Yeast Reduction Research Articles

Evaluating Chlorine Sanitization at Practical Concentrations for Controlling Listeria monocytogenes and Salmonella on Fresh Peaches

Recent foodborne outbreaks and recalls involving Listeria monocytogenes and Salmonella-contaminated peaches have caused significant economic losses to the peach industry. This study evaluated the effectiveness of chlorine, a commonly used sanitizer in the fresh produce industry, against L. monocytogenes and Salmonella and its ability to control cross-contamination in fresh peaches. Peaches inoculated with L. monocytogenes or Salmonella (~6 log10 CFU/peach) were treated with 50–150 mg/L of free chlorine (FC, pH6.8) 24 h post-inoculation. The results revealed that chlorine had similar efficacy against L. monocytogenes and Salmonella on peaches (p > 0.05). A 30 s treatment at 50, 100, and 150 mg/L FC resulted in dose-dependent reductions (p < 0.05), achieving reductions of 0.88–0.92, 1.54–1.61, and 1.73–1.79 log10 CFU/peach, respectively. Extending the contact time to 2 min slightly but significantly enhanced the chlorine efficacy (p < 0.05). Additionally, a 30 s to 2 min exposure to chlorine with 50–150 mg/L FC resulted in a 1.05–1.43 log10 CFU/peach reduction in yeasts and molds. Tap water exposure led to substantial cross-contamination between inoculated and uninoculated fruits and processed water, with Salmonella exhibiting higher transfer rates than L. monocytogenes. The application of chlorine mitigated the cross-contamination of both pathogens but did not entirely prevent it. These findings offer valuable insights for the peach and other stone fruit industries to verify process controls.

Feeding of bakery products as replacement of cereal grains alter fecal microbiome and improve feed efficiency in fattening pigs

The re-integration of former foodstuffs, such as bakery products (BP), into pig feed reduces the feed-food competition and increases the sustainability of pig production. Nevertheless, there are concerns about the altered fatty acid profile in BP compared to standard diets and their effects on meat quality and the intestinal microbiome. The present study investigated the effects of replacing 30% cereal grains with BP in the diet on performance, microbiome composition and metabolites in feces of fattening pigs, economic aspects and meat quality characteristics. A total of 132 pigs (Large White × Piétrain; 11 weeks of age) were fed two diets containing 0 or 30% BP until reaching slaughter weight in three replicate batches. Fecal samples were collected for 16S rRNA amplicon sequencing after 6 weeks, whereas body fat samples were collected after 9 weeks on the diet. The results showed that BP can replace cereals in pig diets by up to 30% without impairing animal performance, while improving feed efficiency and reducing feed costs by 9% compared to the control. Additionally, pigs fed the BP diet had a 50%-higher n-3 fatty acid content in the neck and abdominal fat compared to the control. The improved feed efficiency in BP-fed pigs may be related to positive effects on the fecal microbiome, such as a higher alpha diversity and a reduction of fungi and yeasts. Our study provides valuable insights into the benefits of including BP in diets of fattening pigs, which should be investigated in future studies on other BP types.

Physical, Chemical and Microbiological Changes in Mango Varieties When Cryopreserved Using Solar Energy

Fruits and vegetables are highly perishable living tissues that maintain their metabolic activity even after harvest. This study aimed to monitor the changes of physicochemical and microbiological parameters of two varieties of mango (Valencia and Camerounaise) during conservation in a photovoltaic cold room. The mangoes were stored at 10-12°C with a relative humidity of 80-90% for 3 weeks (Valencia) and 7 weeks (Camerounaise). Mango samples were taken every week for analyses. The physicochemical and microbiological parameters of mangoes were determined using standard methods. Results showed an increase in the reduced sugar content of mangoes (3.12±0.01-4.79±0.02 % for the Valencia variety and 3.01±0.08-6.22±0.02 % for the Camerounaise variety). The water content of the mango remained practically constant (85.42 % to 85.40 %) for the Valencia variety. However, an increase was observed for the Camerounaise variety (86.26±0.00-87.29±0.03 %). The titratable acidity of mangoes decreased (1.07±0.03-0.67±0.01 %) and their Brix level increased (9.8±0.01-16.20±0.01 % for the Valencia variety and 8.00±0.00-13.50±0.14 % for the Camerounaise variety). The maximum relative mass loss observed was 8.25 % for the Camerounaise variety. Regarding the microbiological analyses, the results showed a reduction in total flora and yeast and mold loads during storage. Storage in a solar cold room of fresh mangoes picked at physiological maturity and pretreated in accordance with good hygiene practices, delays the ripening process, inhibits the proliferation of surface microorganisms, preserves the physicochemical characteristics and extends the shelf life of the mangoes. Preserved mangoes are of good quality.

