Recent advances in the contribution of glucosinolates degradation products to cruciferous foods odor: factors that influence degradation pathways and odor attributes.

As one of the most important vegetables and oils consumed globally, cruciferous foods are appreciated for their high nutritional value. However, there is no comprehensive knowledge to sufficiently unravel the "flavor mystery" of cruciferous foods. The present review provides a comprehensive literature on the recent advances regarding the contribution of glucosinolates (GSL) degradation products to cruciferous foods odor, which focuses on key GSL degradation products contributing to distinct odor of cruciferous foods (Brassica oleracea, Brassica rapa, Brassica napus, Brassica juncea, Raphanus sativus), and key factors affecting GSL degradation pathways (i.e., enzyme-induced degradation, thermal-induced degradation, chemical-induced degradation, microwave-induced degradation) during different processing and cooking. A total of 93 volatile GSL degradation products (i.e., 36 nitriles, 33 isothiocyanates, 3 thiocyanates, 5 epithionitriles, and 16 sulfides) and 29 GSL (i.e., 20 aliphatic, 5 aromatic, and 4 indolic) were found in generalized cruciferous foods. Remarkably, cruciferous foods have a distinctive pungent, spicy, pickled, sulfur, and vegetable odor. In general, isothiocyanates are mostly present in enzyme-induced degradation of GSL and are therefore often enriched in fresh-cut or low-temperature, short-time cooked cruciferous foods. In contrast, nitriles are mainly derived from thermal-induced degradation of GSL, and are thus often enriched in high-temperature, long-time cooked cruciferous foods.

Processing and cooking can cause degradation of glucosinolates and formation of volatiles.Structure­odor relationship of glucosinolates degradation products is discussed.Nitriles, isothiocyanates, and sulfides play an important role in cruciferous foods odor.Both enzyme- and thermal-induced degradation of glucosinolates is strongly pH-dependent.

Prognostic significance of nadir platelet count in patients with heatstroke: A multi-center retrospective study.

BACKGROUND: Heatstroke (HS), associated with the early activation of the coagulation system and frequently presenting with thrombocytopenia, poses a significant healthcare challenge. Understanding the relationship of nadir platelet count (PLT) within 24 h for adverse outcomes in HS patients is crucial for optimizing management strategies. METHODS: This retrospective cohort study, conducted in six tertiary care hospitals, involved patients diagnosed with HS and admitted to the emergency departments. The primary and secondary outcomes included in-hospital mortality and various acute complications, respectively, with logistic regression models utilized for assessing associations between nadir PLT and outcomes. The PLT count change curve was described using a generalized additive mixed model (GAMM), with additional analyses involving body temperature (BT) at 2 h also conducted. RESULTS: Of the 152 patients included, 19 (12.5%) died in-hospital. The median nadir PLT within 24 h was 99.5 (58.8-145.0)*10^9/L. Notably, as a continuous variable (10*10^9/L), nadir PLT was significantly associated with in-hospital mortality (OR 0.76; 95% CI 0.64-0.91; P = 0.003) and other adverse outcomes like acute kidney and liver injury, even after adjustment for confounders. GAMM revealed a more rapid and significant PLT decline in the non-survival group over 24 h, with differential PLT dynamics also observed based on BT at 2 h. CONCLUSIONS: Nadir PLT within 24 h were tied to in-hospital mortality and various adverse outcomes in HS patients. Early effective cooling measures demonstrated a positive impact on these associations, underscoring their importance in patient management.

Purification and characterization of limonin D-ring lactone hydrolase from sweet orange (Citrus sinensis (L.) Osbeck) seeds.

