Integrated science-based approach to study quality changes of shelf-stable food products during storage: A proof of concept on orange and mango juices

Caffeic acid, a natural extract, as an activatable molecular probe for viscosity detection in a liquid system

Liquids, functioning as nutrients and energy systems, regulate various functions during storage programs. Microenvironmental viscosity is one of the most important physical parameters associated with the extent of deterioration, and it is crucial to monitor the mutation of viscosity at a molecular level. Herein, we utilized caffeic acid (CaC), a natural product extracted from thistles, as a molecular probe for viscosity sensing. CaC contains phenol hydroxyl (electron-donor) and carboxyl (electron-acceptor) groups, with both moieties connected by conjugated single and double bonds, forming a typical twisted intramolecular charge transfer system. The fluorescent probe CaC, obtained from a natural product without any chemical processing, exhibits high sensitivity (x = 0.43) toward viscosity, with an obvious visualized turn-on signal. Moreover, it displays good photostability, selectivity, and wide universality in commercial liquids. Utilizing CaC, we have successfully visualized viscosity enhancement during the spoilage process, with a positive correlation between the degree of liquid spoilage and microenvironmental viscosity. Thus, this study will provide a convenient and efficient molecular probe for food safety inspection across the boundaries of traditional biological applications.

Green extract rosemary acid as a viscosity-sensitive molecular sensor in liquid systems

The liquid micro-environment plays a momentous role in the regulation of various activities, and the abnormal changes are often closely related to the deterioration phenomena in multiple beverages. The local viscosity fluctuation has long been regarded as a key indicator to reflect the micro-environmental status changes. Herein, we proposed a versatile optical sensor, rosmarinic acid (RA), one kind of green natural product extracted from rosemary, for monitoring liquid micro-environmental viscosity alterations. RA displays a larger Stokes shift (123.8 nm) with narrow-band energy and exhibits wide adaptability, high selectivity, good sensitivity, and excellent photostability in various commercial liquids. When in high viscous media, a bright fluorescent signal of RA is specifically activated, and a high signal-to-noise ratio signal was released (58-fold). With the assistance of the fluorescence analytical technique, we have successfully achieved tracking the viscosity fluctuations during the deterioration stage of liquids via an in situ and visualization method. Our study will spur additional research on the molecular tools extracted from natural products for liquid safety inspection, and a convenient and sustainable application pathway has been established.

Triphenylamine-Modified Cinnamaldehyde Derivate as a Molecular Sensor for Viscosity Detection in Liquids

Liquid safety is considered a serious public health problem; a convenient and effective viscosity determination method has been regarded as one of the powerful means to detect liquid safety. Herein, one kind of triphenylamine-modified cinnamaldehyde-based fluorescent sensor (3-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylaldehyde (DPABA)) has been developed for sensing viscosity fluctuations in a liquid system, where a cinnamaldehyde derivative was extracted from one kind of natural plant cinnamon and acted as an acceptor, which has been combined with a triphenylamine derivate via the Suzuki coupling reaction within one facile step. Twisted intramolecular charge transfer (TICT) was observed, and the rotation could be restricted in the high-viscosity microenvironment; thus, the fluorescent signal was released at 548 nm. Featured with a larger Stokes shift (223.8 nm in water, 145.0 nm in glycerol), high adaptability, sensitivity, selectivity, and good photostability, the capability of high signal-to-noise ratio sensing was achieved. Importantly, this sensor DPABA has achieved noninvasively identifying thickening efficiency investigation, and viscosity fluctuations during the liquid deterioration program have been screened as well. We believed that this unique strategy can accelerate intelligent molecular platforms toward liquid quality and safety inspection.

