Sono-photodynamic inactivation of Escherichia coli and Staphylococcus aureus in orange juice

Efficiency of blue (462 ± 3 nm) light emitting diode (LED) illumination to inactivate Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in freshly squeezed orange juice. Further, the combinational effect of ultrasound (US), photosensitizer (PS) and blue light (BL) on inactivation of microbes was evaluated. The effect of process parameters such as concentration of PS, US and volume of the juice on E. coli and S. aureus inactivation was also investigated. The US alone and PS + BL treatments resulted in 3.02 ± 0.52 and 1.06 ± 0.13 log reduction of E. coli; 0.18 ± 0.14 and 2.34 ± 0.13 log reduction of S. aureus, respectively. The combination of PS + US + BL treatment at optimized conditions resulted in 2.35 ± 0.16 log reduction of S. aureus. An additive effect on the inactivation of E. coli (4.26 ± 0.32 log reduction) was observed with PS + US + BL combination treatment. The US treatment showed significant change in cloud value, colour and browning index of orange juice. The combinational non-thermal processes (PS + BL and PS + US + BL) did not have any significant effect on total phenolic content, total flavonoid content, and hesperidin content of the orange juice. However, these processes affected ascorbic acid content and antioxidant activity negatively. Thus, this study indicated that photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fruit juices could be a potential method for microbial inactivation. Nevertheless, the effect on quality parameters needs to be considered while optimizing the process.

Efficacy of blue LED in microbial inactivation: Effect of photosensitization and process parameters

Efficacy of blue (462 ± 3 nm) Light emitting diode (LED) illumination to inactivate the foodborne pathogens like Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in vitro. The effect of temperature, concentration of photosensitizer and incubation time with photosensitizer for microbial inactivation was investigated and sublethal injury of cells was determined. Mechanism of inactivation by the combination of photosensitizer and blue light was also examined. A maximum reduction of 5.94 ± 0.22 and 5.91 ± 0.20 log CFU/ml was obtained for E. coli and S. aureus, respectively, when treated with photosensitizer (20 μM) at 13 J/cm² of blue light. There was no significant change in the inactivation of these pathogens both at 9 °C and 27 °C in the presence of photosensitizer. Even, the incubation with the photosensitizer didn't show any significant difference on the inactivation of these food-borne pathogens. Sublethal injury (>90% injury) was also observed for the cells treated with photosensitizer and blue light simultaneously. Confocal laser scanning microscopy analysis revealed that membrane integrity was disturbed due to photodynamic activity of curcumin in both the bacteria. Further, both cells produced intracellular reactive oxygen species by the action of photosensitizer and blue light. Scanning electron microscopy of E. coli and S. aureus cells treated with photosensitizer and blue light showed morphological changes in the cell wall compared to untreated group. The study indicated that photodynamic inactivation of foodborne pathogens using LED-based photosensitization can be explored as a potential technique for food safety.

Recent Developments in Superheated Steam Processing of Foods-A Review

Although the use of superheated steam has been known for quite a long time, only in the recent past has it emerged as a viable technology for food processing. Superheated steam, having higher enthalpy, can quickly transfer heat to the material being processed, resulting in its rapid heating. The major advantages of using superheated steam for food processing are better product quality (color, shrinkage, and rehydration characteristics), reduced oxidation losses, and higher energy efficiency. This review provides a comprehensive overview of recent studies on the application of superheated steam for food-processing operations such as drying, decontamination and microbial load reduction, parboiling, and enzyme inactivation. The review encompasses aspects such as the effect of superheated steam processing on product quality, mathematical models reported for superheated steam drying, and the future scope of application in food processing. Recent studies on process improvisation, wherein superheated steam is used at low pressure, in fluidized bed mode, sequential processing with hot air/infrared, and in combination with micro droplets of water have also been discussed.

Application of microwaves for microbial load reduction in black pepper (Piper nigrum L.)

BACKGROUND

Black pepper (Piper nigrum L.) is exposed to microbial contamination which could potentially create public health risk and also rejection of consignments in the export market due to non-adherance to microbial safety standards. The present study investigates the use of microwave (MW) radiation for microbial load reduction in black pepper and analyses the effect on quality.

RESULTS

Black pepper was exposed to MWs at two different power levels (663 and 800 W) at an intensity of 40 W g(-1) for different time intervals (1-15 min) and moisture content (110 and 260 g kg(-1) on a wet basis). The exposure of black pepper to MWs at 663 W for 12.5 min was found to be sufficient to reduce the microbial load to the permissible level suggested by the International Commission on Microbiological Specifications for Foods and the European Spice Association. The retention of volatile oil, piperine and resin was 91.3 ± 0.03, 87.6 ± 0.02 and 90.7 ± 0.05%, respectively, in MW-treated black pepper. The final moisture content after MW treatment was found to be 100 ± 1 g kg(-1) for black pepper containing initial moisture of 260 ± 3 g kg(-1) .

CONCLUSION

These results suggest that MW heating can be effectively used for microbial load reduction of black pepper without a significant loss in product quality. © 2016 Society of Chemical Industry.

Efficacy of reverse micellar extracted fruit bromelain in meat tenderization

Reverse micellar extraction (RME) was used for the separation and purification of bromelain from pineapple core and efficacy of RME purified bromelain (RMEB) in tenderization of beef meat was compared with that of commercial stem bromelain (CSB). RME resulted in reasonably high bromelain activity recovery (85.0 %) and purification fold (4.0). Reduction in meat toughness was higher in RMEB treated meat (52.1 %) compared to raw (control) and CSB treated (26.7 %). Significant increase in water holding capacity (WHC) was observed in RMEB treated meat (91.1 %) as against CSB treated (55.6 %) and control (56.6 %). No change in cooking loss was observed in RMEB treated meat, whereas the loss increased by nearly 14.0 % in case of CSB treated. While the meat color was retained, trichloroacetic acid (TCA) soluble protein content increased due to hydrolysis of protein in RMEB treated meat. Scanning electron microscopy (SEM) analysis revealed that RMEB treatment completely ruptures myofibril tissues, indicating a higher degree of tenderization.

Use of reverse micellar systems for the extraction and purification of bromelain from pineapple wastes

Reverse micellar systems of CTAB/isooctane/hexanol/butanol and AOT/isooctane are used for the extraction and primary purification of bromelain from crude aqueous extract of pineapple wastes (core, peel, crown and extended stem). The effect of forward as well as back extraction process parameters on the extraction efficiency, activity recovery and purification fold is studied in detail for the pineapple core extract. The optimized conditions for the extraction from core resulted in forward and back extraction efficiencies of 45% and 62%, respectively, using reverse micellar system of cationic surfactant CTAB. A fairly good activity recovery (106%) and purification (5.2-fold) of bromelain is obtained under these conditions. Reverse micellar extraction from peel, extended stem and crown using CTAB system resulted in purification folds of 2.1, 3.5, and 1.7, respectively. Extraction from extended stem using anionic surfactant AOT in isooctane did not yield good results under the operating conditions employed.