Mesophilic Bacteria Counts Research Articles

Use of Ozone to Reduce the Proportion of Mesophilic and Psychrotrophic Bacteria Among Aquatic Organisms: A Systematic Review and Meta‐Analysis

ABSTRACTMesophilic and psychrotrophic bacteria are agents of spoilage in aquatic organisms. Aquaculture aims to provide safe and nutritious foods from microbiological, physico–chemical, and sensory perspectives. Ozone (O3) is a gas used as an efficient antimicrobial agent for inactivating microorganisms in various foods. Therefore, this study aimed to determine whether O3 is effective in reducing or eliminating mesophilic and psychrotrophic bacteria in fish and seafood. To this end, a systematic review was performed to evaluate the data obtained from published primary studies. Articles were retrieved from the PubMed, Web of Science, Scopus and SciELO databases, and papers published between 2002 and 2024 were considered. A total of 1415 studies were identified, 11 of which met all eligibility criteria and were included in the meta‐analysis. The results indicated that O3 reduced mesophilic and psychrotrophic bacteria counts by 0.31 log CFU g−1 in fish and seafood. Significant heterogeneity persisted in the data set even after separation into subgroups, indicating that the studies were significantly diverse in terms of methodology. Therefore, the data obtained in this meta‐analysis indicates low inactivation of the microorganisms studied using O3. However, more research into the O3 treatment of aquatic organisms should be encouraged, since the included studies had methodological variations in the forms of O3 used, and investigated species, since all species have their own specificities.

Uso de máscaras descartáveis contra Staphylococcus aureus na indústria de abate de frangos

ABSTRACT: The present study evaluated the effectiveness of using disposable masks in mitigating the spread of Staphylococcus aureus during the chicken cutting process in a large poultry abattoir. The identification of carriers of S. aureus and the influence of the time of use of disposable masks was carried out. Contamination of utensils and equipment by S. aureus and products by mesophilic aerobes was determined, with and without the use of masks. The efficiency of different commercial masks was evaluated against S. aureus under simulated conditions. The results revealed that 36% of workers on processing lines at the abattoirs carried S. aureus. An increase in S. aureus counts was observed in masks worn by employees for up to 3 h. The transfer of microbial load to utensils was enhanced in the absence of the mask and over time. The breast fillets evaluated showed no difference in the count of mesophilic bacteria with and without the use of masks by employees, conversely, the cuts of thigh and drumstick, thigh fillet and drumstick and wings showed a significant difference with average counts lower than 2 .96 Log CFU/g. Tests under simulated conditions demonstrated the effectiveness of commercial masks in retaining microorganisms. The test mask used by the abattoirs proved to be inefficient, allowing the passage of sprays containing S. aureus, at 6, 15 and 25 cm, with 2.53, 1.74 and 0.66 Log CFU/plate, respectively. This mask saturated, creating a barrier effect that increased contamination in the employees’ work area.

Simultaneous Application of Electron Beam Irradiation and Freezing as an Effective Method for Shelf Life Extension of Minced Turkey Meat.

In this study, minced turkey meat samples were subjected to electron-beam irradiation with dosages of 0, 1.5, 3, and 5 kGy, and then microbial (mesophilic and psychrotrophic bacteria), physiochemical (pH, water activity [aw], thiobarbituric acid reactive substances [TBARS], and peroxide value [PV]), and sensory (color, odor, texture, and overall acceptability) analyses were performed at 0 and 6 months of freezing storage (-18°C). Results showed that by 5 kGy irradiation and freezing treatments, the counts of psychrotrophic and mesophilic bacteria reduced remarkably (p < 0.05) and reached from 4.44 to 2.05 and from 4.9 to 2.00 log cfu/g, respectively. pH and aw of samples did not change notably after treatment and 6 months of freezing storage, the pH and aw of the minced turkey meat were 5.74 and 0.95 for 5 kGy irradiated samples, respectively. Despite the increase of TBARS and PV values, electron-beam irradiation at 1.5 and 3 kGy had no notable impact on the sensory characteristics of minced turkey meat. The obtained findings revealed that the simultaneous use of irradiation and freezing is a promising method for the increase of shelf life and preservation of minced turkey meat quality.

