Improving radio frequency heating uniformity in milled rice with different packaging shapes by changing temperature of forced air

Radio frequency (RF) treatment is a promising physical method for disinfesting and pasteurizing foods but the non-uniform RF heating is still a major obstacle for industrial applications. In this study, a three-dimensional model was established with COMSOL software to simulate temperature distributions in milled rice with different packaging shapes and experiments using a 6 kW, 27.12 MHz RF system were carried out to evaluate the improvement of heating uniform of sample by changing temperature of forced air. The established model was validated by temperature-time histories at three points in the sample and temperature distributions at the top and bottom surfaces. The results showed that the cold spot of the regular shape sample was found at the part with small thickness, and the RF heating uniformity was improved by increasing temperature of forced hot air. When the temperature of forced hot air increased from 40 to 60 °C, all the sample temperatures were above 50 °C, which might meet the required temperature of disinfestation, and the heating uniformity index decreased from 0.113 to 0.099. For the cuboid shape sample, the corner/edge effect was observed and the heating uniformity index firstly decreased and then increased with reduced temperature of forced cold air. When the temperature of forced air decreased to 10 °C, the best heating uniformity of the cuboid shape sample was obtained. The results of this research can help to select packaging shape and improve the heating uniformity of samples for RF treatment in large-scale applications.     

Fibrillation of whey protein isolate by radio frequency heating for process efficiency: Assembly behavior,structural characteristics,and in-vitro digestion

In this study, a novel technology involving radio frequency heating (RF) was applied to promote the production of whey protein isolate (WPI) nanofibrils. As the prolonged treatment time, gradual increases were observed in the conversion rate (>16 h with the conventional processes), fluorescence intensity, and free amino acid content of WPI. During the fibrillation process, WPI was hydrolyzed into small molecular weight peptides that self-assembled into fibrils, resulting in a significant increase in the ζ-potential and surface hydrophobicity. Conformational and structural changes that favored an increased content of β-sheets were confirmed by Fourier transform infrared and circular dichroism spectroscopy. A linear fibril structure with a proper aspect ratio (length/diameter, 35.50 ± 0.39) formed at 7 h. Moreover, the good resistance to proteolytic digestion (especially gastric stage) of certain fibrils makes them suitable for application as nutraceutical delivery vehicles. Our findings move a step forward for WPI fibrillation by RF heating.     

Numerical simulation approach for predicting rice milling performance under different convex rib helix angle based on discrete element method

Rice milling, as a critical process in rice processing, determines the subsequent storage, nutritional quality and economic value of rice. Unfortunately, due to the complex milling mechanism and few quantitative methods to predict the milling effect of rice, the improvement of the key components of rice mill has become one of the issues restricting the development of rice milling industry. In this work, rice milling performance in rice mill with different convex rib helix angle α was studied through the combination of simulation and experiment. Modified actual milling time distribution can accurately quantify the uniformity of rice milling. Milling uniformity of rice gradually deteriorated with α. Compared with traditional evaluation methods, the regional energy algorithm can reflect the rice milling degree more accurately. Besides, the friction effect between rice become more intense with increased α. These results can provide theoretical guidance for the parameter optimization of rice mill.     

Multi-step ozone treatments of malting barley: Effect on the incidence of Fusarium graminearum and grain germination parameters