Effect of dehydration and pulsed light treatment on decontamination of minced onions: Microbial safety and physicochemical properties.

Microbial contamination of dehydrated onion products is a challenge to the industry. The study focused on opting for a suitable drying condition for minced onion and exploring the decontamination efficacy of pulsed light (PL) treatment conditions for the dehydrated product. The minced onions were hot air dried at 55-75°C for 280min. The drying condition selected was 195min at 75°C with a final water activity of 0.5 and moisture content of 7% (wet basis [w.b.]). The weight losses, browning indexes (BI), shrinkage volumes (%), and thiosulfinate content were considered. The dehydrated product was exposed to PL treatment corresponding to an effective fluence range of 0.007-0.731 J/cm2. A fluence of 0.444 J/cm2 (1.8kV for 150 s) achieved 5.00, 3.14, 2.96, and 2.98 log reduction in total plate count, yeast and mold count, Bacillus cereus 10876, and Escherichia coli ATCC 43888, respectively. The PL-treated sample (0.444 J/cm2) produced a microbially safe product with no significant difference in the moisture contents (%w.b.) and water activity (aw) from the untreated dehydrated sample. Further, a 30.9% increase in the BI and a 4.25% depletion in thiosulfinate content were observed after PL treatment. An optimum drying combination (75°C for 195min) of minced onion followed by decontamination using pulsed light treatment at 0.444 J/cm2 fluence satisfies the microbial safety and quality. PRACTICAL APPLICATION: Dehydrated minced onion can be used for dishes requiring low water content and short cooking time. It is helpful during shortages, high price fluctuations, and famines.

Comparison of the Chemical and Microbial Composition and Aerobic Stability of High-Moisture Barley Grain Ensiled with Either Chemical or Viable Lactic Acid Bacteria Application

This experiment was aimed at comparing how a chemical additive or an inoculant would affect the dry matter (DM) losses, fermentation pattern, yeast and mold counts, and aerobic stability (AS) of the ensiled high-moisture barley grain (675 g kg−1 DM). Crimped barley grain was ensiled with or without chemical additive AIV Ässä Na and an inoculant SiloSolve FC, totaling three treatments (1 × 3 factorial scheme) for the fermentation periods lasting 7, 14, 28, 60, and 90 days. The application of a chemical additive showed higher pH levels, retained water-soluble carbohydrates (WSCs) better, lowered DM loss, and reduced concentrations of fermentation products. Barley grain treated with chemicals initially showed a marked reduction in yeast and fungal growth and a higher AS up to day 60 of storage but became less effective in later stages of storage, leading to decreased AS. Barley grain inoculated with homo- and heterofermentative strains had decreased silage pH; its WSC content was similar to control and had higher content of weak acids and 1,2 propanediol, reducing mold and yeast counts. With fermentation duration from 28 days and beyond (i.e., 90 days), the inoculant treatment achieved the longest AS and the lowest increase in pH and weight loss during the period of air exposure.

Effect of gamma irradiation on post-harvest quality of king oyster mushrooms (Pleurotus eryngii)

The consumption of king oyster mushrooms has steadily increased owing to their unique flavor and delicate texture. This study extended the storage period of king oyster mushrooms (Pleurotus eryngii) via gamma irradiation. Irradiated samples (0, 0.5, 1, 2, and 3 kGy) were stored at 4°C with 80% relative humidity for up to 28 days, and the experiments were conducted every 7 day. Microbiological analysis revealed a dose-dependent reduction in total aerobic bacteria, Pseudomonas spp., and yeasts and molds, and gamma irradiation above 2 kGy effectively controlled microbial contamination for up to 28 days. At the 28th day of storage, the irradiated king oyster mushrooms exhibited delayed browning through the reduction of tyrosinase activity. Moreover, firmness reduction (%) was 80.59±1.89% for the non-irradiated group and 42.80±1.28, 34.57±1.13, 31.05±3.24, and 39.73±0.94% for the irradiated group (0.5, 1, 2, and 3 kGy), respectively. These results were supported by the scanning electron microscopy photos, which showed smaller pores in the irradiated group than in the non-irradiated group. This study demonstrated that 2 kGy of gamma irradiation effectively reduces microbial contamination and delays the browning and softening of king oyster mushrooms for up to 28 days.

