Microbial Quality Changes Research Articles

Milk Spoilage Model Predicts that Share Tables Would Not Meaningfully Increase Spoilage and Improved Storage Systems Can Reduce Spoilage

School share tables offer opportunities for food recovery and increased access to healthy foods by allowing students to donate or consume unopened items, such as cartons of milk. However, stakeholders have concerns about temperature abuse potentially causing premature milk spoilage. While previous research showed short ambient temperature abuse of milk (under conditions representing share tables) does not meaningfully impact microbial milk quality, differences across school cafeterias (e.g., ambient temperatures, storage systems, bell schedules, refrigeration temperature) may limit the generalizability of this conclusion. To address this, the overnight refrigeration temperature and the milk's initial contamination were predicted to be the main drivers for milk spoilage. Share tables were predicted to only cause inconsequential microbial quality changes (4 spoiled milk per million served, which would be ≤2 milk cartons spoiled per school year) under short and medium bell schedules (≤125 min of total service), even without temperature control during the lunch period. Under long (221 min) and very long (266 min) bell schedules, share tables with ambient temperature storage were predicted to have higher milk spoilage (19 and 42 spoiled milk cartons per million served, respectively), and adding storage systems was predicted to reduce the decline in milk quality (12 and 24 spoiled milk cartons per million served, respectively). These results provide a resource to support science-based decision-making for the inclusion of milk in school cafeteria share tables, ultimately working to reduce food waste and address food insecurity.

Influence of storage on physico-chemical physiognomies of fermented whey cereal (pearl millet and moth bean) beverage.

The present study concludes the impact of storage on changes in physico-chemical characteristics of fermented whey cereal (pearl millet and moth bean) beverage. The beverage was prepared by fermented whey (standardised to 4% fat and 18% total solids) supplemented with germinated pearl millet and moth bean slurry & using NCDC-167 as starter culture for 6-8h at 37°C. The developed beverage was then stored at 5°C for 4weeks. The samples were analysed for physico-chemical characteristics (pH, titrable acidity, viscosity, tyrosine, FFA, wheying off), sensory qualities changes and microbial quality changes (standard plate count, lactic acid bacteria count, coli form counts) at 3days' interval for 4weeks at 4°C. Control was prepared standardised whey (4% fat and 18% total solids) while treatments were prepared using standardised milk. During storage: acidity, tyrosine values, free fatty acid values and wheying off increased in all the samples The upsurge was on higher side in non nisin treated and non thermised samples compared to control formulation. However, all the samples remained sensorily acceptable upto 12th day of storage. Basic and thermised as well as nisin treated fermented whey cereal products epitomize innovative dairy products with desired functional characteristics with decent shelf life.

Changes in microbial quality of fruit juices, syrups, and ready-to-serve carbonated drinks produced with different processing parameters and stored in different conditions within six months

The research was carried out during 2015-2017, aimed to consider the microbial quality of juice, syrup, and ready-to-serve (RTS) carbonated beverage prepared from mandarin fruit (Nagpur cultivar). Fully ripened, mature, fresh fruits were washed and peeled, then the juice was extracted using a screw-type pulper. The syrup and ready-to-serve carbonated beverage prepared from the extracted juice. Microbial analysis of juice was carried out by using Potato Dextrose Agar (PDA) culture medium. The results revealed no microbial growth in the ready-to-serve carbonated beverage up to 60 d of storage, after that from 90 to 180 d of storage was negligible. In the syrup, up to 90 d was no detection of microbes; after that, up to 180 d of storage was negligible. In the juice samples under cold storage (S2), all the treatments were within acceptable levels for 180 d. But under room temperature (S1), eight treatments (T1, T2, T3, T4, T5, T6, T8, T9) showed microbial colonies more than acceptable level, and only one treatment (T7-S1P3B1= juice sample in the room storage (SI) which added 350 ppm sodium benzoate as chemical preservative (P3) and packed in the glass bottle (B1) was remained safe for consumption during 180 d of storage. The microbial quality, viz. yeast and mold count were increased during 180 d of storage in the ready-to-serve carbonated beverage, syrup and juice. The microbial growth was observed within the acceptable level in all treatment combinations of ready-to-serve carbonated beverage, syrup; and juice in cold storage and T7 of juice under ambient conditions.

