Comparative evaluation of volatiles, phenolics, sugars, organic acids and antioxidant properties of Sel-42 and Tainung papaya varieties

Induced electric field as alternative pasteurization to improve microbiological safety and quality of bayberry juice

Recently, unconventional techniques like induced electric field (IEF) for continuous pasteurization of liquid food have received great attention. In this study, the effect of IEF on temperature rise, microbiological and quality characteristics of bayberry juice was investigated. Voltage, current, and flow rate affected the terminal temperature. Both IEF (600 V, 4 L/h; 700 V, 6 L/h) and thermal pasteurization (95 °C, 2 min) completely inactivated total plate count, coliforms, yeast and mold in bayberry juice. The pH, total soluble solid and titratable acidity did not vary significantly post-IEF, but conductivity changed slightly. IEF-treated samples exhibited the lowest ΔE values without exceeding 3. Thermal pasteurization (95 °C, 2 min) scored the lowest in color, flavor, odor, and acceptance. GC-MS results demonstrated a significant increase in the content of total volatile compounds following IEF treatments, with the maximum increment reaching 10.65 %. Generally, IEF is a potential technology for processing liquid beverages.

Antioxidant Capacity, Sugar Content, and Tandem HPLC-DAD-ESI/MS Profiling of Phenolic Compounds from Aronia melanocarpa Fruits and Leaves (Nero and Viking Cultivars)

This study examined the phenolic profile, sugar composition, and antioxidant capacities of chokeberry fruits and leaves obtained from four different Turkiye provinces. A total of 21 phenolics including phenolic acid and its derivatives, flavanols, anthocyanins, and flavonols were determined in the fruits, while the leaves had 19 phenolics, including phenolic acid and its derivatives, flavanols, and flavonols. The total amount of phenolic compounds was the highest in both fruits and leaves in the samples from the Bursa province. Cis 5-O-p-coumaroylquinic acid and secoxyloganin were quantified for the first time in both fruits and leaves. In summary, it was found that different geographical locations significantly affected the phenolics, sugar contents, and antioxidant activities of the fruits and leaves.

Carnauba wax-based edible coatings retain quality enhancement of orange (Citrus sinensis cv. Moro) fruits during storage

Fruit coatings serve a dual purpose in preserving the quality of fruits. Not only do they act as a barrier against water evaporation and fungal infiltration, but they also enhance the fruit's visual appeal in the market. Yet, their influence on the fruit's quality components, which play a crucial role in determining its nutritional value, taste, and overall flavor, has remained relatively unexplored. This study aimed to evaluate the effects of carnauba wax coating on the quality of Moro oranges during storage. The selected fruits were meticulously chosen for uniformity in size. The experiment involved applying carnauba wax, a commonly used type among local producers, at four different concentrations: 0%, 0.5%, 1%, and 1.5%. These treatments were applied during various storage periods, including immediately after fruits were harvested and after 40 and 80 days. Following the application of these treatments, the oranges were stored in a controlled environment (morgue) at a temperature of 4 ± 1 °C. Subsequently, several physicochemical parameters of both the fruit flesh and skin were examined. The results unveiled a decline in the overall ascorbic acid content of the fruits. In terms of phenol content, a general decreasing trend was observed after harvesting. At each sampling interval during storage, the phenol content in uncoated fruits consistently exceeded that of their waxed counterparts. Significant reduction in fruit weight was observed throughout the storage period. Both vitamin C and total acidity levels in the fruit exhibited decreases during the storage period. As time passed, fruit firmness gradually declined, while fruit decay increased during the 40- and 80-day storage periods for untreated Moro oranges. The anthocyanin content showed an increasing trend. The study also unveiled a decline in the antioxidant capacity of citrus fruits during storage. Strong significant positive correlations were observed between total phenol content and key parameters, such as antioxidant activity (0.941**), MDA (0.364*), vitamin C content, and total carbohydrate content (0.475**). Skin radiance showed a perfect correlation with chroma and hue (1.000**). Principal component analysis revealed that the first principal component accounted for 34.27% of the total variance, out of a total of five principal components that explained 77.14% of the variance. Through cluster analysis, the variables were categorized into three distinct groups; one associated with weight loss and another with ion leakage. Considering these findings, carnauba wax-based coating emerges as a promising solution for preserving Moro oranges. It effectively mitigates fruit weight loss and helps maintain fruit firmness during storage, making it a valuable tool for fruit preservation.