Effect of Cold PlasmaTreatment on Physicochemical and Microbiological Properties of Clotted Cream

The aim of this study was to determine the effect of cold plasma treatment, which was applied by using two different gases (O2 and Ar) and their mixtures onto sample surfaces for different intervals, on the physicochemical and microbial parameters of clotted cream during storage for up to 10 days. Cold plasma treatment caused a decrease in pH, aw, L*, and b* values of clotted cream samples and an increase in their a* and TBA values. The pH values of samples ranged from 4.68 to 6.67, and the range for aw values was between 0.903 and 0.803. For TBA, the highest change was observed in the K2 sample with 0.479 mg malondialdehyde/kg. The color L* values of all samples were between 99.79 and 93.82, a* values between 1.82 and 1.22, and b* values between 6.22 and 4.74. Among the treatments, the treatment of O2-Ar gas mixture (50-50%) resulted in the highest decrease in the total counts of aerobic mesophilic bacteria (TMAB), total aerobic psychrophilic bacteria, proteolytic bacteria, yeast-molds, coliform group bacteria, and Staphylococcus aureus. Compared to the control sample, at the end of 10 days of storage, a decrease of 2.41 for TMAB, 3.64 for total yeast-mold, 4.23 for coliform group bacteria, and 4.72 log cfu/g for S. aureus was achieved. Results indicated that the cold plasma treatment did not cause significant changes in the physicochemical values of clotted cream samples but reduced their microbial load.

The Effects of High Pressure Processing on Total Mesophilic Aerobic Bacteria Number and Color Properties of Frozen and Unfrozen Beef Mince

High hydrostatic pressure processing (HPP) is a cold pasteurization technology that can be applied after packaging to products damaged by heat treatment. In this study, the effects of different levels (300, 350 and 450 MPa) of pressure applied at different temperatures (-5, 0 and 10 oC) and durations (5, 10 and 15 min) on the total mesophilic aerobic bacteria count (TMAB) and color values of frozen and unfrozen beef mince were investigated. The most effective factor on the number of TMAB was pressure. Freezing resulted in increased inactivation. In the application performed at constant temperature (10 oC), the difference in inactivation between frozen and unfrozen samples was seen maximum at 300MPa pressure application. Inactivation increased with increasing pressure level and time. At different application temperatures, the most effective inactivation of 300 MPa HPP in frozen and unfrozen samples occurred at -5 oC in 15 minutes. The increase in L* value of frozen samples was less than that of non-frozen samples. This contributes to the preservation of freshness properties in meat. An increase in the L* value was observed with the increase in pressurization time. Increasing the pressure level caused a decrease in the a* value, and freezing caused an increase in the a* value. It was determined that the 300-450 MPa HPP range was not large enough to observe changes in b* values. ΔE values in frozen samples were determined to be higher than in non-frozen samples. If freezing and pressure are applied in combination, a microbiologically safer product with a color closer to fresh properties can be obtained.

The Effect of Different Storage Conditions on Textural, Microbiological and Color Properties of Phyllo (Yufka)

The effect of different storage conditions on textural, microbiological and color properties of phyllo was investigated. Phyllo samples were stored at room temperature (20 ⁰C) for 3, 5 and 7 days, in refrigerator (4 ⁰C) for 7, 14 and 21 days, and in deep freezer (-18 ⁰C) for 20, 40 and 60 days. It was determined that phyllo samples stored in the deep freezer exhibited higher L* color values (82.33-82.97), followed by samples stored in the refrigerator (78.53-81.75) and samples stored at room temperature (75.74-77.75), respectively. A statistically similar and lower total color change (∆E) occurred in the phyllo samples stored at room temperature and in the refrigerator than the samples stored in the deep freezer. The samples stored in the refrigerator exhibited higher hardness, chewiness and gumminess values, while the samples stored in the deep freezer exhibited lower values. Most of samples produced were similar to the control sample in terms of elasticity property. In terms of relaxation time value, the samples stored at room temperature and in the deep freezer exhibited statistically similar and lower values than the samples stored in the refrigerator. Additionally, the samples stored in the deep freezer had higher breaking force and breaking length values. The total mesophilic aerobic bacteria count of the samples varied between 3.38-12.30 log cfu/g and mold and yeast count varied between

The Microbiological Quality of Raw Ovine Milk in the Banat Region of Romania with a Focus on Escherichia coli and Its Pathogenic Potential and Antimicrobial Resistance.

