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Water activity (aw) influences the thermal resistance (D-value) of pathogens in low-moisture foods (LMF). However, the influence of food matrices on aw at elevated temperatures is complicated. A recent study reported that a novel thermal water activity cell (TAC) could be used to control aw of LMF using LiCl solution (select molality) during the isothermal determination of D-values of Salmonella. This research proposed a new version of TAC (TAC II) that could significantly reduce the time to establish the moisture-equilibrium between LMF and LiCl solutions during D-value measurements. Wheat flour (WF) samples inoculated with Salmonella (aw at room temperature = 0.45) were treated in TAC II at 80 °C under controlled relative humidity (RH) (50%) provided by LiCl solution (9.37 mol kg−1). Results showed that the moisture-equilibrium was established to the controlled RH condition at 80 °C in 14 min for TAC. The D-value of Salmonella PT30 in WF (80 °C, RH 50%) tested with TAC II (20.7 ± 1.1 min) was significantly higher (p

A novel test cell was developed to study the influence of water activity (aw) on thermal inactivation of food pathogens in low-moisture foods (LMF). The cell consisted of multiple wells with a shared headspace; aw of the inoculated food sample was controlled by lithium chloride (LiCl) solution of selected molality during heating. The performance of the test cell was evaluated by studying sample heating uniformity using finite element simulation and by comparing measured headspace relative humidities (RH) with predicted RH provided by LiCl solutions. The new cells were used to determine thermal resistance (D-value) of Salmonella at 80 °C in organic wheat flour (OWF) maintained at aw of 0.45. The D-value of Salmonella was also determined in conventional thermal death time test cells in which aw of OWF samples increased from 0.45 at room temperature to 0.73 at 80 °C according to the measured isotherm. The results demonstrated that aw significantly influenced the D-values of Salmonella, and the new test cells can be used to directly relate thermal resistance of food pathogens to water activities of LMF at processing temperatures.

Water activity (aw) is a major factor affecting pathogen heat resistance in low-moisture foods. However, there is a lack of data for aw at elevated temperatures that occur during actual thermal processing conditions, and its influence on thermal tolerance of pathogens. The objective of this study was to gain an in-depth understanding of the relationship between temperature-induced changes in aw and thermal resistance of Salmonella in all purpose flour and peanut butter at elevated temperatures (80 oC). Equilibrium water sorption isotherms (water content vs. water activity) for all purpose wheat flour and peanut butter over the range of 20 to 80 °C were generated using a vapor sorption analyzer and a newly developed thermal cell. The thermal resistance (D80-values) of Salmonella in all purpose wheat flour and peanut butter with initial aw of 0.45 (measured at room temperature, ~ 20 °C) was determined via isothermal treatment of small (

Salmonella spp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters of Salmonella spp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (a w, treatment temperature ) plays an important role in the sharply increased thermal resistance of Salmonella enterica serovar Enteritidis PT 30 and its potential surrogate Enterococcus faecium NRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding a w,80°C values for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model ( R 2 , 0.83 to 0.97). Reductions in the a w,80°C values of bacterial cells exponentially increased the D 80°C (the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values for S . Enteritidis and E. faecium on silicon dioxide. The log-linear relationship between the D 80°C values for each strain in silicon dioxide and its a w,80°C values was also verified for organic wheat flour. E. faecium showed consistently higher D 80°C values than S . Enteritidis over the a w,80°C range tested. The estimated z aw (the change in a w,80°C needed to change D 80°C by 1 log) values of S . Enteritidis and E. faecium were 0.31 and 0.28, respectively. This study provides insight into the interpretation of Salmonella thermal resistance that could guide the development and validation of thermal processing of low-moisture foods. IMPORTANCE In this paper, we established that the thermal resistance of the pathogen S . Enteritidis and its surrogate Enterococcus faecium , as reflected by D values at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between the D 80°C values of each strain in silicon dioxide and its a w,80°C values was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.

