In this study, lipase-producing lactic acid bacteria (LAB) were isolated from traditional fermented foods and screened for their growth characteristics and lactone-producing ability in a fast-ripened cheese slurry model. The selected strains were used as an adjunct starter culture for making Cheddar cheese. Sensory evaluation and gas chromatography-mass spectrometry (GC-MS) were used to compare changes in the flavor and lactone content of Cheddar cheese made with and without an adjunct starter during ripening at 4, 10 or 14 ℃ for up to 150 days. The results showed that Pediococcus acidilactici 4D and Lactococcus garvieae Y3, two strains with the ability to produce lipase, exhibited better lactone production performance. Sensory evaluation showed that compared with Cheddar cheese without adjunct starter, the cheese added with P. acidilactici 4D had the highest milky and fruity aroma intensity after 90 days of ripening at 10 and 14 ℃, respectively. The cheese added with L. garvieae Y3 showed the highest milky aroma intensity after 120 days of ripening at 14 ℃. Four lactones were identified by GC-MS. The contents of δ-decalactone and δ-dodecalactone in Cheddar cheese with P. acidilactici 4D or L. garvieae Y3 were higher than those in Cheddar cheese without adjunct starter at all three ripening temperatures, and both strains could promote the formation of δ-octolactone. In addition, γ-butyrolactone was identified only in Cheddar cheese fermented by L. garvieae Y3. By exploring the effects of ripening temperature and time on the formation of lactones, it was found that the optimal ripening temperature was 14 ℃. The total lactone content of cheese added with P. acidilactici 4D reached the highest level at 90 days of ripening, while that with L. garvieae Y3 reached the highest level at 120 days.

This study systematically investigated the difference in flavor between commercial western sour cream and Inner Mongolian sour cream by the combined use of physicochemical analysis, sensory evaluation, gas chromatographymass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), and electronic nose. The results demonstrated that Inner Mongolian sour cream exhibited significantly higher acidity, fat content, and total volatile compound content than western sour cream (P < 0.05). Sensory evaluation revealed that western sour cream possessed a stronger milky aroma and higher overall acceptability. Volatile compound analysis indicated that the major flavor substances in Inner Mongolian sour cream were acids, alcohols, and esters, whereas those in western sour cream were acids and ketones. Nine key differential flavor compounds were identified based on odor activity values (OAV > 1) combined with variable importance in projection (VIP) values. Partial least squares regression demonstrated that ketones were significantly positively correlated with milky aroma and overall acceptability (P < 0.05), serving as the core flavor compounds contributing to the characteristic milky aroma and consumer preference of western sour cream. In contrast, the high concentration of acids in Inner Mongolian sour cream was associated with undesirable sensory attributes. This research provides theoretical and technical references for the flavor improvement, product development, and quality enhancement of Inner Mongolian sour cream.

A series of biochemical reactions triggered by microorganisms and their metabolic enzymes during fruit wine fermentation play an important role in flavor formation. However, there are still some problems restricting the development and quality improvement of fruit wine such as imperfect biological regulation methods and unclear understanding of the flavor formation mechanism. In this paper, the types and synthetic pathways of aroma compounds in various fruit wines are described, and the contribution of flavor precursors and microbial fermentation to the aroma compounds of fruit wines are clarified. This review is focused on the changes of aroma compounds during fermentation and the mechanism of the effect of microorganisms and enzymes on fruit wine flavor from the perspective of biological regulation. In addition, the effects of starter cultures, fermentation methods, microbial enzyme production and activities on the formation of the aroma of fruit wine are analyzed and the relationship of wine flavor with microorganisms and enzymes are dissected. In addition, future research hotspots are discussed. We hope that this review will provide a theoretical basis and technical support for flavor regulation of fruit wine.

Condiments are necessary to improve the flavor of foods and are a major source of salt intake for people. Excess salt intake can be a health risk, but reducing salt can reduce the umami and taste of foods, thus reducing product quality. This paper reviews the technical strategies for salt reduction while ensuring saltiness and umami as well as their harmony. The salt reduction strategies include reducing the amount of salt, using salt substitutes and enhancing saltiness perception. The umami enhancement strategies include adding yeast extracts, umami peptides, umami amino acids and peptide derivatives. Besides, salt reduction and umami enhancement can be achieved by using lactic acid bacteria, Maillard reaction intermediates, flavor enhancers and taste-active peptides. The application of the salt reduction and umami enhancement strategies will promote the development of the condiment industry, but these strategies have the problems of insufficient basic research, few practical applications, narrow application scope and high production cost. At present, it is difficult to solve these problems. In this paper, the basic principles and characteristics of the strategies for salt reduction and umami enhancement in condiments and the current problems existing in this field of research are reviewed in detail. Future development directions are put forward in order to provide a reference for research on salt reduction and umami enhancement of condiments.

Cyclodextrin, which has a unique “outer hydrophilic and inner hydrophobic” structure, can be used as an excellent carrier to protect volatile bioactive compounds that are susceptible to oxidative degradation for improved solubility, stability, and bioavailability. In this paper, we summarize the structures and properties of cyclodextrins and elucidate their inclusion mechanism with respect to the interactions between the host cyclodextrins and guest molecules and the factors influencing them including the inclusion reaction between cyclodextrin monomers and guests, the self-assembly behavior of cyclodextrin monomers, and the inclusion mechanism between the supramolecular system formed by this self-assembly behavior and guest molecules. Then, the mechanism for the interface stability of cyclodextrins in the presence and absence of surfactants and the mechanism by which composite emulsifiers formed from the self-assembly of cyclodextrins with a surfactant stabilize guests. Finally, the release mechanism and the kinetic models of sustained release of guest molecules from inclusion complexes of cyclodextrins as well as the factors affecting them are elucidated, and future research prospects of cyclodextrins in the supramolecular field are discussed in order to provide a reference for follow-up research.

