Synergistic effect of naringenin and mild heat for inactivation of E. coli O157:H7, S. Typhimurium, L. monocytogenes, and S. aureus in peptone water and cold brew coffee.

The impact of the roasting degree on ultra-high-pressure cold brew (UHP) coffee remains unclear, although it has been found that UHP technology accelerates the extraction of cold brew (CB) coffee. Therefore, this study investigated the effects of three different degrees of roasting (light, medium, and dark) on the physicochemical characteristics, volatile and non-volatile components, and sensory evaluation of UHP coffee. Orthogonal partial least-squares-discriminant analysis (OPLS-DA) and principal component analysis (PCA) were used to assess the effects of different roasting degrees. The results showed that most physicochemical characteristics, including total dissolved solids (TDSs), extraction yield (EY), total titratable acidity (TTA), total sugars (TSs), and total phenolic content (TPC), of UHP coffee were similar to those of conventional CB coffee regardless of the degree of roasting. However, the majority of physicochemical characteristics, non-volatile components, including the antioxidant capacity (measured based on DPPH and ABTS) and melanoidin, caffeine, trigonelline, and CGA contents increased significantly with an increase in roasting degree. The sensory evaluation revealed that as the roasting degree rose, the nutty flavor, astringency, bitterness, body, and aftertaste intensities increased, while floral, fruity, and sourness attributes decreased. The HS-SPME-GC/MS analysis showed that most volatile components increased from light to dark roasting. Moreover, 15 representative differential compounds, including hazelnut pyrazine, linalool, butane-2,3-dione, and 3-methylbutanal, were identified by calculating the odor-active values (OAVs), indicating that these contributed significantly to the odor. The PCA showed that the distance between the three roasting degree samples in UHP coffee was smaller than that in CB coffee. Overall, the effect of roasting degrees on UHP coffee was less than that on CB coffee, which was consistent with the results of physicochemical characteristics, volatile components, and sensory evaluation.

Cold brew coffee (CBC) has gained in popularity due to its distinct sensory experience. However, CBC can pose a risk for bacterial pathogens if not stored properly. High-Pressure Processing (HPP) is a nonthermal technology that can improve the safety of CBC while maintaining its quality. In this study, CBC made from ground roasted coffee grains was processed at 600 MPa for 3 min and stored at 4 or 23 °C for 90 days. The microbiological quality indicators remained stable throughout the study period. Physicochemical and quality parameters, such as pH, total dissolved solids, titratable acidity, color, total phenolic compounds and antioxidant activity, were not significantly affected by HPP. Both unprocessed and HPP CBC samples showed changes in pH, titratable acidity and color stability after 60 days at 23 °C. Unprocessed CBC samples spiked with Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica showed decreased counts, but the pathogens were still detectable after 60 days at 4 °C and after 90 days at 23 °C. HPP achieved a >6-log10 reduction in the species tested, with non-detectable levels for at least 90 days at both storage temperatures. These findings suggest that HPP can effectively control vegetative pathogens and spoilage microorganisms in CBC while preserving its quality attributes.

Although cold brew coffee is becoming increasingly popular among consumers, the long coffee extraction time is not conducive to the further development of the market. This study explored the feasibility of ultrahigh pressure (UHP) to shorten the time required for preparing cold brew coffee. The effects of pressure and holding time on the physicochemical characteristics and sensory evaluation of UHP-assisted cold brew coffee were also determined. The extraction yield; total dissolved solid, total phenol, and melanoid content; antioxidant capacity; and trigonelline and chlorogenic acid contents of UHP-assisted cold brew coffee increased as the pressure increased. The extraction yield and the total dissolved solid, total phenol, total sugar, and chlorogenic acid and trigonelline contents were higher when the holding time was longer. The HS-SPME-GC/MS analysis demonstrated that the furan, aldehyde, and pyrazine contents in coffee increased as the pressure and holding time increased. The pressure did not significantly impact the concentrations of volatile components of esters and ketones in coffee samples. However, the increase in holding time significantly increased the ester and ketone contents. The sensory evaluation results revealed that as pressure rose, the intensities of nutty, fruity, floral, caramel, and sourness flavors increased, whereas bitterness and sweetness decreased. Longer holding time increased nutty, caramel, sour, bitter, sweet, and aftertaste flavors. Principal component analysis (PCA) results indicated that holding time is a more crucial factor affecting the physiochemical indices and flavor characteristics of coffee. UHP can shorten the preparation time of cold brew coffee. Pressure and holding time significantly affected the physiochemical indices and volatile components of UHP-assisted cold brew coffee. UHP-assisted cold brew coffee had lower bitterness, higher sweetness, and a softer taste than conventional cold brew coffee.

Cold brew coffee has gained significant popularity in the global market. This study examined the differences in chemical properties and flavor of cold brew coffee during storage, which was subjected to low-temperature pasteurization using induced electric field (IEF) at temperatures of 52 °C and 58 °C for 92 s, corresponding to 18.52 V/cm and 25.92 V/cm. Then, a high-temperature short-time (HTST) pasteurization was performed at 93 °C for 2 min as the control. Microbial analysis demonstrated that IEF treatment at 58 °C achieved a bactericidal effect. Both the IEF and HTST groups exhibited consistent trends in total sugar and total phenol content, showing approximately 28 μg GAE/mL after 28 days for IEF-2 group, compared to 25 μg/mL for HTST. Flavor analysis indicated that IEF group preserved the aroma characteristics during storage period. Further, IEF treatment effectively retained the key aroma compounds in cold brew coffee through GC–MS analysis, particularly pyrazine compounds with a relative content increased by 0.96 % in IEF-2 group after 28 days. Moreover, the bioactive compounds initially increased and subsequently decreased over the storage.

