Effects of traditional and advanced drying techniques on the physicochemical properties of Lycium barbarum L. polysaccharides and the formation of Maillard reaction products in its dried berries

Effect of dipping pre-treatments and drying methods on Aronia melanocarpa quality

This study examined the impact of different dipping pre-treatments (PO: potassium carbonate-olive oil emulsion, HW: hot water) and drying methods (sun, oven, hot air, and freeze) on aronia berry quality. Freeze-drying showed the highest process yield (29.07%-29.43%), while sun-drying had the lowest (24.60%-25.74%). PO pre-treatment showed superior moisture and water activity reductions across all drying methods. Notably, it enhanced carotenoid levels (PO: 399.5, HW: 371.4 mg BCE/kg), antioxidant activity (PO: 9602.8, HW: 9403.3 mg TE/kg), total phenolics (PO: 38176.5, HW: 34804.0 mg GAE/kg) and flavonoids (PO: 6537.1, HW: 6141.5 mg CE/kg) during freeze-drying. Additionally, PO-treated samples exhibited superior rehydration properties, with a ratio of 293.32% and a 1.01 g/g capacity. On the other hand, HW pre-treatment increased ascorbic acid levels (PO: 377.0, HW: 391.7 mg/kg). The highest quality dried aronia berries are generally observed in PO-treated samples, especially in freeze drying, followed by hot-air, oven, and sun drying processes.

Comparison of characterization and composition of melanoidins from three different dried apple slices

The composition of melanoidins in dried apple that affects quality remains unclear. The composition and structure of melanoidins in dried apple slices by hot air drying (HAAM), instant controlled pressure drop drying (DICAM), and vacuum freeze-drying (FDAM) were investigated. It showed that the melanoidins were highly heterogeneous mixtures with a light-yellow color and blue-green fluorescence, belonging to polysaccharide-type melanoidins. Specifically, HAAM had a large molecular weight (929.5 g/mol) and wide molecular weight distribution, with more double-bond conjugated systems. DICAM (610.9 g/mol), possessing the strongest fluorescence intensity, was mainly composed of compounds with fewer π-conjugated structures and more electron-donating groups. As a control, the low level of Maillard reaction in FDAM resulted in the formation of the smallest molecular weight (458.6 g/mol) with weak fluorescence intensity. Moreover, 10 compounds were tentatively identified in apple melanoidins. This study provides the foundation for the future functional preparation of apple melanoidins.

Agar-gelatin Maillard conjugates used for Pickering emulsion stabilization

A few protein- and polysaccharide-based particles have shown promising potential as stabilizers in multi-phase food systems. By incorporating polymer-based particles and modifying the wettability of colloidal systems, it is possible to create particle-stabilized emulsions with excellent stability. A Pickering emulsifier (AGMs) with better emulsifying properties was obtained by the Maillard reaction between acid-hydrolysed agar and gelatin. Laser confocal microscopy imaging revealed that AGMs particles can be used as solid emulsifiers to produce a typical O/W Pickering emulsion, with AGMs adsorbing onto the droplet surface to form a dense interfacial layer. Cryo-scanning electron microscopy analysis showed that AGMs self-assembled into a three-dimensional network structure, which prevented droplets aggregation through strong spatial site resistance, contributing to emulsion stabilization. These emulsions exhibited stability within a pH range of 1 to 11, NaCl concentrations not exceeding 300 mM, and at temperatures below 80 °C. The most stable emulsion oil-water ratio was 6:4 at a particle concentration of 0.75 % (w/v). AGMs-stabilized Pickering emulsion was utilized to create a semi-solid mayonnaise as a replacement for hydrogenated oil. Rheological analysis demonstrated that low-fat mayonnaise stabilized with AGMs exhibited similar rheological behavior to traditional mayonnaise, offering new avenues for the application of Pickering emulsions in the food industry.

Bioactive metabolite profiles and quality of Rosa rugosa during its growing and flower-drying process

Rosa rugosa is extensively cultivated in China for its remarkable fragrance and flavor, however, the metabolic changes in roses during growth and drying remain unclear. Our results revealed significant variations in phenol and flavonoid contents and antioxidant capacity in roses (Rosa rugosa f. plena (Regel) Byhouwer) under different conditions. Phenol contents were positively correlated with antioxidant capacity, with phytochemicals being most prominent in unfolded petals. The highest antioxidant capacity and phenol and flavonoid contents were observed in April. Considering their greater consumption value, whole flowers were more suitable than petals alone. Furthermore, considerable sensory and nutritional differences were observed in dried roses. Different drying methods increased their total phenol content of roses by 4.2-5.4 times and the antioxidant capacity by 2.9 times. Metabolomics revealed the altered contents of flavonoids, anthocyanins, lipids, amino acids, and saccharides. This study provides baseline data for the potential of roses as a natural source of antioxidants in the food and pharmaceutical industries.

