Effect Of Pulsed Light Treatment Research Articles

Variations in quality attributes of pulsed light-treated table grape juice during refrigerated storage (4°C) and ambient conditions (25°C).

Pulsed light (PL) pasteurization is being explored as a substitute for the conventional thermal pasteurization of juices in recent times due to better retention of nutrients and overall quality. However, the long-term stability of the PL-pasteurized juice must be investigated to promote its application by the industry. The effect of PL treatment (effective fluence of 1.15 J·cm-2) and thermal treatment (90°C for 60 s) on microbial quality, enzyme activity, bioactive compounds, sensory acceptance, and color profile of table grape juice during storage at 4 and 25°C was investigated in this study. The PL pasteurization enhanced the microbial shelf-life of the juice (<6 log10cfu·mL-1) from 5 to 35 days at 4°C. The PL and thermally-pasteurized juice demonstrated a shelf-life of only 10 days when stored at 25°C. The total soluble solids and titratable acidity did not alter significantly throughout the storage period. The peroxidase, polyphenol oxidase, and pectin methylesterase activities were below 10% for the PL and thermally-treated beverage when stored at 4°C. The sensory acceptability of the PL-pasteurized juice after 35 days of refrigerated storage (6.9±0.3) was close to the untreated juice (7.2±0.3) and greater than thermally-treated juice (6.2±0.2). After the 35th day of storage at 4°C, PL-treated grape juice retained 55%, 12%, and 15.3% more phenolics, flavonoids, and antioxidant capacity, respectively, than the thermally-pasteurized juice. Hence, PL pasteurization can effectively prolong the shelf-life of table grape juice while achieving microbial and enzymatic stability, along with high sensory and nutritional appeal. PRACTICAL APPLICATION: Exploring non-thermal methods like pulsed light (PL) pasteurization as a substitute for conventional thermal methods is gaining recognition for its ability to retain nutrients and improve overall juice quality. However, the industry's adoption depends on understanding the shelf-stability of PL-pasteurized juice. This study specifically investigates the practical applications of PL treatment in comparison with conventional thermal treatment in enhancing microbial safety and enzymatic stability in table grape juice. The findings contribute insights into optimizing the shelf life of table grape juice and preserving its quality, supported by microbial, enzymatic, and sensory evaluations.

A multi-omics study revealed the effect of pulsed light treatment on germinated brown rice: Promotion of sprouting efficiency and gamma-aminobutyric acid enrichment

Physical fields are increasingly proposed in the production of germinated grain foods, thus shorting the preparation cycle of high value-added sprouted grain foods. Here, pulsed light treatment (PLT) with 300 times at a single energy of 400 J was found to significantly promote the shoot length and gamma-aminobutyric acid (GABA) content in 8 varieties of germinated brown rice (GBR). Functional annotation analysis showed that the brown rice germination was promoted by the biosynthesis of phenylalanine, carbohydrate metabolism, and energy metabolism pathway. Moreover, PLT influenced the genes and metabolites involved in the GABA shunt and the polyamine degradation pathway, promoting the accumulation of GABA. Transcription factor OsbZIP56 was closely related to the transcript level of regulatory gene for germination and GABA enrichment. Furthermore, overexpression of OsbZIP56 in rice significantly promoted germination and GABA accumulation. These findings would be significant for improving the germination efficiency of edible seeds, promoting accumulation of active ingredients, and exploring gene functions in food materials.

Effect of pulsed light treatment on the physicochemical properties of wheat flour and quality of fresh wet noodles

AbstractBackground and ObjectivesPulsed light (PL) was first applied to the production of low bacterial wheat flour—treating wheat kernels with PL. The effect of PL on the physicochemical properties of wheat flour and the quality of fresh wet noodles (FWN) were investigated.FindingsAfter treatment, the total plate count (TPC), yeast and mold count (YMC) in wheat flour decreased significantly. Wet gluten content and the stability time reached their maximums when the pulsed flash frequency was 10 c. Starch viscosity increased slightly, mainly due to an increase in damaged starch content. Secondary structures altered remarkably, which were consistent with changes in gluten protein microstructures. Moreover, the textural properties of FWN were improved greatly. Browning of FWN was significantly inhibited because of low polyphenol oxidase (PPO) activity in wheat flour.ConclusionPL was effective in decreasing the initial microorganisms in wheat flour as well as improving the quality of dough and FWN, and the optimum treatment was pulsed energy of 500 J, pulsed flash distance of 9 cm, and pulsed frequency of 10 c.Significance and NoveltyThese results showed that PL treatment could decrease TPC and YMC in wheat flour significantly, improve farinograph and pasting properties, change gluten protein microstructures and secondary structures, as well as improve textural properties of FWN and inhibit its darkening greatly, which provided a new method for low bacterial wheat flour production and promoted PL's industrialization.