This study investigated the bacteriological quality of raw ovine milk produced by farms located in the Banat region of Romania. Additionally, the pathogenic potential and antimicrobial resistance of the isolated Escherichia coli strains were evaluated. A total of 95.8% (69/72) of the screened bulk tank milk samples, collected at the farm level immediately after milking, demonstrated appropriate total aerobic mesophilic bacteria (TMB) counts, varying from 3.32 to 6.09 log10 CFU/mL. However, 4.2% (3/72) of the samples were above the regulatory limit of 6.18 log10 CFU/mL. E. coli was identified in 66.6% of the examined samples, and from the total number (n = 48) of isolates, 18.8% harbored the stx2 gene, highlighting pathogenic potential. Antimicrobial susceptibility testing with the Vitek2 system of the isolated E. coli strains revealed resistance against ampicillin (45.8%), gentamicin (20.8%), ticarcillin-clavulanic acid (18.8%), cephalexin (18.8%), amoxicillin-clavulanic acid (8.3%), and trimethoprim-sulfamethoxazole (2.1%). Additionally, 64.6% of the strains showed intermediate resistance against amoxicillin-clavulanic acid, while no resistance was recorded against imipenem. Five (18.5%) strains were multidrug-resistant. This study's results underline hygienic sanitary deficiencies during the milking phase and indicate that raw ovine milk can be contaminated with pathogenic and multidrug-resistant E. coli strains, highlighting a potential risk to public health. Further studies are encouraged to better understand the risk posed to the consumer via the consumption of ovine milk and derived products.

Effect of UV-C Treatment on the Quality of Fresh-Cut Potatoes Obtained from Tubers of Different Ages

The physico-chemical properties of potato tubers change with age, which can affect not only the quality of the tubers but also the quality and shelf-life of fresh-cut potatoes (FCP) produced from older tubers. One of the methods that has proven useful for extending the shelf-life of some foods is ultraviolet-C (UV-C) irradiation. This study investigated whether UV-C irradiation can mitigate the negative effects of tuber age. FCP from tubers after storage (1 and 9 months), vacuum-packaged, were irradiated with UV-C (2.70 kJ m−2) and stored (6 °C/15 days). The total aerobic mesophilic bacteria count (TAMBC), total and soluble solids content, pH, firmness, color, chlorogenic acid, reducing sugars, sensory properties of raw FCP and subsequently boiled and fried FCP, and acrylamide content in fried FCP were monitored. UV-C irradiation of FCP does not affect all parameters equally for both tuber ages, but was generally effective in reducing TAMBC, and UV-C-treated samples reached a shelf-life of 15 days. UV-C irradiation improved the sensory properties of raw and thermally processed FCP at both ages. UV-C irradiation caused an increase in acrylamide content in fried FCP, regardless of. the tubers age, but all samples were safe in this respect.

Ozonation as an emerging technique for inactivating microorganisms and mitigating pesticides in apple juice

ABSTRACT Microorganisms and pesticide residues are among the major health concerns associated with food products. Although ozone (O3) is currently being employed in various applications in apple processing, there are few studies investigating the effects of O3 treatments on microorganisms and pesticides in apple juice. The purpose of this study was to investigate the effects of O3 treatment on microorganisms, pesticide residues, and physicochemical properties of apple juice and to compare with that of classical pasteurization. O3 was as effective as pasteurization against E. coli and coliform bacteria; the counts of these microorganisms were below the detectable level after a treatment for 15 min. O3 was also effective in reducing the counts of total aerobic mesophilic bacteria and yeast-mold, but longer treatments were required for total inactivation. All the pesticides investigated were degraded by O3, but at different rates. Reduction rates were quite high (75–100%) for methoxyfenozide, dimethoate, and pyrimethanil, however, acetamiprid and imidacloprid were degraded by only 7.1% and 14.5%, respectively. O3 treatment caused drastic decreases in color and turbidity values, total phenolic content, and antioxidant activity of apple juice. Results revealed that the use of ozone in juice processing has potential as a technological solution to product contamination problem.