BACKGROUND: Citrus products often suffer from delayed bitterness, which is generated from the conversion of non-bitter precursors (limonoate A-ring lactone, LARL) to limonin under the catalysis of limonin D-ring lactone hydrolase (LDLH). In this study, LDLH was isolated and purified from sweet orange seeds, and a rapid and accurate high-performance liquid chromatography method to quantify LARL was developed and applied to analyze the activity and enzymatic properties of purified LDLH. RESULTS: Purified LDLH (25.22 U mg-1) showed bands of 245 kDa and 17.5 kDa molecular weights in native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate PAGE analysis respectively. After a 24 h incubation under strongly acidic (pH 3) or strongly alkaline (pH 9) conditions, LDLH still retained approximately 100% activity. Moreover, LDLH activity was not impaired by thermal treatment at 50 °C for 120 min. Enzyme inhibition assays showed that LDLH was inactivated only after ethylenediaminetetraacetic acid treatment, and other enzyme inhibitors showed no significant effect on its activity. In addition, the LDLH activity of calcium ion (Ca2+) intervention was 108% of that in the blank group, and that of zinc ion (Zn2+) intervention was 71%. CONCLUSION: LDLH purified in this study was a multimer containing 17.5 kDa monomer with a wide pH tolerance range (pH 3-9) and excellent thermal stability. Moreover, LDLH might be a metallopeptidase, and its activity was stimulated by Ca2+ and significantly inhibited by Zn2+. These findings improve our understanding of LDLH and provide some important implications for reducing the bitterness in citrus products in the future. © 2024 Society of Chemical Industry.

Structural and functional properties of whey protein isolate-inulin conjugates prepared with ultrasound or wet heating method.

BACKGROUND: Whey protein isolate (WPI) generally represents poor functional properties such as thermal stability, emulsifying activity and antioxidant activity near its isoelectric point or high temperatures, which limit its application in the food industry. The preparation of WPI-polysaccharide covalent conjugates based on Maillard reaction is a promising method to improve the physical and chemical stability and functional properties of WPI. In this research, WPI-inulin conjugates were prepared through wet heating method and ultrasound method and their structural and functional properties were examined. RESULTS: In conjugates, the free amino acid content was reduced, the high molecular bands were emerged at sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), new C-N bonds were formed in Fourier-transform infrared (FTIR) spectroscopy, and fluorescence intensity was reduced compared with WPI. Furthermore, the result of circular dichroism (CD) spectroscopy also showed that the secondary structure of conjugates was changed. Conjugates with ultrasound treatment had better structural properties compared with those prepared by wet heating treatment. The functional properties such as thermal stability, emulsifying activity index (EAI), emulsion stability (ES) and antioxidant activity of conjugates with wet heating treatment were significantly improved compared with WPI. The EAI and ES of conjugates with ultrasound treatment were the highest, but the thermal stability and antioxidant activity were only close to that of the conjugates with wet heating treatment for 2 h. CONCLUSION: This study revealed that WPI-inulin conjugates prepared with ultrasound or wet heating method not only changed the structural characteristics of WPI but also could promote its functional properties including thermal stability, EAI, ES and antioxidant activity. © 2024 Society of Chemical Industry.

Glasgow Coma Scale on admission as predictor of neurological sequelae at discharge and acute respiratory failure in patients with heatstroke.

BACKGROUND: Transient neuronal dysfunction may occur in most brain regions with heatstroke (HS). This study aimed to explore the prognostic significance of initial Glasgow Coma Scale (GCS) scores in HS. METHODS: Retrospective data regarding HS were obtained from six hospitals. The primary outcome was neurological sequelae at discharge. Secondary outcomes included acute respiratory failure (ARF) and intensive care unit (ICU) admission. Logistic regression models and random forest imputation were used to assess the independent association between GCS score and outcomes. Interaction and stratified analyses of body temperature (BT) at 0.5 hours were also conducted. Receiver operating characteristic curves and decision curve analysis were used to estimate prognostic values. RESULTS: Of 206 patients, 44 (21.36%) had neurological sequelae at discharge. The mean ± standard deviation initial GCS score was 8.17 ± 4.05. After adjustment for confounders, GCS, as a continuous variable, was significantly related to neurological sequelae at discharge [odds ratio (OR): 0.65; 95% confidence interval (CI): 0.50-0.85; P = 0.002], ARF (OR: 0.76; 95% CI: 0.66-0.87; P = 0.001), and ICU admission (OR: 0.68; 95% CI: 0.53-0.87; P = 0.003). These relationships were consistent in the random forest imputation cohort. The OR between GCS and neurological sequelae at discharge was much lower (P = 0.048) in participants with BT at 0.5 hours ≤39°C than in those with BT at 0.5 hours >39°C. The GCS and National Early Warning Score (NEWS) had similar prognostic ability for all outcomes, whereas the net benefits were greater with the GCS compared with the NEWS. CONCLUSIONS: Initial GCS score was an independent prognostic factor for neurological sequelae at discharge in HS. Rapid cooling played a positive role in this relationship. Key messages What is already known on this topic Brain damage caused by heatstroke (HS) can be transient or result in irreversible injury. Early recognition of those at risk of death or developing neurological complications is very important for improving the outcomes of HS. What this study adds Initial Glasgow Coma Scale (GCS) score was an independent prognostic factor for neurological sequelae at discharge, acute respiratory failure, and intensive care unit (ICU) admission in HS. Rapid cooling played a positive role in this relationship. How this study might affect research, practice, or policy The GCS upon emergency department admission can be a useful predictor of prognosis in patients with HS.