Effect of pulsed light treatment on enzymes and protein allergens associated with their structural changes: a review.

The pulsed light (PL) technique is used for food and surface decontamination widely. The sterilization effect of PL is well known and identified as the photo-chemical effect. Besides, PL is used to inactivate enzymes, reduce the immunoreactivity of proteins, and change protein function properties at a laboratory level. The current study aims to review the effect of PL on proteins by highlighting the differences between proteins in buffer solutions or food systems. Although PL is known as a non-thermal technique, most studies done on food systems, food temperature raised considerably. Therefore, PL inactivated many enzymes in buffer solution non-thermally, while mostly with a high increase in temperature of a food system. PL reduced food allergens several folds in some foods. However, immunoreactivity responses of some protein were increased after PL treatment. Also, the current study covers the conformational changes of proteins that occur because of PL treatment. Therefore, some techniques used to follow proteins structural changes such as polyacrylamide gel electrophoresis (SDS-PAGE), high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), etc. were defined. Studies reported that PL altered proteins structure differently. For example, some studies reported that PL degraded some proteins, while other studies suggested that PL aggregated proteins. Also, there were contrary results regarding α-helix and ß-sheet concentration for the treated proteins. In conclusion, some techniques, such as amino acid sequencing, specially when some small new fragments proteins appeared on SDS-PAGE, should be used to detect the effect of PL on proteins precisely.

Pulsed UV-C radiation of beef loin steaks: Effects on microbial inactivation, quality attributes and volatile compounds

The aim of this study was to investigate the effect of pulsed light treatment at fluences of 0.525, 1.05, 2.1 and 4.2 J/cm2 on the chemical composition, microbiological quality and volatile compounds of beef loin steaks. Pulsed light treatment did not affect total moisture, total protein, total lipid and ash content of samples significantly (P > 0.05). The a* and b* values of the pulsed light treated samples significantly decreased compared to control samples with maximum difference of 2.11 and 1.33 unit, respectively (P < 0.05). The highest reduction (3.49 ± 0.67 log CFU/g) in total aerobic mesophilic bacterial counts (compared to naturally occuring microbiota in control group) was achieved for samples treated with 4.2 J/cm2 of UV-C fluence level. A total of 14 volatiles, mainly aldehydes, alcohols, ketones and terpen compounds were identified in the raw samples and pulsed light treatment caused an increase in the amounts of some volatile compounds, including hexanal (from 33.41 μg/kg to 69.67 μg/kg), 2-heptenal (from 0.60 μg/kg to 1.52 μg/kg), 2-octenal (from 0.39 μg/kg to 1.58 μg/kg), 2,4-nonadienal (from 0.05 μg/kg to 0.24 μg/kg), 2,4-decadienal (from 0.04 μg/kg to 0.26 μg/kg), 3-octen-2-one (from 0.37 μg/kg to 2.53 μg/kg), limonene (from 2.06 μg/kg to 18.42 μg/kg). Otherwise, pulsed light decreased the levels of some compounds coming from microbial metabolism such as 1-heptanol (from 0.57 μg/kg to 0.39 μg/kg), 1-octen-3-ol (from 1.83 μg/kg to 1.12 μg/kg), 2-octen-1-ol (from 0.28 μg/kg to 0.09 μg/kg). In conclusion, pulsed light treatment can enhance the microbial safety of meat and has potential for use in the meat industry.