Comparing the Volatile and Soluble Profiles of Fermented and Integrated Chinese Bayberry Wine with HS-SPME GC-MS and UHPLC Q-TOF

To evaluate the flavor characteristics of Chinese bayberry alcoholic beverages, fermented bayberry wine (FBW) and integrated bayberry wine (IBW) were investigated for their volatile and soluble profiles using HS-SPME GC-MS and UHPLC Q-TOF and were analyzed with multidimensional statistical analysis, including PCA and OPLS-DA. The volatile compounds 1-pentanol, β-caryophyllene and isopentanol were only detected in IBW. β-caryophyllene, the key flavor component of bayberry, was found to be the most abundant volatile compound in IBW (25.89%) and was 3.73 times more abundant in IBW than in FBW. The levels of ethyl octanoate, ethyl nonanoate, and ethyl decanoate were also several times higher in IBW than in FBW. These compounds contributed to the strong bayberry aroma and better fruity flavor of IBW. On the other hand, high levels of ethyl acetate and octanoic acid in FBW, representing pineapple/overripe or sweat odor, were key contributors to the fermented flavor of FBW. Soluble sugars, such as sucrose, D-glucose, and D-tagatose, as well as amino acids, such as L-glutamate and L-aspartate, had much higher levels in IBW. The anthocyanin pigment cyanidin 3-glucoside, which generates red color, was also higher in IBW. On the other hand, most of the differentially expressed alcohols, acids, amino acids, purines/pyrimidines and esters were present in higher concentrations in FBW compared to IBW. This demonstrated that IBW has a much sweeter and more savory taste as well as a better color generated by more anthocyanins, while FBW presents a more acidic and drier taste as well as a complex formation of alcohols and esters. The study also prompts the need for further research on the flavor profiles of IBW and its potential application and market value.

Spatial and Compositional Variations in Fruit Characteristics of Papaya (Carica papaya cv. Tainung No. 2) during Ripening

Papaya fruit (Carica papaya) has different degrees of ripening within each fruit, affecting its commercial market value. The fruit characteristics of "Tainung No. 2" Red papaya were investigated at the stem-end, middle, and calyx-end across 3 ripening stages and categorized based on fruit skin coloration: unripe at 16 weeks after anthesis (WAA), half-ripe at 18 WAA, and full-ripe at 20 WAA. The fruits maintained an elliptical shape during ripening with a ratio of 2.36 of the length to the width. The peel and pulp color changed from green to white to yellow during ripening, regardless of the three parts. In the pulp, soluble solid contents increased, and firmness decreased during ripening but did not differ among the three parts. Individual nutrient contents, including metabolites and minerals, changed dynamically between the ripening stages and fruit parts. Total carbohydrates and proteins, N, and K, were accumulated more at the stem-end during ripening; meanwhile, fructose, glucose, Mg, and Mn were accumulated more at the calyx-end. In the principal component analysis, ripening stages and fruit parts were distinctly determined by the first and second principal components, respectively. Understanding the nutrient and metabolite dynamics during ripening and their distribution within the fruit can help optimize cultivation practices, enhance fruit quality, and ultimately benefit both growers and consumers.

Can consumption of local micronutrient- and absorption enhancer-rich plant foods together with starchy staples improve bioavailable iron and zinc in diets of at-risk African populations?

Iron and zinc deficiencies remain prevalent in developing countries, often due to monotonous starchy diets that are low in bioavailable minerals. This review addresses the question as to whether consumption of starchy staple foods in Africa together with micronutrient-dense and absorption enhancer-rich plant foods can enhance iron and zinc bioavailability in the diets of at-risk populations. While green leafy vegetables (GLVs) fortification of starchy staples can improve mineral contents, especially iron, it may not improve bioavailable iron and zinc, due to GLVs' high contents of mineral absorption inhibitors, notably polyphenols, phytate and calcium. Fruits, although low in minerals, could improve bioavailable iron and zinc in the staples because of their high ascorbic and citric acid and/or β-carotene contents, which can form soluble chelates with the minerals. More human studies are needed to establish whether such a technology or fortification strategy can improve bioavailable iron and zinc in African-type plant-based diets.