Based on quality, energy consumption selecting optimal drying methods of mango slices and kinetics modelling

Mangoes have a short shelf life because of their high-water content. This study aimed to compare the effect of three drying methods (HAD, FIRD and VFD) on mango slices to improve product quality and reduce costs. Mangoes were dried at various temperatures (50, 60, 70 °C) with different slice thicknesses (3, 5, 7, 10 mm). Results indicated that FIRD was the most cost-effective with the dried mango containing the highest sugar-acid ratio, and when the mango slices thickness was 7 mm and drying at 70 °C, the ascorbic acid content, rehydration ratio, sugar-acid ratio, and energy consumption per unit volume reached 56.84 ± 2.38 mg/100 g, 2.41 ± 0.05, 83.87 ± 2.14, and 0.53 kWh/L. Among three mathematical models, the Page model described the most satisfactory drying behaviour of mango slices in FIRD. This study provides useful information in mango processing industry and FIRD is supposed to be a promising drying method.

Sustainable natural chlorogenic acid as a functional molecular sensor toward viscosity detection in liquids

Liquids are perishable at ease during the long-term transportation and storage processes, non-invasive and in situ inspection method is urgent to be developed. In consideration of the important role of viscosity, one kind of sustainable natural product chlorogenic acid (CA) extracted from honeysuckle has been used as a versatile optical sensor for viscosity determination during the liquid spoilage process. The natural molecule was conducted by the O-diphenyl and carboxylic acid ester groups in coincidence, a typical twisted intramolecular charge transfer phenomenon was formed. This sensor features wide adaptability, high selectivity, good sensitivity, and excellent photo stability in various liquids. And CA displays a larger Stokes shift, high viscosity sensitive coefficient (0.62), and narrower energy band. The rotatable conjugate structure can be acted as the recognition site, and the bright fluorescent signal of CA is specifically activated when in the high viscous micro-environment. Inspired by this objective phenomenon, CA has been applied to detect the thickening efficiency of various food thickeners. More importantly, the viscosity fluctuations during the deterioration stage of liquids can be screened through non-invasive and in situ monitoring. We expected that more natural products can be developed as molecular tools for liquids safety investigation, and fluorescent analytical methods can be expanded toward interdisciplinary research.

Evaluation of Active LDPE Films for Packaging of Fresh Orange Juice

Microbial development, enzymatic action, and chemical reactions influence the quality of untreated natural orange juice, compromising its organoleptic characteristics and causing nutritional value loss. Active low-density polyethylene (LDPE) films containing green tea extract (GTE) were previously prepared by a blown film extrusion process. Small bags were prepared from the produced films, which were then filled with fresh orange juice and stored at 4 °C. Ascorbic acid (AA) content, sugar content, browning index, color parameters, pH, total acidity (TA) and microbial stability were evaluated after 3, 7, and 14 days of storage. The packaging containing GTE maintained the microbial load of fresh juice beneath the limit of microbial shelf-life (6 log CFU/mL) for the bacterial growth, with a more prominent effect for LDPE with 3%GTE. Regarding yeasts and molds, only the CO_LDPE_3GTE package maintained the microbial load of fresh juice below the limit for up to 14 days. At 14 days, the lowest levels of AA degradation (32.60 mg/100 mL of juice) and development of brown pigments (browning index = 0.139) were observed for the packages containing 3% of GTE, which had a pH of 3.87 and sugar content of 11.4 g/100 mL of juice at this time. Therefore, active LDPE films containing 3% of GTE increase the shelf-life of fresh juice and can be a promising option for storage of this food product while increasing sustainability.

Activatable molecular rotor based on bithiophene quinolinium toward viscosity detection in liquids

The development of non-invasive and effective viscosity inspection methods during the liquid deterioration process is urgently needed since viscosity is one of the most important physical parameters of liquids. Methods featuring rapid detection, high sensitivity, cheap equipment, and fast result output are greatly desired. In this study, a viscosity-sensitive molecular rotor (BTPEQ) with a large Stokes shift (187 nm), and long emission wavelength (648 nm) has been developed. The rotor is comprised of a bithiophene donor and quinolinium acceptor, and displays a typical twisted intramolecular-charge transfer (TICT) feature, with good photostability, selectivity, and universality in various commercial liquids. With the aid of BTPEQ, the thickening effects of liquid thickeners can be determined. More importantly, BTPEQ was explored to visualize the viscosity variations in liquids at different metamorphic stages, and it was found that the viscosity level in microenvironments is highly dependent on the liquid food metamorphic period. It is worth noting that this approach can facilitate the continued perfection of fluorescent analytical methods for food quality and safety inspection.