Physicochemical and Microbiological Changes in Non-Sulfitted Dried Apricots as Affected by Storage Condition

The present study was conducted for the determination of physicochemical and microbial quality changes for the non-sulfited sun dried apricots (NSDAs) with three various moisture contents (MCs); 137 g/kg (MC137), 235 g/kg (MC235), and 270 g/kg (MC270); at different temperatures (4, 10, 20, and 30°C) during 12 months in bulk and packaged storage. NSDAs were subjected to physical (moisture, water activity, pH and reflectance color values), chemical (browning formation, β-carotene, and acidity), and microbial (counts for total aerobic mesophilic and psycrofilic bacteria, yeast and mould, xerofilic mould and yeast, osmophilic yeast, lactic acid bacteri, Enterobacteriaceae, Staphylococcus-Micrococcus spp.) analyses at one-month intervals. Results indicated that the fastest brown colour formation occurred in the samples containing 235 g/kg MC at 30°C, and the browning was decelerated below 10°C. No significant change in β-carotene contents of NSDAs during storage was observed (P> 0.05). After rehydration, osmophilic yeast count of NSDAs increased by 2.5 log colony-forming units (cfu/g). Significant reductions were observed in the microbial loads of MC235, and MC270 samples with the decreasing water activity (P<0.05) and increasing storage temperatures. However, yeasts and moulds counts exceeded 5.0 log cfu/g of the samples containing 270 g/kg MC after 2 month of storage at 20°C. Overall, the results of the study suggest that NSDAs should not be stored above 10°C, and the MC should be kept below 235 g/kg to maintain microbial and physicochemical quality.

Effect of incorporating roasted sesame (Sesamum indicum) seeds on the quality parameters of chicken nuggets

The present study was aimed to develop a value-added chicken nugget by incorporating roasted sesame seeds (RSS) and elucidate its sensory and quality parameter changes during a 28-d frozen storage. Chicken nugget samples were processed to have four treatments as; 1) Nuggets with 0% RSS (w/w) [Control], 2) Nuggets with 5% RSS (w/w) [SN5], 3) Nuggets with 10% RSS (w/w) [SN10] and 4) Nuggets with 15% RSS (w/w) [SN15] with six replications per treatment. The two best nugget samples with RSSs were selected by a sensory panel and tested for physicochemical and microbial quality changes with the control sample during a 28-d frozen storage. Results revealed that SN10 had the highest (p&lt;0.05) crude fat (8.84%), crude protein (14.24%) and ash (3.15%) contents compared to SN5 and the control. During the 28-d frozen storage, the pH of nuggets diminished gradually (p&lt;0.05) in all treatments. SN10 had the highest (p&lt;0.05) thiobarbituric acid reactive substance (TBARS) value compared with its counterparts throughout the 28-d frozen storage. The TBARS values and total plate count values increased (p&lt;0.05) in all treatments during the frozen storage, but within the acceptable limits. The water holding capacity of nuggets in all treatments decreased (p&lt;0.05) and cooking loss increased (p&lt;0.05) during the frozen storage. In conclusion, RSSs could be mixed up to 10% to the nugget mixture to prepare nuggets with improved proximate composition, and physicochemical and sensory properties.

WHAT IS HIDDEN BEHIND ACTIVATED SLUDGE SUPERNATANT? FLUORESCENT STAINING AND LASER GRANULOMETRY INVESTIGATION SUPPORTED BY MACHINE LEARNING

Studies on the biological composition of activated sludge flocs in the operating conditions of wastewater treatment plants are generally limited to the estimation of respiratory activity or to the analysis of images made with optical microscopy. The results of these studies indirectly provide information on the microbiological composition. To date, molecular methods, although very promising, have not found a wider application in operational monitoring of wastewater treatment plants. In this paper, the supernatant was under discussion as a potential source of sampling for analyzing microbial quality changes. The results of 270 activated sludge and treated wastewater samples showed that the smallest flocs leaching to the outflow constitute a group of microorganisms that is most numerous. The studies carried out using the fluorescence in situ hybridization method have shown that the microorganisms responsible for the nitrification processes occur both in activated sludge and supernatant. Image analysis of microorganisms from activated sludge and supernatant stained with Live/DEAD reagent indicate that microflocs and bacteria in the outer flocs, which are relatively loosely attached to the flocculent matrix are more exposed to external factors. The results suggest that it is advisable to find information about the condition of the whole community especially for group of particles in the supernatant. In addition, the authors recommend using machine learning methods to evaluate predicting anomalies in biological composition of activated sludge flocs.

