Inactivation Of Molds Research Articles

Possibilities of using the continuous type of UV light on the surface of lor (whey) cheese: impacts on mould growth, oxidative stability, sensory and colour attributes during storage.

This research paper addresses the hypothesis that the optimum doses of a continuous type of ultraviolet (UV) light applied to the surface of lor (whey) cheese needs to be identified to maximize mould inactivation and shelf life while minimizing quality deterioration. Therefore, the mould inactivation, protein and lipid oxidation products, sensory and colour attributes of lor cheese subjected to different doses of UV light (1.617, 4.018, and 36.832 kJ/m2) in a continuous type of UV system were evaluated. UV treated samples presented mould counts lower than those of untreated ones. UV treatment at more than 4.018 kJ/m2 allowed around 0.7-2.7 log reductions on mould growth during storage. The increase in UV light dose caused significant increases in primary and secondary lipid oxidation products. In particular, the highest doses applied to the surface of cheese samples had the highest values of protein carbonyls, as well as lipid oxidation products. Strong positive correlations were recorded between lipid and protein oxidation markers. Exposure to the highest doses of UV light increased foreign flavour perception, probably due to the oxidative reactions. The results indicated that the application of UV light to the lor cheese surface allowed delaying mould growth during storage but extreme doses could induce lipid and protein oxidation reactions, leading to quality deterioration.

Enhancing the Efficacy of Microwave Blanching-cum-black Mould Inactivation of Whole Garlic (Allium sativum L.) Bulbs Using Ultrasound: Higher Inactivation of Peroxidase, Polyphenol Oxidase, and Aspergillus niger at Lower Processing Temperatures.

The freshly harvested whole garlic bulbs require the inactivation of peroxidase (POD), polyphenol oxidase (PPO), and Aspergillus niger. However, the conventional hot water blanching and modern pretreatment like ultrasound (US) and microwave (MW) cannot individually inactivate both the enzymes and Aspergillus niger to the desired levels without compromising the quality of the garlic due to either of the higher process temperatures (> 85 °C) or prolonged treatment times. Therefore, a two-stage sequential US followed by MW pretreatment for garlic bulbs was developed for simultaneous inactivation of POD, PPO, and Aspergillus niger to the desired levels and overcome the individual pretreatment drawbacks. The separate experiments were conducted for US and MW pretreatment using central composite design, and optimization was carried out using response surface methodology. When temperature constraint was considered during optimization, the US was able to reduce POD, PPO, and Aspergillus niger by 80.87%, 93.80%, and 2.60 logs, respectively, whereas MW reduced POD, PPO, and Aspergillus niger by 77.84%, 77.04%, and 1.90 logs, respectively. The US treatment (58.43 WL−1 ultrasound power density for 40 min with an initial bath temperature of 60 °C) followed by MW treatment (3 Wg−1 MW power density for 120 s) resulted in 90.37% POD and 92.38% PPO inactivation with 2.62 log reduction in Aspergillus niger. The maximum temperature reached in US + MW process was 83 °C which ensured no severe thermal damage to the garlic bulbs. The scanning electron microscopic images indicated that ultrasonication induced the porous structure in garlic and helped microwaves increase the product temperature rapidly and achieve the higher inactivation of enzymes and Aspergillus niger. Thus, the US was found to be enhancing the efficacy of the MW heating process.

Application of batch system ultraviolet light on the surface of kashar cheese, a kind of pasta-filata cheese: effects on mould inactivation, lipid oxidation, colour, hardness and sensory properties.

This research paper addresses the hypothesis that the application of ultraviolet (UV) light before packaging of pasta-filata cheese has the potential to eliminate or control post-processing contamination whilst maintaining chemical and sensorial quality. The surfaces of kashar cheese were treated at different doses of UV light (0.32-9.63 kJ/m2) in a batch UV cabinet system to determine effects on physicochemical and sensorial quality as well as mould inactivation. Untreated cheese samples were also used for comparison. Kashar cheese was naturally contaminated in a mouldy environment to provide the desired mould numbers before UV treatments. Log reductions of 0.34, 0.69 and 2.49 were achieved in samples treated at doses of 0.32, 0.96 and 1.93 kJ/m2, respectively and the mould count of sample treated at 9.63 kJ/m2 was below the detection limit. We found no significant differences in composition and hardness values between any of the treated or control cheeses. Although some individual colour values increased as the UV doses increased, this change was not observed visually in sensory analysis. Increased light intensity accelerated the lipid oxidation causing a perception of off-flavour. The results of this study show that it is necessary to examine the relationship between the oxidative and sensory interactions while determining the effective doses applied to cheese surface for microbial inactivation.