Effects of Capsaicin on Glucose Uptake and Consumption in Hepatocytes.

Obesity represents a major health challenge because it substantially increases the risk of metabolic diseases. Capsaicin, the major active ingredient of Capsicum spp., has been reported to possess anti-obesity activity. Hereon, the effect of capsaicin on glucose uptake and consumption in hepatocytes was extensively studied. Capsaicin was shown to accelerate the glucose uptake/consumption and the ATP production of hepatocytes. The elevation of intracellular Ca2+ was thought to be a potential mechanism. By transcriptome analysis, 78, 146 and 507 differentially expressed genes (DEGs) were identified between capsaicin and the control group for 4 h, 12 h and 24 h treatments. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that most of the DEGs were involved in canonical pathways, like MAPK and PI3K-AKT signaling pathways. Clustering analysis showed that many DEGs were associated with glucose and amino acid metabolism. The variation trend in genes related to glucose and amino acid metabolism (like CTH, VEGFA, PCK2 and IGFBP3) in the quantitative PCR (q-PCR) assay was consistent with the transcriptome data. These results demonstrated that capsaicin efficiently accelerated the glucose uptake and consumption of hepatocytes.

Isolation, purification, and mass spectrometry identification of the enzyme involved in citrus flavor (+)-valencene biotransformation to (+)-nootkatone by Yarrowia lipolytica.

BACKGROUND: (+)-Nootkatone is a highly valuable sesquiterpene compound that can be used as an aromatic in the food industry because of its grapefruit flavor and low sensory threshold. The unconventional yeast Yarrowia lipolytica has many unique physical and chemical properties, metabolic characteristics, and genetic structure, which has aroused the interest of researchers. Previous research showed that Y. lipolytica possesses the ability to transform the sesquiterpene (+)-valencene to (+)-nootkatone. The aim of this study was to isolate, purify, and identify the enzyme involved in the (+)-valencene bioconversion to (+)-nootkatone by Y. lipolytica. RESULTS: In this study, ultrasonic-assisted extraction, ammonium sulfate precipitation, anion-exchange chromatography, and gel-filtration chromatography were used to separate and purify the enzyme involved in the (+)-valencene bioconversion by Y. lipolytica. The protein was identified as aldehyde dehydrogenase (ALDH) (gene0658) using sodium dodecyl sulfate polyacrylamide gel electrophoresis and liquid chromatography-tandem mass spectrometry analysis. The ALDH had the highest activity when the pH value was 6.0 and the temperature was 30 °C. The activity of ALDH was significantly stimulated by ferrous ions and inhibited by barium, calcium, and magnesium ions. CONCLUSION: This is the first time that ALDH was found to participate in (+)-valencene biotransformation by Y. lipolytica. It may be involved in regulating the microbial transformation of (+)-valencene to (+)-nootkatone through redox characteristics. This study provides a theoretical basis and reference for the biological synthesis of citrus flavor (+)-nootkatone. © 2023 Society of Chemical Industry.

Effect of different ways of ingesting orange essential oil on blood immune index and intestinal microflora in mice.