Effect of packaging material on the quality of fresh‐cut beet leaves packed in modified atmospheres

This study aims to evaluate the effect of packaging system, including packaging materials with low, medium, and high oxygen permeance (OP), with or without initial atmosphere modification (IAM: 5kPaO2–10kPaCO2–85kPaN2) on minimally processed beet leaves (MPBL) overall quality during 8 days of storage at 12°C. Changes in microbial quality, pH, moisture content, and antioxidant capacity were independent of the packaging system. Samples with or without IAM achieved dynamic equilibrium in 24 or 144 hr, respectively. High, medium, and low OP material stabilized at 8kPaO2–3.5kPaCO2, 6kPaO2–6kPaCO2, and 0kPaO2–20kPaCO2, respectively. Low-OP presented anoxia conditions. High-OP material maintained total soluble solids and carotenoids and presented the highest retentions of betalains, chlorophyll, and total phenolics during storage. Moreover, active modified atmosphere packaging (with IAM) yielded significant improvements on bioactive retention. Hence, high-OP material with IAM is recommended for MPBL preservation. Practical applications This research addresses one of the major challenges facing the growing industry of minimally processed fruit and vegetables, the rapid deterioration of their quality, and their reduced shelf-life. The results obtained are significant since give a practical and effective response to this challenge.

Online microbial fingerprinting for quality management of drinking water: Full-scale event detection

Microbial regrowth during drinking water distribution can result in a variety of problems such as a deviating taste and odor, and may even pose a risk to public health. Frequent monitoring is essential to anticipate events of biological instability, and relevant microbial parameters for operational control of biostability of drinking water should be developed. Here, online flow cytometry and derived biological metrics were used to assess the biological stability of a full-scale drinking water tower during normal and disturbed flow regime. Pronounced operational events, such as switching from drinking water source, and seasonal changes, were detected in the total cell counts, and regrowth was observed despite the short hydraulic residence time of 6–8 h. Based on the flow cytometric fingerprints, the Bray-Curtis dissimilarity was calculated and was developed as unambiguous parameter to indicate or warn for changing microbial drinking water quality during operational events. In the studied water tower, drastic microbial water quality changes were reflected in the Bray-Curtis dissimilarity, which demonstrates its use as an indicator to follow-up and detect microbial quality changes in practice. Hence, the Bray-Curtis dissimilarity can be used in an online setup as a straightforward parameter during full-scale operation of drinking water distribution, and combined with the cell concentration, it serves as an early-warning system for biological instability.

Effect of the combination of natural antioxidants and packaging methods on quality of pork patties during storage.

The effect of combination of phyto-extracts (sea buckthorn extract (SBTE), grape seed extract (GSE)) on different physico-chemical, oxidative stability, instrumental colour and texture, sensory and microbiological properties of pork patties were investigated under aerobic and MAP (50% CO2: 50%N2) packaging conditions. Treatments viz. T-1 (aerobic packaged control), T-2 (aerobic packaged containing 0.3% SBTE+ 0.1% GSE), T-3 (MAP packaged control) and T-4 (MAP packaged containing 0.3% SBTE+ 0.1% GSE) at 4 ± 1°C for 35days and samples were drawn at 7days interval. The pH decreased initially up to 21days and thereafter increased on further storage whereas water activity followed a decreasing trend throughout the storage period, irrespective of the treatment and packaging conditions. Results of oxidative stability parameters revealed that peroxide value, TBARS and FFA followed an increasing trend in both the packaging groups during storage however, the rate of increase was significantly lower (P < 0.05) in MAP packaged products than aerobic packaged products and phyto extracts incorporated products than their respective control. Instrumental colour and texture profiles were best maintained in MAP packaged treated products (T-4) which has higher redness (a*) value whereas lightness (L*) and yellowness (b*) showed lower (P < 0.05) value. MAP packaging resulted in superior sensory properties of pork patties as compared to aerobic packaged products. Standard plate count, psychrophiles and Coliforms were significantly (P < 0.05) lower in treated products than control and microbial count was better maintained in MAP than aerobic condition. Results concluded that the combined use of antioxidants and MAP packaging would be a useful method to control the oxidative and microbial quality changes of pork patties and it can be successfully stored for 35days.

Changes in Microbial Quality of Irrigation Water Under Different Weather Conditions in Southeast Norway

A short-term study concerning the impact of weather fluctuations in Southeast Norway on microbiological quality of irrigation water sources was performed. The weather variations were related to a relatively dry and warm period followed by rainfall events associated with lower air temperatures. Samples of water from a ground well, a pond and a stream, all used for sprinkler irrigation of fruit and vegetable crops, were investigated for contamination with faecal indicator bacteria (Escherichia coli – E. coli) and intestinal parasitic protozoa (Cryptosporidium oocysts and Giardia cysts). Although the groundwater was not contaminated with these microbes during either period, contamination was detected in surface waters, with concentrations up to three times higher during the wet/cool period than during the dry/warm period. An increase in microbial concentrations was observed immediately after the first rainfall events. These results demonstrate that surface waters commonly used for irrigation in Southeast Norway are vulnerable to contamination with microbes and this is related to weather fluctuations. These outcomes are of relevance when considering the impact of predicted climate change and contamination of agricultural water supplies.