Effect of radiation processing on physico-chemical quality and inhibition of yeast and mold and aerobic bacterial count in natural plum juice during refrigerated storage

Fully red plums (Cv. Santa Rosa) harvested at proper maturity were processed into juice and packed in polypropylene (PP) bottles. The packaged juice was irradiated at 0.5 kGy and stored at 3 ± 1 °C for 50 days. Samples were evaluated at intervals of 10 days for physico-chemical, microbiological and sensory quality attributes. Results indicated that dose of 0.5 kGy maintained higher levels of total soluble solids, sugars and total ascorbic acid in juice towards later storage periods compared to control. Dose of 0.5 kGy significantly (p ≤ 0.05) enhanced total phenols in plum juice by 2.3 % following irradiation. Anthocyanins content of plum juice decreased both with dose and storage, however after 50 days decrease in anthocyanin content was 30.8 % in un-irradiated juice compared to 23.3 % in 0.5 kGy treated juice. Among individual anthocyanins, monoglycoside anthocyanins especially cyanidin-3-rutinoside was less stable to irradiation compared to diglycoside anthocyanins. DPPH and hydroxyl radical scavenging activity of juice increased by 6.8 % and 4.9 % above control after irradiation at 0.5 kGy. Microbial populations significantly reduced by irradiation at 0.5 kGy and about 1 log reduction in yeast and mold count was observed after irradiation. Dose of 0.5 kGy was sufficient to reduce total bacterial levels below detection limit up to 20 days of storage. Sensory analysis indicated that un-irradiated plum juice was unacceptable within 20–30 days while 0.5 kGy treated juice was acceptable up to 50 days of refrigerated storage.

Pulsed light, microwave, and infrared treatments of jaggery: Comparing the microbial decontamination and other quality attributes

Jaggery, a traditional nutritive sweetener made from sugarcane juice, is contaminated due to poor handling during processing and storage. The study focuses on decontamination of jaggery using microwave (420–700 W, 30–60 s), infrared (80–90 °C, 4–12 min), and pulsed light treatment (1600–2200 V, 5–120 pulses). The process efficacy was compared based on microbial quality and physicochemical parameters. Microbial quality represents the reduction of aerobic mesophile (AM), yeast and mold (YM), and inoculated Saccharomyces cerevisiae. A maximum log reduction of 2.17, 2.04, and 2.78 for AM, YM, and S. cerevisiae, respectively, was observed during pulsed light (PL) treatment at 1.70 kJ/cm2 fluence. AM was the most resistant microbial entity, and PL irradiation demonstrated a maximum linear inactivation rate (k) of 17.5 s−1 and minimum non-linear decimal reduction time (δ) of 0.3 min. IR treatment at 90 ± 5 °C caused the maximum change in physicochemical properties, thermal stability, functional groups, and crystallinity index of jaggery. Microwave (MW) heating at 700 W showed maximum improvement in total phenolic content (TPC), minimum change in colour, and fastest inactivation of YM and S. cerevisiae. Finally, PL treatment exhibited better overall microbial safety, enhanced TPC, and minimum modifications in jaggery's thermal, chemical, and structural aspects.

A Novel Strategy Based on Zn(II) Porphyrins and Silver Nanoparticles to Photoinactivate Candida albicans.