Effect of pulsed light treatment on inactivation kinetics of Escherichia coli (MTCC 433) in fruit juices

The inactivation kinetics of Escherichia coli (MTCC 433) inoculated in the tender coconut water, orange and pineapple juice was investigated using a laboratory model continuous flow pulsed light system with a fixed flow rate of 100 ml/s and the experimental data were fitted with different inactivation models. The E. coli inactivation was examined by the effect of pulsed light fluence rate (0.18, 2 and 5.6 W/cm2) and exposure time (between 0 and 15 s). Log reduction of maximum 4.0, 4.5 and 5.33 was determined in orange, pineapple juice and tender coconut water, respectively, when treated with the pulsed light doses of 95.2 J/cm2, which follows the FDA recommendation. The Weibull, Biphasic and Log linear plus tail models were compared to predict the survival curves of E. coli. Inactivation kinetics of E. coli for liquid foods used in this study were best fitted by weibull model (R2 = 0.9926 to 0.9989; RMSE = 0.0462 to 0.0981). The E.coli inoculated liquid foods treated with pulsed light resulted in flattening out of the cells from the edges due to its membrane integrity degradation which were examined using scanning electron microscopy. Pulsed light could be an effective alternative non-thermal treatment for the pasteurization of liquid foods.

Effect of pulsed light treatment on Listeria inactivation, sensory quality and oxidation in two varieties of Spanish dry-cured ham

The efficacy of pulsed light (PL) for the surface decontamination of ready-to-eat dry-cured ham was studied in two Spanish varieties, Serrano and Iberian. Listeriainnocua was inoculated on the surface of ham slices that were vacuum-packaged and flashed with 2.1, 4.2 and 8.4 J/cm2. Survivors were enumerated immediately after treatment. Peroxide values, sensory analysis and volatile profile were investigated during storage at 4 and 20 °C. Inactivation of Listeria was higher in Iberian (ca. 2 log cfu/cm2) than in Serrano ham (ca. 1 log cfu/cm2) with 8.4 J/cm2. PL did not increase the peroxide values above the usual levels reported in dry-cured ham, and no rancid notes were observed in the sensory analysis. PL-treated samples showed an increase in the concentration of some volatile compounds, such as methional, dimethyl disulfide and 1-octen-3-one, which imparted slight sulfur and metallic notes, although they disappeared during storage.

Effects of postharvest pulsed light treatments on the quality and antioxidant properties of persimmons during storage

Pulsed light (PL) treatment for food consists in the application of a polychromatic light (wavelength: 200–1100 nm) in the form of intense but short pulses, frequently investigated as a decontamination method. In this work, the effects of PL treatments on the physicochemical properties, total phenolic content, vitamin C, and antioxidant capacity of persimmons (Diospyros kaki L. cv. Vanilla) at two different maturity stages (unripe yellow-green and ripe orange-red) during postharvest storage were investigated. The fruit were exposed to PL treatments at a dose of 20 kJ m−2 and 60 kJ m−2. Untreated and treated samples were allowed to ripe in dark conditions at 15 ± 1 °C for up to 6 d. The effects of PL treatments on the color, total soluble solids (TSS) as well as on total phenolic content, vitamin C and antioxidant capacity by three different methods were evaluated during storage and compared with those of untreated samples. Results showed that the physicochemical properties (color and TSS) and vitamin C content of the fruit were not affected by the PL treatments over the storage period. On the other hand, the total phenols content and the antioxidant capacity were significantly (p < 0.05) affected by the treatments. Considering that these parameters were related to the soluble tannins in persimmons and these compounds are related to the astringency of these fruit, this work encourages the research of the potential application of PL as a de-astringency method for persimmons.

Manipulation of seedling traits with pulsed light in closed controlled environments

There is substantial interest in growing crops in closed controlled environments, yet the energy requirements are high. Energy is required to produce light, but also to remove the heat generated when producing light. The goal of the current work examines a possible approach to decrease the energy requirement. The effect of pulsed light treatments was examined by monitoring seedling traits during early photomorphogenic development. Daily light integral remained unchanged between treatments, but the frequency of the pulses was varied. Developmental traits (such as inhibition of hypocotyl elongation rate) were most conspicuous during a normal photoperiod, as in twelve hours light, twelve hours darkness. Consistent with historical reports, when treatments were delivered in shorter durations (e.g. 1 h on/off) photomorphogenic development was hindered with the same daily light integral. However, at even shorter light intervals (e.g. seconds) seedlings developed as if they were provided full 12 h treatments. Extension of the dark period following a 5 s pulse was tested to determine the effect on seedling traits. The results showed that the dark period could be extended to at least 10 s without affecting seedling development, and extension to 20 s only had slight effects on seedling traits. The mechanism of the phenomenon was examined in Arabidopsisthaliana photosensory mutants, and showed substantial contributions from the phyA and cry1 pathways. The results suggest that pulsed light with extended dark periods can decrease energy input by at least 30% to >50% without affecting visible seedling traits. These pilot experiments in seedlings demonstrate that implementation of short-interval, pulsed-light strategies may lower energy requirements for growing crops in artificially illuminated environments.

