Quality of sour cherry juice of different clones and cultivars (Prunus cerasus L.) determined by a combined sensory and NMR spectroscopic approach

Flavor Profiling Using Comprehensive Mass Spectrometry Analysis of Metabolites in Tomato Soups

Trained sensory panels are regularly used to rate food products but do not allow for data-driven approaches to steer food product development. This study evaluated the potential of a molecular-based strategy by analyzing 27 tomato soups that were enhanced with yeast-derived flavor products using a sensory panel as well as LC-MS and GC-MS profiling. These data sets were used to build prediction models for 26 different sensory attributes using partial least squares analysis. We found driving separation factors between the tomato soups and metabolites predicting different flavors. Many metabolites were putatively identified as dipeptides and sulfur-containing modified amino acids, which are scientifically described as related to umami or having "garlic-like" and "onion-like" attributes. Proposed identities of high-impact sensory markers (methionyl-proline and asparagine-leucine) were verified using MS/MS. The overall results highlighted the strength of combining sensory data and metabolomics platforms to find new information related to flavor perception in a complex food matrix.

An optimized organic acid human sensory sourness analysis method

BACKGROUND

Sour taste perception builds on both chemical and physiological foundations, and plays an important role in food flavor, including that of fruit, beer, wine, and other beverages. A uniform sourness standard and sourness conversion method for researchers and food enterprises is necessary to obtain uniform conclusions.

RESULTS

This study established an optimized organic acid sensory sourness analysis and sourness conversion method. It is based on sour sensory difference strength curves, which consist of an absolute threshold value and sensory difference threshold values. Defining the absolute threshold value of citric acid sourness as 1, sourness could be calculated according to the curve. With a logarithmic curve form, the acid sourness indexes (AI) were calculated as 1, 0.74, 0.77, 1.31, and 1.21 for citric, malic, fumaric, lactic, and tartaric acid samples, respectively. Consequently, each acid's sourness and concentration could be obtained and converted. Single acid and mixed acid sourness comparison evaluation's result implied that the novel method was more accurate (91.7-100%) than the hydrogen ion concentration method.

CONCLUSION

The novel sourness determination and conversion equation would provide more accurate sourness standard and calculation method in food sensory areas. © 2021 Society of Chemical Industry.

Enzyme-based amperometric biosensors for malic acid - A review

Malic acid is a key flavour component of many fruits and vegetables. There is significant interest in technologies for monitoring its concentration, particularly in winemaking. In this review we systematically and comprehensively chart progress in the development of enzyme-based amperometric biosensors for malic acid. We summarise the components and analytical parameters of malic acid sensors that have been reported over the past four decades, discussing their merits and pitfalls in terms of accuracy, sensitivity, linear range, response time and stability. We discuss how advances in electrode materials, electron mediators and the use of coupled enzymes have improved sensitivity and minimised interference, but also uncover a trade-off between sensitivity and linear range. A particular focus of our review is the three types of malate oxidoreductase enzyme that have been used in malic acid biosensors. We describe their different properties and conclude that identifying and/or engineering superior alternatives will be a key future direction for improving the commercial utility of malic acid biosensors.

Amino Acid Profile of Fruits as Potential Fingerprints of Varietal Origin

This study aims to assess the capability of the ¹H-NMR profiling of fruits from different genera in combination with multivariate data analysis to provide feasible information for fruit juices’ authenticity in terms of botanical origin. Nine fruit varieties from four genera were selected for the experimental plan. The juice obtained from the fruits was characterized using the ¹H-NMR technique, selecting the obtained amino acid profile of fruits as a potential specific fingerprint. Due to the complex information provided by the NMR spectra, a chemometric approach of the data was further applied to enable the differentiation of the fruit samples, highlighting thus its suitability as a discrimination tool for the varietal origin. The advantage of this analytical approach is given by the relatively simple working procedure, which consists of an easy, fast, and accessible preparation stage while providing complex information on fruit composition.