Photodynamic inactivation (PDI) is an attractive alternative to treat Candida albicans infections, especially considering the spread of resistant strains. The combination of the photophysical advantages of Zn(II) porphyrins (ZnPs) and the plasmonic effect of silver nanoparticles (AgNPs) has the potential to further improve PDI. Here, we propose the novel association of polyvinylpyrrolidone (PVP) coated AgNPs with the cationic ZnPs Zn(II) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin or Zn(II) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin to photoinactivate C. albicans. AgNPs stabilized with PVP were chosen to allow for (i) overlap between the NP extinction and absorption spectra of ZnPs and (ii) favor AgNPs-ZnPs interaction; prerequisites for exploring the plasmonic effect. Optical and zeta potential (ζ) characterizations were performed, and reactive oxygen species (ROS) generation was also evaluated. Yeasts were incubated with individual ZnPs or their respective AgNPs-ZnPs systems, at various ZnP concentrations and two proportions of AgNPs, then irradiated with a blue LED. Interactions between yeasts and the systems (ZnP alone or AgNPs-ZnPs) were evaluated by fluorescence microscopy. Subtle spectroscopic changes were observed for ZnPs after association with AgNPs, and the ζ analyses confirmed AgNPs-ZnPs interaction. PDI using ZnP-hexyl (0.8 µM) and ZnP-ethyl (5.0 µM) promoted a 3 and 2 log10 reduction of yeasts, respectively. On the other hand, AgNPs-ZnP-hexyl (0.2 µM) and AgNPs-ZnP-ethyl (0.6 µM) systems led to complete fungal eradication under the same PDI parameters and lower porphyrin concentrations. Increased ROS levels and enhanced interaction of yeasts with AgNPs-ZnPs were observed, when compared with ZnPs alone. We applied a facile synthesis of AgNPs which boosted ZnP efficiency. We hypothesize that the plasmonic effect combined with the greater interaction between cells and AgNPs-ZnPs systems resulted in an efficient and improved fungal inactivation. This study provides insight into the application of AgNPs in PDI and helps diversify our antifungal arsenal, encouraging further developments toward inactivation of resistant Candida spp.

Application of ultra-high pressure homogenization (UHPH) at different stages of wine production

Ultra-High Pressure Homogenization (UHPH) is an emerging, efficient and fast technology that can be applied at different stages in winemaking in order to reduce or avoid the use of sulphites or other antimicrobial and antioxidant treatments. During 2022 vintage, four batches of must of three different white cultivars (Vitis vinifera L.) were processed by UHPH at 300 MPa with an inlet temperature (Ti) of 4 ºC and their effectiveness was compared with control batches (without SO2 addition) and musts that were sulphited with 60 mg/L of total SO2. A complete inactivation of yeasts and bacteria was achieved when grape juices were processed by UHPH, reaching up to 7 log of reduction in yeasts, 4.6 log for acetic acid bacteria and 4.3 log for lactic acid bacteria. All UHPH musts remained stable from a microbiological point of view for more than 8 months stored at 4 ºC in aseptic containers. Results showed that when antioxidant activity, colour intensity and total phenol index were measured, UHPH can be considered a protective technique, with a similar action to that of adding SO2. Furthermore, PPO enzymatic activity was completely inactivated in UHPH and sulphited musts. When a red wine contaminated by Brettanomyces was treated by UHPH at 300 MPa and Ti = 17 ºC, a 6.6 log reduction was obtained for this spoilage microorganism and no increase of volatile phenols were detected after 2 months.

Optical and AFM microscopy of grape juices treated with UHPH: Effects of microstructure and nanostructure

UHPH treatment of Vitis vinifera must for winemaking leads to fragmentation of colloidal particles into smaller structures. The shear and fracture forces experienced by grape juice during valve pressurization are sufficient to reduce the particle size of grape juice to below 500 nm. As a result, the applied force can disrupt bacterial and yeast cell structures, altering or breaking down proteins, polysaccharides and enzymes. This effect is not observed for low molecular weight compounds such as monomeric pigments and phenolic structures, varietal aroma precursors, fermentable sugars, etc. Treated and untreated samples can be compared using optical and atomic force microscopy. Optical microscopy images show reduction or elimination of bacteria and yeast and changes in microstructure. On the other hand, in addition to describing topography in the nanometer range, AFM can also measure particles in comparison to other techniques such as laser diffraction (LD). This work contributes to the characterization and better understanding of the effects of UHPH on grape juice for winemaking.