BACKGROUND: Studies have found that the addition of plant essential oils to feed had a positive effect on intestinal microflora and immunity in mice. However, the effect of different ways of ingestion of orange essential oil on mice has seldom been reported. In the present study, we investigated the effects of ingestion of orange essential oil by gavage, sniffing and feeding on intestinal microflora and immunity in mice. RESULTS: The results obtained showed that a low concentration of essential oil feeding significantly increased the spleen index of mice (P < 0.05). The effect of different ways of ingestion on the thymus index, immunoglobulin G and immunoglobulin M of mice was not significant (P > 0.05). High and medium concentrations of essential oil feeding increased the level of interleukin-2 in mice (P < 0.05). H+ K+ -ATPase activity was significantly increased in mice fed with gavage and different concentrations of essential oil feed compared to the control group (P < 0.05). The analysis of the results of the microflora in the cecum and colon of mice indicated that the medium concentration of essential oil feeding group and the sniffing group significantly changed the structure of the flora and increased the diversity of the intestinal microflora. All three essential oil ingestion methods increased the abundance of Bacteroidetes and Lactobacillus in the intestine of mice. CONCLUSION: Compared with gavage and feeding, sniffing had a significant effect on immunoglobulins in mice. All the three ingestion methods could affect the intestinal microflora of mice and increase the abundance of Lactobacillus. © 2022 Society of Chemical Industry.

Citrus juice off-flavor during different processing and storage: Review of odorants, formation pathways, and analytical techniques.

As the most widespread juice produced and consumed globally, citrus juice (mandarin juice, orange juice, and grapefruit juice) is appreciated for its attractive and distinct aroma. While the decrease of characteristic aroma-active compounds and the formation of off-flavor compounds are easy to occur in processing and storage conditions. This review provides a comprehensive literature of recent research and discovery on citrus juice off-flavor, primarily focusing on off-flavor compounds induced during processing and storage (i.e., thermal, storage, light, oxygen, package, fruit maturity, diseases, centrifugal pretreatment, and debittering process), formation pathways (i.e., terpene acid-catalyzed hydration, caramelization reaction, Maillard reaction, Strecker degradation, and other oxidative degradation) of the off-flavor compounds, effective inhibitor pathway to off-flavor (i.e., electrical treatments, high pressure processing, microwave processing, ultrasound processing, and chemical treatment), as well as odor assessment techniques based on molecular sensory science. The possible precursors (terpenes, sulfur-containing amino acids, carbohydrates, carotenoids, vitamins, and phenolic acids) of citrus juice off-flavor are listed and are also proposed. This review intends to unravel the regularities of aroma variations and even off-flavor formation of citrus juice during processing and storage. Future aroma analysis techniques will evolve toward a colorimetric sensor array for odor visualization to obtain a "marker" of off-flavor in citrus juice.

(1) Processing and storage can cause the degradation of nutrients in citrus juice and the formation of off-flavor compounds.(2) Terpene degradation products, sulfur-containing compounds, phenols, acids, and furans are contributed to citrus juice off-flavor.(3) Nonthermal techniques such as electrical treatments, high pressure, microwave, and ultrasound processing is beneficial to preservation of the original aroma and sensory qualities of citrus juice.(4) Potential off-flavor compounds (especially trace level) explored by molecular sensory science also significantly impact the aroma of citrus juice.

Identification of functional genes associated with the biotransformation of limonene to trans-dihydrocarvone in Klebsiella sp. O852.