Quality and Sensory Study of Fresh Sour Cherry Juices Upon Cultivar, Growing Area and Weather Conditions

Freshly squeezed sour cherry (Prunus cerasus L.) juices of Maraska Brač (BR), Maraska MA (MA), Oblačinska 18 (18), Oblačinska Osječka (OS), Rexelle (REX), Heimann conserved (HEI), and Kelleris 16 (KEL) grown in different climate regions (Mediterranean and continental) in two consecutive harvest years were analyzed for quality and sensory properties. Obtained results showed that investigated sources of variation (cultivar, growing area, harvest year) significantly influenced physical, chemical, and sensory properties of tested juices. All juices had high soluble solids (SS) (17.26% to 25.89%), especially BR (24.19%), MA (25.89%), 18 (24.66%), and OS (23.61%). Juices also had considerable total phenols (TP) content (2.19 to 5.87 mg GAE ml^-1 ) and antioxidant capacity (AC) (0.020 to 0.045 mmol TE mL^-1 ) with BR, MA, REX, and HEI containing the highest amounts of bioactive compounds (BR = 5.87 mg GAE mL^-1 , MA = 5.68 mg GAE mL^-1 , REX = 4.42 mg GAE mL^-1 , HEI = 4.27 mg GAE mL^-1 ). Sensory evaluation showed that all juices had satisfying sensory profiles with BR, MA, 18, OS, and KEL juices scoring particularly high (5.3 to 8.9 of 10) in desirable sensory properties (color intensity [CI], sour cherry taste [SCT], harmonious taste [HT], taste fullness [TF], sour cherry odor [SCO], and viscosity [V]) of fresh sour cherry cloudy juice. Juices from Mediterranean area achieved higher values for SS, pH, SS/TA ratio, TP, AC, SCT, HT, TF, SCO, and V compared to continental zone juices. Harvest year with higher temperatures and less rainfall also resulted in higher SS, pH, TP, and AC as well as stronger expression of desirable sensory properties. PRACTICAL APPLICATION: The results of this study provide an insight into sour cherry potential for use in functional food products, including today's popular smoothies, since it is fruit rich with health contributing compounds and possesses desirable sensory characteristics (color intensity, sour cherry taste, harmonious taste, taste fullness, sour cherry odor, and viscosity) at the same time, which can differ due to cultivar, climate diversity as well as weather conditions.

Quality and Authenticity Control of Fruit Juices-A Review

Food fraud, being the act of intentional adulteration of food for financial advantage, has vexed the consumers and the food industry throughout history. According to the European Committee on the Environment, Public Health and Food Safety, fruit juices are included in the top 10 food products that are most at risk of food fraud. Therefore, reliable, efficient, sensitive and cost-effective analytical methodologies need to be developed continuously to guarantee fruit juice quality and safety. This review covers the latest advances in the past ten years concerning the targeted and non-targeted methodologies that have been developed to assure fruit juice authenticity and to preclude adulteration. Emphasis is placed on the use of hyphenated techniques and on the constantly-growing role of MS-based metabolomics in fruit juice quality control area.

A new sensory sweetness definition and sweetness conversion method of five natural sugars, based on the Weber-Fechner Law

This study's aim is to establish a new sensory sweetness definition and conversion method for five sugars. A "closed-type" question based on triangle test and paired comparison was used for sensory evaluation. The absolute threshold and nine sensory difference threshold values were determined and used to generate a sweet sensory difference strength curve. Defining absolute threshold of sucrose sweetness as 1, the sucrose sweetness at any concentration could be calculated via the curve. After taking the logarithm of each curve, sweetness index was calculated as 1, 1.12, 0.94, 1.29, and 1.25 for sucrose, glucose, fructose, lactose and maltose, respectively. Based on this, each sugar concentration and sweetness could be converted and calculated. Single sugar and mixed-sugars sweetness comparison experiments verified the new sweetness index and sweetness values were more accurate (83.3-100%) than those reported in previous studies. Therefore, this new definition and conversion method established more reliable references for sweet taste sensory applications.