Characterization of psychrotrophic and thermoduric bacteria in raw milk using a multi-omics approach.

Psychrotrophic and thermoduric bacteria are the main reasons for the spoilage of dairy products. This study aims to address the composition and function of psychrotrophic and thermoduric bacteria in eight groups of raw milk samples obtained from Heilongjiang Province and Inner Mongolia (China). Microbial enumeration showed an average total bacterial count of 4.63 log c.f.u. ml-1 and psychrotrophic bacterial counts of 4.82 log c.f.u. ml-1. The mean counts of mesophilic and thermophilic thermoduric bacteria were 3.68 log and 1.81 log c.f.u. ml-1, respectively. Isolated psychrotrophic bacteria (26 genera and 50 species) and mesophilic thermoduric bacteria (20 genera and 32 species) showed high microbial diversity. Through metagenomic and proteomic analyses, significant disparities in the concentration and community structure of psychrotrophic and thermoduric bacteria were observed among different locations. A large number of peptidases were annotated by metagenomics, which may result in milk spoilage. They mainly come from some typical psychrotrophic and thermoduric bacteria, such as Chryseobacterium, Epilithonimonas, Pseudomonas, Psychrobacter, Acinetobacter, Lactococcus, Escherichia and Bacillus. However, the main proteins detected in fresh raw milk were associated with bacterial growth, reproduction and adaptation to cold environments. This investigation provides valuable insights into the microbial communities and protein profiles of raw milk, shedding light on the microbial factors contributing to milk deterioration.

Comparison of microbiological loads of enteral products at two different ambient room temperatures.

Despite the high risk of bacterial contamination, no studies have been found that evaluate the optimal hanging time of open-system enteral sets under room temperature and intensive care conditions. This study aims to determine the differences in microbial loads of solutions taken from open-system enteral feeding sets hanging for 24 h under room temperature and intensive care conditions. This study is a descriptive type of research. The study sample consisted of a total of 40 samples, with 20 samples under room temperature (25.2-23.3°C) and 20 samples under intensive care conditions (21.1-24.2°C). A simple random sampling method was used for sample selection. The assessment of microbial quality was based on the US Food and Drug Administration online Bacteriological Analytical Manual. In this study, it was determined that 5% of the samples taken from intensive care and 15% of the samples taken at room temperature exceeded the accepted limit for aerobic mesophilic bacteria count. The count of catalase and coagulase-negative Staphylococcus spp was 5% in intensive care samples and 40% in room temperature samples. The total coliform count was not detected in intensive care samples but was 35% in room temperature samples. Escherichia coli was not detected in either group. Differences in microbial loads were observed when commercial enteral solutions were administered using open-system enteral feeding sets under room and intensive care conditions for 24 h. Therefore, large-scale studies are needed to determine the safe use of open-system enteral feeding sets under room temperature conditions.

Atmospheric Cold Plasma to Maintain Sea Bass Quality: An Opportunity for International Fish Trade

Whole chilled sea bass is an essential product for the European food market, and Türkiye is the foremost supplier. The importance of sea bass in the world food trade reveals the significance of food safety risks that may arise during or after harvest. This study aimed to examine the impact of atmospheric cold plasma (ACP) on delaying the spoilage of sea bass. The ACP is generated by an original device that produces a dielectric barrier discharge plasma using an alternating current (AC) power supply, applying a 30 kV high voltage with a sinusoidal frequency of 20 kHz. Whole sea bass samples were treated for 1 min (ACP1) or 7 min (ACP7), and then stored at 2 ± 1 °C. Sensory scores of plasma-treated sea bass were higher throughout the storage period. Both treatments decreased the initial bacterial load and delayed bacterial growth (p ≤ 0.05) during storage. The mesophilic aerobic bacteria count of control samples exceeded 6 log CFU/g on the second day of storage. However, ACP1 and ACP7 did not reach this value until the third and fourth days. The control samples had higher TMA-N and TBARS (p ≤ 0.05) than plasma-treated groups. The treatment did not significantly change the texture. Although ΔE was higher in ACP samples, a discoloration that could affect acceptability was not reported during the sensory test. Cold plasma can improve the overall market value by maintaining quality, benefiting the global fish trade. It has been shown that cold plasma has promising potential in the fresh fish industry.