Effects of Freeze-Thaw Pretreatment Combined with Hot Air on Snake Gourd (Trichosanthes anguina L.)

Snake gourd is a seasonal vegetable with a high water content and medicinal value, but the short harvest period limits the large-scale application of snake gourd. Therefore, the effects of freeze-thaw pretreatment (FT) combined with hot air (HD) on the drying characteristics, active ingredients and bioactivities of snake gourd were investigated. The results showed that FT pretreatment reduced browning and shortened the drying time by 44%; the Page model was the best fit for describing the drying process. The polysaccharide contents (21.70% in alcoholic extract (TG1) and 44.34% in water extract (TG2)) and total phenol contents (1.81% in TG1 and 0.88% in TG2) of snake gourd pretreated by FT-HD were higher than those of snake gourd pretreated by the corresponding HD treatment. The FT pretreatment decreased the molecular weight of snake gourd polysaccharides and increased the molar ratio of glucose. The extracts pretreated by FT-HD showed greater chemical, cellular antioxidant capacity and α-amylase and α-glucosidase inhibition than those pretreated by HD. FT-HD can be recommended for achieving a short drying time and high quality of snake gourd and can be used for the drying of other fruits and vegetables.

Determination of α-Dicarbonyl compounds in traditional Chinese herbal medicines

α-DCs (α-dicarbonyls) have been proven to be closely related to aging and the onset and development of many chronic diseases. The wide presence of this kind of components in various foods and beverages has been unambiguously determined, but their occurrence in various phytomedicines remains in obscurity. In this study, we established and evaluated an HPLC-UV method and used it to measure the contents of four α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), and diacetyl (DA) in 35 Chinese herbs after they have been derivatized with 4-nitro-1,2-phenylenediamine. The results uncover that 3-DG is the major component among the α-DCs, being detectable in all the selected herbs in concentrations ranging from 22.80 μg/g in the seeds of Alpinia katsumadai to 7032.75 μg/g in the fruit of Siraitia grosuenorii. The contents of the other three compounds are much lower than those of 3-DG, with GO being up to 22.65 μg/g, MGO being up to 55.50 μg/g, and DA to 18.75 μg/g, respectively. The data show as well the contents of the total four α-DCs in the herbs are generally in a comparable level to those in various foods, implying that herb medicines may have potential risks on human heath in view of the α-DCs.

Organic acid and aromatic compounds create distinctive flavor in the blackening process of jujube

Previous studies demonstrated jujube blackening effectively increased cyclic adenosine phosphate and triterpene acid levels, improving its nutritional value. However, compositional changes during this process require further elucidation. The objective aimed to analyze compositional transformations during this process with SEM, TPA, UPLC-MS, E-nose. Results showed decreased hardness, springiness, and chewiness coupled with increased gumminess over blackening durations. Untargeted omics analysis revealed increases of 2-aminooctadec-8-ene-1,3,4-trioland carbendazim. Targeted organic acid analysis showed initial citric acid accumulation (1481.62 to 1645.78 mg/kg) in the first 24 h, then declines to 1072.96 mg/kg. Meanwhile, oxalic and lactic acids steadily rose, peaking at 96-120 h before slightly decreasing. E-nose analysis implied alterations in organic sulfide aromatics engendered the characteristic flavors. Organic acid fluctuations likely resulted from sugar biotransformation and thermal degradation. These comprehensive analyses demonstrate jujube blackening imparts a rich and unique flavor, providing theoretical support for investigating the mechanisms and products underlying this process.

Quantitative N-glycoproteomic analysis of egg yolk powder during thermal processing

The production of egg yolk powder often involves critical processes such as pasteurization and spray drying, however, these thermal processes will inevitably affect the functional properties of egg yolk (especially gelation and emulsification). The aim of this study was to elucidate the mechanism of the effect of pasteurized egg yolk (P-EY) and spray-dried egg yolk (SD-EY) on the functional properties through quantitative N-glycoproteomic. The results showed, compared with fresh egg yolk (F-EY), emulsifying property of mild heat-treated P-EY was slightly reduced while the gelation property did not undergo significant changes, whereas emulsifying activity (EAI) and gelation strength of vigorously heat-treated SD-EY were significantly reduced by 48.72 % and 35.73 %, respectively. During thermal processing in SD-EY, larger aggregate particles (particle size ∼10 um) were formed, and the surface hydrophobicity was reduced (93.0 %) and the zeta potential was enhanced (62.8 %). The results of quantitative N-glycoproteomic showed that 13 N-glycosylated proteins (APOB, vitellogenin, etc.) were down-regulated while only 2 N-glycosylated proteins were up-regulated; 21 N-glycosylation sites were down-regulated and 2 N-glycosylation sites were up-regulated in SD-EY, suggesting that covalent cross-linking of protein N-glycoproteins may have occurred in the process of spray-drying, which altered molecular physicochemical characteristics of the yolk solution that further affecting the processing properties of egg yolk.

