Food component influence on water activity of low-moisture powders at elevated temperatures in connection with pathogen control

Microwave Heating Characteristics on Lipid Quality in Sterilized Rainbow Trout (Oncorhynchus mykiss) Using Designed Heating Processing

The aim of this study was to simulate microwave heating characteristics to investigate the lipid quality in rainbow trout, including the impact of the heating rate, maximum temperature, and thermal processing level on the extent of lipid oxidation and on the fatty acid extraction coefficient. Increasing F0 from 3 to 6 min improved fatty acid retention at high heating rates but led to a decrease in the measured results at low heating rates. Elevated thermal processing levels and maximum temperatures were observed to intensify the oxidation. At F0 = 3 min, an increase in maximum temperature led to an increase in the total lipid extraction coefficient but a decrease in the fatty acid extraction coefficient. However, an increase in maximum temperature resulted in a decrease in both extraction coefficients when F0 was 6 min. The coefficient spectra of fatty acid extraction obtained from the microwave and traditional heat treatments showed nonparallel trends, confirming the presence of non-thermal effects during microwave thermal processing. In conclusion, compared to conventional heat treatment methods, microwave processing has significant potential for enhancing the lipid quality of ready-to-eat rainbow trout products and effectively reducing production costs.

Peach Palm Fruit (Bactris gasipaes) Peel: A Source of Provitamin A Carotenoids to Develop Emulsion-Based Delivery Systems

The peach palm fruit (Bactris gasipaes) peel is a byproduct after fruit consumption. The peel flour of two varieties (yellow and red) was separately obtained by hot air drying and was subsequently milled. The proximate analysis showed that the red variety exhibited higher protein, fat, and fiber contents than the yellow one. A higher carotenoid (836.5 ± 24.5 μg/g), phenolic compounds (83.17 ± 1.76 mg GAE/100 g), and provitamin A activity (33.10 ± 0.83 μg retinol/g) were found in the cooked red variety. The carotenoid and phenolic compositions were analyzed by HPLC-PDA-MS, finding β-carotene and γ-carotene to be major compounds. The effect of thermal treatment increased the amount of these provitamin A carotenoids and lycopene, which were detected only in the red variety. Among phenolic compounds, procyanidin dimer (isomer I), feruloyl quinic acid, and several apigenin C-hexosides were identified as major constituents of peach palm epicarp. A carotenoid-rich emulsion-based delivery system was obtained after the optimization (RSM model) of carotenoid extraction with ultraturrax and sunflower oil and further development of an ultrasound-assisted emulsion. The best conditions for a stable emulsion were 73.75% water, 25% carotenoid-rich oil extract, 1.25% emulsifiers, and 480 W of ultrasonic power for 5 min. The optimized emulsion had a total carotenoid content of 67.61 μg/g, Provitamin A activity of 3.23 ± 0.56 μg RAE/g, droplet size of 502.23 nm, polydispersity index of 0.170, and zeta potential of -32.26 mV. This emulsion was chemically and physically stable for 35 days at 30 ± 2 °C, showing potential as a food additive with biofunctional properties. The strategy here developed is an economical and environmentally friendly process that allows the reuse of the byproduct of B. gasipaes.

Extraction-depended and thermally-modulated physical and chemical properties of powders produced from cranberry pomace extracts

Recovering bioactives from botanical by-products in the form of powders has been attempted through a number of multidirectional approaches. Yet understanding the processing of such plant formulations requires dedicated research owing to the manifold factors shaping the quality of powders. Therefore, the study aimed at production of cranberry powders from pomace extracts and to evaluate how different solvent type, carriers and drying techniques modulate their physico-chemical properties. Freeze- and vacuum drying significantly differentiated samples in terms of physical properties, while the extraction solvent and carrier type had substantial impact on chemical ones. For carrier-added products pomace extraction with acidified 50% ethanol resulted in the highest content of identified phenolics in powders (up to 5.87 g · 100 g-1 dry matter), while 30% acetone in the lowest (on average, 3.94 g · 100 g-1 dry matter). Acetone extraction strengthened the formation of hydroxymethyl-L-furfural that was higher when compared to acidified 50% ethanol, while trace amounts were reported for non-acidified counterpart. Similar observation was made in the case of flavan-3-ols. Addition of carriers during powders production led to the lower hydroxymethyl-L-furfural formation even down to 74% with regard to carrier-free samples. The study confirmed feasibility of managing cranberry pomace into high-value powders in extraction-depended and thermally-modulated quality matter.

