Volatile Organic Compound Detection by Graphene Field-Effect Transistors Functionalized with Fly Olfactory Receptor Mimetic Peptides

An olfactory receptor mimetic peptide-modified graphene field-effect transistor (gFET) is a promising solution to overcome the principal challenge of low specificity graphene-based sensors for volatile organic compound (VOC) sensing. Herein, peptides mimicking a fruit fly olfactory receptor, OR19a, were designed by a high-throughput analysis method that combines a peptide array and gas chromatography for the sensitive and selective gFET detection of the signature citrus VOC, limonene. The peptide probe was bifunctionalized via linkage of a graphene-binding peptide to facilitate one-step self-assembly on the sensor surface. The limonene-specific peptide probe successfully achieved highly sensitive and selective detection of limonene by gFET, with a detection range of 8-1000 pM, while achieving facile sensor functionalization. Taken together, our target-specific peptide selection and functionalization strategy of a gFET sensor demonstrates advancement of a precise VOC detection system.

Headspace volatolome of peel flours from citrus fruits grown in Brazil

Citrus fruit peel comprises a pleasant mix of volatile compounds together with fibers, nutrients, and bioactive compounds. Therefore, it has great potential for use as a food ingredient. Studies evaluating the volatile composition of citrus peel flours are limited for most citruses. The goal of this study was to characterize, by HS-SPME/GC-MS, the volatile profile of citrus peel flours made from fruits commonly grown in Brazil. Two composite samples of ten types of citrus peel flours from consecutive harvests were evaluated. 69 volatile compounds were assigned, 49 in Tahiti acid lime, 49 in Sicilian lemon, 37 in Persian lime, 34 in Italian tangerine and oval kumquat, 33 in Valencia orange, 32 in Baia orange and round kumquat, 28 in Blood-of-Mombuca orange and 26 in Lima orange. 26 major compounds represented 93-99% of the total chromatogram peak area. Terpenic compounds were predominant in all samples, especially monoterpenes (about 48-97% of the total chromatogram peak area), while lower proportions of aldehydes (0.2-16.1%), monoterpene alcohols (0.4-11.8%) and esters (0.0-7.7%) were observed. Even though a few compounds like limonene, β-myrcene, linalool, α-pinene and valencene were detected in all citrus, volatile compounds followed specific patterns in the different citruses, with a clear distinction among them, especially between lemon flours and the remaining flours. The variety of volatile profiles and singular specific volatolomic signatures in citrus peels can be explored for different applications related to food flavoring and preservation, and promotion of good health. These aspects should be thoroughly investigated in future studies.

Molecular Insights into the Effects of Rootstocks on Maturation of Blood Oranges

Rootstock choice has important effects on the horticultural and pathological traits of the citrus cultivars. Thus, the scion/rootstock combination can affect tree vigour, nutrition, and stress resistance; it can also have positive influences on the fruit quality traits. Although the study of rootstock effects has been a relevant research topic in citrus for many years, the main body of such study has been conducted at the biochemical level, while little effort has been directed to the determination of the rootstock influences at the molecular level. A comparative study of three combinations of scion and rootstock shows a positive correlation between the regulation of the fruit quality-related genes and the accumulations of bioactive compounds, as well as with acid degradation. Monitoring the anthocyanin accumulation during ripening shows the scion/rootstock combination can increase anthocyanin synthesis in the fruit, as well as vitamin C accumulation and acid degradation. Our results show that the rootstock genotype can exert important influences on citrus fruit quality by affecting gene expression in the scion. New insights into the molecular interactions between scion and rootstock may help unravel the systems through which rootstocks exert their influences on the regulatory networks in the scion, so as to influence relevant agronomic traits. This information should result in an improved rootstock breeding selection and definition of scion/rootstock combinations to enhance fruit quality traits.

Application of accelerating energies to the maceration of sherry vinegar with citrus fruits

BACKGROUND

In the present work we propose the use of accelerating energies (microwaves and ultrasounds) to the maceration process of sherry vinegar with citrus fruit peels (orange and lemon). For the application of microwaves, an experimental design has been developed in order to optimize the maceration conditions. To evaluate the effect of these energies on the maceration, the volatile and polyphenolic content of the samples has been analyzed, as well as their sensory characteristics.