BACKGROUND: Natural dihydrocarvone has been widely used in the food, cosmetics, agrochemicals and pharmaceuticals industries because of its sensory properties and physiological effects. In our previous study, Klebsiella sp. O852 was shown to be capable of converting limonene to trans-dihydrocarvone with high catalytic efficiency. Thus, it was essential to identify and characterize the functional genes involved in limonene biotransformation using genome sequencing and heterologous expression. RESULTS: The 5.49-Mb draft genome sequence of Klebsiella sp. O852 contained 5218 protein-encoding genes. Seven candidate genes participating in the biotransformation of limonene to trans-dihydrocarvone were identified by genome analysis. Heterologous expression of these genes in Escherichia coli BL21(DE3) indicated that 0852_GM005124 and 0852_GM003417 could hydroxylate limonene in the six position to yield carveol, carvone and trans-dihydrocarvone. 0852_GM002332 and 0852_GM001602 could catalyze the oxidation of carveol to carvone and trans-dihydrocarvone. 0852_GM000709, 0852_GM001600 and 0852_GM000954 had high carvone reductase activity toward the hydrogenation of carvone to trans-dihydrocarvone. CONCLUSION: The results obtained in the present study suggest that the seven genes described above were responsible for converting limonene to trans-dihydrocarvone. The present study contributes to providing a foundation for the industrial production of trans-dihydrocarvone in microbial chassis cells using synthetic biology strategies. © 2021 Society of Chemical Industry.

Separation and purification of nootkatone from fermentation broth of Yarrowia lipolytica with high-speed counter-current chromatography.

Nootkatone is an important functional sesquiterpene, which can be obtained by the biotransformation of valencene. It is increasingly important because of its pleasant citrus aroma and physiological effects. Yarrowia lipolytica is beneficial for biotechnology applications and has ability to transform valencene to nootkatone. High-speed counter-current chromatography (HSCCC) was used to isolate and purify the product of nootkatone in this study. The suitable two-phase solvent system was selected and the optimum separation conditions were determined. The partition coefficients of nootkatone and the separation factor between nootkatone and valencene were considered as the indexes. The results showed that there were numerous products during the transformation of valencene by Yarrowia lipolytica, and the content of nootkatone was 13.75%. The obtained nootkatone was separated by HSCCC with a solvent system n-hexane/methanol/water (5/4/1, v/v). The final purity of nootkatone was 91.61 ± 0.20% and the elution time was 290-310 min. The structure of nootkatone was identified by gas chromatography-mass spectrometry (GC-MS), infrared spectrum and nuclear magnetic resonance hydrogen spectroscopy (1H NMR). This was the first report on the separation of nootkatone from the fermentation broth by HSCCC. This study proved that HSCCC could be used as an effective method to separate and purify the nootkatone from valencene transformed by Yarrowia lipolytica with n-hexane/methanol/water (5/4/1, v/v).

Advances on (+)-nootkatone microbial biosynthesis and its related enzymes.

(+)-Nootkatone is an important functional sesquiterpene and is comprehensively used in pharmaceutical, cosmetic, agricultural and food flavor industries. However, (+)-nootkatone is accumulated trace amounts in plants, and the demand for industry is mainly met by chemical methods which is harmful to the environment. The oxygen-containing sesquiterpenes prepared using microbial methods can be considered as "natural." Microbial transformation has the advantages of mild reaction conditions, high efficiency, environmental protection, and strong stereoselectivity, and has become an important method for the production of natural spices. The microbial biosynthesis of (+)-nootkatone from the main precursor (+)-valencene is summarized in this paper. Whole-cell systems of fungi, bacteria, microalgae, and plant cells have been employed. It was described that the enzymes involved in the microbial biosynthesis of (+)-nootkatone, including cytochrome p450 enzymes, laccase, lipoxygenase, and so on. More recently, the related enzymes were expressed in microbial hosts to heterologous produce (+)-nootkatone, such as Escherichia coli, Pichia pastoris, Yarrowia lipolytica, and Saccharomyces cerevisiae. Finally, the development direction of research for realizing industrialization of microbial transformation was summarized and it provided many options for future improved bioprocesses.

Screening a Strain of Klebsiella sp. O852 and the Optimization of Fermentation Conditions for Trans-Dihydrocarvone Production.

Flavors and fragrances have high commercial value in the food, cosmetic, chemical and pharmaceutical industries. It is interesting to investigate the isolation and characterization of new microorganisms with the ability to produce flavor compounds. In this study, a new strain of Klebsiella sp. O852 (accession number CCTCC M2020509) was isolated from decayed navel orange (Citrus sinensis (L.) Osbeck), which was proved to be capable of converting limonene to trans-dihydrocarvone. Besides, the optimization of various reaction parameters to enhance the trans-dihydrocarvone production in shake flask was performed for Klebsiella sp. O852. The results showed that the yield of trans-dihydrocarvone reached up to 1 058 mg/L when Klebsiella sp. O852 was incubated using LB-M medium for 4 h at 36 °C and 150 rpm, and the biotransformation process was monitored for 36 h after adding 1680 mg/L limonene/ethanol (final ethanol concentration of 0.8% (v/v)). The content of trans-dihydrocarvone increased 16 times after optimization. This study provided a basis and reference for producing trans-dihydrocarvone by biotransformation.