Characterization of damage on Listeria innocua surviving to pulsed light: Effect on growth, DNA and proteome

The effect of pulsed light treatment on the lag phase and the maximum specific growth rate of Listeria innocua was determined in culture media at 7 °C. Fluences of 0.175, 0.350 and 0.525 J/cm2 were tested. The lag phase of the survivors increased as fluence did, showing significant differences for all the doses; an 8.7-fold increase was observed at 0.525 J/cm2. Pulsed light decreased the maximum specific growth rate by 38% at the same fluence. Both parameters were also determined by time-lapse microscopy at 25 °C in survivors to 0.525 J/cm2, with an increase of 13-fold of the lag phase and a 45% decrease of the maximum specific growth rate. The higher the fluence, the higher the variability of both parameters was. To characterize pulsed light damage on L. innocua, the formation of dimers on DNA was assessed, and a proteomic study was undertaken. In cells treated with 0.525 J/cm2, cyclobutane pyrimidine dimers and pyrimidine (6–4) pyrimidone photoproducts were detected at 5:1 ratio. Pulsed light induced the expression of three proteins, among them the general stress protein Ctc. Furthermore, treated cells showed an up-regulation of proteins related to metabolism of nucleotides and fatty acids, as well as with translation processes, whereas flagellin and some glucose metabolism proteins were down-regulated. Differences in the proteome of the survivors could contribute to explain the mechanisms of adaptation of L. innocua after pulsed light treatment.

Effect of pulsed light treatments on quality and antioxidant properties of fresh-cut strawberries

Fresh-cut strawberries were subjected to pulsed light treatments (4, 8, 12 and 16 J·cm−2) combined with a stabilizing dip. Quality changes and antioxidant properties were evaluated for 14 days at 5 °C. The treatments delayed fungal for the studied period. Surface color of treated fresh-cut strawberries was preserved in both internal and external surfaces. Doses of 4 and 8 J·cm−2 reduced softening incidence over storage. No significant differences between the total phenolic contents of untreated and treated fresh-cut strawberries were observed during storage. Vitamin C and total anthocyanin contents of the samples treated at low energy doses were maintained, whereas those of slices treated at the highest energy dose decreased between 20 and 30%, respectively. On the other hand, initial antioxidant capacity was better kept in all samples during storage regardless the applied dose. Hence, 4 and 8 J·cm−2 were the most effective treatments for maintaining quality and antioxidant properties of fresh-cut strawberries. Industrial relevanceFresh-cut strawberries may be sold as a highly convenient, healthy and fully edible product. However, processing and packaging conditions need to ensure the maintenance of their quality characteristics and content of bioactive compounds. This study provides scientific evidence regarding the beneficial effects of pulsed light treatments combined with a quality-stabilizing dip for extending the shelf-life of fresh-cut fruit. These combined treatments may be economically viable at industrial level because of their low energy requirements and reduced treatment time.

Effect of pulsed light treatment on the phytochemical, volatile, and sensorial attributes of lactic-acid-fermented mulberry juice

ABSTRACTLactic-acid-fermented mulberry juice (LFMJ) was subjected to pulsed light (PL) treatment at exposure time of 2, 4, and 8 s at high insensitive pulses of 14.0 J/cm2. The effect of PL treatment on the microbial inactivation, physicochemical, phytochemical, volatile, and sensory characteristics of LFMJ was evaluated. It was found that the PL was able to reduce the microbial load to acceptable levels (1.02 ± 0.04 log10 cfu/mL) with no significant impact on the physicochemical properties of LFMJ. It was also observed that the PL treatment caused a slight decrease in anthocyanin concentration at 8 s exposure time. The color difference (∆E) of the juice treated for 2 and 4 s fell below the slightly noticeable range 0.5<ΔE<1.5 while ∆E values for the 8 s (0.55 ± 0.02) and the thermal (0.50 ± 0.02) treated samples were slightly noticeable. The volatile profile and odor activity values were positively affected by increasing the exposure time. The results depict that, under the present experimental conditions, the application of the PL resulted in a fermented juice with superior quality attributes as compared to the thermal treated juice.

