Reduction effect of the selected chemical and physical treatments to reduce L. monocytogenes biofilms formed on lettuce and cabbage

As people shift their attention away from unhealthy foods, healthy fresh produce has become popular. However, fresh produce has contributed to many outbreaks of Listeria monocytogenes, which can form a mature biofilm within 24 h. Recent control strategies have proved ineffective in ensuring safe food production. This study focuses on L. monocytogenes biofilms formed on lettuces and cabbages using a viable plate count method and field emission electron microscopy. We investigated the reduction efficacy of treatment with 200 parts per million (ppm) chlorine, 2% each of citric, lactic, and malic acids, 32 Hz ultrasonication (US), 390 mJ/cm² ultraviolet-C (UV-C), or 750 mJ/cm² cold oxygen plasma (COP) on L. monocytogenes biofilms. Following treatment, the quality of the vegetables was analyzed with standard procedures. UV-C and COP showed the best CFU reduction, regardless of the nature of the vegetable surface, while US failed to produce any significant reduction (P > 0.05). Furthermore, chemical treatments reduced count by < 1 log colony forming unit (CFU)/cm² on lettuces, whereas a > 2 log reduction was observed on cabbages. The effect of chemical treatment largely depended on the particular vegetable, while UV-C and COP achieved high reduction regardless of the vegetable, and had no effect on quality. We, therefore, speculate that UV-C and COP show promise in overcoming L. monocytogenes biofilms on food produce.     

UV-C irradiation as an alternative disinfection technique: Study of its effect on polyphenols and antioxidant activity of apple juice

Ultraviolet (UV-C) irradiation is a non-thermal disinfection method, effective against a range of bacteria and viruses, which is being considered as an alternative to pasteurization of fruit juices. The objective of this study was to investigate the effect of UV-C irradiation on the polyphenolic content and in-vitro total antioxidant activity of apple juice. UV irradiation doses ranging from 0 to 240 mJ·cm^− 2 were delivered to apple juice and polyphenols, sugars, in-vitro total antioxidant activity and total phenols were profiled. The results demonstrated that UV-C irradiation in apple juices at relevant commercial disinfection doses induced significant reduction in the concentrations of chlorogenic acid, phloridzin, and epicatechin (p < 0.05). The induced changes were relatively minor for the above mentioned polyphenols, except phloridzin (50% reduction) at 240 mJ·cm^− 2. Epicatechin concentrations were reduced significantly (p < 0.05), whereas increase in catechin concentration was observed with increase in UV-C exposure to 240 mJ·cm^− 2. There was a minor reduction in sugar (glucose and fructose) concentrations with increasing exposure levels from 0 to 40 mJ·cm^− 2 (p > 0.05). In contrast, a slight increase in sugar concentrations as increase in UV-C exposure after 40 mJ·cm^− 2 was observed. These changes were not significantly different from control. Total phenolic content was well retained regardless of the UV-C exposure for apple juice. In-vitro total antioxidant activity changed when UV-C exposure exceeded 40 mJ·cm^− 2, but remained unchanged at the maximum UV-C dose of 240 mJ·cm^− 2. These results suggested that UV-C irradiation could be an effective alternative to conventional thermal processing for production of high quality apple juice.Industrial RelevanceThis research paper provides scientific evidence of the potential for UV-C irradiation to achieve meaningful levels of disinfection while retaining important bioactive compounds (polyphenols) in apple juice. In-vitro antioxidant activity and individual polyphenols were well retained at commercially relevant doses of 40 mJ·cm^− 2. From a nutritional perspective, UV-C irradiation is an attractive food preservation technology and offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products. Therefore, UV-C irradiated foods could be sold at a premium price to their thermally-processed counterparts, as they have retained their fresh-like properties. This study would provide technical information relevant for commercialization of UV-C treatment of juices.     

