Bengang Wu

Effective Disinfection of Rough Rice Using Infrared Radiation Heating

The objective of this study was to investigate the effect of infrared (IR) heating and tempering treatments on disinfection of Aspergillus flavus in freshly harvested rough rice and storage rice. Rice samples with initial moisture contents (IMCs) of 14.1 to 27.0% (wet basis) were infected with A. flavus spores before the tests. The infected samples were heated by IR radiation to 60°C in less than 1 min, and then samples were tempered at 60°C for 5, 10, 20, 30, 60, or 120 min. High heating rates and corresponding high levels of moisture removal were achieved using IR heating. The highest total moisture removal was 5.3% for the fresh rice with an IMC of 27.0% after IR heating and then 120 min of tempering. IR heating followed by tempering for 120 min resulted in 2.5- and 8.3-log reductions of A. flavus spores in rough rice with the lowest and highest IMCs, respectively. To study the effect on disinfection of rewetting dried storage rice, the surface of the dry rice was rewetted to achieve IMCs of 14.7 to 19.4% (wet basis). The rewetting process for the dry rice had a significant effect on disinfection. IR heating followed by tempering for 60 min resulted in 7.2-log reductions in A. flavus on rewetted rough rice. The log-linear plus tail model was applied to estimate the tempering time needed to achieve a 5-log reduction of A. flavus in rice of different IMCs. At least 30 and 20 min of tempering were needed for fresh rice and rewetted rice, respectively, with the highest IMCs. The recommended conditions of simultaneous disinfection and drying for fresh rice was IR heating to 60°C followed by tempering for 120 min and natural cooling, resulting in a final MC of 16.5 to 22.0%, depending on the IMC. For the rewetted dry rice with an IMC of 19.4%, the recommended condition for disinfection and drying involved only 20 min of tempering. The final MC of the sample was 13.8%, which is a safe MC for storage rice.

Effect of pulsed light on activity and structural changes of horseradish peroxidase

The objective of this research was to investigate the effects of pulsed light on the activity and structure of horseradish peroxidase in buffer solution. Enzyme residual activities were measured. Surface topography, secondary, and tertiary structures of horseradish peroxidase were determined using atomic force microscopy (AFM), Raman spectroscopy, and fluorescence spectroscopy, respectively. Results showed that a complete inactivation of horseradish peroxidase was achieved by application of 10 pulses of pulsed light treatment at an intensity of 500J/pulse. The AFM analysis revealed that the aggregation of enzyme protein increased and surface roughness decreased with the increase in the treatment time. Fluorescence and Raman spectroscopy analysis exhibited that pulsed light destroyed the tertiary and secondary protein structures. The β-sheet composition was decreased while β-turn and random coils were increased. Pulsed light could effectively inactivate horseradish peroxidase by destroying the secondary and tertiary structures of protein in the active center of the enzyme.

Simultaneous decontamination and drying of rough rice using combined pulsed light and holding treatment

BACKGROUND Pulsed light (PL) technology has been proven effective in food disinfection. However, increasing the light intensity or treatment time could swiftly increase the temperature of the food product. Using the thermal effect in an appropriate way may achieve a simultaneous disinfection and drying effect. The objective of this study was to investigate the feasibility of simultaneous disinfection and drying of rough rice using PL and holding treatment. RESULTS Freshly harvested rice samples were inoculated by Aspergillus flavus (A. flavus) and treated using PL under different intensities and durations followed by holding treatment. The PL treatment under intensity of 1.08 W cm(-2) for 21 s led to a reduction of 0.29 log cfu g(-1) on the population size of A. flavus spores. After holding treatment, a 5.2 log cfu g(-1) reduction was achieved. The corresponding total moisture removal reached 3.3% points. No adverse effect on milling quality was detected after the treatment. CONCLUSION The obtained results revealed that the combined PL and holding treatment had good potential for successful application in the rice industry to simultaneously achieve disinfection and drying.

Application of pretreatment methods on agricultural products prior to frying: a review

Frying is one of the methods of processing foods, which imparts flavour, taste, colour and crispness in the fried foods. In spite of an increase in the demand for fried foods by consumers all over the world, the danger posed by consuming too much fat is still a challenge. Many researchers have put forward many ideas on how to reduce the oil uptake and improve the nutritional and organoleptic qualities of foods during frying. Several pretreatment techniques applied to food materials prior to frying have been investigated by researchers in a bid to reduce the oil uptake and improve the quality parameters of fried foods. Therefore, this review focuses on the various pretreatment methods and the recent novel methods like ultrasound, infrared, superheated steam drying, microwave technique and pulsed electric field applied to foods prior to frying and its effects on the qualities of fried foods.

Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration as a novel method for garlic slices dehydration

This study investigated the effects of multi-frequency mode ultrasound and vacuum technology on the water loss (WL) of garlic slices during osmotic dehydration (OD), and their effects on the microstructure of garlic. A new method of OD for garlic slices was proposed - Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration (VUOD). The results indicated that the WL of the garlic slices treated with VUOD (21.12%) was significantly (p < 0.05) higher than slices treated with normally OD (NOD) (10.67%), vacuum pretreatment OD (VOD) (14.18%), and multi-frequency mode ultrasound assisted OD (UOD) (11.20-13.56%). A mass transfer mechanism of VUOD was proposed. Low-field nuclear magnetic resonance results quantified the moisture migration in the vacuole, cytoplasm and intercellular space, and the cell wall of garlic cells. The quality properties (allicin content, surface color change and firmness) of VUOD treated garlic slices are predominately better than NOD, VOD and UOD treated samples.

Drying Performance and Product Quality of Sliced Carrots by Infrared Blanching Followed by Different Drying Methods

Abstract The objective of this study was to investigate the processing parameters and quality of carrots under sequential infrared (IR) dry-blanching and (1) hot air drying (IRB-HAD), (2) infrared drying (IRB-IRD), and (3) Infrared-hot air drying (IRB-IRHAD). Water blanching at 90oC was used for comparison. The quality of dried carrot was evaluated based on vitamin C content, rehydration ratio, color, shrinkage and hardness. Applying IR dry-blanching for 15 min resulted in the reductions of about one log in peroxidase (POD) activities and 54 % in moisture reduction. A notable change in the surface color and retention of vitamin C were obtained with IR blanching. IRB-IRD and IRB-IRHAD had higher drying rates and higher quality. The recommended processing parameters for IRB-IRHAD are IR blanching for 15 min, followed by IR drying to a moisture content of 30–40 % wet basis (w.b.), and then finished by HA drying to a targeted MC (8 % w.b.).

Effect of catalytic infrared dry-blanching on the processing and quality characteristics of garlic slices

This study investigates the effects of catalytic infrared (CIR) dry-blanching (CIRDB) on the processing and quality of garlic slices. CIRDB processing parameters of CIR processing temperature, slice thickness and processing time were studied versus the processing characteristics of internal temperature, peroxidase (POD) activity and moisture reduction. Blanched garlic quality characteristics of surface color change (ΔE), allicin retention rate, vitamin C retention rate and microbial content were determined. Hot water blanching (WB) was used as a comparison. The results indicated that increasing CIR processing temperature and/or reducing the slice thickness accelerated internal temperature rise and POD inactivation and moisture reduction. To achieve 90% inactivation of POD, the CIRDB treatment resulted in moisture reductions of 15.87-40.37%, microbial reductions of 1.76-3.91-log, ΔE between 2.03 and 10.01, retention rate of allicin between 10.63 and 33.31%, and retention rate of vitamin C between 55.00 and 81.13%. CIRDB achieved the high-quality garlic products compared with WB.