Inactivation of molds on the surface of wheat sprouts by chlorophyllin-chitosan coating in the presence of visible LED-based light

The present study clearly demonstrated the significant antifungal activity of chlorophyllin-chitosan complex (Chl-CHS) after activation with visible light. This phenomenon afterwards was successfully applied for better microbial control of highly popular food- germinated wheat sprouts.Obtained results indicated that photoactivated Chl-CHS complex (0.001% Chl-0.1% CHS and 0.005% Chl-0.5% CHS, 405 nm, 76 J/cm2) considerably inhibited (83%) the growth of dominating sprout pathogenic microfungus Fusarium graminearum in vitro. Moreover, obvious delay of fungus growth by 4 days after treatment was observed. The efficiency of antifungal treatment strongly depended on used Chl-CHS complex concentration.The coating of wheat grains with Chl-CHS (0.005% Chl–0.5% CHS) and illumination with visible light (405 nm; 76 J/cm2) inactivated the molds on the surface of grains by 79%. It is important to note, that no grain surface microstructure damage observed by SEM imaging have been found. No inhibiting effects on seed germination process, viability, average weight of grains, length of seedlings and content of chlorophyll a and chlorophyll b in the seedlings or eventually visual quality after Chl-CHS coating of grains and illumination with visible light have been observed.In conclusion, chlorophyllin-chitosan coating in the concert with visible light has great potential as cost-effective, environmentally friendly and sustainable strategy for better microbial control of highly contaminated sprouts.

Inhibition or Stimulation of Ochratoxin A Synthesis on Inoculated Barley Triggered by Diffuse Coplanar Surface Barrier Discharge Plasma.

Ochratoxin A (OTA) is one of the most abundant food-contaminating mycotoxins. Besides their high toxicity, mycotoxins are highly stable to physical, chemical or biological detoxification. Therefore, the treatment with cold atmospheric plasma could be one approach to reduce the amount of mycotoxins in different products. The aim of this study was to determine the influence of cold atmospheric plasma on the inactivation of Aspergillus niger and Penicillium verrucosum inoculated on barley and their production of OTA. Inoculated barley was treated with plasma generated by dry air, CO2 or CO2 + O2 for 1 or 3 min and stored for up to two weeks at 9, 25, or 37°C. Three minutes of air plasma treatment effectively significantly reduced the total mold count of both microorganisms by 2.5–3 log cycles. The production of OTA from A. niger was only low, therefore the treatment effect was indistinguishable. The treatment of P. verrucosum on barley after an incubation of five days using a CO2 + O2 plasma resulted in a reduction of the OTA content from 49.0 (untreated) to 27.5 (1 min) and 23.8 ng/g (3 min), respectively. In contrast, CO2 plasma caused an increase of the OTA amount from 49.0 (untreated) to 55.8 (1 min) and 72.9 ng/g (3 min). Finally, the use of air plasma resulted likewise in a decrease of the OTA concentration from 56.9 (untreated) to 25.7 (1 min) and 20.2 ng/g (3 min), respectively. Reducing the incubation time before the treatment to 24 h caused in contrast an increase of the OTA content from 3.1 (untreated) to 29.1 (1 min) and 20.7 ng/g (3 min). Due to the high standard deviation, these changes were not significant, but the tendencies were clearly visible, showing the strong impact of the plasma gas on the OTA production. The results show, that even if the total mold count was reduced, under certain conditions the OTA amount was yet enhanced, probably due to a stress reaction of the mold. Concluding, the plasma gas and incubation conditions have to be considered to allow a successful inactivation of molds and in particular their toxic metabolites.

Viability of Molds and Bacteria in Tempeh Processed with Supercritical Carbon Dioxides during Storage.