Inactivation kinetics of Listeria monocytogenes,Salmonella enterica serovar Typhimurium,and Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation

To investigate the applicability of UV-C irradiation on the inactivation of foodborne pathogenic bacteria in ready-to-eat sliced ham, UV-C treatment was evaluated. Irradiation dose required for 90% reduction of the populations of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Campylobacter jejuni were determined to be 2.48, 2.39, and 2.18 J/m². Ready-to-eat sliced hams were inoculated with the pathogens and irradiated with UV-C light of 1000, 2000, 4000, 6000, and 8000 J/m². Microbiological data indicated that foodborne pathogen populations significantly (p < 0.05) decreased with increasing UV-C irradiation. In particular, UV-C irradiation at 8000 J/m² reduced the populations of L. monocytogenes, S. Typhimurium, and C. jejuni in the ham by 2.74, 2.02, and 1.72 log CFU/g. The results indicate that UV-C irradiation can be used as a microbial inactivation method for ready-to-eat sliced ham, and inactivation kinetics of the foodborne pathogens fit the Weibull model better than the first-order kinetics model.     

UV-C treatment of soymilk in coiled tube UV reactors for inactivation of Escherichia coli W1485 and Bacillus cereus endospores

Coiled tube UV reactors were used to investigate the influence of tube diameter (1.6 mm ID, and 3.2 mm ID) and Reynolds number (Re) to inactivate Escherichia coli W1485 and Bacillus cereus spores in raw soymilk (RSM). Four levels of Re (343, 686, 1029 and 1372) were tested in RSM inoculated separately with each bacterium and treated in the UV reactors at a constant residence time of 11.3 s with UV-C dose of 11.187 mJ/cm² at 253.7 nm. Inactivation efficiency of both microorganisms increased with Re. Maximum reductions of 5.6 log₁₀ CFU/ml of E. coli and 3.29 log₁₀ CFU/ml of B. cereus spores were achieved in the 1.6 mm ID UV reactor. Inactivation efficiency was higher in the 1.6 mm ID UV reactor than the 3.2 mm ID UV reactor for both the organisms. Effect of UV-C light on lipid oxidation of untreated RSM, measured as malondialdehyde and other reactive substances (MORS) content, was much higher (95 nmol/ml) than the UV-treated (58 nmol/ml) and thermally pasteurized (55 nmol/ml) RSM during the storage period of 7 days. The UV-C treatment can be effectively used for reducing E. coli cells and B. cereus spores in soymilk without compromising its quality.     

Removal of meat biofilms from surfaces by ultrasounds combined with enzymes and/or a chelating agent

A curved ultrasonic transducer was devised to standardise biofilm removal for hygiene testing in internal or curved food contact surfaces. Meat biofilms made with Escherichia coli and Staphylococcus aureus on stainless steel sheets were studied. Ultrasounds (10 s at 40 kHz) alone failed to completely remove biofilms: 49 ± 5% and 39 ± 5% recovery rates were obtained for E. coli and S. aureus biofilms, respectively. A combined treatment, which involved the application of ultrasounds to EDTA and/or in enzymes solutions, allowed to remove up to 75 ± 4% and 100 ± 15% of E. coli and S. aureus biofilms, respectively. This application was in agreement with an industrial control i.e. a combined treatment: ultrasound generation in enzymes preparation restricted to an active chamber area with a fast and good reproducible recovery.Industrial relevanceThe biofilm phenomenon has been under intensive research for several years in food industry. A curved ultrasonic transducer was devised to standardise biofilm removal for hygiene testing in internal or curved food contact surfaces. This apparatus uses the mechanical effects of ultrasonic cavitation produced at 40 KHz (10 s) for the non-destructive detection of biofilms in food processing equipment. We report the utilisation of a combined treatment, which involved the application of ultrasounds to EDTA and/or in enzymes solutions on meat biofilms made with E. coli and S. aureus on stainless steel sheets. This application was in agreement with an industrial control i.e. a combined treatment: ultrasound generation in EDTA and/or enzymes preparation restricted to an active chamber area with a fast and good reproducible recovery.     