Comprehensive Assessment of Antioxidant and Anti-Inflammatory Properties of Papaya Extracts

Antioxidant and anti-inflammatory properties of papaya (Carica papaya) fruits were evaluated to provide comprehensive information associated with the bioactive compounds. ‘Tainung No. 2’ papaya fruits, cultivated in a greenhouse, Korea, were harvested at unripe and ripe stages and then divided into seed and peel-pulp. Total phenolic and flavonoid contents were determined using spectrophotometry, and individual phenolic compounds were relatively quantified by HPLC-DAD and fifteen standards. Antioxidant activities were measured using four assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) scavenging activities, inhibition of lipid peroxidation, and FRAP (ferric reducing antioxidant power). Anti-inflammatory activities were measured by the regulation of NF-κB signaling pathways with the measurements of ROS and NO productions as the degree of oxidative stress. Total phenol contents increased in seed and peel–pulp extracts during ripening; flavonoid contents increased only in seed extracts. Total phenolic contents were associated with ABTS radical scavenging activity and FRAP. Of fifteen phenolic compounds, chlorogenic acid, cynarin, eupatorine, neochlorogenic acid, and vicenin II were identified among papaya extracts. ROS and NO productions were inhibited in papaya extracts. Especially, NO productions were inhibited higher in ripe seed extracts than in other extracts, which would be associated with the suppression of NF-κB activation and iNOS expression. These results suggest that papaya fruit extracts, including seeds, peels, and pulps, could be potential raw materials for functional foods.

Biochemical, Sensory, and Molecular Evaluation of Flavour and Consumer Acceptability in Australian Papaya (Carica papaya L.) Varieties

Inconsistency in flavour is one of the major challenges to the Australian papaya industry. However, objectively measurable standards of the compound profiles that provide preferable taste and aroma, together with consumer acceptability, have not been set. In this study, three red-flesh papayas (i.e., ‘RB1’, ‘RB4’, and ‘Skybury’) and two yellow-flesh papayas (i.e., ‘1B’ and ‘H13’) were presented to a trained sensory panel and a consumer panel to assess sensory profiles and liking. The papaya samples were also examined for sugar components, total soluble solids, and 14 selected volatile compounds. Additionally, the expression patterns of 10 genes related to sweetness and volatile metabolism were assessed. In general, red papaya varieties had higher sugar content and tasted sweeter than yellow varieties, while yellow varieties had higher concentrations of citrus floral aroma volatiles and higher aroma intensity. Higher concentrations of glucose, linalool oxide, and terpinolene were significantly associated with decreased consumer liking. Significant differences were observed in the expression profiles of all the genes assessed among the selected papaya varieties. Of these, cpGPT2 and cpBGLU31 were positively correlated to glucose production and were expressed significantly higher in ‘1B’ than in ‘RB1’ or ‘Skybury’. These findings will assist in the strategic selective breeding for papaya to better match consumer and, hence, market demand.

Prediction of the ripening stages of papayas using discriminant analysis and support vector machine algorithms

BACKGROUND

Evaluation of the quality properties of papaya becomes essential due to the acceleration of the fruit shelf-life senescence and the deterioration factor of the expected postharvest operations. In this study, the colour features in RGB, normalised RGB, HSV and L*a*b* channels were extracted and correlated with mechanical properties, moisture content (MC), total soluble solids (TSS) and pH for the prediction of quality properties at five ripening stages of papaya (R1-R5).

RESULTS

The mean values of colour features in RGB R m , G m , B m , normalised RGB R nm , G nm , B nm HSV H m , S m , V m , and L*a*b* L m , a m , b m were the best estimator for predicting TSS with R²  ≥ 0.90. All colour channels also showed satisfactory accuracies of R² ≥ 0.80 in predicting the bioyield force, apparent modulus and mean force. The highest average classification accuracy was obtained using linear discriminant analysis (LDA) with an average accuracy of more than 82%. The study showed that LDA, linear support vector machine, quadratic discriminant analysis and quadratic support vector machine obtained the correct classification of up to 100% for R5, whereas R1, R2, R3 and R4 gave classification accuracies in the range 83.75-91.85%, 85.6-90.25%, 85.75-90.85% and 77.35-87.15%, respectively. This indicates that R5 colour information was obviously different from R1-R4. The mean values of the HSV channel indicated the best performance to predict the ripening stages of papaya, compared to RGB, normalised RGB and L*a*b* channels, with an average classification accuracy of more than 80%.