Application of supercritical carbon dioxide for processing of food products has an impact on microbial inactivation and food quality. This technique is used to preserve tempeh due to no heat involved. The quality of tempeh is highly influenced by mold growth because of its role in forming a compact texture, white color, and functional properties as well as consumer acceptance. This study aims to observe viability of molds and bacteria in tempeh after processed with supercritical CO2 and to determine the best processing conditions which can maintain mold growth and reduce the number of bacteria in tempeh. For that purpose, tempeh was treated using high pressure CO2 at 7.6 MPa (supercritical CO2) and at 6.3 MPa (sub/near supercritical CO2) with incubation period of 5, 10, 15, and 20 min. The best treatment obtained was used to process tempeh for storage study. The results showed that there was a significant interaction between pressure and incubation period for bacterial and mold viability at ρ>0.05. Reduction of bacteria and molds increased with longer incubation period. Molds were undetectable after treatment for 20 min with either supercritical CO2 or sub-supercritical, and bacteria significantly reduced up to 2.40 log CFU/g. On the other hand, sub-supercritical CO2 for 10 min was the best processing method because molds survived 4.3x104 CFU/gram after treatment and were able to grow during storage at 30°C, producing white mycelium as indicated by increasing the L⁎ color value and tempeh acceptability. The inactivation of mold was reversible causing it to grow back during storage under suitable conditions. Tempeh matrix composition can provide protection against the destructive effects of supercritical CO2. Gram-positive bacteria were more resistant than Gram-negative. In conclusion, sub-supercritical CO2 can act as a method of cold pasteurization of tempeh and can be used as an alternative method to preserve tempeh.

Comparing high pressure thermal processing and thermosonication with thermal processing for the inactivation of bacteria, moulds, and yeasts spores in foods

Bacterial and fungal spores might germinate/grow after food processing, causing food-borne diseases or food spoilage. High pressure processing (HPP) and power ultrasound are two technologies that can be combined with heat (HPP-thermal or HPTP, TS) to increase the rate of spore inactivation. The objective of this study was to compare HPP, HPTP and TS with exclusively thermal processing to inactivate spores of two pathogenic bacteria (Clostridium perfringens, Bacillus cereus) as well as fruit spoilage microorganisms (Alicyclobacillus acidoterrestris bacteria, Byssochlamys nivea and Neosartorya fischeri moulds, and Saccharomyces cerevisisae yeast). For a 20 min process at 75 °C, 600 MPa HPTP was the best technology for the inactivation of spores of C. perfringens in beef slurry (2.2 vs. 0.9 log for 0.33 W/g TS and no inactivation for thermal treatment). Likewise, at 70 °C 600 MPa HPTP was better to inactivate B. cereus spores in milk than single thermal treatment (4.0 vs. 0.3 log after 20 min process). At 75 °C 600 MPa HPTP was also the best technology for the inactivation of mould ascospores of N. fischeri in apple juice (4.3 log) and B. nivea in strawberry puree (2.0 log) vs. no effect for thermal and even increase in the spores with TS after a 20 min process. TS was a better technology than thermal treatment to reduce A. acidoterrestris spores in orange juice (0.6 vs. 0.2 log after 20 min at 78 °C). Regarding S. cerevisiae ascospores inactivation in beer, non-thermal HPP was much better than TS and thermal processing: 3 log reductions required only 30 s at 400 MPa vs. 5 min for 16.2 W/mL-TS-55 °C and 84 min for 55 °C thermal. Overall, the heat assisted HPP technology was better than TS and thermal treatment alone for the inactivation of bacteria, mould, and yeast spores, requiring lower processing times thus allowing a better food quality.

Change of microbial and quality attributes of mango juice treated by high pressure homogenization combined with moderate inlet temperatures during storage

Abstract The effects of high pressure homogenization (HPH) on microbial inactivation and quality attributes (physio-chemical properties, bioactive components and antioxidant capacity) of mango juice, as well as their changes during storage at 4 °C and room temperature were investigated. Pressure levels ranged from 40 to 190 MPa, the inlet temperature from 20 °C to 60 °C and the number of passes from 1 to 5. Complete inactivation of molds and yeasts was achieved by 1 and 3 passes at 190 MPa and 60 °C, while total plate count was below 2.0 log10 CFU/mL. No multiplication of microorganisms was observed in mango juice over 60 days of storage at 4 °C. HPH treatment could retain or even increase the carotenoids and total phenols by 11.8% and 21.4%, respectively, while significant reductions were found for heat treatment (HT) samples. During the storage of 60 days, HPH treatment also provided better preservation of color, bioactive components and antioxidant capacity of mango juice than HT. Industrial relevance High pressure homogenization (HPH) is a novel non-thermal technique, particularly suitable for continuous production of liquid foods limiting thermal damage and promoting “freshness”. Results showed that high pressure homogenization had the advantage of notably reducing the microbial load to levels equivalent to thermal pasteurization. Moreover, HPH treatment was superior to heat treatment with regard to post-treatment levels of bioactive.