Tannic acid and Gallic Acid as Alternative Compounds for the Application as Preservatives in Cosmetic Products

Introduction: Tannic acid and gallic acid have been known as natural compounds with antibacterial activity. In this work, the antimicrobial efficiency of tannic acid (TA) and gallic acid (GA), as well as their mixtures, was tested. Method: During the research, the minimal inhibitory concentration, minimal bactericidal concentration, and fractional inhibitory concentration were defined. Based on them, for further study, mixtures of TA/GA in ratios 50:50 and 80:20 were chosen as a preservation mixture applied to the cosmetic emulsion. Results: The obtained cosmetics emulsions were analyzed for the total mesophilic aerobic bacteria count and the total combined yeast count. The preservation efficiency test was performed according to the ISO 11930 standard. A stability test for cosmetics formulation was also carried out. Conclusion: The preservation mixture of TA/GA in an 80:20 ratio incorporated in the cosmetics formulation showed good preservation efficiency and could be considered a natural origin preservative.

Development and Application of the Quality Index Method for Ice-Stored King Weakfish (Macrodon ancylodon).

The freshness of raw fish has become one of the industry's and consumers' main concerns regarding quality, safety, and shelf-life estimation. To determine the freshness of the king weakfish (Macrodom ancylodom), the quality index method (QIM) was employed for sensory analyses, along with the assessment of proximate composition, pH, total volatile bases (TVB-N), thiobarbituric acid reactive substances (TBARS), biogenic amines, fatty acids, texture, and microbiological parameters. The results show that the QIM obtained over the storage period exhibited a linear increase, ranging from 2 to 21 demerit points, with a high correlation (R2 = 0.9868) among the data. The microbiological results indicated an increase in the counts of psychrotrophic and mesophilic bacteria throughout the storage period. TVB-N values ranged from 11 to 28 mg/100 g, and TBARS values ranged from 0.235 to 0.298 mg MDA/kg when stored in ice. The presence of putrescine, cadaverine, spermidine, and toxic volatile compounds was a potential indicator of fish freshness. Based on the correlation between the methods considered indicators of freshness and quality, it can be concluded that the king weakfish maintains its commercial stability for up to 11 days when stored in ice.

Films of polylactic acid with graphene oxide-zinc oxide hybrid and Mentha longifolia essential oil: Effects on quality of refrigerated chicken fillet

This study was conducted to investigate the morphological, thermal, mechanical, FTIR, physicochemical (thickness, humidity, solubility in water and water vapor permeability) and antimicrobial properties of polylactic acid film (PLA) containing hybrid graphene oxide‑zinc oxide (GO-ZnO: 1.5 % w/v) and Mentha longifolia essential oil (ML:1 % v/v) on chicken fillet kept in the refrigerator. The studied groups were microbially (total count of mesophilic aerobic bacteria, psychrotrophic bacteria, Enterobacteriaceae, Staphylococcus aureus, and lactic acid bacteria), chemically (pH, TVB-N) and sensory (color, odor, and taste) evaluated at 8-day interval (0, 2, 5 and 8). In the examination of the morphological characteristics, the PLA film had a smooth and uniform surface and the addition of ML essential oil created a discontinuous structure and the addition of GO-ZnO led to the production of a denser and more homogeneous film. The presence of GO-ZnO increased the thickness, decreased moisture content and solubility in water, and added ML essential oil increased moisture content and decreased solubility in water (p˂0.05). The results of the mechanical evaluation showed that the addition of ML essential oil and GO-ZnO reduced elongation at break and tensile strength (p˂0.05). The addition of ML essential oil increased the thermal resistance and the addition of GO-ZnO decreased the thermal resistance compared to the film containing ML essential oil. The antimicrobial effect of films containing ML essential oil was confirmed in this study (p˂0.05). The addition of GO-ZnO did not change the count of any of the microbial groups. TVB-N showed that groups containing ML essential oil had lower levels of volatile nitrogenous bases than the control group (p˂0.05). Sensory evaluation of the studied groups showed that chicken fillets packed with films containing ML essential oil had the highest score in terms of color, smell and taste. The results of the present study showed that PLA film containing GO-ZnO and ML essential oil can be used to increase the shelf life and maintain the sensory characteristics of chicken fillets, and it can be used as a suitable packaging to increase the shelf life of food products.