CONCLUSION

The study has shown the versatility of a machine vision system in predicting the quality changes in papaya. The results showed that the machine vision system can be used to predict the ripening stages as well as classifying the fruits into different ripening stages of papayas. © 2021 Society of Chemical Industry.

Papaya (Carica papaya L.) for cancer prevention: Progress and promise

Cancer is a leading cause of morbidity and mortality across the globe. Emerging evidence suggests that consumption of a well-balanced diet containing a wide variety of vegetables, fruits, and whole grains can prevent the development of, halt, or reverse cancer progression. Carica papaya L. (papaya) has a wide distribution throughout many countries. Although the fruits of C. papaya are primarily consumed as food, various parts of this tree, including the bark, fruits, latex, seeds, and roots, have been used in traditional medicine for health promotion and disease mitigation. While numerous individual studies have investigated anticancer efficacies of various products and constituents of C. papaya, an up-to-date, comprehensive, and critical evaluation of available research data covering its role in the prevention and intervention of various human malignancies has not been conducted according to our knowledge. The purpose of this review is to present a systematic, comprehensive, and critical analysis of the cancer-preventive potential of C. papaya extracts, fractions, and isolated phytochemicals with a special emphasis on the cellular and molecular mechanisms of action. Moreover, the bioavailability, pharmacokinetics, and safety profiles of individual phytochemicals of C. papaya, as well as current limitations, challenges, and future directions of research, have also been discussed.

Analysis of Free Sugars, Organic Acids, and Fatty Acids of Wood Apple (Limonia acidissima L.) Fruit Pulp

Wood apple (Limonia acidissima L.) is an underutilized, fruit-yielding tree that is native to India and Sri Lanka. Wood apple trees are also cultivated in India, Sri Lanka, Bangladesh, Myanmar, Thailand, Malaysia, Vietnam, Kampuchea, Laos, and Indonesia for delicious fruits and medicinal purposes. The major objective of the present work was the analysis of the nutritional status of wood apple fruit pulp.The fruits are rich in total carbohydrates (24.74 ± 0.19%), total proteins (9.30 ± 0.16%), oil (0.99 ± 0.01%), fiber (3.32 ± 0.02%), and ash (2.73 ± 0.12%). Further analysis and quantification of free sugars, organic acids, and fatty acid methyl esters were carried out by using high-performance liquid chromatography (HPLC) and gas chromatographic (GC) methods. In total, five sugars and nine organic acids were detected and quantified. The predominant sugars were fructose (16.40 ± 0.23%) and glucose (14.23 ± 0.10%), whereas the predominant organic acids were D-tartaric (4.01 ± 0.03%), ascorbic (4.51 ± 0.05%), and citric acid (4.27 ± 0.04%). The oil content of fruit pulp was 0.99 ± 0.01% and GC-MS analysis revealed that, it comprise of 16 fatty acid methyl esters. The percentage of saturated fatty acids were 32.17 ± 0.35%, that includes palmitic (18.52 ± 0.12%) and stearic acids (9.02 ± 0.08%), whereas, the unsaturated fatty acids were 51.98 ± 0.94%, including oleic acid (23.89 ± 0.06%), α-linolenic acid (16.55 ± 0.26%), linoleic acid (10.02 ± 0.43%), and vaccenic acid (1.78 ± 0.23%).

Fruit Volatile Fingerprints Characterized among Four Commercial Cultivars of Thai Durian (Durio zibethinus)

Ripe durian fruits produce unique volatiles of pungent odor comprising esters, alcohols, ketones, and sulfur-containing compounds. Recently, “Chanthaburi 1” hybrid bred from 2 famous commercial cultivars of “Chanee” and “Monthong” claimed to be less fragrant during ripening, but there was no report. The present study compared the volatile profiles from 3 Thai commercial cultivars of “Kanyao,” “Chanee,” and “Monthong” compared to “Chanthaburi 1”, and the relationships of the cultivars were organized using the volatile fingerprints. Out of 41 volatile compounds detected by SPME/GC-MS in ripe durian flesh, 33 compounds were esters, but only 14 esters were found in “Chanthaburi 1.” Ripe flesh of most durian cultivars contains ethyl-2-methyl butanoate and ethyl hexanoate as the active volatiles. “Chanthaburi 1” contained fewer components with low odor activity value (OAV) of the volatiles. “Chanee” ripe flesh exhibited the strongest durian smell among the four varieties, whereas “Monthong” exhibited a strong apple-like fruity odor and “Kanyao” was more green fruity. Diethyl disulfide and 3, 5 dimethyl-1, 2, 4-trithiolane contributing pungent smells of garlic or onion were found only in “Chanthaburi 1” and “Monthong.” In terms of detected volatiles, “Kanyao” and “Chanee” were highly close when “Monthong” was apart. PCA analysis revealed that “Chanthaburi 1” contained ester compounds ancestrally related to the parents, “Chanee” in the component I and “Monthong” in the component II. These data could be beneficial for managing the status of Thai durians in global markets.