Effect of pulsed light treatment on structural and functional properties of whey protein isolate

This work aimed at investigating the effects of Pulsed Light (PL) processing at different fluences (from 4 to 16J/cm2) on the structure and functional properties of Whey Protein Isolate (WPI) solution. The determination of the free and total sulfhydryl (SH) groups was used to detect the variation of WPI tertiary and quaternary structure. Additionally, PL-induced changes in secondary structure were determined by FT-IR spectroscopy and the differential scanning calorimetry (DSC), and primary structure by carbonyl content.The experimental data demonstrated that PL treatments increased the concentration of total and free sulfhydryl groups and protein carbonyls. A decrease of the denaturation temperature and enthalpy ratio with increasing the intensity of PL treatments was observed in DSC measurements. Small but significant changes in the secondary structure of PL treated WPI solution were also taking place and detected. The extent of whey protein structure modifications was fluence dependent. The results of this investigation demonstrated the potential of PL treatments to induce dissociation and partial unfolding of WPI, thus improving some of their functional properties, such as solubility and foaming ability.

Effects of Exposure to Pulsed Light on Surface and Structural Properties of Edible Films Made from Cassava and Taro Starch

Edible films derived from starch have been proposed as packaging materials. However, they may suffer physicochemical changes due to a variety of factors, such as pulsed light (PL) treatments. In this study, the effect of PL treatment as a crosslinking method on films made from cassava (Manihot esculenta C.) and taro (Colocasia esculenta L. Schott) starch, plasticized with glycerol was evaluated. The average molecular weight, contact angle, moisture content, X-ray diffraction pattern, color, and mechanical and microstructural properties were evaluated. Films subjected to PL showed deterioration compared with control films as demonstrated by an increase in the contact angle, surface roughness, and crystallinity, and a decrease in the tensile strength, transparency, and water content, independent of the amylose content of the starches evaluated. Finally, the surface properties of these materials are defined by intermolecular interactions such as van der Waals-type force interactions (hydrogen bond), new bonds (crosslinking) formed between the biopolymeric chains (starch), and by breakage of covalent bonds.

Effects of pulsed light treatments and pectin edible coatings on the quality of fresh‐cut apples: a hurdle technology approach

Pulsed light (PL) treatments stand as an alternative for the shelf-life extension of fresh-cut products. The antimicrobial effects of PL are well known; however, its influence on quality attributes needs to be assessed. This study was aimed at evaluating the application of PL treatments in combination with pectin-based edible coatings enriched with dietary fiber for the preservation of fresh-cut apples. Dipping of fresh-cut apples in ascorbic acid/calcium chloride solution prior to pectin coating and PL treatments was effective to minimize browning and softening of apple surfaces. Incorporation of fiber in the pectin coating did not cause any change in microbial loads and sensory acceptability of apple cubes. Pectin-coated PL-treated apple pieces exhibited significantly higher antioxidant activity values than fresh and PL control samples. At the end of storage, the combination of both treatments resulted in an almost 2 log CFU g-1 reduction of microbial counts. Sensory attribute scores did not fall below the rejection limit throughout 14 days, although the presence of off-odors limited the acceptability of the pectin-coated samples. The results demonstrate that PL treatments applied to pectin-coated fresh-cut apples may be used to maintain quality attributes, thus conferring prebiotic potential and extending the shelf-life of the product. © 2016 Society of Chemical Industry.

