Incorporation of hydrogen-producing magnesium into minced beef meat protects the quality attributes and safety of the product during cold storage.

The impact of hydrogen (H2) producing magnesium (Mg) incorporation into minced beef meat (MBM) on the quality and safety of the product was investigated. The H2-producing Mg (H2-P-Mg)-incorporated MBMs were vacuumed (VP) and stored at 4 °C for 12 days. Other MBMs were vacuumed and gassed with H2 or N2. At the end of storage, the lowest browning index values were for H2 and H2-P-Mg samples. H2- PMg and VP methods generally decreased the counts of mesophilic and psychrotrophic bacteria and yeast molds and restricted the formation of thiobarbituric acid reactive substances and biogenic amines. Heat mapping, PCA, and multivariate analysis methods confirmed chemical analysis results. The volatile compounds were at their highest levels in the control samples at the end of storage, followed by H2, N2, H2-P-Mg, and VP samples. Using the H2-P-Mg method in MBM preparation could protect the quality characteristics and safety of the product during cold storage.

The effect of hydrogen-rich water consumption on premenstrual symptoms and quality of life: a randomized controlled trial.

BACKGROUND: Premenstrual syndrome (PMS) consists of psychiatric or somatic symptoms negatively affecting the daily life. PMS treatment can involve the use of complementary-alternative approaches. Hydrogen-rich water (HRW) has antioxidant and anti-inflammatory properties that may treat PMS. This study aimed to investigate the effect of drinking HRW on the severity of premenstrual symptoms and the quality of life of women who suffer from PMS. METHODS: This study is a randomized controlled trial. Participants were randomized into two groups (intervention group=33, control group=32) using the block randomization method. Participants were requested to consume 1500-2000 mL of HRW daily in the intervention group and drink water in the placebo group. Participants began drinking either HRW or placebo water from day 16 of their menstrual cycle until day 2 of the following cycle for three menstrual cycles. The research data were collected using a Demographic Information Form, Premenstrual Syndrome Scale (PMSS), and Short form of the World Health Organization Quality of Life Questionnaire (WHOQOL- BREF). RESULTS: The intervention group had significantly lower mean scores than the control group in both the first and second follow-ups on the PMSS (P<0.05). In the first follow-up, the intervention group had significantly higher mean scores in the Physical Health and Psychological domains of the WHOQOL-BREF compared to the control group (P<0.05). Group × time interaction was significant for PMSS (F = 10.54, P<0.001). Group × time interaction was insignificant for WHOQOL- BREF (P>0.05). CONCLUSIONS: The consumption of HRW reduces the severity of premenstrual symptoms and improves individuals' quality of life in physical and psychological domains.

Hydrogen-rich water supplementation improves metabolic profile during peripartum period in Gurcu goats and enhances the health and survival of kids.

In this study, the effect of intaking hydrogen-rich water (HRW) on the metabolic profile of Gurcu goats during the peripartum period and the survival/growth performance of kids were evaluated. Twenty-three pregnant goats were divided into two groups 21-23 days before the due date. Group 1 (G1, n = 10) was given HRW from day 21 before delivery until day 21 after delivery. Group 2 (G2, n = 13) served as the control. Blood samples were weekly taken from 21 days before delivery until 21 days after delivery. Hydrogen-rich water increased serum glucose concentration on the delivery day more than in G2 (P = 0.016). Hydrogen-rich water decreased serum total cholesterol (P = 0.02) and creatinine (P = 0.05) concentration at delivery. Group effect and time effect were significant in triglyceride (P < 0.001, P = 0.001, respectively) and albumin (P < 0.001, P = 0.002, respectively) concentration. Aspartate transaminase decreased towards the delivery day in G1 (P < 0.05). Serum non-esterified fatty acids concentration was lower in G1 than in G2, but there was no significant differences (P > 0.05). Beta-hydroxybutyric acid concentration an increased in both groups during the prepartum period, although there was no significance (P > 0.05). Hydrogen-rich water did not affect the birth weight and growth performance of the kids (P > 0.05), but it increased their survival rates and overall health, although there was no significance (P > 0.05). In conclusion, HRW may have an impact on the metabolic profiles during the peripartum period and have a positive effect on lipid profiles. Additionally, intaking HRW to goats during the peripartum period may improve the health and survival of kids and reduce their mortality.

Hydrogen-rich solvent method in phytochemical extraction: Potential mechanisms and perspectives.

