Comprehensive review of clean-label antimicrobials used in dairy products

Consumers expect safe, healthy, natural, and sustainable food. Within the food industry, ingredient use is changing due to these consumer demands. While no single agreed-upon definition of clean label exists, a "clean label" in the context of food refers to a product that has a simplified and transparent ingredient list, with easily recognizable and commonly understood components to the general public. Clean-label products necessitate and foster a heightened level of transparency between companies and consumers. Dairy products are vulnerable to being contaminated by both pathogens and spoilage microorganisms. These microorganisms can be effectively controlled by replacing conventional antimicrobials with clean-label ingredients such as protective cultures or bacterial/fungal fermentates. This review summarizes the perspectives of consumers and the food industry regarding the definition of "clean label," and the current and potential future use of clean-label antimicrobials in dairy products. A key goal of this review is to make the concept of clean-label antimicrobial agents better understood by both manufacturers and researchers.

Listeria monocytogenes Outbreaks Related to Commercially Produced Caramel Apples: Developments in Sanitation, Product Formulation, and Packaging: A Review

ABSTRACT

Prior to a deadly 2014 listeriosis outbreak, caramel apples were not thought to be vehicles for the foodborne pathogen Listeria monocytogenes. The purpose of this review article is to summarize what has been learned from research prompted by this outbreak. This overview includes descriptions of the two L. monocytogenes infection outbreaks related to prepackaged caramel apples and a brief discussion of apple sanitation, the production processes used to make caramel apples, and research on ways to prevent future outbreaks associated with caramel apples. A qualitative analysis of the literature and interviews with current caramel apple manufacturers were conducted. Sanitation, packaging, and storage procedures used by manufacturers in the past may not effectively inactivate L. monocytogenes from contaminated product. Novel apple sanitation methods and product formulations to control L. monocytogenes on caramel apples have been developed and, in some cases, implemented in commercial production.

HIGHLIGHTS

Dietary nitrate and nitrite: Benefits, risks, and evolving perceptions

Consumers have an illogical relationship with nitrite (and its precursor, nitrate) in food. Despite a long history of use, nitrite was nearly banned from use in foods in the 1970s due to health concerns related to the potential for carcinogenic nitrosamine formation. Changes in meat processing methods reduced those potential risks, and nitrite continued to be used in foods. Since then, two opposing movements continue to shape how consumers view dietary nitrate and nitrite. The discovery of the profound physiological importance of nitric oxide led to the realization that dietary nitrate contributes significantly to the nitrogen reservoir for nitric oxide formation. Numerous clinical studies have also demonstrated beneficial effects from dietary nitrate consumption, especially in vascular and metabolic health. However, the latest wave of consumer sentiment against food additives, the clean-label movement, has renewed consumer fear and avoidance of preservatives, including nitrite. Education is necessary but may not be sufficient to resolve this disconnect in consumer perception.

Growth of Listeria monocytogenes within a caramel-coated apple microenvironment

A 2014 multistate listeriosis outbreak was linked to consumption of caramel-coated apples, an unexpected and previously unreported vehicle for Listeria monocytogenes. This outbreak was unanticipated because both the pH of apples (<4.0) and the water activity of the caramel coating (<0.80) are too low to support Listeria growth. In this study, Granny Smith apples were inoculated with approximately 4 log10 CFU of L. monocytogenes (a cocktail of serotype 4b strains associated with the outbreak) on each apple's skin, stem, and calyx. Half of the apples had sticks inserted into the core, while the remaining apples were left intact. Apples were dipped into hot caramel and stored at either 7°C or 25°C for up to 11 or 28 days, respectively. Data revealed that apples with inserted sticks supported significantly more L. monocytogenes growth than apples without sticks under both storage conditions. Within 3 days at 25°C, L. monocytogenes populations increased >3 log10 in apples with sticks, whereas only a 1-log10 increase was observed even after 1 week for caramel-coated apples without sticks. When stored at 7°C, apples with sticks exhibited an approximately 1.5-log10 increase in L. monocytogenes levels at 28 days, whereas no growth was observed in apples without sticks. We infer that insertion of a stick into the apple accelerates the transfer of juice from the interior of the apple to its surface, creating a microenvironment at the apple-caramel interface where L. monocytogenes can rapidly grow to levels sufficient to cause disease when stored at room temperature.

IMPORTANCE

Neither caramel nor apples are a food where the pathogenic bacterium Listeria monocytogenes should grow, as caramel does not contain enough free water and apples are too acidic. Caramel-coated apples, however, were recently linked to a deadly outbreak of listeriosis. We hypothesized that inserting a stick into the apple releases juice to the interface between the apple and caramel, providing a more hospitable environment than either component alone. To test this hypothesis, apples were inoculated with L. monocytogenes prior to caramel dipping. Some apples had sticks inserted into them before dipping, while others did not. No growth of L. monocytogenes occurred on refrigerated caramel apples without sticks, whereas slow growth was observed on refrigerated caramel apples with sticks. In contrast, significant pathogen growth was observed within 3 days at room temperature on caramel apples with sticks inserted. Food producers should consider interfaces between components within foods as potential niches for pathogen growth.

The vitamin D analogue 2MD increases bone turnover but not BMD in postmenopausal women with osteopenia: results of a 1-year phase 2 double-blind, placebo-controlled, randomized clinical trial

Most osteoporosis drugs act by inhibiting bone resorption. A need exists for osteoporosis therapies that stimulate new bone formation. 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D(3) (2MD) is a vitamin D analogue that potently stimulates bone formation activity in vitro and in the ovariectomized rat model. In this randomized, double-blind, placebo-controlled study of osteopenic women, the effect of daily oral treatment with 2MD on bone mineral density (BMD), serum markers of bone turnover, and safety were assessed over 1 year. Volunteers were randomly assigned to three treatment groups: placebo (n = 50), 220 ng of 2MD (n = 54), and 440 ng of 2MD (n = 53). In general, 2MD was well tolerated. Although 2MD caused a marked increase in markers of bone formation, it did not significantly increase BMD. Since 2MD also shows marked activity on bone resorption (as revealed by dose-dependent increases in serum C-telopeptide cross-links of type I collagen in this study), 2MD likely stimulated both bone formation and bone resorption, thereby increasing bone remodeling.

Sequential folding of UmuC by the Hsp70 and Hsp60 chaperone complexes of Escherichia coli

Replication-blocking lesions generate a signal in Escherichia coli that leads to the induction of the multigene SOS response. Among the SOS-induced genes are umuD and umuC, whose products are necessary for the increased mutation rate in induced bacteria. The mutations are likely to result from replication across the DNA lesion, and such a bypass event has been reconstituted in vitro (Rajagopalan, M., L, C., Woodgate, R., O'Donnel, M., Goodman, M. F., Echols, H. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 10777-10781). In this work, we show that the chaperone proteins promote the proper folding of UmuC protein in vitro. We treated purified and inactive UmuC with Hsp70 and Hsp60. After Hsp70 treatment, the DNA binding activity of UmuC was recovered, but the ability to promote replication across DNA lesions was not. However, lesion bypass activity was recovered upon further treatment with Hsp60. The biological significance of such a folding pathway for UmuC protein is strengthened by in vivo evidence for a role of DnaK in UV-induced mutagenesis.