Effect of processing and accelerated storage on the volatile composition and sensory profile of a tomato soup

The volatile and sensory profile of pasteurised (95 °C, 18 min) and sterilised (120 °C, 14 min) tomato soup and its changes at accelerated storage conditions (37 and 42 °C) were identified, characterised and correlated by predictive models. Sterilisation led to more profound changes over storage compared to pasteurisation, showing enhanced levels of "dark" odour, "burnt" flavour and "complexity", while pasteurised soup had more pronounced "green" odour, "vegetables" flavour, "harmony" and "freshness". Over time, "dark" and "burnt" significantly increased for sterilised soups, whereas "green" decreased significantly only for sterilised soup stored at 42 °C. The changes of "dark", "green", "off-flavour", "burnt", "harmony" and "freshness" were associated with formation of furans (furfural and 2-acetyl-5-methylfuran), and decline of unsaturated aldehydes like E-2-octenal and E,E-2,4-heptadienal. These compounds were identified to represent potential shelf-life markers, yet more studies on their odour activity in the tomato soup matrix are necessary to understand their contribution to the sensory quality. The construction of PLS models allowed the prediction of "green", "off-flavour", "burnt" and "freshness" based on selected volatiles. These models will be important tools in the process of predicting the end of shelf-life, but need to be supplemented with consumer acceptability levels.

Restoring trilinearity with the purpose of advanced modeling: towards a more effective analysis of Pericarpium Citri Reticulatae during storage periods

To accurately quantify Pericarpium Citri Reticulatae samples, trilinear structure was restored in the stacked fingerprints for more robust modeling. Initially, liquid chromatography - diode array detector - mass spectrometry (LC-DAD-MS) and head space-solid phase micro extraction coupled to gas chromatography - mass spectrometry (HS-SPME/GC-MS) were utilized to analyze Pericarpium Citri Reticulatae. Faced with the time-shifts in two-dimensional (2D) matrices across different samples, three algorithms were developed to synchronize them. Furthermore, bilinear and trilinear models were used to realize the quantifications with different principles. Through real cases based on LC-DAD, the advantages and disadvantages of trilinear decomposition over multivariate curve resolution-alternating least-squares can be clarified in the quantification of raw or synchronized fingerprints. Also in the data processing, a modification version of multi-scale peak alignment (^mMSPA) was proved to be more suitable for trilinearity restoring than the other two algorithms. Recognizing these facts, restoring trilinearity were developed for more robust modeling in the application of the Pericarpium Citri Reticulatae fingerprints from different storage periods. After effective analysis, the upward/downward trend of 13 flavonoids were drawn accurately; and several flavour components having the highest contribution rate during storage were outlined reasonably. In conclusion, more robust modeling can be realized in trilinear data synchronized by appropriate algorithms, leading to an accurate quantification in herbal quality researches.

Triphenylamine indanedione as an AIE-based molecular sensor with one-step facile synthesis toward viscosity detection of liquids

AIE-based triphenylamine indanedione molecular sensors were synthesized in a one-step facile manner and designed for viscosity detection in liquids.

Visual detection of viscosity through activatable molecular rotor with aggregation-induced emission

Food safety has become one of the urgent affairs in the global public health studies, and irregular viscosity is closely associated with the food spoilage extent. In this study, one kind of activatable molecular rotor (TPA-PBZ) based on triphenylamine derivates has been synthesized via the Schiff base condensation reaction. This rotor is comprised by donor-accepter conjugated structure, with aggregation induced-emission feature and a large Stokes shift of 160 nm in water. The rotation of aromatic rings in TPA-PBZ is restricted in high-viscosity microenvironment, with the gradually increasing fluorescence emission signal at 568 nm. Significantly, this rotor TPA-PBZ has successfully been applied not only in the determination of thickening effects of food gum, but also in the detection of viscosity enhancement during the liquid food spoilage process. This molecular rotor can be utilized as an intelligent monitor platform for food quality and safety inspection in viscosity-related conditions.