Nuclear Magnetic Resonance (NMR) Spectroscopy in Food Science: A Comprehensive Review

Nuclear magnetic resonance (NMR) spectroscopy is a robust method, which can rapidly analyze mixtures at the molecular level without requiring separation and/or purification steps, making it ideal for applications in food science. Despite its increasing popularity among food scientists, NMR is still an underutilized methodology in this area, mainly due to its high cost, relatively low sensitivity, and the lack of NMR expertise by many food scientists. The aim of this review is to help bridge the knowledge gap that may exist when attempting to apply NMR methodologies to the field of food science. We begin by covering the basic principles required to apply NMR to the study of foods and nutrients. A description of the discipline of chemometrics is provided, as the combination of NMR with multivariate statistical analysis is a powerful approach for addressing modern challenges in food science. Furthermore, a comprehensive overview of recent and key applications in the areas of compositional analysis, food authentication, quality control, and human nutrition is provided. In addition to standard NMR techniques, more sophisticated NMR applications are also presented, although limitations, gaps, and potentials are discussed. We hope this review will help scientists gain some of the knowledge required to apply the powerful methodology of NMR to the rich and diverse field of food science.

A Broad-Spectrum Sweet Taste Sensor Based on Ni(OH)₂/Ni Electrode

A broad-spectrum sweet taste sensor based on Ni(OH)₂/Ni electrode was fabricated by the cyclic voltammetry technique. This sensor can be directly used to detect natural sweet substances in 0.1 M NaOH solution by chronoamperometry method. The current value measured by the sensor shows a linear relationship with the concentration of glucose, sucrose, fructose, maltose, lactose, xylitol, sorbitol, and erythritol (R² = 0.998, 0.983, 0.999, 0.989, 0.985, 0.990, 0.991, and 0.985, respectively). Moreover, the characteristic value of this sensor is well correlated with the concentration and relative sweetness of eight sweet substances. The good correlation between the characteristic value of six fruit samples measured by the sensor and human sensory sweetness measured by sensory evaluation (correlation coefficient = 0.95) indicates that it can reflect the sweetness of fruits containing several sweet substances. In addition, the sensor also exhibits good long-term stability over 40 days (signal ratio fluctuation ranges from 91.5% to 116.2%). Thus, this broad-spectrum sensor is promising for sweet taste sensory application.

1H-NMR-based metabolomic profiles of different sweet melon (Cucumis melo L.) Salento varieties: Analysis and comparison

Melon (Cucumis melo L.) is a significant source of substances able to provide human health benefits. From the 18th century in the Salento area (Apulia region), the cultivation of melon varieties (C. melo L.) has always been intense. Over the years, the production of this fruit has involved a large number of selected and preserved varieties in the different local districts. Unfortunately, most of the characteristics of locally grown vegetable varieties do not match the food industry requirements. Moreover, the agricultural land abandon leads these varieties to quickly disappear, thus affecting the intraspecific biodiversity. In order to characterize the inter-variety diversity of sweet melon (C. melo L. ssp. melo group inodorus) and the potential differences in the nutritional quality of fruits, a first investigation on the juice of five sweet melon varieties (locally known as "allungato", "scurzune", "egiziano", "minna de monaca", "pinto"), cultivated exclusively in the Salento area, was performed by ¹H-NMR spectroscopy and Multivariate Analysis (MVA). The analysis grouped the samples into clusters according to the different variety. Interestingly, a different sugar (mono and disaccharides) content was observed among the grouped varieties, being sweetness the main characteristic of sweet melon quality and taste. A relative higher accumulation of monosaccharides (α-d and β-d glucose and α/β-d fructose) was found, in particular for the "minna de monaca" with respect to "allungato", "egiziano" and "pinto" varieties. Moreover, a marked high content of polyphenols and aromatic aminoacids as phenylalanine and tyrosine characterize the "allungato", "minna de monaca" and "pinto" varieties. An NMR-based metabolomic approach was used for the first time to describe these local landraces. This method may integrate other actions in order to achieving a reduction in the current rate of erosion of the biodiversity of Apulian horticultural species.

