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The influence of freeze and convection (at 40 and 50 °C) drying on the physical, functional, and rheological attributes of sunflower protein (SP) and its hydrolysate (SPH) was investigated. Compared with convectively-dried samples, the lightness, turbidity, bulk density, and particle size values of the freeze-dried SP and SPH were substantially higher, but the browning index was lower (p < 0.05). Additionally, freeze-dried samples exhibited good solubility and foaming characteristics, whereas lower emulsion properties with the most pH values were observed. Furthermore, SPHs possessed higher solubility as well as foamability over SPs under varying pH values (2.0–10.0), whilst reduction in the emulsion activity index was clearly observed (p < 0.05). Convectively-dried powders exhibited greater viscosity and consistency coefficient; and significantly lower flow behavior index of dispersions, relative to the respective freeze-dried preparations, indicating that dehydration methods influenced the flow behavior of the investigated samples. From a molecular weight analysis, convectively-dried samples at various temperatures were characterized with high proportion of small-sized particles at ≤1 kDa fractions over the respective powders obtained by freeze drying. The observations made, thus, would benefit food processors and manufacturers in electing better dehydration technique based on the desired traits of SP and SPH powders for successful application in food product formulations.

Highlights • Ultrasound freeze-thawing pretreatments improved the vacuum freeze-drying. • Pretreatment reduced the drying time and energy consumption. • Pretreatment changed the microstructure to various extent. • Ultrasound pretreatment retained most of the quality characteristics. • Pretreatment had no effect on the function groups and structure of pectin., Vacuum freeze-drying is a new and high technology on agricultural product dehydrating dry, but it faces the high cost problem caused by high energy consumption. This study investigated the effect of ultrasound (US), freeze-thawing (including the freeze-air thawing (AT), freeze-water thawing (WT), freeze-ultrasound thawing (UST), and freeze-air ultrasound thawing (AT + US)) pretreatments on the vacuum freeze-drying efficiency and the quality of dried okra. The results indicated that the application of ultrasound and different freeze-thawing pretreatments reduced the drying time by 25.0%–62.50% and the total energy consumption was 24.28%–62.35% less. The AT pretreatment reduced the time by of okra slices by 62.50% and the total energy consumption was 62.35% less. The significant decrease in drying time was due to a change in the microstructure caused by pretreatment. Besides, the okra pretreated with the US retained most of the quality characteristics (flavor, color, hardness, and frangibility) among all methods, while, AT + US had the most changeable characteristics in quality, which is deprecated in our study. The okra pretreated with the US and AT, separately, had the best dry matter content loss (9.008%, 5.602%), lower chlorophyll degradation (5.05%, 5.44% less), and higher contents of total phenolics, total flavonoids, and pectin, with strong antioxidant capacity, compared to other methods. The pretreatments did not have a large effect on the functional groups and the structure of pectin, but slightly affected the viscosity. It can be concluded that AT and US pretreatment methods are better than others.

Ultrasound requires high power and longer treatment times to inactivate microorganisms when compared to ultrasound combined with other technologies. Also, the antimicrobial efficiency of aqueous ozone increases with an increase in its concentration and exposure time, but with a detrimental effect on the quality of the treated food. In this study, the effect of aqueous ozone at low concentration, multi-mode frequency irradiation and their combination on microbial safety and nutritional quality of cherry tomato was investigated. Individual washing with aqueous ozone and mono-mode frequency irradiation resulted in1 log CFU/g reduction in the spoilage microorganisms, while dual-mode frequency irradiation (DMFI) resulted in higher microbial reduction (1.3-2.6 1 log CFU/g). The combined system (20/40 kHz + aqueous ozone) on the other hand, resulted in3 log CFU/g microbial reduction. The application of DMFI enhanced the antimicrobial efficiency of aqueous ozone without any detrimental effect on the physicochemical properties (except the firmness), bioactive compounds, and antioxidants of the cherry tomato during 21 days refrigerated storage. The result obtained indicates the promising substitute to the single washing technique for microbial safety as well as preserving the nutritional quality and enhancing the shelf life of cherry tomato.