Approaches for a more microbiologically and chemically safe dried fruit supply chain

Global production of dried fruits has increased significantly in the past decade. Both the increased consumer acceptance of nutritious packaged food and the broad use of dried fruits in products such as confectionery and bakery goods have fueled the dried fruit demand. Unfortunately, outbreaks and recalls due to contamination by pathogenic bacteria and viruses as well as the detection of mycotoxins highlight the need for optimizing current approaches, and evaluating and adopting newer interventions to protect the microbial and chemical safety of dried fruits. Drying processes alone are inadequate to control these hazards. Pre- and post-drying treatments serve as promising opportunities, with or without combination with the drying step, to achieve the goals of efficient hazard control.

Interlaboratory Evaluation of Enterococcus faecium NRRL B-2354 as a Salmonella Surrogate for Validating Thermal Treatment of Multiple Low-Moisture Foods

ABSTRACT

This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision.

HIGHLIGHTS

Mango (Mangifera indica L.) Dehydration as a Women Entrepreneurship Alternative in Vulnerable Communities

In Colombia, most commercial drying processes are frequently performed through the burning of wood and fossil fuels with high costs and environmental damage. Nevertheless, solar drying is a technique that could also be used to reduce many of the problems present in traditional drying techniques. Finding low-cost technology to install a solar dryer in a vulnerable community of women is an appropriate alternative; the transfer of knowledge on this technique could lead to greater empowerment of women and prevent gender inequality. This study evaluated the color and water activity of the mango (Mangifera indica L.) after a drying process in a greenhouse dryer. Furthermore, this study showed the relevance of implementing this technique in a community of women affected by the military conflict in Colombia. Results showed that a solar dryer achieved drying times of around 23–26 h, reaching water activity values below the 0.5 threshold which, according to international standards, has been considered as a food safety value. In addition, the color of the dry mango is slightly affected through this drying technique, providing a more acceptable consumer product. The application of the solar dryer has proven to be an easy-to-use and environmentally friendly method. On the other hand, it is also an opportunity to improve, with a low-cost investment, the living conditions of vulnerable communities.

Water sorption characteristics of freeze-dried bacteria in low-moisture foods

Water sorption isotherms of bacteria reflect the water activity with the change of moisture content of bacteria at a specific temperature. The temperature-dependency of water activity change can help to understand the thermal resistance of bacteria during a thermal process. Thermal resistance of bacteria in low-moisture foods may differ significantly depending on the physiological characteristics of microorganisms, including cell structure, existence of biofilms, and growth state. Previous studies demonstrated that the incremental change of a_w in bacterial cells during thermal treatments resulted in changes in their thermotolerance. In this study, a pathogen associated with low-moisture foods outbreaks, Salmonella Enteritidis PT30 (in planktonic and biofilm forms), and its validated surrogate, Enterococcus faecium, were lyophilized and their water sorption isotherms (WSI) at 20, 40, and 60 °C were determined by using a vapor sorption analyzer and simulated by the Guggenheim, Anderson and De Boer model (GAB). The published thermal death times at 80 °C (D_{80 °C}-values) of these bacteria in low-moisture environments were related with their WSI-derived a_w changes. The results showed that planktonic E. faecium and biofilms of Salmonella, exhibiting higher thermal resistance compared to the planktonic cultures of Salmonella, had a smaller increase in a_w when thermally treated from 20 to 60 °C in sealed test cells. The computational modeling also showed that when temperature increased from 20 to 60 °C, with an increase in relative humidity from 10% to 60%, freeze-dried planktonic E. faecium and Salmonella cells would equilibrate to their surrounding environments in 0.15 s and 0.25 s, respectively, suggesting a rapid equilibration of bacterial cells to their microenvironment. However, control of bacteria with different cell structure and growth state would require further attentions on process design adjustment because of their different water sorption characteristics.

Survival of Salmonella on Red Meat in Response to Dry Heat

ABSTRACT

Red meat is associated with Salmonella outbreaks, resulting in negative impacts for the processing industry. Little work has been reported on the use of dry heat as opposed to moist heat against Salmonella on red meat. We determined the effect of drying at 25°C and dry heat at 70°C with ∼10% relative humidity for 1 h against 11 Salmonella strains of multiple serovars on beef, lamb, and goat and rubber as an inert surface. Each strain at ∼108 CFU/mL was inoculated (100 μL) onto ±1 g (1 cm2) of each surface and allowed to attach for 15 min in a microcentrifuge tube. Samples were then exposed to 70 and 25°C with ∼10% relative humidity in a heating block. Surviving Salmonella numbers on surfaces were enumerated on a thin agar layer medium. If numbers were below the limit of detection (2.01 log CFU/cm2), Salmonella cells were enriched before plating to determine the presence of viable cells. Water loss (percent) from meat after at 25 and 70°C was determined. Whole genomes of Salmonella were interrogated to identify the presence-absence of stress response genes (n = 30) related to dry heat that may contribute to the survival of Salmonella. The survival of Salmonella at 25°C was significantly higher across all surfaces (∼6.09 to 7.91 log CFU/cm2) than at 70°C (∼3.66 to 6.33 log CFU/cm2). On rubber, numbers of Salmonella were less than the limit of detection at 70°C. Water loss at 70°C (∼17.72 to 19.89%) was significantly higher than at 25°C (∼2.98 to 4.11%). Salmonella cells were not detected on rubber, whereas survival occurred on all red meat at 70°C, suggesting its protective effect against the effect of heat. All Salmonella strains carried 30 stress response genes that likely contributed to survival. A multi-antibiotic-resistant Salmonella Typhimurium 2470 exhibited an increase in heat resistance at 70°C on beef and lamb compared with other strains. Our work shows that dry heat at 70°C for 1 h against Salmonella on red meat is not a practical approach for effectively reducing or eliminating them from red meat.

