The ATP monitoring device had a lower limit of detection for L. innocua at 4.5 log CFU per coupon. The type of leafy green on a food contact surface did not affect the ATP reading (P = 0.88). Leafy greens with added L. innocua had a higher ATP reading when compared with saline and L. innocua, demonstrating the presence of leafy green matter contributes to ATP reading when combined with L. innocua. The different food contact surfaces had different ATP response readings (P = 0.03), resulting in no detectable levels of bacteria and/or leafy green material from bamboo wood surfaces (P = 0.16). On the basis of our results, the ATP measurement is an appropriate tool to measure produce or bacterial contamination on stainless steel or high-density polyethylene plastic surfaces; however, it is not recommended for wood surfaces.

Sodium reduction strategies through use of meat extenders (white button mushrooms vs. textured soy) in beef patties.

Lowering the sodium content in meat products, particularly in beef patties, can be challenging because sodium plays many functional roles in these products. Meat extenders can contribute to lower sodium content by imparting complementary flavors while reducing caloric and sodium content. A systematic comparison of two meat extenders, namely mushrooms and textured soy (TSP) in terms of physical and sensory characteristics, is presented herein. The physical properties of the samples suggested that the use of mushroom and TSP extender would perform statistically similar to an all-meat control depending on the level of substitution. Hedonic sensory analysis showed meat extension using mushrooms yielded liking scores more similar to the all-meat formulations than TSP in reduced sodium applications. The results of this research suggest that mushrooms have the potential to be successfully incorporated into reduced sodium meat products to provide a healthier product.

Utilizing Mushrooms to Reduce Overall Sodium in Taco Filling Using Physical and Sensory Evaluation.

This project investigated the use of integrating mushrooms into beef taco filling as a means to reduce overall sodium for food service applications. Initial product development used physical characterization analysis (moisture, yield, color, and texture) to determine initial threshold of mushroom inclusion with minimal differences against an all-meat control. Increasing mushroom inclusion increased moisture and yield before draining but decreased yield after draining, lightness, redness, and texture. Results showed that inclusion under 50% by weight minimized physical attribute deviation from an all-meat control. Additional physical analysis investigated a variety of other factors (mushroom type, blanching, and particle size) to determine if other attributing mushroom characteristics would yield statistical similarity to the all-meat control. Results showed that a formulation containing up to 45% mushrooms can be integrated into beef fillings using un-blanched, white button mushrooms with small grind (1 to 5 mm), which maximized mushroom usage while minimizing differences from the all-meat control. Additional sodium analysis showed that varying salt level in formulations did not affect physical characteristics and mushroom inclusion could not significantly reduce overall sodium level. Optimized mushroom samples were then fielded in a hedonic sensory study to untrained consumers to evaluate product liking attributes (overall liking, aroma, color, flavor, juiciness, saltiness, and texture). Samples with overall liking scores that closely matched the control were then fielded in a paired-preference test to determine acceptance. Consumers preferred a 45% mushroom with reduced sodium taco filling compared to its full sodium counterpart in a food service fielded paired-preference sensory test. PRACTICAL APPLICATION: Although diet can significantly reduce the risk of heart disease, American consumers continue to eat detrimental diets high in fat and sodium. Products need to be made that decrease fat and sodium intake while still delivering acceptable taste. Mushroom substitution into meat-based products can be a strategy to develop products that can decrease fat and sodium consumption while increasing vegetable intake without compromising the quality and taste consumers demand. This research shows how consumers can accept meat-based products containing mushrooms with potential for direct food service application.

Effect of surface roughness and stainless steel finish on Listeria monocytogenes attachment and biofilm formation.

The purpose of this study was to evaluate the effect of surface roughness (Ra) and finish of mechanically polished stainless steel (Ra = 0.26 +/- 0.05, 0.49 +/- 0.10, and 0.69 +/- 0.05 microm) and electropolished stainless steel (Ra = 0.16 +/- 0.06, 0.40 +/- 0.003, and 0.67 +/- 0.02 microm) on Listeria adhesion and biofilm formation. A four-strain cocktail of Listeria monocytogenes was used. Each strain (0.1%) was added to 200 ml of tryptic soy broth (TSB), and coupons were inserted to the mixture for 5 min. For biofilm formation, coupons with adhesive cells were incubated in 1:20 diluted TSB at 32 degrees C for 48 h. The experiment was performed by a randomized block design. Our results show that the level of Listeria present after 48 h of incubation (mean = 7 log CFU/cm2) was significantly higher than after 5 min (mean = 6.0 log CFU/cm2) (P < 0.01). No differences in initial adhesion were seen in mechanically finished (mean = 6.7 log CFU/cm2) when compared with electropolished stainless steel (mean = 6.7 log CFU/cm2) (P > 0.05). Listeria initial adhesion (values ranged from 5.9 to 6.1 log CFU/cm2) or biofilm formation (values ranged from 6.9 to 7.2 log CFU/cm2) was not significantly correlated with Ra values (P > 0.05). Image analysis with an atomic force microscope showed that bacteria did not colonize the complete surface after 48 h but were individual cells or grouped in microcolonies that ranged from 5 to 10 microm in diameter and one to three cell layers in thickness. Exopolymeric substances were observed to be associated with the colonies. According to our results, electropolishing stainless steel does not pose a significant advantage for food sanitation over mechanically finished stainless steel.