Exploring alternative salting methods to reduce sodium content in blue-veined cheeses

Reducing sodium content in food is a major public health challenge, especially for cheeses. Different salt reduction methods in surface dry-salted blue cheese and their effect on biochemical, physicochemical, microbiological, rheological and sensory characteristics of cheese were investigated. The cheeses were salted with coarse or fine salt using various methods. All methods decreased sodium content in cheese core (−11% to −67%) and induced higher water activity. Sprinkling (−45% NaCl content) and calcium lactate substitution (−10% NaCl content) were technically feasible. The sanitary quality and cheese microbiota were not impacted except for a reduction of yeasts and moulds. Higher indices of richness and diversity were found on salt-reduced cheeses with Streptococcus, Lactococcus and Leuconostoc mesenteroides dominating. Texture and appearance of the cheeses were also affected. The research identified the limits of salt reduction in blue-veined cheeses; sprinkling and partial substitution with calcium lactate should be further studied.

Comparative randomized trial study about the efficacy of photobiomodulation and curcumin antimicrobial photodynamic therapy as a coadjuvant treatment of oral mucositis in oncologic patients: antimicrobial, analgesic, and degree alteration effect.

As conventional treatments currently available for mucositis are not considerably effective, there is a need to implement an adjuvant protocol for the treatment of oral mucositis in patients undergoing radiotherapy and chemotherapy. To evaluate the effect of photobiomodulation (PBM) and antimicrobial photodynamic therapy (aPDT) mediated by curcumin and blue LED as an adjunct treatment of oral mucositis for oncology patients using chemotherapy and/or radiotherapy. Clinical, randomized study, in a single location, in an oncology service of a general hospital, with a total of 30 patients (over 18years old) with stable oral mucosa lesions in the process of chemotherapy and/or radiotherapy. The patients were divided into 3 groups: control group (treated with nystatin), PBM group (treated with low-level laser therapy), and the aPDT group (treated with 450-nm blue LED and curcumin photosensitizer). The results showed, by means of intra-group comparisons, that the two experimental treatments promoted yeast reduction of the genus Candida in the last two evaluations (21days and 30days), but not in the first two evaluations (7days and 14days). The intra-group comparisons showed that the control and aPDT group showed a significant difference in the degree of mucositis over the four evaluations performed, with the results pointing out that the mucositis worsened in the control group from the 14th day, while reduced in the aPDT group from the 21st day of treatment. A reduction in the degree of mucositis and pain score was observed in the PBM and aPDT groups, with the aPDT group standing out when presenting early clinical improvement in relation to the PBM group and the control group, thus emphasizing its effectiveness within the desired aspects. Regarding the antimicrobial effect, aPDT showed a greater reduction of yeasts of the genus Candida in the tested parameters.

In-package cold plasma treatment of braised chicken: voltage effect

This study investigated the effect of different dielectric barrier discharge cold plasma (DBD-CP) treatment voltages on the microbiological growth and quality characteristics of braised chicken during storage at (4 ± 1) °C. Argon-packed samples were subjected to DBD-CP treatment for 3min at voltages of 50, 60 and 70kV. As a result, there was no significant (P > 0.05) difference in L⁎, a⁎, b⁎ and pH of braised chicken between control and treatment groups at the same storage time. However, the development of lipid oxidation in DBD-CP treatment samples was slower than that in air-packed samples. Compared to air-packed samples, the reduction of total viable count, yeasts and molds, lactic acid bacteria and Pseudomonads spp. in 70kV treated samples on day 15 were 3.21, 2.41, 2.44 and 1.96 lg (CFU/g), respectively. The results indicate that DBD-CP treatment could extend the shelf life of braised chicken without negative impacts on quality characteristics.

COMPARISON OF ANTIFUNGAL PROPERTIES OF LACTOBACILLUS RHAMNOSUS AND LACTOBACILLUS REUTERI WITH POTASSIUM SORBATE IN THE IRANIAN UF-FETA CHEESE