Effectiveness of pulsed light treatment for degradation and detoxification of aflatoxin B1 and B2 in rough rice and rice bran

Aflatoxins primarily accumulate in the hull and bran layers of rough rice making these by-products of rice milling unsuitable for animal feed or human consumption. Contaminated rough rice is also a potential source of aflatoxin exposure to workers handling the grain during post-harvest storage and processing. Currently, no technologies are available to remove or detoxify these toxic and mutagenic fungal metabolites from contaminated rough rice. Pulsed light (PL) is a novel technology with the potential to degrade and detoxify aflatoxins in foods and their processing by-products. Rough rice was inoculated with Aspergillus flavus to produce aflatoxin B1 (AFB1) and B2 (AFB2) contamination, followed by PL treatments of 0.52 J/cm2/pulse for various durations. A PL treatment time of 80 s reduced AFB1 and AFB2 in rough rice by 75.0% and 39.2%, respectively; while a treatment time of 15 s reduced AFB1 and AFB2 in rice bran by 90.3% and 86.7%, respectively. Since PL treatments result in the degradation of aflatoxins in situ, the toxicity and mutagenic activity of the residual by-products of AFB1 and AFB2 after PL treatment were evaluated. Toxicity was estimated using the brine shrimp (Artemia salina) lethality assay and mutagenicity measured by the fluctuation test with Salmonella typhimurum tester strains TA98 and TA100. The mutagenic activity of AFB1 and AFB2 was completely eliminated by PL treatment, while the toxicity of these two aflatoxins was significantly decreased. The obtained results suggest that PL technology has a promising potential to degrade, detoxify, and inactivate the mutagenic activity of aflatoxins in rough rice and rice bran.

Pulsed light inactivation of Bacillus subtilis vegetative cells in suspensions and spices

The aim of our study was to assess the impact of a pulsed light (PL) technology on Bacillus subtilis grown on two model matrixes, through bacterial inactivation and cell integrity. First, the effect of PL treatment on B. subtilis vegetative cells in liquid state was evaluated. We found that PL treatment leads to 8 log reduction of B. subtilis vegetative cells while bacterial morphology was not affected. Second, spices, among which ground caraway, ground red pepper and ground black pepper were artificially inoculated with a known concentration of B. subtilis in vegetative state and then exposed to PL. In this case, PL treatment leads to a bacterial reduction of about 1 log and serious damage of the microorganisms parietal structure occurred. To conclude, this work highlights that pulsed light has a potential for inactivation of B. subtilis in both, liquid and dry state but through different mechanisms.

Effects of pulsed light treatments on quality and antioxidant properties of fresh-cut mushrooms ( Agaricus bisporus)

This study investigated the impact of pulsed light treatments on microbial quality, enzymatic browning, texture and antioxidant properties of fresh-cut mushrooms. The reduction of the native microflora of sliced mushrooms ranged from 0.6 to 2.2 log after 15 days of refrigerated storage by flashing at 4.8, 12 and 28 J cm −2. Pulsed light treatments allowed extension of the microbiological shelf life of fresh-cut mushrooms by 2–3 days in comparison to untreated samples, while providing a high quality product. The use of high pulsed light fluencies (12 and 28 J cm −2) dramatically affected the texture of sliced mushrooms due to thermal damage induced by the treatments. Enzymatic browning was also promoted by an increase in polyphenol oxidase activity when the highest dose of pulsed light was applied. At 28 J cm −2, phenolic compounds, vitamin C and antioxidant capacity were significantly reduced. Our results suggest that the application of pulsed light at doses of 4.8 J cm −2 could extend the shelf life of fresh-cut mushrooms without dramatically affecting texture and antioxidant properties.

Effect of Pulsed-Light Treatment on Milk Proteins and Lipids

Pulsed-light treatment offers the food industry a new technology for food preservation. It allows the inactivation of numerous micro-organisms including most infectious foodborne pathogens. In addition to microbial destruction, one can also question whether pulsed-light treatment induced conformational changes in food components. To investigate this question, the influence of pulsed-light treatment on protein components of milk was evaluated by using UV spectroscopy, spectrofluorometry, electrophoresis, and determination of amino acid composition. Pulsed-light treatment resulted in an increase of UV absorbance at 280 nm. The intrinsic tryptophan fluorescence of beta-lactoglobulin (BLG) showed a 7 nm red shift after 10 pulses. SDS-PAGE showed the formation of dimers after treatment of BLG by 5 pulses and more. No significant changes in the amino acid composition of proteins and lipid oxidation were observed after pulsed-light treatment. The obtained results indicated changes in the polarity of the tryptophanyl residue microenvironment of BLG solutions or changes in the tryptophan indole structure and some aggregation of studied proteins. Hence, pulsed-light treatment did not lead to very significant changes in protein components; consequently, it could be applied to process protein foods for their better preservation.