Analysis of Fungal Diversity in Ready-to-Eat Pizza and Effectiveness of Pulsed Ultraviolet-Light Treatment for Inactivation of Mold on Agar Surface

Fungal contamination is a significant issue in the food production industry; therefore, identification and characterization of food spoilage fungi would allow for early intervention to limit the amount of fungal contamination, particularly in cereal-based industries. In the present study, culture-dependent and culture-independent methods were applied to study the microbiota of ready-to-eat pizza. The study was pursued by evaluating the effectiveness of a broad-spectrum pulsed ultraviolet light for the decontamination of Penicillium roqueforti (a dominant spoilage mold in bakery products) on the surface of solid agar as a representative of a flat food surface. The average population of mesophilic aerobic bacteria (MAB), mesophilic anaerobic bacteria (MANB), lactic acid bacteria (LAB), molds and yeasts (M+Y) on naturally spoiled pre-cooked pizza were 6.7 ± 0.5, less than 2.3, 2.8 ± 0.6 and 5.4 ± 0.4 log10 CFU g-1, respectively. Cloning and sequencing identified at least 5 genera and species of fungi (Penicillium spp., Saccharomyces spp., Rhodotorula mucilaginosa, Monascus fuliginosus, Galactomyces geotrichum) from 2 phyla (Ascomycota and Basidiomycota). Pulsed light process parameters evaluated were treatment time (1, 3, 5, 7 and 10 min) and voltage input (500, 750 and 1,000 V) at 5 cm distance from the pulsed UV-light. An increase of the input voltage of the lamps and of the duration of the treatment resulted in a higher inactivation of P. roqueforti. The population of P. roqueforti was reduced after 10 min of exposure to pulsed light by 3.74, 5.36 and 6.14 log10 CFU ml-1 at 500, 750 and 1,000 V, respectively. The inactivation kinetics was best described by the Weibull model (2 parameters) with the smallest root mean squared error (RMSE) and R2 ≥ 0.92. The results of this work show that pulsed light is a promising technique for fungi elimination or decontamination in the bakery industry.

The effect of high-power ultrasound and gas phase plasma treatment on Aspergillus spp. and Penicillium spp. count in pure culture.

The aim of this study was to investigate and compare two nonthermal techniques in the inactivation of moulds. High power ultrasound (20kHz) and nonthermal gas phase plasma treatments were studied in the inactivation of selected moulds. Aspergillus spp. and Penicillium spp. were chosen as the most common mould present in or on food. Experimental design was introduced to establish and optimize working variables. For high power ultrasound, the greatest reduction of moulds (indicated by the total removal of viable cells) was obtained after ultrasound treatments at 60°C (thermosonication) for 6 and 9min (power applied, 20-39W). For plasma treatment, the greatest inactivation of moulds was observed for the longest treatment time (5min) and lowest sample volume (2ml), (AP12, AP13, PP12 and PP13). The great amount of applied energy required for achieving a partial log reduction in viable cells is the limiting factor for using high-power ultrasound. However, both treatment methods could be combined in the future to produce beneficial outcomes. This study deals with nonthermal food processing techniques and the results and findings present in this study are the root for further prospective studies. The food industry is looking for nonthermal methods that will enable food preservation, reduce deterioration of food compounds and structure and prolong food shelf life.

Pulsed light inactivation of naturally occurring moulds on wheat grain

Pulsed light (PL) is emerging as a non-thermal technology with excellent prospects for the decontamination of foods and food contact surfaces. Its application for mould inactivation on cereal grains would allow a reduction of storage losses as well as the prevention of mycotoxin contamination at a post-harvest level. The potential of PL for the decontamination of naturally occurring moulds on wheat grain was investigated in this study. Treatments of up to 40 flashes of a fluence of 0.4 J cm⁻² per pulse were applied to both sides of the grain, with an overall energy release ranging from 6.4 to 51.2 J g⁻¹. The most powerful treatment applied to wheat in this study (51.2 J g⁻¹) resulted in a mould reduction of approximately 4 log cycles on samples displaying an initial mould contamination level of 2.2 × 10⁵ CFU g⁻¹. At the same time, the seed germination percentage was only slightly affected. For PL treatments causing an inactivation of 3-4 log cycles, only 14-15% of the germination power of the wheat seeds was lost. The PL treatments attained greater microbial reductions for higher treatment times and lower initial mould loads. The absence of the UV portion of the radiation spectrum was found to significantly reduce the treatment effectiveness.