Reduction of Total Phenols in Virgin Olive Oil as a Preservation Medium during Cold Storage of Whey Cheese and Tofu.

Virgin olive oil, known as a good source of health-promoting hydrophilic phenols, is traditionally used as a medium for preserving various foods. Phenols in general can form complexes with proteins, but there is little information on the direct contact of virgin olive oil with protein-rich food during long-term storage. In this study, the dynamics of the decline of total phenols in oil used as preservation medium for a traditional (whey cheese skuta) and a modern product (tofu) were compared. Pieces of skuta or tofu immersed in virgin olive oil at different food-to-oil mass ratios were stored in the refrigerator for up to 21 days. The oil quality indices, water content and the total count of aerobic mesophilic bacteria in the immersed materials were monitored. To determine the total phenols in the oil, the optimal conditions of the Fast Blue BB test, which is a suitable alternative to the standard method, were tested and selected. The effect of both materials on the indicators of hydrolytic and oxidative deterioration of the oil is almost identical (a gradual decrease), which is most likely due to the continuous release of water from the immersed food. A sharp decrease in total phenols in the oil (by about 50 %) after seven days of storage in contact with both materials indicates a combination of causes (water-to-oil migration and phenol-protein interactions). The form of the rational function is highly representative of the decrease in total phenols during the first seven days of tofu/oil storage, indicating a very rapid interaction with tofu proteins. The preservative effect of virgin olive oil in terms of microbiological spoilage was not observed. The results of this study contribute to the knowledge on the dynamics of phenol-protein interactions and emphasise the need for further investigations on traditional or newly used protein-rich foods preserved in direct contact with virgin olive oil, taking into account possible changes in the functional, nutritional and sensory properties of phenols and proteins.

The Effect of Grape Pomace Fiber Addition on Quality Parameters of Yogurt

Reducing food and industrial waste is essential to match the novel objectives of sustainable living. In this context, grape pomace, a fiber-rich by-product of wine production, was used as a fiber supplement in yogurt after enriching its fiber content through preprocessing. Within the aim of this study, 0.5% and 1% grape pomace fiber were incorporated into yogurt, and the effect on physicochemical, microbial, and sensory quality was investigated. Throughout the 14-day storage period, no significant changes were observed in pH, acidity, and water holding capacity. The total mesophilic aerobic bacteria count ranged between 2-3 log.cfu/g, and the addition of fiber did not result in any undesirable alterations in these counts. Similarly, the fiber did not affect the counts of specific yogurt bacteria, which was 8-9 log.cfu/g. Moreover, sensory evaluations consistently resulted in scores above “5” for all products, with acidity rated level as moderate as expected for yogurt. There were no adverse effects on sensory quality concerning color, flavor, texture, acidity, and overall acceptability. In conclusion, fiber-enriched yogurt from wine waste is feasible without compromising product quality. This study is expected to contribute to the progress of current sustainable living goals.

Combined Ascorbic Acid and Mild Heat Treatment to Improve the Quality of Fresh-Cut Carrots.

Mild heat (MH) treatment and ascorbic acid (AsA) addition can improve the quality of fresh-cut produce when used individually; however, their combined effect remains unclear. Herein, fresh-cut carrots were used as models to explore the effects of MH (50 °C)-AsA (0.5%) on quality properties including reactive oxygen species (ROS) metabolism, antioxidants, lignin metabolism, naturally present microbes, and inoculated pathogens (Escherichia coli O157: H7 and Salmonella Typhimurium) during storage (0-5 d, 4 °C). The results indicate that the antioxidant properties in the MH-AsA group were consistent with those of single treatments, resulting in a consistent ROS-scavenging effect. From day 3-5, lignin synthesis was significantly inhibited by MH-AsA as compared with single treatments, probably because the two enzymes (phenylalanine ammonia-lyase and peroxidase) responsible for lignin synthesis exhibited lower expressions. Microbial analysis revealed that MH-AsA treatment led to the lowest counts of both pathogens and aerobic mesophilic bacteria at 0-5 d. Conversely, the inhibitory effect of MH-AsA treatment on mold and yeast was consistent with the single treatments. These results suggest that MH-AsA is a low-cost and safe approach to improve the physiological characteristics of fresh-cut produce while reducing microbial risk.