Processing of clear and turbid grape juice by a continuous flow UV system

The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm² of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm², respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples.Industrial relevanceUV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products.     

Combination of natural antimicrobials and sodium dodecyl sulfate for disruption of biofilms formed by contaminant bacteria isolated from sugarcane mills

Bacterial contamination is found during ethanol production in the form of biofilms, which can decrease ethanol yield by 30%. Carvacrol, nisin, and hops extract, alone and in combination with SDS, were tested against planktonic and preformed biofilms of Lactobacillus fermentum, Lactobacillus plantarum, and/or Leuconostoc mesenteroides. MICs of carvacrol, nisin, hops extract and SDS were 250, 30, 5 and 37.5 mg/L, respectively, against all bacteria. Synergism between SDS and carvacrol (FIC_index = 0.125), and SDS and nisin (FIC_index = 0.25) was also found against all bacteria. Bacterial viability within biofilms and removal of biomass were indirectly measured using MTT and crystal violet methods, respectively. Metabolic activity of biofilms was inhibited up to 92% with nisin + SDS, while carvacrol + SDS could remove 82% of the biomass. Thus, combined use of these antimicrobials and SDS may provide an effective method for cleaning equipment of ethanol plants and prevent formation of biofilms.     

Minimal processing of mucilage from the pulp of yam (Dioscorea pseudojaponica Yamamoto) using bubble separation and ultraviolet irradiation

Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required. A novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. The objectives of these studies were to follow the previous design for continuously separating, recovering and irradiating yam slurry mucilage for inactivation of microorganisms. The UV-C dose of 32000 μW/sec/cm² at 254 nm has a germicidal effect against microorganisms and is used for the disinfection. Two sets of custom made UV-C irradiators containing four UV-C germicidal lamps were added to the system. The effectiveness of this UV-C irradiator for reducing the aerobic bacteria count (APC) and yeasts and molds (YM) count in yam slurry mucilage was investigated. The results showed UV-C irradiation was successfully applied to reduce the microbial load in the yam slurry mucilage. If the slurry mucilage completes the process for both two sets of UV-C irradiators, a 4.5 log₁₀ APC reduction and a 4.1 log₁₀ YM reduction were achieved after 200 sec irradiation at a UV-C dosage of 32000 μW/sec/cm², resulting in zero cfu/ml APC and YM. Escherichia coli and Salmonella are both negative. This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only separate and recover mucilage but also reduce the microorganisms to acceptable levels.Industrial relevanceThis novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required.This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only to separate and recover mucilage but also reduce the microorganisms to acceptable levels. Actually the pilot scale of this system is going to build in our university. We also try to further use it for non-thermal fermentation. There are many potential industrial applications using this idea.     

Persistence and Biofilm Assessment of Campylobacter Jujeni in Poultry Abattoir

Persistence of Campylobacter sp and its biofilm forming ability was assessed in two poultry abattoirs at two weeks intervals. Average prevalence (63.75%) of Campylobacter spp. was observed on assessing a total of 160 samples collected from the surfaces of packaging table (80%), dressing table (75%), floor source (70%) and washing table (30%). Biofilm assessment formed by Campylobacter jejuni within 5-days at 37°C were in decreasing order of washing table > packaging table > dressing table > floor. An average rate (19.6%) of isolates to develop biofilm observed in both sites was considered relatively low. Absorbance value (Optical Density-OD_590nm) of formed biofilms ranged from 0.483 – 0.952. Wastewater from the facilities showed higher TDS (643 – 820 mgl⁻¹), TSS (1200 – 1775 mgl⁻¹), COD (152 – 141 mgl⁻¹) and BOD (30.3 – 32.5mgl⁻¹) than the WHO standards of 500 mgl⁻¹, 100 mgl⁻¹, 10 mgl⁻¹ and 6 mgl⁻¹ respectively. This is a clear indication of heavy microbial presence in the wastewater. Total bacterial count (TBC) was slightly higher in site A (4.4 × 10⁵ CFU/ml) than site B (3.5 × 10⁵ CFU/ml). Efficiency index ratio (≈/> 1) observed in all tested drugs suggests their effectiveness in campylobacteriosis management. Decreasing drug sensitivity pedigree was observed with streptomycin > erythromycin & gentamincin > tetracycline & neomycin > penicillin > riphapicin & ampicillin > norflaxicin & cephalexin. These results of frequency and biofilm forming tendencies of Campylobacter spp. observed in this study can be of value in checkmating campybacteriosis outbreak from poultry abattoir facility.     