The effect of multi-step ozone treatments at 20 ± 1 °C in aqueous phase on the reduction of the incidence of Fusarium graminearum in artificially contaminated malting barley (10⁴ CFU/g) was studied. Samples (50 g of infected barley) were ozonated in a bubble column that contained 500 mL water. Percentage of infected grains was assessed at three incubation temperatures (15, 20, and 25 °C). Ozonation in three steps of 45 min each (9.0 g ozone/L water per step) led to a significant reduction of the mould's incidence in barley, from 100% to 47%, 81%, and 78% at the three incubation temperatures, respectively. Germination parameters were tested separately in non-infected samples to evaluate the effect of ozone treatments on the grains' suitability for malting: germinative capacity and germinative energy were not significantly affected by the treatments (100% and 98%, respectively), whereas water sensitivity (related to the excessive absorption of water by grains, which impairs germination) was reduced from 19 to 11%. Grains treated in three steps achieved the moisture content (42%, wet basis) needed to start the germination stage in a steeping period (2.25 h) shorter than the traditional ones (36–52 h).Industrial relevance: The reduction of the incidence of F. graminearum in barley by the multi-step application of ozone in the steeping stage of the malting process is proposed as a strategy for improving the quality of malt and beer, without significant impact on barley germinative capacity and germinative energy, and reduction of water sensitivity. Shorter steeping periods are feasible, as well as the possibility of water reutilization, by these residue-free treatments.     

Plasma-activated water for disinfection and quality retention of sea bream fillets: Kinetic evaluation and process optimization

The efficacy of plasma-activated water (PAW) in the decontamination of sea bream fillets at various processing conditions including fish/immersion agent ratio (1/1–1/5) and immersion times (0–20 min), was evaluated. Deionized water (as control samples) and artificially produced water (artificial) with equal reactive species (H₂O₂, NO₂⁻, and NO₃⁻) concentrations to PAW were also used as immersion agents for comparison purposes. All the fillets were assessed in terms of their microbiological (total aerobic bacteria – TAB, yeasts/molds, hydrogen sulfide (H₂S)-producing microorganisms, lactic acid bacteria – LAB, Pseudomonas spp., Brochotrix thermosphacta, and Enterobacteriaceae) and physicochemical (color, texture, lipid oxidation) characteristics. PAW-treated samples exhibited the highest microbial reduction; the loads of TAB, Pseudomonas spp., yeasts/molds, Enterobacteriaceae, H₂S-producing bacteria and Brochotrix thermosphacta were reduced by approximately 1.58, 2.25, 3.95, 2.14, 1.96 and 1.48 logCFU/g, respectively compared to the fish initial natural microbiota (6.81, 6.25, 3.95, 5.14, 4.96 and 4.81 logCFU/g, respectively) at the most intense process conditions (fish/immersion agent ratio of 1/5 and immersion time of 20 min) (p < 0.05). Shelf-life study of all treated fillets was conducted to validate the efficiency of PAW. During 10-d storage at 4 °C, the PAW-processed sea bream fillets had lower microbial growth rates (i.e. for TAB growth, the rate was 0.440 d⁻¹ for PAW-treated compared to 0.640 d⁻¹ for untreated fillets) and retained their color and hardness, while total volatile basic nitrogen (TVB-N) remained at low levels (14.90 mg N/100 g) compared to the untreated ones (21.84 mg N/100 g). Their shelf-life was extended by approximately 60% and 30% for PAW- and artificially processed samples, respectively, (2.8- and 1.4-day shelf-life extension compared to control samples, respectively). These aforementioned data show that PAW can be efficiently used as a disinfectant agent to control microbial degradation, while retaining the quality of fish fillets.Industrial relevanceFish fillets are perishable food products, while none of the conventional or novel processing technologies or techniques may be applied for initial microbial population decrease. Storage and transportation at refrigeration temperatures below 1 °C (within Styrofoam insulated boxes full of ice flakes) is the target of the relevant companies for extending the shelf-life as much as possible.An alternative approach for reducing the initial microbial load and the microbial growth rate of fish fillets during storage and transportation is proposed, by immersing the fillets into Plasma activated water with antimicrobial properties. The microbial load is significantly reduced, resulting in a shelf-life extension by at least 60%. This allows for more distant transportation of the fillets and for less food waste since there is more time for consumption before spoilage.     