In this study, effects of conveyor belt catalytic infrared blanching (CBCIRB) on peroxidase (POD), moisture reduction, physical and chemical properties, and microstructure of sweet potato slices were investigated. The parameters of CBCIRB were infrared irradiation distance (6, 12, and 18 cm), sample thickness (3, 5, and 7 mm), and conveyor speed (0.7, 0.35, 0.1 m/min, etc.). Meanwhile, the effect of conventional hot water blanching (HB) on sweet potato slices were also investigated. The results showed that shortening the infrared irradiation distance and reducing the slice thickness could both accelerate the POD inactivation rate. When 90% POD inactivation was achieved, CBCIRB samples yielded better hardness and higher preservation of phytochemicals than HB samples. The appropriate CBCIRB parameters were the slice thickness of 3 mm, infrared radiation distance of 12 cm and conveyor belt speed of 0.16 m/min, the moisture reduction, surface colour change, hardness, vitamin C retention rate, β-carotene retention rate, and total phenol content were: 78.34%, 7.41, 1690.4 g, 75.16%, 133.49%, and 1.03 mg/g, respectively. The microstructure observation showed that the damage of sweet potato slice cells by HB was more severe than CBCIRB. Overall, CBCIRB achieved higher product quality in a relatively uniform air environment.

This work aimed to study the rehydration characteristics of vacuum freeze- (VFD) and hot air-dried (HAD) garlic slices and explain the rehydration mechanism. It was observed that VFD samples had significantly faster water absorption rates than HAD samples. However, VFD samples had lower final moisture contents than the HAD samples. Additionally, the effect slice thickness on rehydration characteristics of samples was lower than that of drying methods. The contact angle and microstructure analysis of dried samples revealed that the strong water wettability and the porous structure contributed to the faster water absorption rate of VFD samples. Moreover, we found and confirmed, for the first time, that numerous air bubbles trapped in the VFD samples hindered the absorption of water. This resulted in a lower water holding capacity in VFD samples compared with HAD samples, which had less air bubbles.

The low molecular weight (≤3 kDa) collagen peptide (CPLW) was prepared from white carp skin by intestinal simulation digested and ultrafiltration membranes. CPLW and calcium ions were combined to form a peptide-calcium complex (CPLW-Ca), and the structure and stability of the complex were characterized. The single factor optimization results indicated that the highest protein conversion rate and the maximum calcium binding ability were 60%, and 22.16 ± 0.55 mg/g, respectively. Structural analysis demonstrated that calcium ions bound to CPLW mainly via the formation of ionic bonds with carboxyl oxygen, hydroxyl oxygen and amino nitrogen atom of CPLW. The CD and particle size analyses showed that after CPLW was combined with calcium ions, the spatial structure was folded, which reduced the particle size with the formation of irregular nanoparticles. Stability analysis revealed that the calcium retention rate of the prepared CPLW-Ca remained substantially at 90% below 90 °C, and the calcium content of CPLW-Ca was significantly decreased under high acidic conditions. CPLW-Ca has the potential to be applied as an alternative for dietary calcium supplements.

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.

The suitability of some non-linear kinetic models (Weibull {with or without tail}, Log-linear, Log-linear shoulder {with or without tail}, Biphasic linear, Logistic, Multi-target and Single-target models) were evaluated to determine the inactivation kinetics of inoculated E. coli, and natural microbiota (i.e. mesophilic aerobic bacteria, and mold and yeast) on cherry tomato treated with fixed multi-frequency ultrasound. Almost all the studied model fitted well (R2 ≥ 0.9) for the inactivation kinetics; however, the Weibull, Log-linear shoulder, and Biphasic linear model showed the highest statistical parameters (0.9 ≤ adj. R2 ≤ 0.99 and smallest RMSE and SSE values). All the three models could be used to compare the kinetic behavior of E. coli and the first two models for the kinetic behavior of mesophilic aerobic bacteria and mold and yeast during sonication treatment. Two distinctive inactivation curves were obtained for the mono-frequency and the multi-frequency (dual and tri-frequency) for all the microbial inactivation. The remarkable results obtained for dual and tri-frequency sonication shows to be an effective and promising alternative to the traditional microbial inactivation techniques and the common practice of using ultrasound with other sanitizing methods.