HIGHLIGHTS

Moisture Content of Bacterial Cells Determines Thermal Resistance of Salmonella enterica Serotype Enteritidis PT 30

Salmonella spp. are resilient bacterial pathogens in low-moisture foods. There has been a general lack of understanding of critical factors contributing to the enhanced thermal tolerance of Salmonella spp. in dry environments. In this study, we hypothesized that the moisture content (X_W ) of bacterial cells is a critical intrinsic factor influencing the resistance of Salmonella spp. to thermal inactivation. We selected Salmonella enterica serotype Enteritidis PT 30 to test this hypothesis. We first produced viable freeze-dried S. Enteritidis PT 30, conditioned the bacterial cells to different X_W s (7.7, 9.2, 12.4, and 15.7 g water/100 g dry solids), and determined the thermal inactivation kinetics of those cells at 80°C. The results show that the D-value (the time required to achieve a 1-log reduction) decreased exponentially with increasing X_W We further measured the water activities (a_w) of the freeze-dried S. Enteritidis PT 30 as influenced by temperatures between 20 and 80°C. By using those data, we estimated the X_W of S. Enteritidis PT 30 from the published papers that related the D-values of the same bacterial strain at 80°C with the a_w of five different food and silicon dioxide matrices. We discovered that the logarithmic D-values of S. Enteritidis PT 30 in all those matrices also decreased linearly with increasing X_W of the bacterial cells. The findings suggest that the amount of moisture in S. Enteritidis PT 30 is a determining factor of its ability to resist thermal inactivation. Our results may help future research into fundamental mechanisms for thermal inactivation of bacterial pathogens in dry environments.IMPORTANCE This study established a logarithmic relationship between the thermal death time (D-value) of S. Enteritidis PT 30 and the moisture content (X_W ) of the bacterial cells by conducting thermal inactivation tests on freeze-dried S Enteritidis PT 30. We further verified this relationship using literature data for S. Enteritidis PT 30 in five low-moisture matrices. The findings suggest that the X_W of S. Enteritidis PT 30, which is rapidly adjusted by microenvironmental a_w, or relative humidity, during heat treatments, is the key intrinsic factor determining the thermal resistance of the bacterium. The quantitative relationships reported in this study may help guide future designs of industrial thermal processes for the control of S. Enteritidis PT 30 or other Salmonella strains in low-moisture foods. Our findings highlight a need for further fundamental investigation into the role of water in protein denaturation and the accumulation of compatible solutes during thermal inactivation of bacterial pathogens in dry environments.

Effect of curing and heat treatments on the Salmonella survival and physicochemical properties of chicken egg yolk

Cured egg yolk is a novel gastronomic preparation, which a salt and sugar mixture gradually diffuses into the egg yolk, promoting its solidification from the exterior to the inner parts and greatly concentrates fat and flavor. This study was undertaken to analyze the effect of curing and its association with heat treatments on the Salmonella survival and physicochemical properties of chicken egg yolks. Contaminated egg yolks (8.4 log₁₀ CFU/g) were covered by a mixture of sugar and salt and stored at 4.5 °C for curing, for 2, 24, 72 and 144 h. The cured yolks were subjected to the heat treatments: 62 °C for 30 min in temperature-controlled water circulator or at 80 °C for 3 h in oven. None of the treatments promoted the complete inactivation of Salmonella (detection limit of 100 CFU/g). However, Salmonella populations were significantly reduced (p ≤ 0.05) when heat processes were applied, reaching a maximum reduction of 5.6 log₁₀ CFU/g when the yolks were cured for 2 h and subsequently treated in temperature-controlled water circulator (62 °C for 30 min). This treatment kept the physicochemical properties similar to the ones without heat treatment, while the oven treatment showed considerable changes on texture, water activity and visual color. In conclusion, the use of curing time of 2 h followed by temperature-controlled water circulator process can improve the safety of cured egg yolks made from high quality eggs. However, other methods should be considered and analyzed to promote a complete inactivation of Salmonella.