Comparison of microbial quality of irrigation water delivered in aluminum and PVC pipes

Microbial quality of irrigation water attracts substantial attention due to the increased incidence of gastrointestinal illness caused by contaminated produce. Little is known about the changes in microbial quality of water during its delivery to crops. Studies were conducted to compare the biofilm formation and changes in microbial water quality in aluminum and PVC irrigation pipes. Irrigation events were conducted weekly and sections of irrigation pipe (coupons) analyzed for total protein, for total and fecal coliform bacteria, and for Escherichia coli. Coliform and E. coli concentrations along with nitrate, orthophosphate, and total organic carbon were monitored in the intake surface water, output irrigation water, and measured in residual standing water in pipes just prior to each irrigation event. Proteins accumulated to a greater extent in aluminum-associated biofilms than in plastic-associated biofilms. Numbers of total coliforms associated with aluminum coupons increased with time while numbers of total coliforms associated with plastic coupons fluctuated. Nitrates disappeared in standing water after one week in aluminum pipes and remained present in plastic. No detectable E. coli remained in standing water in both types of pipe. There was a high probability that coliform concentrations in output irrigation water were different from the intake concentrations in plastic pipes but not in aluminum pipes. Further research is required to evaluate how pipe material may affect the potential of biofilms in irrigation distribution systems to serve as reservoirs of pathogens that can be disseminated to crops during irrigation.

Effect of high pressure processing on the quality of herring ( Clupea harengus) and haddock ( Melanogrammus aeglefinus) stored on ice

Fresh herring and haddock were vacuum-packed and subjected to high pressure processing (200, 250 and 300 MPa at 10 °C for both 1 and 3 min) or left untreated as controls. The samples were stored in ice at 2 °C for up to 14 days, during which time the changes in microbial quality, total volatile base nitrogen (TVBN) and trimethylamine (TMA) production were monitored. Microbial shelf-life was determined as the storage time required for psychrotrophic counts to reach 10 6 CFU g −1, while chemical shelf-life was estimated as the time taken for TVBN and TMA values to reach 35 mg N 100 g −1 and 15 mg N 100 g −1 respectively. High pressure significantly delayed microbial growth ( p < 0.05) in both herring and haddock. In the case of herring the microbiological shelf-life was extended from ∼4 days in controls to ˜13 days in fish pressure-treated at 200 MPa/3 min. Microbial numbers in all the haddock samples tended to be lower throughout the storage period, compared to herring, irrespective of pressure treatment, and none of the pressure-treated samples reached unacceptable psychrotrophic numbers until 14 days in ice compared to 10 days in the controls. The microflora of both the control and pressure-treated herring and haddock at day 0 were predominantly Gram-positive cocci (Micrococcus spp. and Staphylococcus spp.) and spore-forming rods (Clostridium spp. and Bacillus spp.). This microflora did not change significantly during storage of the fish in ice at 2 °C for 10 days. Pressure treatment also delayed TVBN and TMA production in the fish. In the case of herring, predicted values did not reach unacceptable levels until at least 18 days (200 MPa/3 min) compared to 5.5 days in controls. With haddock, TMA and TVBN values in control samples reached unacceptable limits between 6 and 10 days of storage. However, the levels remained below the limits of acceptability in all pressure-treated samples during storage, apart from on day 14, when the TVBN value in samples treated at 200 MPa/1 min exceeded the level of acceptability. Overall, taking account of the various spoilage indicators, the minimum treatment required to increase shelf-life in herring and haddock to ∼13 days on ice was found to be 200 MPa for 3 min.

Effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality changes of seer fish ( Scomberomorus commerson) steaks stored in ice

The effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality of seer fish ( Scomberomorus commerson) steaks was determined during chilled storage (1–2 °C). The O 2 absorber reduced the oxygen content in the pack to less than 0.01% corresponding to 99.96% reduction within 24 h. The use of O 2 absorber with sodium acetate dip treatment (2% w/v) extended the sensory shelf life up to 25 days compared to only 12 days for control air packs and 20 days for untreated samples with O 2 absorber. A prominent lag phase was observed for many bacterium studied, particularly for the sodium acetate treated samples with O 2 absorber. On the day of sensory rejection, both the total mesophilic and psychrotrophic counts reached 7.7–8.1 and 7.1–7.9 log cfu/g, respectively. The sodium acetate treatment and reduced O 2 atmosphere affected the type of major spoilers. In air packed samples, H 2S-producers predominated followed by Brochothrix thermosphacta, Pseudomonas spp., where as in the untreated samples with O 2 absorber, H 2S-producers predominated the microbial flora followed by Lactobacillus spp. For treated samples with O 2 absorber, B. thermosphacta formed the major micro-flora followed by Lactobacillus spp. The use of O 2 absorber inhibited the growth of Pseudomonas spp., and total Enterobacteriaceae.

A Study on the Microbiological Quality of Drinking Water and Changes During Storage

To assess possible risks from the consumption of drinking water from various sources, a survey of the microbiological quality of tap water, commercial bottled drinking water which is exploited from natural mineral water, and natural spring water was conducted. A total of 4 different brands of commercial bottled drinking water, and 4 types of spring water from different sources, and tap water from 4 private houses were tested for four index microorganisms, and the microbial quality changes of the water during the storage at room temperature or refrigerated temperature for 7 days. Aerobic plate counts of all of the initial water samples were still within 100 CFU/ml (drinking water standard of Korea). Total coliforms, fecal coliforms, and E. coli were not detected in all of the water samples at initial. However, aerobic plate counts of three types of spring water and three types of bottled drinking water stored at room temperature showed higher levels than the standards in 5 days. Total coliforms were detected in three types of spring water after one day's storage at room temperature, and in one type of bottled drinking water after 5 days' storage. These results indicate that some of the spring water surveyed are not safe to drink, and the spring water and bottled drinking water after opening the lid should not be stored at room temperature, if they are used for drinking.

Consumer acceptance and physicochemical quality of processed red sorrel/roselle (Hibiscus sabdariffa L.) sauces from enzymatic extracted calyces

AbstractThe objectives of this study were to utilize sorrel puree from enzymatic extracted sorrel or roselle (Hibiscus sabdariffa L.) calyces in the processing of sauces and to determine consumer acceptance of sauces with the addition of 0.3% and 0.4% xanthan gum. The physicochemical (particularly colour) and microbial quality changes in sauces were monitored during storage. Pectolase treatment of sorrel calyces resulted in a high yield (94.5%) of puree, but the hue changed (P &lt; 0.05) from red to orange‐yellow. Adjustment of puree to pH 2.3 resulted (P &lt; 0.05) in an intense red colour. Sensory and physicochemical attributes did not differ significantly between sauces except for consistency and hue. Sensory colour was the most liked (P &lt; 0.05) attribute with an instrumental colour ‘L’ 23.5, ‘a’ 3.5 and ‘b’ 0.40. Total soluble solids and pH were 41.0–43.5°Brix and 2.62 ± 0.04, respectively. Sauces were liked slightly to moderately in overall acceptability. A positive correlation (P &lt; 0.05) was noted between the overall acceptability to other sensory attributes. Colour became less dark and red (P &lt; 0.05) on storage at 20°C for 6 weeks. Sauces had &lt; 10 cfu/mL of yeasts and moulds, lactobacilli and total mesophilic aerobes throughout storage at 20°C for 8 weeks. A 25‐g sauce serving provided 0.7‐g dietary fibre or 3% of the daily value. The overall acceptability of sorrel sauce makes it an ideal ingredient for use in the food service industry and inclusion in a number of dishes.

Changes in water microbial quality during bank filtration of lake water.

We studied, during a 2-year period, how the microbial stability of water changed when humus-rich lake water was filtered through the ground at a bank filtration water plant. The changes in microbial quality were followed as microbial numbers and growth activity. The filtration decreased microbial counts and growth ([3H]thymidine technique) in water up to 90%. The reduction in bacterial counts and growth depended on the filtration distance. The reduction was greatest between the lake and the first sampling point. Microbial numbers and growth declined steadily after infiltration with increased filtration distance. Viable counts of heterotrophic bacteria decreased faster than total bacterial counts along filtration. The microbial numbers and bacterial production in water followed seasonal changes in water temperature. Simultaneously with the microbial numbers, the concentrations of total organic carbon and assimilable organic carbon decreased during bank filtration. These results showed that microbial stability of humus-rich water was increased by filtration to a level generally found in natural groundwaters.