Determination of the efficacy of ultrasound in combination with essential oil of oregano for the decontamination of Escherichia coli on inoculated lettuce leaves

Recent outbreaks related to fresh produce have shown that there is a need to develop new efficient and effective decontamination technologies that protect consumers' safety. Ultrasound and assisted ultrasound, i.e., the combination of ultrasound with another decontamination technology has been shown to be effective against bacteria. In this study equal surfaces of free-bacteria of Romaine lettuce were inoculated with Escherichia coli O157:H7 NCTC 12900. Leaves were then treated with an ultrasound probe system (26 kHz, 90 μm, 200 W, 14 mm Ø). Same processing time (300 s) was applied with continuous and pulsed modes of: (i) 10 s on/6 s off, (ii) 5 s on/5 s off and (iii) 2 s on/8 s off. Thus, total treatment durations were 5, 8, 10 and 25 min. Moreover, concentrations of essential oil (i.e. 0.010% v/v, 0.014% v/v. 0.018% v/v, 0.022% v/v and 0.025% v/v) of oregano were tested, operating with continuous and 2 s on/8 s off pulsed mode. The structure of treated samples was also analysed by SEM and light microscopy. Continuous ultrasound treatments led to a reduction of 2.65 ± 0.23 log CFU/cm² of E. coli on the lettuce. No significant differences were found among the tested pulsed and continuous modes. In addition no significant differences were found between injured and no-injured cells among all the applied treatments on the leaves of the lettuce. Application of the different concentrations of EO alone, at the levels mentioned previously reduced the bacteria on the surface of the lettuce. Less than 2 logs of total inactivation (on the lettuce and the treated water) were achieved when different concentrations of EO were tested alone. Assisted ultrasound enhanced the levels of microbial reduction on the surface of the lettuce at concentrations higher than 0.010% (v/v) of oregano EO. Significant differences were found at 0.018%, 0.022% and 0.025% (v/v) both in continuous and pulsed US modes when compared with samples treated only with US. Same concentrations of EO combined with continuous or pulsed mode of US reduced the level of E. coli in water below the limit of detection. When continuous or pulse mode of US was combined with 0.025% (v/v) of EO of oregano the result was synergetic. Images reported neither structural differences nor damage of the leaves among treated samples and controls. Concluding, the effectiveness of the assisted ultrasound process was dependent on the processing time rather than on the different configurations (continuous or on/off) or the total treatment duration. Furthermore, EO combined with US could work synergistically on enhancing the inactivation of the tested bacteria.     

