Comparative analysis of aroma compounds in French fries and palm oil at three crucial stages by GC/MS-olfactometry, odor activity values, and aroma recombination

Exploring potential correlations between bacterial communities, organic acids, and volatile metabolites of traditional fermented sauerkraut collected from different regions of Heilongjiang Province in Northeast China

In this study, the bacterial communities and flavor metabolites of 27 traditional naturally fermented sauerkraut samples collected from nine regions of Heilongjiang Province in Northeast China were investigated. The dominant genera were Lactobacillus, Pseudomonas, Alcaligenes, Arcobacter, Pseudarcobacter, Lactococcus, Comamonas, Pediococcus, Prevotella, and Insolitispirillum. A total of 148 volatile compounds were detected in seven categories; esters and acids were the most abundant volatiles. Additionally, the highest content (15.96 mg/g) of lactic acid was detected in YC1. Acetic acid, oleic acid, palmitic acid, elaidic acid, and dehydroacetic acid were the key differential volatile compounds, which may be related to the bacterial communities. Spearman's correlation analysis revealed that Lactococcus and Lactobacillus were significantly positively correlated with flavor metabolites, suggesting that they may play a more significant role in flavor formation. The results of this study can help in the development of better quality of fermented vegetables.

Effects of processing procedures on the formation of aroma intensity and odor characteristic of Benshan tea (Oolong tea, Camellia sentences)

Benshan tea is a kind of oolong tea, and Benshan (Camellia sinensis) tea tree originates from Anxi County of Fujian Province in China, which is a national tea tree breed. Tea processing is the key to the formation of its odor characteristics. It is extremely important to step by step analyze effects of tea processing on aroma intensity and the formation of odor characteristics for optimizing tea processing process and improving tea quality. The results of this study showed that processing resulted in a significant increase in the content of volatile compounds in tea leaves, i.e., from 25.213 μg/kg to 111.223 μg/kg, in which the volatile compounds were mainly terpenoids. Secondly, the analysis found that 20 kinds of key compounds constituted to odor characteristics of Benshan tea leaves, among which geraniol, trans-β-ionone, gerol, citronellol, benzeneacetaldehyde, and trans-nerolidol were the most key six. Floral and fruity aromas, especially floral aroma, mainly formed odor characteristics of Benshan tea after processing, while floral aroma mainly came from the contribution of geraniol, which was the foremost compound in the formation of floral aroma of Benshan tea.

Characterization of physical properties, volatile compounds and aroma profiles of different salted egg yolk lipids

Salted egg yolks (SEY) have a desirable and unique flavor with multiple underlying applications in food processing, and their abundant lipids contribute to a creamy and pleasant aroma. However, it is important to maintain the stability of the SEY flavor, which depends to a large extent on the egg species and the processing method. This study aimed to extract different SEY lipids with conventional solvents, analyze the fatty acid composition, and screen the volatile compounds to elucidate the flavor differences between salted hen eggs and duck eggs. Compared to ethanol extraction, acetone-extracted lipids had lower acid value and viscosity, and almost had no phospholipid content. Fatty acid analysis revealed that the highest content of fatty acid in SEY lipids was oleic acid, followed by palmitic acid and linoleic acid, while there were significant variations of different SEY lipids in the fatty acid profiles. The volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the overall odor was detected by the electronic nose (E-nose). A total of 27 volatile compounds were analyzed in SEY lipids and divided into 8 chemical classes. The aldehydes, furans and pyrazines were decreased, and the hydrocarbons were increased compared with untreated SEY. The combination of the physical properties and flavor evaluation of SEY lipids could provide a theoretical basis for the extension of the characteristic flavor matrix in SEY.

Effect of processing on aroma intensity and odor characteristics of Shuixian (Camellia sinensis) tea

Processing is extremely important for the formation of aroma characteristic of tea leaves. In this study, the effects of processing on the content of volatile compounds, aroma intensity and odor characteristic of Shuixian tea were analyzed. The results showed that the content of volatile compounds in Shuixian tea increased significantly after processing, among which terpenoids and esters were the highest. There were 18 key compounds constituting the aroma characteristics of Shuixian tea, among which geraniol and nerol were the most important compounds, which contributed 96.28% to the aroma of Shuixian tea. The odor characteristics of Shuixian tea were mainly floral and fruity and the contribution of floral mainly came from geraniol, while fruity mainly came from nerol. Geraniol and nerol compounds increased rapidly after the withering process of tea leaves. This study provided an important reference for the improvement of processing technology and quality enhancement of Shuixian tea.

Comparative characterization of key odorants and aroma profiles of fragrant rapeseed oil under different roasting conditions

Fragrant rapeseed oil (FRO) produced by typical roasting process is popular for its characteristic aroma. Accordingly, key aroma-active compounds were characterized in FRO by the Sensomics approach and then correlated to the crucial roasting parameters revealed by aroma profile analysis and hierarchical cluster analysis. Nineteen key odorants in FRO were identified and quantified, among which dimethyl trisulfide (OAV, odor active value, 323, cabbage-like, sulfury) and 4-isothiocyanato-1-butene (OAV, 88, pungent) were the most important aroma-active compounds in FRO and showed first rising and then decline trends as the increased roasting temperature and time. The oil under high-temperature-short time and low-temperature-long time conditions imparted similar aroma profiles. On the basis of sensory evaluation, roasting at 160, 170, 180, 190, and 200 °C should not exceed 50, 40, 30, 30, and 30 min, respectively to satisfy consumer preference. All findings provide a reference on industrial FRO production in terms of not only aroma but also sustainability.