Recent developments in the food quality detected by non-invasive nuclear magnetic resonance technology

Nuclear magnetic resonance (NMR) is a rapid, accurate and non-invasive technology and widely used to detect the quality of food, particularly to fruits and vegetables, meat and aquatic products. This review is a survey of recent developments in experimental results for the quality of food on various NMR technologies in processing and storage over the past decade. Following a discussion of the quality discrimination and classification of food, analysis of food compositions and detection of physical, chemical, structural and microbiological properties of food are outlined. Owing to high cost, low detection limit and sensitivity, the professional knowledge involved and the safety issues related to the maintenance of the magnetic field, so far the practical applications are limited to detect small range of food. In order to promote applications for a broader range of foods further research and development efforts are needed to overcome the limitations of NMR in the detection process. The needs and opportunities for future research and developments are outlined.

Metabolic profile comparison of fruit juice from certified sweet cherry trees (Prunus avium L.) of Ferrovia and Giorgia cultivars: A preliminary study

Sweet cherries are widely appreciated for fresh consumption as well as for production of juices, jams, jelly fruits and alcoholic beverages. The sweet cherry intake (as fresh fruit and related products) is extensively encouraged for their taste and nutritional qualities, due to the presence of water-soluble (C, B) and fat-soluble (A, E and K) vitamins, carotenoids, polyphenols and minerals, as well as glucose and fructose. However the market often endorses the consumption of a particular sweet cherry cultivar (as for most of vegetables) essentially for organoleptic and/or external appearance rather than nutraceutical qualities. In order to evaluate the potential difference in the nutritional quality of fruits, 56 sweet cherry juice samples from certified trees (Prunus avium L.) of two cultivars (30 from Ferrovia and 26 from Giorgia), grown in the same pedoclimatic Apulian region, were analyzed by ¹H NMR spectroscopy and Multivariate Analysis (MVA). Interestingly, despite the usually lower commercial value with respect to the Ferrovia, Giorgia cultivar shows higher content of malic acid and phenolic compounds with important well known nutraceutical properties such as antioxidant activity and stimulating metabolism.

Selection of Taste Markers Related to Lactic Acid Bacteria Microflora Metabolism for Chinese Traditional Paocai: A Gas Chromatography-Mass Spectrometry-Based Metabolomics Approach

Traditional paocai brine (PB) is continuously propagated by back-slopping and contains numerous lactic acid bacteria (LAB) strains. Although PB is important for the quality of paocai (Chinese sauerkraut), the taste features, taste-related compounds of PB-paocai and the effects of LAB communities from PB on the taste compounds remain unclear. An electronic tongue was used to evaluate the taste features of 13 PB-paocai samples. Umami, saltiness, bitterness, sweetness, and aftertaste astringency were the main taste features of PB-paocai. A total of 14 compounds were identified as discriminant taste markers for PB-paocai via gas chromatography-mass spectrometry (GC-MS)-based multimarker profiling. A LAB co-culture (Lactobacillus plantarum, Lactobacillus buchneri, and Pediococcus ethanoliduran) from PB could significantly increase glutamic acid (umami), sucrose (sweetness), glycine (sweetness), lactic acid (sourness), and γ-aminobutyric acid in PB-paocai, which would endow it with important flavor features. Such features could then facilitate starter screening and fermentation optimization to produce paocai-related foods with better nutritional and sensory qualities.