Surface UV-C light treatments to prolong the shelf-life of Fiordilatte cheese

The possibility to apply UV-C light technology to control surface contamination and extend the shelf-life of Fiordilatte was investigated. First, cheese was inoculated with Pseudomonas spp., exposed to UV-C light for increasing time up to 750 s to estimate the antimicrobial efficacy of the treatments. UV-C light penetration depth in Fiordilatte was also evaluated. Then, a shelf-life test was carried out on samples exposed to 0.1, 0.6, 1.2 and 6.0 kJ/m² UV-C light, compared to untreated control cheese. The samples were packaged with brine, stored at 9 °C and analyzed for microbial growth, sensory quality and pH. A germicidal effect of about 1–2 log cycles on Pseudomonas spp. and Enterobacteriaceae was observed during storage. UV-C light did not promote changes in terms of color, texture and surface appearance. With a minimum transmittance inside the product, this treatment showed an interesting surface microbial decontamination that prolonged cheese shelf-life.Industrial relevanceConsidering that dairy industry represents one of the most important components of the Italian food system, the present work focused on the utilization of UV-C light to preserve one of the most important milk-derived Italian fresh cheese, Fiordilatte, which totalized a consumption of about 20 kg per capita per year in the world. Interesting results were recorded on treated samples, above all at specific UV-C light fluence values (6 kJ/m²). The control of microbial proliferation in these treated samples allowed prolonging shelf-life by 80% compared to untreated cheese. The technique is very rapid and simple to be scaled up; after proper optimization of light parameters, it could be applied at industrial level to prevent surface post-process contamination of Fiordilatte that generally represents the main factor responsible for product deterioration and its short shelf-life.     

Non-destructive evaluation of quality and ammonia content in whole and fresh-cut lettuce by computer vision system

The paper describes the developed hardware and software components of a computer vision system that extracts colour parameters from calibrated colour images and identifies non-destructively the different quality levels exhibited by lettuce (either whole or fresh-cut) during storage. Several colour parameters extracted by computer vision system have been evaluated to characterize the product quality levels. Among these, brown on total and brown on white proved to achieve a good identification of the different quality levels on whole and fresh-cut lettuce (P-value < 0.0001). In particular, these two parameters were able to discriminate three levels: very good or good products (quality levels from 5 to 4), samples at the limit of marketability (quality level of 3) and waste items (quality levels from 2 to 1). Quality levels were also chemically and physically characterized. Among the parameters analysed, ammonia content proved to discriminate the marketable samples from the waste in both product's typologies (either fresh-cut or whole); even the two classes of waste were well discriminated by ammonia content (P-value < 0.0001).A function that infers quality levels from the extracted colour parameters has been identified using a multi-regression model (R² = 0.77). Multi-regression also identified a function that predicts the level of ammonia (an indicator of senescence) in the iceberg lettuce from a colour parameter provided by the computer vision system (R² = 0.73), allowing a non-destructive evaluation of a chemical parameter that is particularly useful for the objective assessment of lettuce quality.The developed computer vision system offers flexible and simple non-destructive tool that can be employed in the food processing industry to monitor the quality and shelf life of whole and fresh-cut lettuce in a reliable, objective and quantitative way.     

Microbial safety considerations of flooding in primary production of leafy greens: A case study

This study evaluated the effects of a flood event, floodplain and climatic parameters on microbial contamination of leafy greens grown in the floodplains. Additionally, correlations between pathogenic bacteria and levels of indicator microorganisms have been also determined. To diagnose the microbial contamination after the flood event, sampling was carried out in weeks 1, 3, 5 and 7 after the flooding in four flooded lettuce fields. To assess the impact of flooding on the microbial contamination of leafy greens, indicator microorganisms (coliforms, Escherichia coli and Enterococcus) and pathogenic microorganisms (Salmonella spp., VTEC (E. coli O157:H7 and other verocytotoxin producing E. coli, O26, O103, O111, O145) and Listeria monocytogenes) were evaluated. Irrigation water, soil and lettuce samples showed levels of coliforms and E. coli higher than 5 and 3 log cfu/g or 100 mL, respectively when sampled 1 week after flooding. However, bacterial counts drastically declined three weeks after the flooding. Climatic conditions after flooding, particularly the solar radiation (6–8 MJ/m²), affected the survival of bacteria in the field. L. monocytogenes was not detected in lettuce samples, except for 2 samples collected 3 weeks after the flooding. The presence of Salmonella was detected in irrigation water, soil and lettuce by multiplex PCR one week after the flooding, but only 2 samples of soil and 1 sample of water were confirmed by colony isolation. Verotoxigenic E. coli was detected in soil and lettuce samples by multiplex PCR. Therefore, the implication of flood water as the source of VTEC contamination of soil and lettuce was not clear. E. coli counts in irrigation water were positively correlated with those in lettuce. A significant correlation (P < 0.005) was found between the presence of pathogens and E. coli counts, highlighting a higher probability of detection of pathogens when high levels of E. coli are found. The results obtained in the present study confirm previous knowledge which defined flooding as a main risk factor for the microbial contamination of leafy greens.     