A point of view on human fat olfaction - do fatty derivatives serve as cues for awareness of dietary fats?

Fat (triglycerides) consumption is critical for the survival of animals, including humans. Being able to smell fat can be advantageous in judging food value. However, fat has poor volatility; thus, olfaction of fat seems impossible. What about fatty acids that comprise fat? Humans smell and discriminate medium-chain fatty acids. However, no conclusive evidence has been provided for the olfactory sense of long-chain fatty acids, including essential acids such as linoleic acid (LA). Instead, humans likely perceive the presence of essential fatty acids through the olfaction of volatile compounds generated by their oxidative breakdown (e.g., hexanal and γ-decalactone). For some people, such scents are pleasing, especially when they come from fruit. Nonetheless, it remains unclear whether the olfaction of these volatiles leads to the recognition of fat per se. Nowadays, people often smell LA-borne aldehydes such as E,E-2,4-decadienal that occur appreciably, for example, from edible oils during deep frying, and are pronely captivated by their characteristic "fatty" note, which can be considered a "pseudo-perception" of fat. However, our preference for such LA-borne aldehyde odors may be a potential cause behind the modern overdose of n-6 fatty acids. This review aims to provide a view of whether and, if any, how we olfactorily perceive dietary fats and raises future purposes related to human fat olfaction, such as investigating sub-olfactory systems for detecting long-chain fatty acids.

Comprehensive Quality Evaluation for Medicinal and Edible Ziziphi Spinosae Semen before and after Rancidity Based on Traditional Sensory, Physicochemical Characteristics, and Volatile Compounds

To comprehensively evaluate the quality of medicinal and edible Ziziphi Spinosae Semen (ZSS, the dried ripe seeds of Ziziphus jujuba var. spinosa) before and after rancidity during storage, some indicators including traditional sensory properties, physicochemical characteristics, and volatile compounds were analyzed. As a result, compared with the normal samples, the rancid samples of ZSS produced a darker color, a bitter taste, and an irritating odor, increased moisture content, electrical conductivity, fatty oil content, and acid value, and decreased water- and alcohol-soluble extract contents and pH value. Among them, the acid value had significant difference (p < 0.01) from 3.90 of normal ZSS to 18.68 mg/g of rancid ZSS. A total of 39 volatile compounds were identified in samples, including 20 in normal ZSS and 38 compounds in rancid ZSS. Nineteen common compounds were identified in normal and rancid samples. Among them, the content of 10 compounds such as δ-limonene, (R,R)-2,3-butanediol, and (R,S)-2,3-butanediol was decreased but that of nine compounds such as acetic acid, n-octanoic acid, and n-nonanoic acid was increased in rancid ZSS. Nineteen unique compounds such as β-phellandrene, α-pinene, and 3-carene were detected and only one compound, δ-cadinene, was not detected in rancid ZSS. In addition, eight short-chain organic acids, acetic, propanoic, butanoic, pentanoic, hexanoic, heptanoic, octanoic, and nonanoic acids, were new products in rancid ZSS, and it was speculated that the production of a series of organic acids might be the material basis of irritating odor after normal ZSS became rancid. This is the first report that a series of short-chain organic acids have been found in a rancid substance. In conclusion, there was a significant difference between normal and rancid ZSS. These indicators could be used as an early warning for judging the rancidity phenomenon of medicinal and edible ZSS. In addition, this is the first comprehensive evaluation about the rancidity process of a medicinal and edible substance.

Digital Evaluation of Aroma Intensity and Odor Characteristics of Tea with Different Types-Based on OAV-Splitting Method

Aroma is one of the most important quality indicators of tea. However, this evaluation method is a subjective one. In this study, the volatiles of tea with 5 types were determined by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography mass spectrometry (GC-MS). The aroma intensity and odor characteristics of teas were comparatively analyzed based on the OAV-splitting method. The results showed that OAV were green tea (492.02), red tea (471.88), oolong tea (302.74), white tea (68.10), and dark tea (55.98). The odor index I(o) indicated that green tea was strong-flavor tea with highlight green accompanied by fruity, woody and fatty odors; oolong tea was strong-flavor tea with fruity and fatty accompanied by woody, floral and green odors; red tea was strong-flavor tea with highlight fruity accompanied by woody, green and floral odors; white tea was a light-flavor tea with floral, woody and green odors; and dark tea was light-flavor tea with woody and floral notes accompanied by fatty and green odors. These results fitted perfectly with the people’s consensus on these teas, and proved that the OAV-splitting method is feasible to evaluate the aroma intensity and odor characteristics of tea aroma. We suggest that the digital evaluation of tea aroma can facilitate people’s communication.