RESULTS

Orange peel provided a higher number of volatile and polyphenolic compounds to the vinegar, while lemon's yielded a greater amount of some of them. The multivariate analysis showed that the samples macerated using microwaves were the most similar to the samples macerated in the traditional way. This aspect was corroborated by the sensory analysis, which was more noticeable when orange peel was used in the macerations.

CONCLUSION

Therefore, it seems that the use of microwaves to accelerate maceration is a good alternative to the traditional method of making sherry vinegars macerated with citrus peel, since it cuts down the maceration time from 3 days to just a few minutes. © 2020 Society of Chemical Industry.

Volatile Profile in Different Aerial Parts of Two Caper Cultivars (Capparis spinosa L.)

This research presents, for the first time, full volatile profiles of four aerial parts of caper plants (Capparis spinosa L.) from southeastern Spain. Volatile compounds in caper leaves and stems (together), flowers, flower buds, and fruits from two cultivars were identified and quantified using headspace-solid phase microextraction (HS-SPME) and gas chromatography with a mass spectrometry detector (GC-MS). Forty-three volatile compounds were identified in the caper shoots, 32 in caper flowers, with only 18, 10, and 6 compounds being found in flower buds, leaves, and fruits, respectively. The predominant compound in all studied materials was methyl isothiocyanate, with nerolidol, trans-2-hexenal, and nonanal playing key roles in flowers, leaves, and flowers buds, respectively. The two studied cultivars had the same volatile compounds but at very different concentrations, although the two studied cultivars are cultivated under the same climatic and agronomic conditions. Additionally, the predominant compounds, especially methyl isothiocyanate (6882 mg·kg−1 fw in flower buds of ORI 3 cultivar), can be separated and concentrated for future applications in food technology.

How a Spanish Group of Millennial Generation Perceives the Commercial Novel Smoothies?

The World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) constantly emphasize the importance of increasing fruit and vegetable consumption; these natural products help in the prevention of major diseases. Smoothies are a simple and convenient way of doing so; thus, their demand is constantly growing and their market is becoming important for the food industry. Therefore, the objective of this research was to determine Millennial consumer opinion towards novel fruit- and vegetable-smoothies available on the retail market. Napping^®, descriptive sensory analysis, and consumer studies were conducted. Napping^® results group samples into four clusters of smoothies; the main grouping factor was the type of fruit and the percentage of vegetables. Penalty analysis showed that smoothies need improvement mainly dealing with sweetness, bitterness, and vegetable flavors. Millennial consumers formed a homogeneous sensory group in which the overall liking was negatively correlated with the level of sweetness, and earthy, carrot, beetroot, and pear flavors. The key liking drivers were sourness and notes of mango, banana, and peach flavors. This research is a new insight into the perception of smoothies, provides comprehensive knowledge for the food industry, and can guide the design of new healthy smoothies.

Determination of the Volatile Profile of Lemon Peel Oils as Affected by Rootstock

Citrus limon (L.) Burm is an important crop that grows between latitudes 30° North and 30° South, the main producers being China, the USA, Mexico, India, Brazil, and Spain. In Spain, lemon grows mainly in Mediterranean areas such as Murcia, Valencia, and Andalucía. The most cultivated varieties are “Fino” and “Verna”. In this study, five varieties of lemon, “Verna”, “Bétera”, “Eureka”, “Fino 49”, and “Fino 95” were evaluated on different rootstocks: three new Forner-Alcaide (“FA13”, “FA5”, “FA517”), Citrus macrophylla, Wester, and Citrus aurantium L. Hydrodistillation was used to obtain essential oil from fresh peels and then the volatile profile was studied by gas chromatography-mass spectrometry (GC-MS). A total of 26 volatile compounds were identified, limonene being the main one followed by β-pinene, γ-terpinene, sabinene, and α-pinene. The results revealed that Forner-Alcaide rootstocks (“FA5” > “FA517” > “FA13”) proved to be the best rootstocks for the aroma quality as they led to high volatile contents, followed by C. aurantium and C. macrophylla. Among the other varieties, the most aromatic one was “Eureka”. The whole trend was as follows (in decreasing order): “Eureka” > “Bétera” > “Fino 95” > “Verna” > “Fino 49”.