INTRODUCTION: Phytochemicals are used in many products, including foods, beverages, pharmaceuticals, and cosmetics. The extraction of phytochemicals is considered one of the best solutions to valorize these underestimated materials. Many methods have been developed to efficiently extract phytochemicals at high quality, high purity, and low costs without harming the environment. Recently, molecular hydrogen (H2 ) has shown its ability to improve the extraction of phytochemicals from plant materials. Due to its unique physicochemical and biological properties, H2 showed an efficient ability to extract phenolics and antioxidants at high yields with cost-effective potential. Without sophisticated equipment and high energy and solvent consumption, the hydrogen extraction method is a green and applicable alternative for the extraction of phytochemicals. OBJECTIVES: This review aims to provide the latest knowledge and results concerning the studies on using hydrogen-rich solvents to extract phytochemicals from different agri-food wastes, by-products, and other plant materials. MATERIALS AND METHODS: Recent literature relating to extracting phytochemicals by the hydrogen-rich solvent method and its potential mechanisms is summarized to provide a basic understanding of how hydrogen can improve the extraction of phytochemicals. RESULTS: This review describes, for the first time, the practical procedure of how researchers and laboratories can apply the hydrogen extraction method under safe conditions at a low-budget scale. The review provides some examples of the hydrogen extraction method and the mechanisms and rationale behind its effectiveness. CONCLUSIONS: It can be concluded that the hydrogen-rich solvent method is a green and cost-effective method for extracting phytochemicals from different plant materials.

The effect of hydrogen-rich water on letrozole-induced polycystic ovary syndrome in rats.

RESEARCH QUESTION: What is the effect of hydrogen-rich water on rats with polycystic ovary syndrome (PCOS)? DESIGN: Female rats were divided into four groups, each consisting of eight animals. The control group received a carboxymethyl cellulose (CMC) solution, the molecular hydrogen (H2) group was given hydrogen-rich water and a CMC solution, the PCOS group was administered letrozole dissolved in a CMC solution and the PCOS + H2 group was given hydrogen-rich water and letrozole dissolved in a CMC solution. Blood and tissue samples were then collected, and biochemical and histopathological analyses were conducted on the samples. RESULTS: The histopathological analysis showed a reduction in the number of cysts in the PCOS + H2 group compared with the PCOS group (P < 0.0001). Additionally, the malondialdehyde, cortisol and testosterone data revealed a significant decrease in the PCOS + H2 group compared with the PCOS group (P = 0.0458, P = 0.0003, P = 0.0041, respectively). The glutathione also showed a statistically significant increase in the PCOS + H2 group compared with the PCOS group (P = 0.0012). CONCLUSION: The study findings demonstrate that hydrogen-rich water reduces the number of cysts and oxidative damage in rats with PCOS.

Protective Effect of Hydrogen-Rich Saline on Spinal Cord Damage in Rats.

The anti-inflammatory and anti-apoptotic effects of molecular hydrogen, delivered as hydrogen-rich saline (HRS), on spinal cord injury was investigated. Four-month-old male Sprague Dawley rats (n = 24) were classified into four groups: (1) control-laminectomy only at T7-T10; (2) spinal injury-dura left intact, Tator and Rivlin clip compression model applied to the spinal cord for 1 min, no treatment given; (3) HRS group-applied intraperitoneally (i.p.) for seven days; and (4) spinal injury-HRS administered i.p. for seven days after laminectomy at T7-T10 level, leaving the dura intact and applying the Tator and Rivlin clip compression model to the spinal cord for 1 min. Levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured in blood taken at day seven from all groups, and hematoxylin-eosin (H & E) and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) were used to stain the tissue samples. IL-6 and TNF-α levels were significantly lower in the group treated with HRS following the spinal cord injury compared to the group whose spinal cord was damaged. A decrease in apoptosis was also observed. The anti-inflammatory and anti-apoptotic effect of IL-6 may be a clinically useful adjuvant therapy after spinal cord injury.

Evaluation of the impact of hydrogen-rich water on the quality attribute notes of butter.

The effects of washing raw butter with hydrogen-rich water (HRW), prepared with hydrogen (H2) and/or magnesium (Mg), on butter quality were investigated in this research paper. During the washing process, titratable acidity (TA) decreased by 12% for all washed samples. During the storage period, TA increased by 28% and 93% (control), 14% and 58% (H2), and 10% and 66% (Mg) for the 60th and 90th days, respectively. Peroxide value (mEq O2/kg) increased to 2.76 and 8.83 (control), 1.92 and 7.25 (H2), and 2.02 and 8.12 (Mg) for the 60th and 90th days. HRW samples showed the lowest acid degree value (ADV) and the highest color notes (L*, C*, and h). The HRW treatment of raw butter has shown improving effects on the product without any harmful residuals in the final product or the environment.