Flavor substances play an important role in foods, but their stability is poor, and they are susceptible to external environments, causing their loss or deterioration. The application of encapsulation and controlled release can effectively improve the stability and release characteristics of flavor substances. Cellulose-based materials are widely used in the encapsulation and controlled release of flavor substances as wall materials, material reinforcing phases or interfacial stabilizers due to their wide range of sources and excellent properties. This article summarizes the classification of cellulose-based materials, the characteristics of flavor encapsulation technology, the interaction between cellulose-based materials and flavor substances and the mechanism and regulatory strategies of flavor release, and discusses recent trends and future prospects for the application of cellulose-based materials in the encapsulation and controlled release of flavor compounds, which will provide a theoretical reference for the application of cellulose-based materials in sustained and controlled release of flavor compounds.

Food flavor is an important factor which affects consumer purchase intention, and the formation of flavor perception is affected by multiple senses such as olfactory and gustatory sense. The application of the interaction between odor and taste in food flavor improvement has become one of the most concerned new directions of food flavor regulation. On this basis, this paper analyzes the main formation pathway and mechanism of the cross-modal perceptual interaction between odor and taste from the neurobiological perspective, and summarizes the main methods used to research the cross-modal perceptual interaction from the aspects of static sensory analysis and dynamic sensory analysis. Finally, the effects of odor substances on taste perception (sweet, salty, bitter, umami and sour) and the effects of taste substances on olfactory perception are reviewed based on relevant literature and cases, in order to provide new ideas for the regulation of flavor quality during food processing.

The difference in the volatile flavors of five different Chinese acid-curd cheeses including milk fan, milk cake, Qula (yak milk cheese), Hurood cheese and milk knot was analyzed by sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS). The results of sensory evaluation showed that the five cheeses had a significant difference in flavor. Among them, dairy fan, with strong milky, fruity and bread-like aromas, had the best overall aroma performance and the highest preference score. The combination of GC-IMS and GC-MS expanded the detection range of volatile flavor compounds, and could more comprehensively reflect the volatile compounds in different Chinese acid-curd cheeses. The sensory evaluation results were verified by GC-IMS analysis. All five samples had their own characteristic peak areas, and the characteristic peak areas of dairy fan and Qula were significantly larger than those of the other samples. GC-MS analysis showed that the proportion of acids in dairy fan, Hurood cheese and Qula was the highest, the proportion of esters in milk cake was the highest, and the proportion of alcohols in milk knot was the highest. The calculation of odor activity value (OAV) combined with the results of principal component analysis (PCA) showed that ethanol, ethyl butyrate, ethyl caproate, 2-heptanone and δ-caprylactone were the major contributors to the flavor of dairy fan. Phenethyl formate, phenethyl acetate, caprylic acid, lauric acid and n-decanoic acid were the major contributors to the flavor of Qula. Dodecyl aldehyde was identified as the characteristic flavor compound of dairy cake. Partial least squares analysis (PLSA) revealed the correlation between aroma properties and volatile flavor compounds. Dairy fan has the potential to be developed and promoted in China because of its excellent flavor and consumer preference.

Grain and oil products, the most basic materials for human survival, are subject to various factors such as temperature, moisture, oxygen and microorganisms, triggering a series of biochemical reactions which can cause the generation of off-flavors such as sour and rancid odor. Clarifying the types and formation mechanism of rancid odor compounds and regulating them can help greatly improve the quality of grain and oil products. This article summarizes the key volatile compounds contributing to rancid odor produced during the storage and processing of grain and oil products, and clarifies their formation mechanisms from three aspects: lipid hydrolysis and oxidation, protein oxidative aggregation and the interaction between volatile and non-volatile compounds. Furthermore, the control measures to remove or mask the rancid odor are reviewed. The removal methods mainly include biological breeding and improvement, new storage and preservation technologies, traditional and emerging processing techniques and chemical methods; the masking methods include encapsulation technology based on host-guest interaction, aroma enhancement with exogenous enzymes and the addition of exogenous aroma enhancing ingredients. This paper can provide a theoretical reference and technical support for rancid odor control and flavor quality improvement of grain and oil products.

Raw almonds are rich in aldehydes, alcohols and other odorants contributing to fresh fruity and hay-like aromas. The flavor of almonds can change significantly due to various chemical reactions during thermal processing and storage, which can greatly affect its flavor quality. In this context, this review summarizes the major aroma compounds in raw almonds and the major aroma compounds formed by the Maillard reaction, the oxidation of fatty acids, and the degradation of amino acids and soluble sugars in roasted almonds, and it compares the effects of different thermal processing methods and conditions on the aroma compounds and aroma properties of almonds. In addition, this review summarizes the changes of the major aroma compounds and off-odor compounds in almonds during storage and the rational storage methods and conditions. Finally, possible future directions for research on almonds and other nuts are outlined. This review could provide a theoretical basis and reference for flavor quality control of almonds and other nuts during thermal processing and storage.