Variations in the key aroma and phenolic compounds of champignon (Agaricus bisporus) and oyster (Pleurotus ostreatus) mushrooms after two cooking treatments as elucidated by GC-MS-O and LC-DAD-ESI-MS/MS

Volatiles, key odorants, phenolics and antioxidant properties of raw, boiled and oven-cooked champignon and oyster mushrooms were investigated. Total concentration of the volatiles was drastically reduced by both cooking treatments and the lowest contents were found in the oven-cooked sample. Alcohols and terpenes were the dominant aroma groups in the raw champignon and oyster sample, respectively. The highest FD factor (FD = 2048) was found for 1-octen-3-one and methional in raw and boiled champignon samples while the same FD factor was determined in 1-octen-3-ol and methional in raw and boiled oyster samples. It was determined that the phenolics were more abundant in champignon samples than the oyster samples and that the boiling process caused a decrease while oven-cooking resulted in an increase in the amount of phenolics in both varieties. It was revealed that cooking was a crucial factor for the key odorants and phenolics in champignon and oyster mushrooms.

Development of alginate-pectin microcapsules by the extrusion for encapsulation and controlled release of polyphenols from papaya (Carica papaya L.)

The papaya fruit (Carica papaya L.) contains a wide variety of bioactive compounds with potential applications in the food and nutraceutical industries. The entrapment and release of such bioactive compounds remain a critical step for the development of functional, stable, and cost-effective storage and delivery systems, since the interaction of polymers on capsules and the payload molecules can influence the performance of the capsule system under operational conditions. The present study describes the encapsulation of rutin and trans-ferulic acid-rich extracts from papaya exocarp in a pectin-alginate composite, evaluating the performance of gallic acid encapsulation obtained through in situ and two-step entrapment methods. The best alginate:pectin ratio for gallic acid encapsulation was 55:45 and 61:39, achieving 6.1 mg and 28.1 mg GAE/g capsules when the papaya exocarp extract was encapsulated by in situ and two-step, respectively. We also evaluated the payload release performance of the obtained capsules under in vitro conditions simulating gastrointestinal conditions. Our results indicate an increased protective effect at gastric pH and targeted release of polyphenols when in situ encapsulation is used to encapsulate the extracts. PRACTICAL APPLICATIONS: Currently, adding value to agroindustry processing waste is an important focus to achieve a more economically and environmentally sustainable food industry. The recovery of bioactive molecules such as polyphenols, for food supplements or formulation additives in the form of by-product extracts is gaining importance as novel sustainable processes in the agricultural industry. Thus, the encapsulation of such bioactive extracts for storage and consumption is an active research field, aiming to overcome the low storage stability and lability to gastric conditions, currently hindering their applications in food or pharmaceutical formulations. In this sense, capsule design and the development of efficient encapsulation methods are very important to obtain a suitable carrier and protector system for the capsulated bioactive extracts or molecules. This research aims to add value to papaya waste and potentially to other agroindustry wastes such as pectin and alginate, resulting in a polyphenol carrier with excellent encapsulation and targeted release properties under gastrointestinal conditions. In conclusion, this kind of works could allow to the application of the agroindustry byproducts to obtain high added-value products, in the form of polyphenol-loaded capsules.