This study was aimed to compare antifungal properties of two lactobacilli strains with potassium sorbate in cheese. In this regard, the effect of 10-fold cell-free extract of Lactobacillus rhamnosus РТСС 1637 and Lactobacillus reuteri РТСС 1655 was studied on the growth of mold and yeast in the Iranian UF-Feta Cheese during a 60-day ripening period at 4 ℃. Additionally, the antifungal effect of potassium sorbate (300 and 500 ppm) and mixture of potassium sorbate and cell-free extract of tested bacteria were evaluated. The results showed that yeast and mold growth was occurred in both control and treated chesses, however, after 30 days storage, mold and yeast count was significantly lower in the cell free supernatant-treated UF-Feta cheese in comparison to the control cheese. Addition of potassium sorbate, as expected, significantly reduced mold and yeast growth in UF-Feta cheese during ripening period than control. On the other hand the result showed that mixture of probiotic extract and potassium sorbate had more efficiency in mold and yeast growth reduction than when the sorbate potassium was used alone. The highest fungal growth inhibition was achieved by application of 2 mL cell-free extract of L. reuteri CCTP 1655 along with 500 ppm potassium sorbate. Generally, it could be concluded that cell-free supernatant of tested bacteria has potential for use as bio preservatives in cheese and although studied probiotic extracts are not as effective as sorbate potassium in preventing fungi and yeast growth, they can be useful in reduction of yeast and mold growth.

Effect of High Hydrostatic Pressure in the Storage of Spanish-Style Table Olive Fermented with Olive Leaf Extract and Saccharomyces cerevisiae.

Olives treated according to the Spanish-style are firstly treated with caustic soda and then fermented in brine to reduce phenols. Next, olives are packed and subjected to pasteurization. The effect of different high hydrostatic pressure treatments (400 MPa, 4 and 6 min) was evaluated in Spanish-style table olives fermented with olive leaf extract (OLE) and S. cerevisiae compared with thermal pasteurization (P) at 80 °C for 15 min. HHP and P led to a significant reduction in yeast and aerobic mesophiles after the conservation treatment and during storage (300 days). The physical–chemical properties changed slightly during storage, except for olive hardness; olives treated with HHP presented a higher hardness than pasteurized ones. The CIELAB parameter L* decreased until day 300 in most of the treatments, as well as phenols. The HHP treatment led to significantly higher contents of phenolics (even during storage) than olives submitted to P. Some sensory attributes (colour, aspect, hardness, and overall evaluation) decreased during storage. P treatment caused a decrease in appearance, aroma, hardness, and overall evaluation compared to olives treated with HHP. Thus, the application of HHP in table olives to increase the shelf-life can be considered a valid alternative to P.

Evaluation of novel Prosopis juliflora water soluble leaf ethanolic extract as preservation coating material of cucumber

Cucumber (Cucumis sativus) is an economically important vegetable worldwide. Cucumbers have short shelf life with sensitivity to chilling injuries and fungal and bacterial postharvest diseases. Prosopis juliflora water-soluble leaf ethanolic (PJ-WS-LE) extract has a strong antimicrobial activity against many spoiling agents with time-stability and no phytotoxicity on fruits. The present study explores PJ-WS-LE extract efficacy as a coating material to preserve cucumber. 8 mg/ml of PJ-WS-LE extract increased cucumber shelf life at 22°C by 77%. At week 2, cucumber coated with PJ-WS-LE extract alone showed less than 10 CFU/g of mold as well as 76.9% and 85.8% reduction of total yeast and aerobic bacterial counts, respectively. PJ-WS-LE extract treated samples maintained the slightest change in total soluble solids and 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity. Embedding PJ-WS-LE extract in 0.5% chitosan did not improve the quality maintaining results. In vivo overall results highlight the potentials of PJ-WS-LE extract as a possible coating replacement of chemical fungicides. Novelty impact statement Prosopis juliflora water-soluable leaf ethanolic (PJ-WS-LE) extract extended cucumbers shelf life at 22°C by 77%. PJ-WS-LE extract served as an antimicrobial agent that lowers surrounding bacterial and fungal counts of coated cucumber samples. 8 mg/ml of Prosopis juliflora water-soluble leaf ethanolic maintained cucumbers storage quality-parameters up to three weeks at 8°C.

Anaerobically Digesting Hazardous Waste Pichia pastoris Associated with Butyric Acid Cleaner Production.