E-Nose and Olfactory Assessment: Teamwork or a Challenge to the Last Data? The Case of Virgin Olive Oil Stability and Shelf Life

Electronic nose (E-nose) devices represent one of the most trailblazing innovations in current technological research, since mimicking the functioning of the biological sense of smell has always represented a fascinating challenge for technological development applied to life sciences and beyond. Sensor array tools are right now used in a plethora of applications, including, but not limited to, (bio-)medical, environmental, and food industry related. In particular, the food industry has seen a significant rise in the application of technological tools for determining the quality of edibles, progressively replacing human panelists, therefore changing the whole quality control chain in the field. To this end, the present review, conducted on PubMed, Science Direct and Web of Science, screening papers published between January 2010 and May 2021, sought to investigate the current trends in the usage of human panels and sensorized tools (E-nose and similar) in the food industry, comparing the performances between the two different approaches. In particular, the focus was mainly addressed towards the stability and shelf life assessment of olive oil, the main constituent of the renowned “Mediterranean diet”, and nowadays appreciated in cuisines from all around the world. The obtained results demonstrate that, despite the satisfying performances of both approaches, the best strategy merges the potentialities of human sensory panels and technological sensor arrays, (i.e., E-nose somewhat supported by E-tongue and/or E-eye). The current investigation can be used as a reference for future guidance towards the choice between human panelists and sensorized tools, to the benefit of food manufacturers.

Antioxidant Packaging Films Based on Ethylene Vinyl Alcohol Copolymer (EVOH) and Caffeic Acid

The main objective of this research activity was to design and realize active films with tunable food functional properties. In detail, caffeic acid (CA), a polyphenol with high antioxidant effect, was used as active ingredient in poly (vinyl alcohol-co-ethylene) (EVOH) films at 5 wt.% and 15 wt.% and successfully realized by means of the solvent casting process. Optical, morphological, thermal and mechanical studies were considered to define the effect of the presence of the CA component on the structural properties of the matrix. In addition, moisture content and antioxidant activity were evaluated, to have clear information on the CA effect in terms of functional characteristics of realized food packaging systems. Results from tensile tests showed increased values for strength and deformation at break in EVOH_CA based films. Results from colorimetric and transparency analysis underlined that the presence of caffeic acid in EVOH copolymer induces some alterations, whereas the addition of the active ingredient determined a positive radical scavenging activity of the formulations, confirming the possibility of practically using these polymeric systems in the food packaging sector.

Storage effects on the quality quartet of orange juice submitted to moderate thermosonication: Predictive modeling and odor fingerprinting approach

The effects of moderate thermosonication (MTS) on the quality quartet: physico-chemical, microbial, nutritional and sensory qualities of orange juice (OJ) inoculated with Alicyclobacillus acidoterrestris (AAT) were studied during 24 days of storage at ambient and refrigerated temperatures. The bioactive compounds and antioxidant activity of OJ decreased with storage, while the pectin methyl esterase (PME) increased. Nonetheless, noticeable changes were observed from the 12th day of storage. There was no obvious (p > 0.05) variation in pH and total soluble solids. To determine the nutritional and microbial quality characteristics of OJ during storage, non-linear kinetic curves were successfully fitted with least square fitting polynomial and four-parameter log-logistic distribution models. The E-nose sensors succeeded in discriminating between the aroma of non-treated and treated OJ based on linear discriminant analysis (LDA). Furthermore, terpenes, alcohol and partially aromatic compounds were the main spoilage indicators of OJ during storage based on E-nose analysis and confirmed by HS-SPME-GC/MS analysis. Thus, MTS significantly extended the shelf life of the quality quartet of natural OJ at 4 °C. E-nose-GC/MS fusion offered odor fingerprints to AAT microorganisms that can be used as spoilage index without using traditional food analysis techniques. The proposed approach can be used as an alternative tool for rapid detection of spoilage microorganisms in OJ.

Tetranitrile-anthracene as a probe for fluorescence detection of viscosity in fluid drinks via aggregation-induced emission

An AIE-based fluorescent probe was developed for monitoring the viscosity change during the spoilage process of fluid drinks.