In recent years, research studies have shown that the thermal resistance of foodborne pathogens in the low moisture foods is greatly influenced by the water activity (aw) at temperatures relevant to thermal treatments for pathogen control. Yet, there has been a lack of an effective method for accurate measurement of aw at those temperatures. Thus, the main aim of this study was to evaluate a new method for measuring aw of food samples at elevated temperatures. An improved thermal cell with a relative humidity and temperature sensor was used to measure the aw of the three different food samples, namely, organic wheat flour, almond flour, and non-fat milk powder, over the temperature range between 20 and 80°C. For a constant moisture content, the aw data was used to estimate the net isosteric heat of sorption (qst). The qst values were then used in the Clausius Clapeyron equation (CCE) equation to estimate the moisture sorption isotherm for all test food samples at different temperatures. For all the tested samples of any fixed moisture content, aw value generally increased with the temperature. The energy for sorption decreased with increasing moisture content. With the experimentally determined qst value, CCE describes well about the changes in aw of the food samples between 20 and 80°C. This study presents a method to obtain aw of a food sample for a specific moisture content at different temperatures which could be extended to obtain qst values for different moisture contents and hence, the moisture sorption isotherm of a food sample at different temperatures.

The present study investigated processing strategies and matrix effects on the antioxidant capacity (AC) and polyphenols (PP) content of fruit-based beverages: (1) strawberry powder (Str) + dairy, D-Str; (2) Str + water, ND-Str; (3) dairy + no Str, D-NStr. Beverages were subjected to high-temperature-short-time (HTST) and high-pressure processing (HPP). AC and PP were measured before and after processing and after a 5 week shelf-life study. Unprocessed D-Str had significantly lower AC compared to unprocessed ND-Str. Significant reductions in AC were apparent in HTST- compared to HPP-processed beverages (up to 600 MPa). PP content was significantly reduced in D-Str compared to ND-Str and in response to HPP and HTST in all beverages. After storage (5 weeks), AC and PP were reduced in all beverages compared to unprocessed and week 0 processed beverages. These findings indicate potentially negative effects of milk and processing on AC and PP of fruit-based beverages.

The present study investigates the effect of strawberry antioxidants in beverage form on meal-induced postprandial inflammatory and insulin responses in human subjects. Overweight adults (n24) consumed a high-carbohydrate, moderate-fat meal (HCFM) accompanied by either a strawberry or a placebo beverage in a cross-over design. Postprandial changes in plasma anthocyanins, their metabolites, insulin, glucose and inflammatory markers were assessed for 6 h. The postprandial concentrations of pelargonidin sulfate and pelargonidin-3-O-glucoside were significantly increased when the strawberry beverage was consumed concurrently with the HCFM compared with the placebo beverage (P P P

Fruits and vegetables are processed by the food industry to extend shelf-life, delivering more options and opportunities for consumers to eat fruits and vegetables. Conventional thermal processing is an effective method for producing safe extended shelf-life and shelf-stable products; however the harsh temperatures impact nutritive quality, destroying essential nutrients and non-essential nutrients/components. Strawberries, along with other berry fruits contain a variety of ‘bioactive’ nutrients and phytochemicals. Strawberries are a significant source of polyphenolic anthocyanins in some diets. Anthocyanins are associated with a number of health benefits. Accordingly, increasing the options for consuming anthocyanin rich fruits, such as strawberries, in a manner that would preserve their rich bioactive profile would benefit human health. Novel processing strategies will indeed be required to deliver on such high demands. In this chapter, research on the application of high-pressure processing (HPP) as a potential method for preserving bioactive components in extended shelf-life foods is discussed. Strawberry beverages serve as a model for assessing effects of HPP, including interactions with matrix on anthocyanins, antioxidant capacity, among other quality indicators. Overall, HPP has emerged as a promising technology for delivering microbiologically safe food products while preserving nutritional quality. However, research in this area of alternative processing methods and novel technologies to deliver products with greater nutritional quality and demonstrated health benefits in humans is under-developed and immense opportunities exist.