Incorporation of hydrogen into the packaging atmosphere protects the nutritional, textural and sensorial freshness notes of strawberries and extends shelf life.

Strawberries are known for their high perishability and short shelf life. The effects of incorporating hydrogen gas into sealed packaging on the quality and shelf life of strawberries were evaluated. Fruits were packaged under reducing atmosphere [RAP1 (5% CO 2 , 4% H 2 , 91% N 2 ) and RAP2 (10% CO 2 , 4% H 2 , 86% N 2 )], modified atmosphere [MAP1 (5% CO 2 , 95% N 2 ) and MAP2 (10% CO 2 , 90% N 2 )], and control, followed by 12 weeks storage at 4 °C. At the end of storage, RAPs exhibited higher total soluble solids (TSS), firmness, L* and a*, phenolic and anthocyanin contents, and antioxidant activity followed by MAPs when compared with control. RAP2 was more potent in protecting the freshness indices than RAP1, and MAP2 outperformed MAP1, with the best protection characteristic attributed to RAP2. RAP technique extended the shelf life by 3-5 times the control, and 1.5-3.0 times the MAP. RAP should be recommended as a green and healthy preservation technique for the long storage of fresh fruits. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05427-y.

Hydrogen-rich water can reduce the formation of biogenic amines in butter.

The formation of biogenic amines in food products forms a serious challenge for food producers and a hazard for consumers. Butter was washed by hydrogen-rich water (HRW) prepared using two methods, i.e. hydrogen-bubbled water (H2 water) and magnesium-incorporated water (Mg water). After 90 days of storage, the lowest formation levels of biogenic amines were shown for butter samples washed with HRW (H2 water and Mg water), while the highest levels were identified for the butter samples washed with normal water. Washing raw butter with HRW led to a significant decrease in tryptamine, 2-phenylethylamine, spermidine, and spermine formation. The lowest histamine level was shown for butter samples washed with H2 and Mg, while the highest level was found for butter washed with normal water. Washing butter with HRW revealed no inhibiting effect on yogurt bacteria during storage. The proposed method involves molecular hydrogen which is non-toxic for humans and the environment.

Evaluation of the hydrogen-rich water alleviation potential on mercury toxicity in earthworms using ATR-FTIR and LC-ESI-MS/MS spectroscopy.

The toxic effects of mercury in earthworms and the potential alleviation effect of hydrogen-rich water (HRW) using ATR-FTIR and LC-MS analysis methods were investigated. Different concentrations of mercury chloride (H1: 5 µg/mL, H2: 10 µg/mL, H3: 20 µg/mL, H4: 40 µg/mL, and C1: control) and mercury chloride prepared in hydrogen-rich water (H5: 5 µg/mL, H6: 10 µg/mL, H7: 20 µg/mL, H8: 40 µg/mL, and C2: control) were injected into earthworms. The changes and reductions in some bands representing proteins, lipids, and polysaccharides (3280 cm-1, 2922 cm-1, 2855 cm-1, 1170 cm-1, and 1047 cm-1) showed that protective effects could occur in groups prepared with hydrogen-rich water. In the FTIR results, it was found that these bands in the H3 group were more affected and decreased by the influence of mercury on earthworms than the H7 group prepared with hydrogen. LC-MS analysis showed that the changes in some ions of the highest dose groups (H4 and H8) were different, and mercury caused oxidative DNA damage in earthworms. When the high-level application groups of mercury, i.e., H4 and H8 were compared with the controls, the ion exchange ([M + H] + ; m/z 283.1) representing the 8-Oxo-dG level in earthworms was higher in the H4 group than the H8 group. This reveals that HRW exhibited the potential ability to alleviate the toxic effects of mercury; however, a longer period of HRW treatment may be necessary to distinguish an obvious effect. The ATR-FTIR spectroscopy provided a rapid and precise method for monitoring the changes in biological tissues caused by a toxic compound at the molecular level.

Hydrogen-Rich Water Alleviates the Nickel-Induced Toxic Responses (Inflammatory Responses, Oxidative Stress, DNA Damage) and Ameliorates Cocoon Production in Earthworm.