Correlation among PME activity, viscoelastic, and structural parameters for Carica papaya edible tissue along ripening

Papaya fruit, widely consumed around the world, is mechanically and structurally affected by several enzymatic processes during ripening, where pectin methylesterase plays a key role. Hence, the aim of this work was to evaluate possible correlations among physicochemical changes, mechanical parameters, viscoelastic behavior, and enzyme activity of pectin methylesterase to provide information about the softening phenomenon by applying the Maxwell and Peleg models. Mechanical parameters were estimated by texture profile analysis, enzyme activity by Michaelis-Menten parameters, and viscoelastic behavior by relaxation test responses fitted to these models. The Maxwell model described properly mechanical changes during ripening, displaying a better adjustment (R² > 0.97) than the Peleg model (0.80 < R² < 0.84). Pearson correlation analysis (P ≤ 0.01) indicated an inversely proportional relation among firmness, total soluble solids, and the first elastic element of the Maxwell model. Besides, the PME Michaelis-Menten affinity constant showed a correlation between the first elastic element and the first viscoelastic element of the Maxwell model. Findings of this work pointed out that the first Maxwell elastic element could explain structural changes as papaya ripening advance, associated with pectin methylesterase activity, cell wall disruption, and cell assembling into the tissue. PRACTICAL APPLICATION: Mechanical and viscoelastic behavior of papaya fruit tissue were described by the Maxwell model associating both viscous and elastic elements to the softening process. The results provide background and practical knowledge to describe structural changes during the ripening process of papaya depending on its enzymatic activity. Outcomes could be further applied to understand changes in other fruits or food matrixes that soften during postharvest, storage, and food chain supply processes.

Comparative metabolites profiling of harvested papaya (Carica papaya L.) peel in response to chilling stress

BACKGROUND

Papaya, as one of the most important tropical fruits in the world, is easily subjected to chilling injury (CI). Research on the effect of chilling temperature storage on the metabolic changes of papaya peel is limited.

RESULTS

Chilling temperature (4 °C) inhibited fruit ripening and induced CI on papaya fruit. Additionally, low temperature altered the concentrations of 45 primary metabolites and 52 aroma volatile compounds in the papaya peel. Papaya fruit stored at different temperatures could be separated using partial least squares-discriminant analysis (PLS-DA) with primary metabolites and volatile compounds as variables. In total, 18 primary metabolites and 22 volatiles with variable importance in projection (VIP) score higher than one might be considered as potential markers in papaya peel in response to chilling stress. Metabolites related to aroma, such as organic acid, amino acids, hexanal, carbonic acid, pentadecyl propyl ester and methyl geranate, caryophyllene accounted for major part of the metabolism changes of papaya peel and contributed a lot in response to cold stress.

CONCLUSION

This study added new insights regarding effect of chilling stress on metabolites in papaya peel. Some important metabolites might be indicator for chilling stress and detection of these metabolites will guide us to regulate the storage temperature to avoid chilling and to prolong storage of papaya fruit. © 2019 Society of Chemical Industry.

Fast and Furious: Ethylene-Triggered Changes in the Metabolism of Papaya Fruit During Ripening

Papaya is a climacteric fleshy fruit characterized by fast ripening after harvest. During the relatively short postharvest period, papaya fruit undergoes several changes in metabolism that result in pulp softening and sweetening, as well as the development of a characteristic aroma. Since papaya is one of the most cultivated and appreciated tropical fruit crops worldwide, extensive research has been conducted to not only understand the formation of the quality and nutritional attributes of ripe fruit but also to develop methods for controlling the ripening process. However, most strategies to postpone papaya ripening, and therefore to increase shelf life, have failed to maintain fruit quality. Ethylene blockage precludes carotenoid biosynthesis, while cold storage can induce chilling injury and negatively affect the volatile profile of papaya. As a climacteric fruit, the fast ripening of papaya is triggered by ethylene biosynthesis. The generation of the climacteric ethylene positive feedback loop is elicited by the expression of a specific transcription factor that leads to an up-regulation of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) and ACC-oxidase (ACO) expression, triggering the system II ethylene biosynthesis. The ethylene burst occurs about 3 to 4 days after harvest and induces pectinase expression. The disassembling of the papaya cell wall appears to help in fruit sweetness, while glucose and fructose are also produced by acidic invertases. The increase in ethylene production also results in carotenoid accumulation due to the induction of cyclases and hydroxylases, leading to yellow and red/orange-colored pulp phenotypes. Moreover, the production of volatile terpene linalool, an important biological marker for papaya's sensorial quality, is also induced by ethylene. All these mentioned processes are related to papaya's sensorial and nutritional quality. We describe the understanding of ethylene-triggered events that influence papaya quality and nutritional traits, as these characteristics are a consequence of an accelerated metabolism during fruit ripening.