Heating patterns of white bread loaf in combined radio frequency and hot air treatment

This research investigated heating uniformities of prepackaged bread loaf using combined radio frequency (RF) and hot air treatments to reduce mold growth. Experiments were conducted in a 6kW, 27.12MHz pilot-scale RF system. Effects of the gap between two RF plate electrodes, horizontal and vertical locations of bread loaf, as well as running speed of conveyor belt were studied. When the bread loaf was located in the center plane between the two electrodes 202mm apart, and on a conveyor belt moving at a speed of 1cm/s to reach a minimum sample temperature of 58°C, the temperature distribution within each slice was relatively uniform, with less than a 5°C difference. The cold spot was located at the core of the bread loaves. Higher surface temperature should be useful to assist in inactivation of molds that are commonly vegetated on the surface of the whole loaf.

Quality of Mango Nectar Processed by High‐Pressure Homogenization with Optimized Heat Treatment

This work aimed to evaluate the effect of high-pressure homogenization (HPH) with heat shock on Aspergillus niger, vitamin C, and color of mango nectar. The nectar was processed at 200 MPa followed by heat shock, which was optimized by response surface methodology by using mango nectar ratio (45 to 70), heat time (10 to 20), and temperature (60 to 85 °C) as variables. The color of mango nectar and vitamin C retention were evaluated at the optimized treatments, that is, 200 MPa + 61.5 °C/20 min or 73.5 °C/10 min. The mathematical model indicates that heat shock time and temperature showed a positive effect in the mould inactivation, whereas increasing ratio resulted in a protective effect on A. niger. The optimized treatments did not increase the retention of vitamin C, but had positive effect for the nectar color, in particular for samples treated at 200 MPa + 61.5 °C/20 min. The results obtained in this study show that the conidia can be inactivated by applying HPH with heat shock, particularly to apply HPH as an option to pasteurize fruit nectar for industries.

Endoscopic exploration

Cold plasma is a novel technology that has been widely studied for microbial inactivation. The generation of chemical reactive species produced by electrical discharge into a working gas lead to microbial inactivation because of the presence of highly oxidizing agents such as O3, NOx, or H2O2, having a disturbing effect on the cell wall and intracellular components. Cold plasma has been successfully tested on the inactivation of molds and yeasts, but also has been proven to achieve spore death. Few studies are reported in viral inactivation with significant results, but still more research needs to be conducted to better understand mechanisms of inactivation. A scarce area explored under cold plasma is food parasites, an important topic that has been neglected but has a high impact on food safety.

Influence of Potassium Sorbate and Sodium Benzoate on Heat Inactivation of Aspergillus flavus, Penicillium puberulum and Geotrichum candidum

Experiments were conducted to determine if two preservatives, potassium sorbate and sodium benzoate, had a synergistic effect with heat on inactivation of conidia of Aspergillus flavus and Penicillium puberulum and vegetative cells of Geotrichum candidum. A second objective was to determine if heated conidia had increased sensitivity to preservatives in a recovery medium. As the pH of heating menstrua was decreased from 7.0 to 2.5, the rates of inactivation of molds were increased. Conidia were not as adversely affected by acid pH as were vegetative cells. At 50 ppm, potassium sorbate caused a significant (P⩽0.05) increase in the rate of thermal inactivation of A. flavus and G. candidum; 100 ppm had a significant effect on P. puberulum. Sodium benzoate caused significant decreases in decimal reduction times of A. flavus and P. puberulum when present at a concentration of 50 ppm in heating media. Viable heated conidia of A. flavus and P. puberulum had increased sensitivity to potassium sorbate and sodium benzoate, indicating heat injury. However, the relative effects of the two preservatives on colony formation in recovery agar were reversed from those noted in heating media, i.e., at comparable concentrations, potassium sorbate was more effective than was sodium benzoate for inhibiting colony formation.

Inactivation of molds by germicidal ultraviolet energy

Inactivation of molds by germicidal ultraviolet energy