In recent years, studies investigating the protective effect of hydrogen-rich water (HRW) against different diseases and the toxicity of some substances have attracted increasing attention. Here, we assessed the effects of hydrogen-rich water on different nickel-induced toxic responses (reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-α), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) of stress responses, histopathological changes) and cocoon production in earthworm model. Earthworms were randomly divided into two main groups: water (W) group including control (CW: ultrapure water), 10 (10W), 200 (200W), and 500 (500W), and hydrogen-rich ultrapure water (HRW) group including control (CHRW: hydrogen-rich ultrapure water), 10 (10HRW), 200 (200HRW), and 500 (500HRW) mg of nickel chloride kg-1 soil for 14 days. We found that cocoon production was less affected by the nickel exposure of earthworms in the 500HRW group compared to the 500W group. The ROS levels in 200HRW and 500HRW groups were less than that of 200W and 500W, respectively. The epithelial degeneration, epithelial necrosis, and necrosis in muscle fibers in tissues of earthworm were less damaged in 200HRW and 500HRW groups compared to 200W and 500W, respectively. HRW groups significantly reduced the expression of 8-OHdG induced by nickel exposure and inflammatory cytokine response including TNF-α. The study showed that hydrogen-rich water could alleviate the toxic effects of nickel-induced oxidative and inflammatory damages in earthworms. The HRW treatment known for its cheap and eco-friendly properties without any negative effects on the ecosystem can be used as a green method for alleviating the toxification effects of heavy metals in contaminated soil and increasing cocoon production of earthworms.

Combating Oxidative Stress and Inflammation in COVID-19 by Molecular Hydrogen Therapy: Mechanisms and Perspectives.

COVID-19 is a widespread global pandemic with nearly 185 million confirmed cases and about four million deaths. It is caused by an infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which primarily affects the alveolar type II pneumocytes. The infection induces pathological responses including increased inflammation, oxidative stress, and apoptosis. This situation results in impaired gas exchange, hypoxia, and other sequelae that lead to multisystem organ failure and death. As summarized in this article, many interventions and therapeutics have been proposed and investigated to combat the viral infection-induced inflammation and oxidative stress that contributes to the etiology and pathogenesis of COVID-19. However, these methods have not significantly improved treatment outcomes. This may partly be attributable to their inability at restoring redox and inflammatory homeostasis, for which molecular hydrogen (H2), an emerging novel medical gas, may complement. Herein, we systematically review the antioxidative, anti-inflammatory, and antiapoptotic mechanisms of H2. Its small molecular size and nonpolarity allow H2 to rapidly diffuse through cell membranes and penetrate cellular organelles. H2 has been demonstrated to suppress NF-κB inflammatory signaling and induce the Nrf2/Keap1 antioxidant pathway, as well as to improve mitochondrial function and enhance cellular bioenergetics. Many preclinical and clinical studies have demonstrated the beneficial effects of H2 in varying diseases, including COVID-19. However, the exact mechanisms, primary modes of action, and its true clinical effects remain to be delineated and verified. Accordingly, additional mechanistic and clinical research into this novel medical gas to combat COVID-19 complications is warranted.

Reducing atmosphere packaging as a novel alternative technique for extending shelf life of fresh cheese.

An atmosphere composed of hydrogen gas-included gaseous mixture was tested for packaging fresh cheese samples. The cheese samples were packaged in reducing atmosphere packaging (RAP) [RAP 1 (90% CO2/6% N2/4% H2), RAP 2 (50% CO2/46% N2/4% H2)], modified atmosphere packaging (MAP) [MAP 1 (90% CO2/10% N2), MAP 2 (50% CO2/50% N2) and MAP 3 (Air)], and unpackaged (control) conditions without using any preservatives, then stored at + 4 °C for 7 weeks. The closest values of color and titratable acidity to the fresh sample were observed for RAP 1. The highest and lowest total mesophilic-aerobic bacteria counts were noted for control and RAP 1 samples, respectively. The yeast-mold counts of all sample groups increased by the time; where RAPs groups exhibited the lowest counts. The similarity between RAP and fresh samples attracts attention to the protective role of hydrogen in preserving the freshness of fresh cheese without using any preservatives.

Importance of consideration of oxidoreduction potential as a critical quality parameter in food industries.