Effectiveness of UV-C light assisted by mild heat on Saccharomyces cerevisiae KE 162 inactivation in carrot-orange juice blend studied by flow cytometry and transmission electron microscopy

ABSTRACTThe unique flavor and taste of cold brew coffee have made it popular in recent years. As the name suggests, it is cold‐brewed, which means the absence of a thermal process in the brewing. Hence, after the roasting step, it only has to rely on the product pH and storage temperature to control the foodborne pathogens such as Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. The purpose of this study is to investigate the effect of pH (4.9 and 5.3) and temperature (4°C and 23°C) on Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes in cold brew coffee. Cold brew coffee samples were inoculated with these organisms for 30 days, and survival data were collected. Results showed that pH affected the survival of Salmonella and E. coli. At pH 4.9, Salmonella was reduced by 5 log CFU/ml after 7 days, reaching the limit of detection in 11 days. However, at pH 5.3, 5 5‐log reduction occurred after 14 days, taking 25 days to reach the limit of detection. At 23°C, both Salmonella and E. coli showed increased survival, making temperature an important factor. Listeria showed resistance to pH variations at both temperatures. Lower RMSE values for Salmonella (pH 4.9) and Listeria (pH 4.9) were observed in the log‐linear model, making it a better fit. However, the Weibull model showed a better fit for Salmonella (pH ‐5.3), Listeria (pH ‐5.3), and E. coli (pH ‐4.9, 5.3). Overall, lower temperatures increase survival, while higher temperatures enhance the reduction in E. coli.These findings are crucial for enhancing the safety of cold‐brew coffee and providing valuable recommendations to producers, regulators, and consumers.

Synergistic inactivation of Escherichia coli O157:H7 by plasma-activated water and mild heat

Effects of combining ultraviolet and mild heat treatments on enzymatic activities and total phenolic contents in pineapple juice

The effects of grinding (medium-coarse) and extraction time (14–22 h) on the physicochemical and sensorial properties of cold brew coffee produced using two types of Colombian specialty coffees (Huila and Nariño) were evaluated. Cold coffee brewed under coarse grinding and 22 h of extraction exhibited the highest values of total dissolved solids, extraction yield, pH, titratable acidity (TA), and total phenolic content. The type of coffee used mainly affected the TA and pH. All cold brew coffee samples had lower TA values than their hot counterparts. Nariño cold brew samples had higher TA values than those of Huila in all treatments evaluated. Higher scores were reported in the sensorial evaluation of cold brew coffee when prepared using the shortest time (14 h) and coarse grinding for both coffee types. These coffees were characterized by strong sweetness, fruity and floral flavours, medium bitterness and acidity, and a creamy body. Furans, pyrazines, ketones, aldehydes, pyrroles, esters, lactones, furanones, and phenols were detected as odour-active compounds. The findings of this study demonstrate that the particle size, contact time, and coffee type affect the physicochemical and sensorial characteristics of cold brew coffee, leading to cold brew coffees with different flavour profiles.

Effect of pilot-scale UV-C light treatment assisted by mild heat on E. coli, L. plantarum and S. cerevisiae inactivation in clear and turbid fruit juices. Storage study of surviving populations

Multi-method approach indicates no presence of sub-lethally injured Listeria monocytogenes cells after mild heat treatment

Inactivation kinetics of Listeria monocytogenes and Salmonella enterica serovar Typhimurium on fresh-cut bell pepper treated with slightly acidic electrolyzed water combined with ultrasound and mild heat

Viability of Clostridium perfringens, Escherichia coli, and Listeria monocytogenes Surviving Mild Heat or Aqueous Ozone Treatment on Beef Followed by Heat, Alkali, or Salt Stress

Modification of membrane properties and fatty acids biosynthesis-related genes in Escherichia coli and Staphylococcus aureus: Implications for the antibacterial mechanism of naringenin

Plasma-activated water (PAW), which is the water treated by cold plasma, represents a promising strategy for food decontamination. However, studies of the influences of heating on the antibacterial efficacy and physicochemical characteristics of PAW are limited. Therefore, the present work is aimed at determining the effect of heating on the bactericidal effects and physicochemical properties of PAW. PAW (1.0 mL) was heated in a water bath at 30–80°C for 10 min. After being cooled to room temperature, the antibacterial efficacy and physicochemical properties of PAW were measured. Heating at 40–80°C for 10 min caused a significant decrease in the antibac-terial activity of PAW against Listeria monocytogenes and Salmonella typhimurium. After heating at 40–80°C for 10 min, the pH value and oxidation reduction potential (ORP) of PAW remained stable, and the level of nitrate and electrical conductivity of PAW remarkably increased, while hydrogen peroxide and nitrite contents significantly decreased. The combination treatment of PAW and mild heating (40–60°C for 4 min) showed greater anti-bacterial effect on L. monocytogenes and S. typhimurium. After the combined treatment of PAW with mild heating at 60°C for 4 min, the populations of L. monocytogenes and S. typhimurium decreased by 7.83 log10 CFU/mL and 9.35 log10 CFU/mL, respectively, which were significantly higher than that caused by PAW at 25°C or mild heating at 60°C alone. In summary, the antibacterial activity of PAW is significantly affected by the treatment temperature. This work provides a basis for the practical application of PAW in the food industry.