Effect of biofilm dryness on the transfer of Listeria monocytogenes biofilms grown on stainless steel to bologna and hard salami.

Listeria monocytogenes continues to be a major cause of class I food recalls in the United States. Very little is known about its transfer and cross-contamination in processing scenarios. The objective of this study was to evaluate the effect of hydration level on L. monocytogenes biofilms grown on stainless steel and its effect on the biofilm transfer to foods. Biofilms were grown on stainless steel in diluted tryptic soy broth 1:20 for 48 h at 32 degrees C. After this, biofilms were equilibrated over saturated salt solutions at 20 degrees C for 24 h (94, 75, 58, and 33% relative humidity; % RH) prior to transferring. Transfer experiments were conducted from inoculated stainless steel to bologna and hard salami at a constant pressure (45 kPa) and time (30 s) with a universal testing machine. The experiment was designed with a factorial design 4 x 2 (biofilms equilibrated at 4% RH and two foods) and duplicated every day, and the whole experiment was repeated nine times. The results were analyzed with an analysis of variance by SAS Statistical Analysis Software. Our results showed that more bacteria were transferred to bologna (mean efficiency of transfer [EOT] = 3.0) than to hard salami (mean EOT = 0.35, P < 0.01). As biofilms became drier, the transfer of Listeria from stainless steel to both foods increased (P < 0.05). The EOT increased from 2 to 3.8 and from 0.2 to 0.51 upon transfer when drying the biofilm for bologna and hard salami, respectively. This study may be an indication that as biofilms were dried, the cell-cell and cell-surface interactions became weaker, and bacterial transfer increased. This phenomenon was enhanced in foods containing higher water activity levels. We hypothesize that this increased in transfer was due to the presence of capillary forces in the food.

Effects of inoculation level, material hydration, and stainless steel surface roughness on the transfer of listeria monocytogenes from inoculated bologna to stainless steel and high-density polyethylene.

The influence of inoculation level, material hydration, and stainless steel surface roughness on the transfer of Listeria monocytogenes from inoculated bologna to processing surfaces (stainless steel and polyethylene) was assessed. Slices of bologna (14 g) were inoculated with Listeria at different levels, from 10(5) to 10(9) CFU/cm2. Transfer experiments were done at a constant contact time (30 s) and pressure (45 kPa) with a universal testing machine. After transfer, cells that had been transferred to sterile stainless steel and polyethylene were removed and counted, and the efficiency of transfer (EOT) was calculated. As the inoculation level increased from 10(5) to 10(9) CFU/cm(2), the absolute level of transfer increased in a similar fashion. By calculating EOTs, the data were normalized, and the initial inoculation level had no effect on the transfer (P > 0.05). The influence of hydration level on stainless steel, high-density polyethylene, and material type was investigated, and the EOTs ranged from 0.1 to 1 under all the conditions tested. Our results show that transfers to wetted processing surfaces (mean EOT = 0.43) were no different from dried processing surfaces (mean EOT = 0.35) (P > 0.05). Material type was shown to be a significant factor, with greater numbers of Listeria transferring from bologna to stainless steel (mean EOT = 0.49) than from bologna to polyethylene (mean EOT = 0.28) (P < 0.01). Stainless steel with three different surface roughness (Ra) values of <0.8 microm (target Ra = 0.25, 0.50, and 0.75 Vmicrom) and two different finishes (mechanically polished versus mechanically polished and further electropolished) was used to evaluate its effect on the transfer. The surface roughness and finish on the stainless steel did not have any effect on the transfer of Listeria (P > 0.05). Our results showed that when evaluating the transfer of Listeria, the use of EOTs rather than the absolute transfer values is essential to allow comparisons of transfer conditions or comparisons between research groups.

Summer Pruning as a Method for Reducing Flyspeck Disease on Apple Fruit.

Summer pruning of apples, as opposed to the conventional commercial practice of dormant pruning, consistently reduced the incidence of flyspeck on apple fruit by approximately 50% in each of 2 years in trees where no fungicides were applied. In commercial orchard blocks using fungicides, summer pruning also produced a slight but significant decrease in disease severity. There appear to be at least two mechanisms contributing to decreased flyspeck incidence and severity in summer-pruned apple trees. Summer pruning resulted in a small change in the apple canopy microclimate, decreasing the hours of relative humidity >95% in the canopy by 63% and increasing the evaporative potential. Summer pruning also resulted in improved spray deposition in the upper two-thirds of the tree canopy when applications were made with an airblast sprayer.