Recombinant Pichia pastoris semisolid hazardous waste treatment is difficult and traditional solid waste treatment is not applicable. However, P. pastoris wastes have features of high density and enriched proteins/polysaccharides, which could supply nitrogen/carbon sources for butyric acid production. The waste P. pastoris was first treated using NaOH to form a waste yeast suspension, and then the suspension was mixed with glucose to obtain a starting medium containing 5.6 g DCW/L (dry cell weight) yeast to initiate butyrate fermentation. The suspension was intermediately supplemented to bring the total waste yeast concentration to 26.3 g DCW/L while continuously feeding the concentrated glucose solution. With the proposed strategy, butyrate concentration reached high levels of 51.0–54.0 g/L using Clostridium tyrobutyricum as the strain. Amino acids/oligosaccharides/SO42– in the suspension, raw material costs, complicated pretreatment process, and butyric acid cleaner production could be effectively utilized, reduced, eliminated, and realized. However, the apparent waste P. pastoris reduction rate was only 49% per batch, thus a “tanks in-series type’s repeated waste treating system” model was developed to theoretically explore the possibility of increasing the waste yeast reduction rate R. The simulation results indicated that when setting the treatment unit numbers at 4, waste solid concentration could decrease from 26.3 to 3.37 g DCW/L and the hazardous waste yeast reduction rate R would increase from 49 to 97%.

Impact of Gamma Irradiation on Physicochemical, Technological, Antioxidant and Microbiology Properties of Whole Sorghum Flours

This study aimed to evaluate the effect of gamma irradiation (GI) on the physicochemical, technological, antioxidant and microbiological characteristics of different whole sorghum flours (WSF), as well as to characterize the profile of chemical constituents by paper spray mass spectrometry (PS-MS). The doses applied interfered in the staining characteristics of the evaluated flours, providing the darkening of the same. For the other physicochemical, technological, and antioxidant parameters, no significant influence of the process was observed. The fingerprint obtained in both ionization modes had not been influenced by irradiation, being flavonoids, phenylpropanoids, amino acids, benzoic acid derivatives, carboxylic acids, and sugars tentatively identified. In microbiological terms, there was a reduction of molds, yeasts, and Bacillus cereus in irradiated WSF compared to control (non-irradiated). Therefore, the application of low doses of gamma irradiation represents an advantageous alternative for the conservation of WSF and maintenance of compounds bioactive identified by the PS-MS technique.

Pulsed light treatment reduces microorganisms and mycotoxins naturally present in red pepper (Capsicum annuum L.) powder

AbstractThe impact of pulsed light (PL) treatment on naturally occurring microorganisms, mycotoxins, and on physicochemical properties in red pepper powder was investigated. Powder samples were exposed to different PL treatments up to 61 pulses, with fluence ranging from 1.0 to 9.1 J/cm2. The highest fluence applied (9.1 J/cm2, 61 pulses, 20 s) resulted in 2.7, 3.1, and 4.1 log CFU/g reduction of yeasts, molds, and total plate counts (TPC), where initial microbial loads were 4.6, 5.5, and 6.5 log CFU/g, respectively. At the same fluence intensity, a maximum reduction of 67.2, 50.9, and 36.9% of aflatoxin B1 (AFB1), total aflatoxins (AF), and ochratoxin A (OTA) were detected, respectively. Proportional increase in temperature of the samples was observed from the absorbed PL energy, reaching maximum of 59.8°C. The inactivation of investigated microorganisms and mycotoxins followed first‐order kinetics (R2 > 0.95). The fluence intensity at 6.9 and 9.1 J/cm2 did not cause degradation, but rather a significant (p < .05) and apparent increase of total phenols. Total color difference (ΔE*) revealed only “slight differences,” compared to the untreated sample. In conclusion, higher reduction of microbial load and mycotoxins in red pepper powder could be achieved, when higher treatment intensity was applied. This suggests the PL as a potential technology for decontamination of red pepper powder and other spice powders.Practical ApplicationsPulsed light could be used for the decontamination of foods and reduce variety of spoilage and pathogenic microorganisms. Exposure of red pepper powder to different levels of doses proposed in this study demonstrates alternative approaches for microbial inactivation and mycotoxins degradation of the product. Moreover, pulsed light treatment is a young technology using short treatment times with potential feasibility. The technique can be of great interest for the scientific and industrial R&D community dealing with pulsed light technology, microbial, and mycotoxins inactivation kinetics, food safety, and quality control.