Inspection of lymph nodes for caseous lymphadenitis and its effect on the density of microbes on sheep carcasses

This study aimed to measure the amount of microbial contamination caused by inspecting the lymph nodes of adult sheep carcasses for caseous lymphadenitis (CLA). Surface swabs from carcasses pre-inspection (N = 296) and post-inspection (N = 296) were obtained for enumeration of indicator organisms at three commercial abattoirs. At the scapular site, inspection doubled the probability of detecting E. coli (Pr before = 0.35, Pr after = 0.67) and increased the expected count of E. coli from 2 cfu/cm² to 13 cfu/cm². Inspection at the rump site increased the probability of detecting E. coli by 1.1 times (Pr before = 0.84, Pr after = 0.93) and increased the expected count from 32 cfu/cm² to 45 cfu/cm². Effects were also observed for Enterobacteriaceae and total viable count. The findings show that routine inspection of adult sheep carcasses for CLA has a detrimental impact on carcass microbiological traits.     

“Blown pack” Probabilistic Modeling for C. Algidicarnis and C. Estertheticum under the Effects of Storage Temperature,Vacuum Level and Package Shrink Temperature

A model for ‘blown pack’ probability (BPP) caused by spores of C.estertheticum DSM8809 and C.algidicarnis, was developed as a function of vacuum packaging variables: storage temperature(ST:-2, 2, 4 and 15 °C), vacuum level(VL:6 and 9mBar) and heat shrink temperature(HST:83 and 87 °C). Beef meat pieces, were inoculated with spore suspensions individually at 10²spores/cm², packed and daily monitored up to 90 days. The lower BPP, estimated by the log-logistic model, for C.algidicarnis was 0.8% at:-1.5 °C/6mBar/87 °C while for C.estertheticum was 99.13% at the same conditions. For both organisms, tested variables were unable to eliminate the risk of blown packaged spoilage, at 10²spores/cm² contamination level.     

Electrostatic spraying of organic acids on biofilms formed by E. coli O157:H7 and Salmonella Typhimurium on fresh produce

Electrostatic spraying which has an even and retained surface coverage could be an effective novel technique to completely cover the surface of fresh produce to disrupt biofilm formation by pathogenic bacteria. Spinach leaves and cantaloupe rind were spot-inoculated with a bacterial culture and stored at 8 °C for 72 h to allow biofilm formation. Among various green fluorescent protein-labeled strains, ED 14 strain of E. coli O157:H7 and SD 10 strain of Salmonella Typhimurium had the best attachment based on colony counts. The produce samples were electrostatically sprayed with malic (MA) and lactic (LA) acid solutions alone (1.0/2.0/3.0/4.0% w/v) or in combination (0.5 + 0.5/1.0 + 1.0/1.5 + 1.5/2.0 + 2.0% w/v) to test for a reduction in the attached bacteria. A combined treatment of LA 2.0% w/v + MA 2.0% w/v had the highest log reduction (CFU/disk) of 4.14 and 3.6 on the attached E. coli strain ED 14 (spinach) and Salmonella strain SD 10 (cantaloupe), respectively. Crystal violet assay demonstrated the disruptive effect of organic acids on biofilms formed by the pathogenic bacteria. Application of electrostatic spray with a combination of malic and lactic acids resulting in a log reduction (CFU/disk) of 3.6 or higher can improve the microbial safety of spinach and cantaloupe by preventing the pathogenic biofilm formation and bacterial growth.     