Comparative Study of Vermicomposting: Apple Pomace Alone and in Combination with Wheat Straw and Manure

Considering the sporadic number of scientific studies on vermicomposting apple pomace waste, this research conducts a comparative analysis of vermicomposting processes using Eisenia fetida, focusing on apple pomace both independently and in combination with wheat straw and/or manure (experiment 1: 60% apple pomace and 40% cattle manure; experiment 2: 60% wheat straw and 40% cattle manure; experiment 3: 80% apple pomace, 10% wheat straw, and 10% cattle manure; and experiment 4: 100% apple pomace). After a 240-day substrate transformation period, all four variations of vermicompost produced demonstrated favorable sensory properties, along with high microbiological and physicochemical quality. Throughout the vermicomposting process, the pH of all vermicomposting mixtures changed, converging towards approximately neutral values by the process’s conclusion. There was an increase in dry matter content, as well as total N, P, K, Ca, and Mg, along with organic matter. Notably, the levels of heavy metals (Zn, Cu, Cd, and Pb) in both the vermicomposting materials and resulting vermicomposts remained significantly below the maximum permissible levels stipulated by Republic of Serbia and European Union legislation, which is directly linked to the ecological origin of the raw materials used. The microbiological quality of the final vermicomposts was deemed satisfactory. Over time, there was a decrease in the counts of aerobic mesophilic bacteria as well as Escherichia coli. The counts of sulfite-reducing clostridia in all substrates remained below 102 CFU/g, while Salmonella spp. and Listeria monocytogenes were not detected in either the composting materials or the resulting composts. The vermiculture of apple pulp exhibited advantageous characteristics, notably a shortened vermicomposting period (150 days) compared to other agricultural waste. This reduction in processing time contributes an additional layer of advantage to the overall quality and efficiency of the resulting vermicompost.

Effects of Process Conditions on Drying of Tomato Pomace in a Novel Daylight Simulated Photovoltaic-Assisted Drying System

The tomato pomace (TP), which is a by-product of the production of tomato paste, was dried in a novel custom-designed daylight simulated photovoltaic assisted dryer (DPVD). The different light applications (daylight, UV light, daylight + UV light, and without light), different air velocities (1.5 and 2 m/s), and different heating source modes (hot air and infrared) were applied to dry TP having a moisture content of 80.60 ± 0.73% to the moisture content of 7.66 ± 1.72%. The average water activity values of all dried samples were measured as 0.52 ± 0.08. Analysis was conducted to compare sun drying with the effects of process conditions on the quality (color properties, lycopene, β-carotene, and total mesophilic aerobic bacteria count) and performance (energy efficiency, exergy efficiency, specific moisture evaporation rate, and improvement potential) characteristics of TP. The effects of process conditions for each heating source mode were determined separately, and the improvement of the system performance for each mode was investigated. The effect of the process conditions on total aerobic mesophilic bacteria (TAMB) count was similar in general. In the infrared heating mode, the loss in lycopene and β-carotene contents was 59.55 ± 2.22 and 57.87 ± 2.51 minimum for 1.5 m/s air velocity without light application and for 2 m/s with ultraviolet + daylight application. In general, the performance of the system decreased in case of using ultraviolet light. The retention in the lycopene and β-carotene contents was higher in the infrared mode with light applications compared to hot air mode without light. The optimum drying conditions were air velocity of 2 m/s with “daylight” assistance in the hot air heating mode and with “ultraviolet + daylight” assistance in the infrared heating mode. All the energy and the daylight source used in drying applications were obtained from the sun, a renewable energy source, thanks to the photovoltaic panel and the solar tube units in the novel custom-designed drying system.