Development of thermoultrasound assisted blanching to improve enzyme inactivation efficiency, drying characteristics, energy consumption, and physiochemical properties of sweet potatoes

Thermoultrasound (USB) as a promising alternative to traditional hot water (HWB) blanching was employed to blanch sweet potatoes and its influence on enzyme activity, drying behavior, energy consumption and physiochemical properties of sweet potatoes were investigated. Results showed that successive increases in blanching temperature and time resulted in significant (p < 0.05) decreases in PPO and POD activities. Compared to HWB, USB led to more effective drying by promoting texture softening, moisture diffusion, microstructure alterations, and microchannels formation, which significantly reduced energy consumption and improved the overall quality of the dried sample. Specifically, USB at 65 °C for 15 min improved water holding capacity and ABTS, while USB at 65 °C for 30 min improved color (more red and yellow), total phenolic content, total carotenoid content, and DPPH. Unfortunately, blanching process showed detrimental effects on the amino acid composition of dried samples. Overall, the development of thermoultrasound assisted blanching for sweet potatoes has the potential to revolutionize the processing and production of high-quality sweet potato products, while also improving the sustainability of food processing operations.

Toxicity, formation, contamination, determination and mitigation of acrylamide in thermally processed plant-based foods and herbal medicines: A review

Thermal processing is one of the important techniques for most of the plant-based food and herb medicines before consumption and application in order to meet the specific requirement. The plant and herbs are rich in amino acids and reducing sugars, and thermal processing may lead to Maillard reaction, resulting as a high risk of acrylamide pollution. Acrylamide, an organic pollutant that can be absorbed by the body through the respiratory tract, digestive tract, skin and mucous membranes, has potential carcinogenicity, neurological, genetic, reproductive and developmental toxicity. Therefore, it is significant to conduct pollution determination and risk assessment for quality assurance and security of medication. This review demonstrates state-of-the-art research of acrylamide focusing on the toxicity, formation, contamination, determination, and mitigation in taking food and herb medicine, to provide reference for scientific processing and ensure the security of consumers.

Understanding the impact of pectin physicochemical variation on browning of simulated Maillard reaction system in thermal and storage processing

Maillard reaction browning is one of the quality deterioration in dried fruit products, but how pectin affects Maillard reaction in the fruit drying and storage process is not clear. This study aimed at investigating the mechanism of pectin variation impact on the browning of Maillard reaction by using simulated system (l-lysine, d-fructose and pectin) in thermal (60 °C and 90 °C for 8 h) and storage (37 °C for 14 days) process. Results showed that apple pectin (AP) and sugar beet pectin (SP) significantly enhanced the browning index (BI) of the Maillard reaction system by 0.01 to 134.51 in the thermal and storage processes, respectively, which were methylation degree of pectin-dependent. The pectin depolymerization product participated Maillard reaction by reacting with l-lysine, and increasing the 5-hydroxymethyl furfural (5-HMF) content (1.25-11.41-fold) and Abs_420nm (0.01-0.09). It also produced a new product (m/z 225.1245), which finally increased browning level of the system.

Effect of Different Drying Techniques on Total Bioactive Compounds and Individual Phenolic Composition in Goji Berries

In recent years, interest in the consumption of dried goji berries has increased due to its high bioactive properties. Alternative drying methods that provide faster drying and better preservation of bioactive properties should be developed. This study aims to investigate the effect of different drying methods on the drying time and quality characteristics of the goji berry; namely, hot-air drying (HAD), ultrasound-assisted vacuum drying (USVD), vacuum drying (VD), freeze-drying (FD), and ultrasound-pretreated freeze-drying (USFD). The drying kinetic, total phenolic content, antioxidant capacity, phenolic profile, carotenoid profile, and color change of the goji berry fruit were determined. The drying times for VD, USVD, and HAD varied between 275–1330 min. USVD treatment showed faster drying behavior than the other two drying methods. The total phenolic content (TPC) value of dry samples varied between 1002.53–1238.59 mg GAE/g DM. USVD treatments exhibited a higher total phenolic content (TPC) value than all other drying methods. DPPH and CUPRAC values varied between 15.70–29.90 mg TE/g DM and 40.98–226.09 mg TE/g DM, respectively. The total color change (ΔE) value ranged between 4.59 and 23.93 and HAD dried samples showed the highest ΔE of all samples. The results of the phenolic profile were consistent with TPC analysis. HAD caused higher phenolic compound degradation than VD, USVD, and FD. The results of this study showed that different drying techniques significantly affected the drying rate and retention of bioactive components of the goji berry fruit, and the USVD and VD methods could be used as an alternative to the HAD method. This study concluded that USVD and FD could be considered as suitable drying methods and could be used as alternatives to HAD in the drying of goji berries.