There are many intrinsic and extrinsic factors affecting the nutritional, organoleptic, microbial-enzymatic and physicochemical characteristics of food products. Some of these factors are commonly considered by food processors such as the temperature, water activity, pH, dissolved oxygen and chemical composition, while others are less considered such as the oxidoreduction potential (Eh). This latter factor is an intrinsic electrochemical parameter expressing the tendency of the substance/medium to give or receive electrons. Contrary to what is expected, the important role of Eh is not limited to inorganic chemistry, metallic chemistry, natural water, and wastewater treatment fields but it also covers many domains in biology such as metabolic engineering, enzymatic functions, food safety, and biotechnology. Unfortunately, although the critical roles of Eh in several key reactions occurred in biological media such as food and biotechnological products, its application or controlling is still uncommon or mis-considered by food processors. The lack of specific studies and reviews concerning the Eh and its influences on the quality parameters of products could be a reason for this lack of interest from the side of food processors. Recent studies reported the potential application of this parameter in novel food processing techniques such as reducing atmosphere drying (RAD) of food products and reducing atmosphere packaging (RAP) of fresh food products for preserving the quality attributes and extending the shelf-life of food products. This paper aims to help the technical and operational personnel working in food industry sectors as well as the scientific community to have an updated and a comprehensible review about the Eh parameter permitting its consideration for potential applications in food industries.

Ion-selective electrode integrated in small-scale bioreactor for continuous intracellular pH determination in Lactobacillus plantarum.

The aim of the present study was to develop an ion-selective electrode method for the continuous determination of the intracellular pH in Lactobacillus plantarum using a small-scale bioreactor. This method employed a salicylate-selective electrode basing on the distribution of salicylic acid across the cytoplasmic membrane. This developed electrode responded to salicylate concentrations above 20 µmol/L with a Nernstian sensitivity. The energized and concentrated cells were added into a thermostated small-scale bioreactor that contained the salicylate anions dissolved in a 100 mmol/L potassium phosphate buffer at different pH values. The changes in salicylate concentration that occurred in the medium containing bacterial suspension were measured as a voltage change. The cells of Lactobacillus plantarum showed maintenance of pH homeostasis at the studied pH ranging from 4.0 to 7.0, and they kept a neutral intracellular pH up to 5.8. The simplicity of the measuring preparation and the relatively low cellular concentration, as well as the advantages of the small-scale bioreactor, lead us to believe that the described method can facilitate the study of the physicochemical factors on the intracellular pH of lactic acid bacteria using a single pH probe in one method.

Determination of trace elements, heavy metals, and antimony in polyethylene terephthalate-bottled local raw cow milk of Igdir region in Turkey.

The presence of several trace elements, heavy metals, and antimony in polyethylene terephthalate-bottled local raw cow milk samples of Igdir region in Turkey was investigated. The milk samples were analyzed by inductively coupled plasma mass spectrometry after microwave-assisted digestion. Milk samples were categorized into three groups according to the element level intensity in the sample. While 70% of samples showed 2.5 times the maximum Turkish and European permissible level of lead, the lowest lead-contaminated sample exhibited 1.25 times this level. All the examined samples exceeded the maximum permissible limit administrated for arsenic and 35% of samples exhibited 5 times this limit. Results showed 40% of samples contain an antimony level higher than the Turkish maximum allowable concentration. The high antimony content of raw milk samples may be related to the release of antimony from the PET (polyethylene terephthalate) bottles. This study showed high contamination levels of the most toxic trace elements, i.e., lead and arsenic in milk and possible antimony contamination from PET bottles which may cause many health hazards for the consumers.

Reducing atmosphere drying as a novel drying technique for preserving the sensorial and nutritional notes of foods.

Reducing atmosphere drying (RAD) was assayed as a novel technique for preserving the color and the nutritional fresh notes of apricot. A freeze, hot air and vacuum drying techniques were applied for a comparison purpose. The results showed that the apricot samples dried by both RADMIX and RADNITROGEN preserved better the fresh color notes while the freeze-drying was characterized by light and dully notes compared to a fresh sample. The total phenolic content significantly differed between fresh, RADMIX, RADAIR, hot air and vacuum with the highest value observed for both vacuum and hot air with 284.8 and 259.5 mg GAE 100 g-1 dm, respectively. DPPH inhibition activity was significantly similar for both fresh (or freeze drying) and each RADMIX, hot air and vacuum dried samples with 83.52, 76.3, 70.31, 67.86%, respectively, with the highest value attributed to RADMIX sample. The RAD-type dried samples (RADMIX, RADNITROGEN, RADAIR) possessed ABTS scavenging activity range of 68.74, 64.49 and 61.61 µmol TE g-1 dm respectively, which were close to that of the fresh sample (63.36 µmol TE g-1 dm) with the highest value attributed to RADMIX sample. The total flavonoid content was significantly similar between fresh (or freeze drying), vacuum, hot air and RADMIX samples with a range of 27.38, 24.25, 19.41 and 18.81 mg QE 100 g-1 dm, respectively, which exhibited an advantageous role of hydrogen in RADMIX system over both RADNITROGEN and RADAIR. For the first time, a technique based on the use of hydrogen in the drying atmosphere of a closed system was successfully proved for drying foods. This novel technique exhibits an opportunity for the food drying processors to produce dried foodstuffs with fresh color and nutritional notes.