Effect and mechanism of high-fat diet on the preference for sweeteners on mice.

BACKGROUND: Male Kunming mice were divided into a normal diet group (control group) and a high-fat diet group (HF group) (185 g·kg-1 protein, 600 g·kg-1 fat and 205 g·kg-1 carbohydrate). After 8 weeks' feeding, behavioral indicators and biochemical indicators in serum were determined. The double-bottle preference experiment was used to study the preferences of mice for five sweeteners. The monoamine neurotransmitter content, gene expression related to dopamine (DA), and opioid receptors were also determined. RESULTS: The body weight of the mice in the HF group increased significantly (P < 0.05) after 36 days compared with the control group. The feed intake of the HF group increased sharply in the first 12 days, and then it became basically unchanged. The preference of the HF group for all of the five sweeteners was highly significantly lower (P < 0.01) than that of the control group. Depression-related behavior was observed in the HF group mice. The triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDLC) content in the HF group were very much higher (P < 0.01) than those of the control group. The gene expression related to DA and opioid receptor in the HF group was significantly lower than that of the control group, except for preproenkephalin (PENK). CONCLUSIONS: In summary, this study suggested that a long-term high-fat diet could result in a decrease in the preference for sweeteners and could result in a state of reward hypofunction in mice. © 2020 Society of Chemical Industry.

Effect of short-term intake of four sweeteners on feed intake, solution consumption and neurotransmitters release on mice.

This study focused on the effect of short-term intake of sweeteners on feed intake, solution consumption and neurotransmitters release on mice. The results showed that the free drinking of 10 mM sucralose solution, 100 mM maltose solution, 3 mM saccharin solution and 3 g/L stevioside solution for 32 days will not affect the normal development of the body weight and feed intake of the mice. The consumption of maltose solution was significantly higher than that of the other sweeteners. The leptin and insulin levels increased significantly after the short-term intake of these four sweeteners. The dopamine (DA) content in the whole brain of the mice increased significantly only in the maltose group. These results indicate that the short-term intake of the preferred concentrations of maltose, stevioside, sucralose and saccharin will not affect the body weight and feed intake of the mice. Mice prefer maltose solution to other sweeteners solutions. The 100 mM maltose solution and 3 mM saccharin solution could result in the oxidative stress on mice after 32 days' short-term intake. Compared with other sweeteners, only sugars that could be broken down into small molecules of glucose might have a positive effect on dopamine levels.

Effects of different sweeteners on behavior and neurotransmitters release in mice.

Four natural sweeteners (sucrose, stevioside, maltose and xylitol) and six artificial sweeteners (acesulfame, sucralose, aspartame, cyclamate, saccharin and neotame) were used to study the effects of different sweeteners on the behavior and neurotransmitter release of mice with two-bottle preference experiments. The results showed that very significant preference behavior for 8% sucrose solution, 0.3% stevioside solution, 10 mM acesulfame, 10 mM sucralose and 10 mM aspartame solutions (p < 0.01) was observed on mice. Long-term exposure of sucrose solution and acesulfame solution can affect the behavioral indicators such as solution consumption, feed intake, body weight and the release of neurotransmitters in mice. The solution consumption and the release of neurotransmitters were significantly greater (p < 0.05) than that of the control group (water group), but there was no significant difference in feed intake. The acesulfame-A and acesulfame-B groups had no significant difference on the consumption of solution and feed intake, but there was significant difference in the release of neurotransmitters. The result also showed that different sweetener solutions with similar sweetness had the same effect on the neurotransmitters release, and it can be inferred that mice have an addictive behavioral characteristic to sucrose.