Fruits contain a variety of nutrients and polyphenols that are associated with health benefits. Year-round availability of fresh fruits is limited due to perishability. Processing fruits extends shelf life. Individual quick-frozen fruit is the most common for fruits, but nowadays, processing fruits into beverages offers extended shelf life and new market opportunities. Conventional thermal processing is an effective method for producing safe, extended shelf life, and shelf-stable products, including beverages. However, the high temperatures negatively affect nutritive quality by destroying essential nutrients and biologically active "non-essential" components such as polyphenols. Therefore, novel technologies that can preserve nutrient quality while ensuring food safety are warranted. In this review, the application of high-pressure processing (HPP) for preserving nutrients and phytochemicals while ensuring microbiological safety in beverages and other foods containing fruits is discussed.

Polyphenolic-rich berry fruits are known to activate redox-sensitive cellular signaling molecules such as phosphatidylinositol-3-kinase (PI3 kinase)/kinase B (Akt), resulting in a cascade of downstream signaling pathways. This study investigated the ability of strawberry (SB), wild blueberry (WBB), and cranberry (CB) extracts to induce the activation of PI3 kinase/Akt signaling in vitro in human umbilical endothelial cells (HUVECs) and whether this activation would enhance cell migration and angiogenesis. Anthocyanin profiles of the extracts were characterized using HPLC-ESI/MS, and Akt activation was investigated using the Alpha Screen SureFire assay. The total anthocyanin contents of SB, WBB, and CB extracts were 81.7, 82.5, and 83.0 mg/100 g fresh weight, respectively. SB, WBB, and CB extracts activated Akt in a dose-dependent manner via PI3 kinase and induced cell migration and angiogenesis in vitro in HUVECs. The results from this study suggest that polyphenolics in berry fruits may play a role in promoting vascular health.

To investigate the effects of Strawberry antioxidants on oxidative stress-mediated impaired insulin signaling in in vitro in Human Skeletal Muscle Cells (HSkMC) • Strawberry antioxidants have a possible protective effect on oxidative stress-induced impaired insulin signaling as measured in vitro in HSkMC • Oxidative stress induced by H2 O2 increased the levels of Serine (307) phosphorylation of IRS-1 and decreased the levels of tyrsosine phosphorylations • Strawberry extract reversed the oxidative stress-induced increased levels of inhibitory phosphorylation (Ser 307) , and decreased levels of tyrosine phosphorylation of IRS-1 • Proposed mechanism of action to restore insulin signaling is through reduced cellular oxidative stress by Strawberry antioxidants Strawberry Extract Attenuates Oxidative Stress-Induced Impaired Insulin Signaling In vitro in Human Skeletal Muscle Cells.

1. Prior, R. L. et al. 2003. Assays for Hydrophilic and Lipophillic Antioxidant Capacity (oxygen radical absorbance capacity (ORAC (FL))) of Plasma and other Biological and Food Samples. J. Agric. Food Chem., 51:3273-3279 2. Benzie, I., F. et al. 1996. ''The Ferric Reducing Ability of Plasma (FRAP) as a Measure of “Antioxidant Power”: The FRAP Assay '' Analytical Biochemistry 239, pp 70-76. Acknowledgments

Objective: This investigation was undertaken to determine whether a grape seed extract (GSE) that is rich in mono-, oligo- and poly- meric polyphenols would modify postprandial oxidative stress and inflammation in individuals with the metabolic syndrome (MetS).Background: MetS is known to be associated with impaired glucose tolerance and poor glycemic control. Consumption of a meal high in readily available carbohydrates and fat causes postprandial increases in glycemia and lipidemia and markers of oxidative stress, inflammation and insulin resistance. Materials/methods: After an overnight fast, twelve subjects with MetS (5 men and 7 women) consumed a breakfast meal high in fat and carbohydrate in a cross-over design. A GSE (300 mg) or placebo capsule was administrated 1 hr before the meal (-1 hr). Changes in plasma insulin, glucose, oxidative stress and inflammatory markers were measured hourly for 6 hr. Results: Plasma hydrophilic oxygen radical absorbance capacity (ORAC) measured as the positive incremental area under the curve (-1 to 5 hr) was significantly increased when the meal was preceded by GSE compared with placebo (P0.05). No changes in inflammatory markers were evident. Conclusion: These data suggest that GSE enhances postprandial plasma antioxidant status and reduces the glycemic response to a meal, high in fat and carbohydrate in subjects with the MetS.