Fluence (UV dose) distribution assessment of UV-C light at 254 nm on food surfaces using radiochromic film dosimetry integrated with image processing and convolutional neural network (CNN)

Uniform Fluence (UV Dose) distribution on food surfaces is essential for an effective UV process design. In this study, the use of radiochromic films (RCFs) with a computer vision system (CVS) integrating image processing and Convolutional Neural Network (CNN) is proposed as an alternative method to assess Fluence distribution of UV-C light at 254 nm on food surfaces. The color difference of RCFs exposed to different UV irradiance and exposure times was correlated with Fluence. The validity of the developed methodology was proved by applying it to the surface of apple fruits of different shapes and sizes. A linear relationship was found between the color difference of RCF and Fluence. The maximum Fluence to be determined using RCFs was ∼60 mJ/cm². The color of the films after UV irradiation remained stable for up to 15 days in darkness when stored at room and refrigeration temperatures. The results showed that RCF can be used as an alternative UV dosimeter.     

Synergism effect of low voltage electrostatic field and antifreeze agents on enhancing the qualities of frozen beef steak: Perspectives on water migration and protein aggregation

In this study, a synergistic strategy utilizing low-voltage electrostatic field (LVEF) and antifreeze agents (4% sucrose +4% sorbitol) was proposed to reduce quality deterioration of prepared beef steak during freezing. The effects of the synergistic treatment on the water holding capacity, texture and muscle ultrastructure, myofibrillar protein (MP) aggregation was studied. Results showed that co-treatment significantly reduced thawing losses (about 41%) by preventing the migration of immobilized water to free water and reduced ice crystal size compared to air freezing (AF). In addition, co-treatment positively affected texture properties by shortening the gap between muscle fibers and maintaining the structural integrity of the sarcomeres. Moreover, synergistic treatment inhibited the unfolding of the MP structure and the formation of MP aggregates by strengthening non-covalent interactions. These results seem to demonstrate that LVEF can remarkably enhance the effects of cryoprotectants, which provides a new perspective on food cryoprotection.Industrial relevanceFreezing is the most common method of preserving prepared meat products, however, the formation of large ice crystals and the denaturation of muscle proteins are two major causes of quality deterioration during conventional air-freezing. In this study, a LVEF system was applied to the freezing process of prepared meat products, and a comparative and synergistic study was carried out with the current industry common chemical freezing protection methods (addition of antifreeze). The results showed that the synergistic treatment greatly promoted the nucleation of food products, shortened the phase transition time, reduced the ice crystal size and effectively reduced the thawing losses by approximately 41%. The green freezing system can be easily adapted to scenarios such as cold chain transport and cold storage. And the LVEF intensifies the interaction of antifreeze molecules with protein and water molecules, which seems to open up even more possibilities in cryopreservation.     

Fungal biodiversity and interaction complexity were the important drivers of multifunctionality for flavor production in a spontaneously fermented vinegar

Zhejiang rosy vinegar (ZRV) is produced by spontaneous fermentation. Compared with the microbial community of the vinegar produced by solid-state fermentation, fungi play more important roles in the fermentation of ZRV. In this study, the composition of the fungal community was determined. Aspergillus (average relative abundance: 33.1%), Thermoascus (18.1%), and Candida (15.3%) dominated the fermentation process. Acetic acid and ethanol drove fungal community succession during 40–90 d, while temperature and lactic acid were the drivers during 70–90 d. Keeping low pH and temperature at the initial stage of fermentation was beneficial to improve the quality of ZRV. Multiple members of Rhizomucor, Pichia, and Wickerhamomyces were network hubs during 40–90 d, and they cooperated to ferment starch into ethanol. Moreover, fungal biodiversity and interaction complexity fueled the multifunctionality of organic acid production. These results guided the targeted control of ZRV fermentation to improve the quality of ZRV.Industrial relevanceThese combined findings represent a significant milestone in the understanding of the dynamic profiles of the fungal community, which can add valuable insights to the ZRV manufacturer. Our findings guide the control of fungal community succession during ZRV fermentation to improve the quality.