Effects of orange essential oil on intestinal microflora in mice.

BACKGROUND: The intestinal microbiota has a wide variety of functions in the host. A positive effect of plant extract on intestinal microbiota in animals has been reported. However, the effect of orange essential oil and its components limonene, linalool and citral on intestinal microflora in mice has seldom been reported. The effects of intragastric administration of orange essential oil and limonene, linalool and citral on intestinal microflora and biochemical indexes in mice were studied. RESULTS: The effect of essential oil, linalool and citral on immune organ index (spleen and thymus index), IgM and IL-2 was not significant (P > 0.05). A significant increase (P < 0.05) of H+ K+ -ATPase activity, IgA, IgG, and IL-2 in the limonene group was observed when compared with the control group. Orange essential oil, limonene, linalool and citral could significantly reduce the content of short-chain fatty acids in the cecum and colon of mice. Principal coordinates analysis showed that intestinal bacterial structure of limonene group cecum and colon was apparently separated from other groups. The relative abundance of Lactobacillus in cecum and colon in essential oil, limonene, linalool and citral groups was higher than that in the control group. CONCLUSIONS: Orange essential oil and limonene, linalool and citral could affect the intestinal microflora of mice, and enhance the relative abundance of Lactobacillus. The intestinal bacterial structure of cecum and colon in the limonene group was quite different from other groups. This indicated a more obvious effect of limonene on intestinal bacteria, also resulting in significant changes in blood immune index and short-chain fatty acids in mice. © 2019 Society of Chemical Industry.

Changes of aroma compounds and qualities of freshly-squeezed orange juice during storage.

This study focused on the changes of physicochemical and microbiological properties and aroma compounds of freshly-squeezed orange juice during storage at different temperatures. Aroma compounds were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The results showed that the total aerobic plate counts of orange juice stored at room temperature and 37 °C was far more than 4 °C. Totally 33 aroma compounds were determined in these orange juices. Significant differences on the aroma compounds in orange juices stored at different temperatures were observed in the present study. Most of the terpenes decreased at 4 °C after 15 days' storage, while 10 and 8 terpenes increased during storage at room temperature and 37 °C. α-Terpineol and p-vinylguaiacol were the only off-flavor compounds found in juice stored at 4 °C and room temperature at late storage respectively. While terpinen-4-ol, 4-ethylguaiacol and p-vinylguaiacol were found in juice stored at 37 °C at late storage. α-Terpineol was the only off-flavor compound found in orange juice stored at 4 °C.

Effect of olive oil on the preparation of nanoemulsions and its effect on aroma release.

The present study focused on the effect of olive oil on Ostwald ripening of flavor nanoemulsions. The release of the aroma compounds from the nanoemulsion system was also investigated. The results showed that the droplets size of the nanoemulsions decreased sharply first and then kept stable with the increase of Tween 80. The optimum surfactant/cosurfactant (Km) ratio was determined at 7:1. The average particle size of nanoemulsion was 39.22 nm. The polydispersity index (PDI) was 0.242 nm, and the particle size distribution was in the range of 20-150 nm at the optimum Km. The stability of the nanoemulsions was improved after the addition of olive oil, and it increased noticeably with the increase of olive oil. The addition of olive oil could help to stabilize the emulsions and hamper Ostwald ripening. All the 11 aroma compounds in the nanoemulsions were detected after 24-h storage. While only 5 aroma compounds were found after 48-h storage, and α-pinene and ß-myrcene were the only two aroma compounds detected after 72-h storage with low contents of 1.41 and 0.5 mg/L. The addition of olive oil inhibited the release of the aroma compounds from the nanoemulsion system. The released ethyl acetate was reduced by 48% after the addition of 10% olive oil. Significant decrease on the release of α-pinene and nonanal was observed after the addition of 3% olive oil. And the decrease was also observed on the release of ß-myrcene, D-limonene, α-terpineol, decanal and eugenol when the olive oil content was ≥ 5%. However, benzyl alcohol, ß-ionone and 1-octanol showed no significant changes with the increase of olive oil. This indicated that the addition of olive oil could provide greater retention of the aroma compounds in the nanoemulsions.