Comparative Evaluation of the Antioxidant Capacities, Organic Acids, and Volatiles of Papaya Juices Fermented by Lactobacillus acidophilus and Lactobacillus plantarum

Fermentation of foods by lactic acid bacteria is a useful way to improve the nutritional value of foods. In this study, the health-promoting effects of fermented papaya juices by two species, Lactobacillus acidophilus and Lactobacillus plantarum, were determined. Changes in pH, reducing sugar, organic acids, and volatile compounds were determined, and the vitamin C, total phenolic content, and flavonoid and antioxidant capacities during the fermentation process were investigated. Juices fermented by Lactobacillus acidophilus and Lactobacillus plantarum had similar changes in pH and reducing sugar content during the 48 h fermentation period. Large amounts of aroma-associated compounds and organic acids were produced, especially lactic acid, which increased significantly (p<0.05) (543.18 mg/100 mL and 571.29 mg/100 mL, resp.), improving the quality of the beverage. In contrast, the production of four antioxidant capacities in the fermented papaya juices showed different trends after 48 hours’ fermentation by two bacteria. Lactobacillus plantarum generated better antioxidant activities compared to Lactobacillus acidophilus after 48 h of fermentation. These results indicate that fermentation of papaya juice can improve its utilization and nutritional effect.

GC-MS profiling, descriptive sensory analysis, and consumer acceptance of Costa Rican papaya (Carica papaya L.) fruit purees

Volatiles of papaya purees from four Costa Rican cultivars were analysed by solid-phase microextraction and gas chromatography-mass spectrometry. A total of 83 volatiles was assigned in the purees, of which 19 were detected for the first time as papaya constituents. As revealed by multivariate statistics, i.e., principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), the purees may be allocated to terpene- and lactone-rich ('SH-5'), ester-containing ('Criolla'), and intermediate chemotypes ('Pococí' and 'Silvestre'). Descriptive sensory analysis and a consumer acceptance test were additionally performed. Floral, fruity, and honey-like notes were perceived at significantly higher intensities in 'SH-5' puree. The latter descriptors strongly correlated with volatiles discriminating 'SH-5' in the PCA and PLS-DA, respectively. Consumer acceptance of the papaya purees differed significantly. 'Pococí' and 'SH-5' purees appear to be suitable for improving the nutritional value of blended fruit juices without impairing their sensory quality.

Optimization of headspace solid phase micro-extraction of volatile compounds from papaya fruit assisted by GC-olfactometry

Optimization of the extraction conditions to investigate the volatile composition of papaya fruit involving headspace solid phase micro-extraction was carried out using multivariate strategies such as factorial design and response surface methodology. The performance of different combinations of time for reaching the equilibrium in the headspace and time for maximum extraction of volatiles was evaluated by GC-olfactometry of the extract (intensity of papaya characteristic aroma), number of peaks and total area in the chromatogram. Thirty-two compounds were identified by GC-MS under the optimized extraction conditions, the majority of which were aldehydes, both in number of compounds and area. Major compounds were δ-octalactone, β-citral, benzaldehyde, heptanal, benzyl isothiocyanate, isoamyl acetate, γ-octalactone, (E)-linalool oxide and benzyl alcohol. Seven aldehydes and two other compounds are reported for the first time in papaya's volatile profile.

p-Coumaric acid and its conjugates: dietary sources, pharmacokinetic properties and biological activities

p-Coumaric acid (4-hydroxycinnamic acid) is a phenolic acid that has low toxicity in mice (LD50 = 2850 mg kg(-1) body weight), serves as a precursor of other phenolic compounds, and exists either in free or conjugated form in plants. Conjugates of p-coumaric acid have been extensively studied in recent years due to their bioactivities. In this review, the occurrence, bioavailability and bioaccessibility of p-coumaric acid and its conjugates with mono-, oligo- and polysaccharides, alkyl alcohols, organic acids, amine and lignin are discussed. Their biological activities, including antioxidant, anti-cancer, antimicrobial, antivirus, anti-inflammatory, antiplatelet aggregation, anxiolytic, antipyretic, analgesic, and anti-arthritis activities, and their mitigatory effects against diabetes, obesity, hyperlipaemia and gout are compared. Cumulative evidence from multiple studies indicates that conjugation of p-coumaric acid greatly strengthens its biological activities; however, the high biological activity but low absorption of its conjugates remains a puzzle. © 2015 Society of Chemical Industry.