Comparison Between Fluorescent Probe and Ion-Selective Electrode Methods for Intracellular pH Determination in Leuconostoc mesenteroides.

The intracellular pH (pHin) of Leuconostoc mesenteroides subsp. mesenteroides 19D was evaluated by two different methods, fluorescent probe and ion-selective electrode. Two fluorescent probes 5 (and-6)-carboxyfluorescein diacetate succinimidyl ester (cFDASE) and 5 (and-6)-carboxy-2',7'-dichlorofluorescein diacetate succinimidyl ester (cDCFDASE) were tested to evaluate the intracellular pH (pHin) of living cells at a medium pH (pHex) ranged from 5.0 to 6.5. Salicylic acid was used as a probe for the ion-selective electrode method. Cells kept 60-80% of cFDASE probe at all pHex values against 5-10% of cDCFDASE probe at pHex ≤ 6.0. The pHin values measured by the ion-selective electrode were higher by 0.1-0.6 pH units at pHex ranged from 5.0 to 6.5 than those determinated by fluorescent probe method. The possibility to study the intracellular pH at a wide external pH range using a single probe, and the simplicity of the material and experimental protocol may make the ion-selective electrode method most useful and easy to measure the intracellular pH of lactic acid bacteria compared with the other techniques like fluorescent probes.

Use of redox potential modification by gas improves microbial quality, color retention, and ascorbic acid stability of pasteurized orange juice.

The aim of this paper was to study the effect of both redox potential (Eh) and pasteurization of orange juice on stability of color and ascorbic acid, and growth recovery of microorganisms during storage at 15 degrees C for 7 weeks. Three conditions of Eh, +360 mV (ungassed), +240 mV (gassed with N2), and -180 mV (gassed with N2-H2) were applied to orange juice. Both thermal destruction and recovery of sublethally heat-injured cells of Lactobacillus plantarum and Saccharomyces cerevisiae were investigated. While oxidizing conditions were the most effective for thermal destruction of L. plantarum and S. cerevisiae, reducing conditions decreased recovery of heated cells of S. cerevisiae. In addition, gassing the juice with N2 or N2-H2 increased color retention and ascorbic acid stability. The present study demonstrated that juice must be reduced just after the heat treatment in order, firstly, to maximize microbial destruction during pasteurization, and secondly, to prevent the development of microorganisms and stabilize color and ascorbic acid during storage.

Behavior of Lactobacillus plantarum and Saccharomyces cerevisiae in fresh and thermally processed orange juice.

Lactobacillus plantarum and Saccharomyces cerevisiae are acid-tolerant microorganisms that are able to spoil citrus juices before and after pasteurization. The growth of these microorganisms in orange juice with and without pasteurization was investigated. Two samples of orange juice were inoculated with ca. 10(5) CFU/ml of each microorganism. Others were inoculated with ca. 10(7) CFU/ml of each microorganism and then thermally treated. L. plantarum populations were reduced by 2.5 and <1 log10 CFU/ml at 60 degrees C for 40 s and at 55 degrees C for 40 s, respectively. For the same treatments, S. cerevisiae populations were reduced by >6 and 2 log10 CFU/ml, respectively. Samples of heated and nonheated juice were incubated at 15 degrees C for 20 days. Injured populations of L. plantarum decreased by ca. 2 log10 CFU/ml during the first 70 h of storage, but those of S. cerevisiae did not decrease. The length of the lag phase after pasteurization increased 6.2-fold for L. plantarum and 1.9-fold for S. cerevisiae, and generation times increased by 41 and 86%, respectively. The results of this study demonstrate the differences in the capabilities of intact and injured cells of spoilage microorganisms to spoil citrus juice and the different thermal resistance levels of cells. While L. plantarum was more resistant to heat treatment than S. cerevisiae was, growth recovery after pasteurization was faster for the latter microorganism.