Effect of thermosonication,pulsed electric field and their combination on inactivation of Listeria innocua in milk

The impact of thermosonication (TS) and pulsed electric field (PEF), individually and combined, on the survival of Listeria innocua 11288 (NCTC) in milk was investigated. TS (400 W, 160 s) without pre-heating reduced L. innocua by 1.2 log₁₀ cfu mL^?1, while shorter treatment times produced negligible inactivation, suggesting TS to be a hurdle rather than an effective standalone treatment. PEF (30 and 40 kV cm^?1, 50 μs) at 10 °C caused a reduction of L. innocua of 1.1 and 3.3 log cycles, respectively. The highest field strength (40 kV cm^?1) combined with TS (80 s) led to 6.8 log₁₀ cfu mL^?1 inactivation. Milk pre-heated to 55 °C (over 60 s) prior to TS followed by PEF (30 and 40 kV cm^?1) showed inactivation between 4.5 and 6.9 log₁₀ cfu mL^?1, the latter being comparable (P > 0.05) with thermal pasteurisation. The data indicate that TS followed by PEF represents a valid alternative for L. innocua inactivation in milk.     

Compositional and thermal characteristics of palm olein-based diacylglycerol in blends with palm super olein

Palm olein-based diacylglycerol (POL-DAG) was blended with palm super olein (POoo) in various concentrations (10–90%), with increments of 10% (wt/wt) POL-DAG. The physical and chemical characteristics, i.e., iodine value, acylglycerol content, fatty acid composition, melting and crystallization profiles and solid fat content, for POL-DAG, POoo and their binary blends were evaluated. The mid-infrared FTIR was used to determine the absorption bands of the different concentrations of the oil blends. Only slight differences of FAC and IV were observed. POL-DAG:POoo blends showed significant changes (p < 0.05) in DAG content and decreases in TAG content with increasing POL-DAG content. The DSC thermograms showed that the addition of different concentrations of POL-DAG changed the melting and crystallization behavior of the oil blends (POL-DAG:POoo). The crystallization onset point increased (p < 0.05) with an increasing POL-DAG concentration (10–90%). POL-DAG has the same absorption bands as POoo, with the exception of several minor peaks that appeared at (I) 2954 cm^− 1, (II) 1267 cm^− 1, (III) 1199 cm^− 1, (IV) 1222 cm^− 1 and (V) 966 cm^− 1. This study will provide essential information for the palm oil industry to identify the most suitable POL-DAG blends with desirable physicochemical properties for food application purposes.     

The role of surface tension of re-used caustic soda on the cleaning efficiency in dairy plants

During the cleaning in place with recycled cleaning solutions, an increase of suspended solids (SS) and a decrease of the surface tension (γ) of caustic soda (NaOH) solutions were observed for various types of dairy equipment. The decrease of γ was shown to result from the chemical reactions of the milk protein and fat with the cleaning solutions. In this work, the respective roles of SS and γ on the cleaning efficiency, cleanliness and cleaning rate were determined. The cleaning test consisted of an ultrafiltration membrane fouled with skimmed milk and cleaned using four NaOH-based solutions: newly prepared NaOH (high γ), re-used NaOH (low γ) with and without pre-clarification and a newly prepared commercial detergent solution. In the range of γ (28.7–74.0 mJ m⁻²) and SS (0.0–1.7 g kg⁻¹) studied, the cleaning efficiency and the membrane hydraulic cleanliness were similar (0.91–0.94 and 0.69–0.71, respectively). However, it was found that solutions with a low γ resulted in a much faster cleaning rate. The presence of SS was mainly detrimental to the cleaning rate. For an efficient cleaning rate, high pH and low γ were important. A re-used NaOH solution with both low γ and SS was as fast as the commercial detergent solution at the same temperature (50 °C).