NMR fingerprinting as a tool to evaluate post-harvest time-related changes of peaches, tomatoes and plums

The time-related changes of three agricultural products, coming from two distribution routes, have been followed using NMR fingerprinting to monitor metabolic variations occurring during several days of cold storage. An NMR profiling approach was employed to evaluate the variations in metabolic profile and metabolite content in three different agricultural products highly consumed in Italy (peaches, tomatoes and plums) coming from Tuscanian farms and how they change with time after collection. For each product, we followed the time-related changes during cold storage along three different collection periods. We monitored the variations in metabolic fingerprint and the trend of a set of metabolites, focusing our attention on nutritive and health-promoting metabolites (mainly, essential amino acids and antioxidants) as well as metabolites that contribute to the taste. Concurrently, for comparison, the time-dependent changes of the same kind of products coming from large-scale distribution have been also analyzed under the same conditions. In this second category, only slight variations in the metabolic fingerprint and metabolite levels were seen during cold storage. Unsupervised and supervised multivariate statistics was also employed to enlighten the differences between the three collections. In particular it seems that the metabolic fingerprint of large-scale distribution products is quite similar in the early, middle and late collection, while peaches and plums locally collected are markedly different among the three periods. The metabolic profiles of the agricultural products belonging to these two different distribution routes are intrinsically different, and they show different changes during the time of cold storage.

An NMR-based metabolomics study of pork from different crossbreeds and relation to sensory perception

Meat extracts from five different pig crossbreeds including Duroc/Landrace/Yorkshire (DLY), Iberian/Duroc (ID), Iberian/Duroc/Landrace (ILY), Mangalitza/Duroc (MD), and Mangalitza/Landrace/Yorkshire (MLY) were analysed by nuclear magnetic resonance (NMR)-based metabolomics. The results were compared with technological traits and sensory analyses in order to elucidate the potential of NMR-based metabolomics to highlight meat metabolites of importance for technological and sensory attributes of meat. Amino acids including alanine, carnosine, isoleucine, methionine, phenylalanine, and valine, as well as lactate, inosine monophosphate (IMP), inosine, glycerol and choline-containing compounds were found to be significantly affected by crossbreed. The breed-specific differences in the metabolome were ascribed to differences in ante mortem metabolism, differences in the membrane properties and glycolytic potential of muscle fibres and differences in lipolysis and proteolysis. A high content of carnosine in the meat was associated with a low value of many sensory attributes related to meat flavor/taste, while IMP and inosine were in general not correlated with sensory attributes related to meat flavor/taste.

Application of one- and two-dimensional NMR spectroscopy for the characterization of Protected Designation of Origin Lambrusco wines of Modena

Lambrusco is a Protected Designation of Origin (PDO) red wine of Modena (Italy) produced according to the production regulation (Decreto Ministeriale (DM) July 27, 2009; GU no. 184-187-188, 13/08/2009). Here the use of (1)H NMR spectroscopy as molecular fingerprints of several PDO Lambrusco wines was proposed to serve as indicators of authenticity and quality control. Application of partial least squares discriminant analysis (PLS-DA) revealed a good varietal discrimination by analyzing the low-frequency spectral region. This model explains 68.8% of the variance for the Y vector (classification factor: varietal source). In particular, the signals of 2,3-butanediol, lactic, succinic and malic acids, and threonine were found to be the most statistically significant variables in the model. These findings seem to be very promising in the attempt to extend the study to geographical discrimination.

NMR-based metabolic profiling of rice wines by F(2)-selective total correlation spectra

In this study, we performed NMR-based metabolic profiling of major rice wines (Japanese sake, Chinese Shaoxing wine, and Korean makgeolli). In the (1)H NMR spectra, the rice wines showed broad resonances in the region of about 7.9-9.0 ppm. These resonances showed many and complex correlations with approximately 0.5-4.5 ppm in the F(2)-selective TOCSY (total correlation spectroscopy) spectra, and these correlations were attributed mainly to peptides. These spectral patterns were characteristic of individual rice wines, and the combination of F(2)-selective TOCSY spectra and principal component analysis enabled us to classify the rice wine species. Furthermore, it also provided information about raw materials, namely, what type of koji (rice koji or wheat koji) was used. These spectra may be useful as a new "fingerprint" for quality control or food authentication.