The increasing consumption of fresh-like food products requires the development of mild processing technologies without loss of nutritional value and sensory quality of foods. Non-thermal plasma ...(NTP) is an emerging and promising technology for extending the shelf-life of food products. However, the further development of a novel preservation technology should base on the adequate understandings of the effects on microbial behaviors. Therefore, the aim of this review is to provide an overview of the inactivation mechanisms of NTP technology on microbes. Topics covered are the basic introduction of NTP, the intrinsic and extrinsic factors affecting microbial inactivation effect and the probable mechanisms for microbial inactivation. Many factors, including processing parameters, environmental conditions and microbial properties have been shown to influence the bactericidal effect of NTP. According to previous research, the inhibitory activity of NTP against microbes includes biological and physical scenarios, though the exact mechanisms still remain unknown, requiring more investigations in the future.
•The intrinsic and extrinsic factors affecting bactericidal efficacy of non-thermal plasma were reviewed.•The probable inactivation mechanisms in biological and physical aspects by non-thermal plasma were summarized.•The non-thermal plasma induced microbial physiological alterations were shown.•The safe application of non-thermal plasma in the future for food industry was proposed.
Lead pollution has increasingly become the focus of environmental pollution, which is a great harm to the ecological environment and human health. Strict control of the emission of lead pollutants ...and accurate monitoring of lead are very important. The lead ion detection technologies are introduced here, including spectrophotometry, electrochemical method, atomic absorption spectrometry, and other detection methods, and the methods' applicability, the advantages, and disadvantages are discussed. The detection limits of voltammetry and atomic absorption spectrometry are as low as 0.1 μg/L, and those of atomic absorption spectrometry are as low as 2 μg/L. The detection limit of photometry is higher (0.01 mg/L), but this method can be achieved in most laboratories. The application of different extraction pretreatment technologies in lead ion detection is introduced. The new technologies develop at home and abroad, such as precious metal nanogold technology, paper microfluidic technology, fluorescence molecular probe technology, spectroscopy, and other emerging technologies in recent years, are reviewed, and the principle and application of various technologies are expounded.
•Domestic cooking methods on phytochemicals and antioxidant activity were systemic evaluated.•Stir-frying and air frying on phytochemicals and antioxidant were first studied.•Antioxidant activity was ...well accordance with total phenolic while showed least accordance with vitamin C.
The effects of domestic cooking methods (boiling, baking, steaming, microwaving, frying, and stir-frying) and a new cooking method (air-frying) on the composition of phytochemicals (phenolics, anthocyanins, and carotenoids) and the antioxidant activity in purple-fleshed potatoes were investigated. Compared with raw potatoes, reductions of 23.59–90.42%, 7.09–72.44%, 7.45–83.15%, and 20.15–76.16% in the vitamin C, total phenolic, anthocyanin and carotenoid contents, respectively, was observed after cooking. Decreases of 7.88%, 21.55%, 22.48, 6.31%, and 61.38% in DPPH radical-scavenging activity was also observed after boiling, steaming, baking, microwaving and stir-frying, respectively, whereas an increase of 30.52% was noted after air-frying. A correlation analysis revealed that the antioxidant activity was in accordance with the total phenolic content and that this activity showed the lowest correlation with the vitamin C content. Among all of the cooking methods investigated in this study, stir-frying retained only slight levels of the phytochemicals and antioxidant activity observed in raw potatoes, whereas steaming and microwaving were able to retain most of the health-promoting compounds found in raw potatoes and may thus be suitable methods for cooking potatoes.
The impact of high-pressure processing (HPP) extraction on the structural, rheological, and functional properties of goji berry and raspberry pectic polysaccharides were investigated under acidic and ...alkaline conditions. These properties were compared with those of pectic polysaccharides extracted by conventional hot-acid and cold-alkali methods. Extraction yield, molecular weight, rheological behavior, and antioxidant activity of pectic extracts depended on the source materials of extraction. The solvent pH was the driving factor for the degree of esterification, as revealed by NMR and FTIR analysis. Monosaccharide composition was the primary variable between the extracts. The hot-acid extraction led to the highest galacturonic acid (GalA) contents, 46.9% for goji berry and 65.2% for raspberry, indicating the prevalence of homogalacturonans (HG) regions. HPP-assisted acidic/alkaline extractions gave rise to higher rhamnogalacturonan-I (RG-I) regions, pointing to the prevalence of hairy regions. The antioxidant activity of raspberry extracts was significantly (P ≤ 0.05) higher than goji berry extracts. The higher amount of RG-I may determine the higher antioxidant activity of raspberry pectic polysaccharides. The correlation between structural parameters and the lipase inhibitory activity also revealed that the higher lipase inhibitory activity of pectic polysaccharides is mostly correlated with the higher content of RG-I (r = 0.9259, P = 0.00033). Thus, HPP-assisted extraction may intensify the lipase inhibitory activity of pectic polysaccharides by increasing their RG-I content.
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•Goji berry and raspberry pectins were obtained by high-pressure processing, hot-acid, cold-alkali.•Effects of extraction method on extracts yield, Mw and rheology were source-dependent.•Hot-acid extraction led to the highest galacturonic acid content (high HG region).•HPP-assisted extractions increased rhamnogalacturonan-I (RG-I) regions.•Higher RG-I is correlated with higher lipase inhibitory activity of pectin.
As a nonthermal sterilization technique, ultrasound has attracted great interest in the field of food preservation. In this study, flow cytometry and transmission electron microscopy were employed to ...investigate ultrasound-induced damage to Escherichia coli and Staphylococcus aureus. For flow cytometry studies, single staining with propidium iodide (PI) or carboxyfluorescein diacetate (cFDA) revealed that ultrasound treatment caused cell death by compromising membrane integrity, inactivating intracellular esterases, and inhibiting metabolic performance. The results showed that ultrasound damage was independent of initial bacterial concentrations, while the mechanism of cellular damage differed according to the bacterial species. For the Gram-negative bacterium E. coli, ultrasound worked first on the outer membrane rather than the cytoplasmic membrane. Based on the double-staining results, we inferred that ultrasound treatment might be an all-or-nothing process: cells ruptured and disintegrated by ultrasound cannot be revived, which can be considered an advantage of ultrasound over other nonthermal techniques. Transmission electron microscopy studies revealed that the mechanism of ultrasound-induced damage was multitarget inactivation, involving the cell wall, cytoplasmic membrane, and inner structure. Understanding of the irreversible antibacterial action of ultrasound has great significance for its further utilization in the food industry.
Rhamnogalacturonan I (RG-I) pectin is composed of backbone of repeating disaccharide units →2)-α-L-Rhap-(1→4)-α-D-GalpA-(1→ and neutral sugar side-chains mainly consisting of arabinose and galactose ...having variable types of linkages. However, since traditional pectin extraction methods damages the RG-I structure, the characteristics and health effects of RG-I remains unclear. Recently, many studies have focused on RG-I, which is often more active than the homogalacturonan (HG) portion of pectic polysaccharides. In food products, RG-I is common to fruits and vegetables and possesses many health benefits. This timely and comprehensive review describes the many different facets of RG-I, including its dietary sources, history, metabolism and potential functionalities, all of which have been compiled to establish a platform for taking full advantage of the functional value of RG-I pectin.
Starch is the main carbohydrate in human nutrition and shows a range of desired food properties. It has been demonstrated that fast digestion of starchy food can induce many health issues (e.g., ...hyperglycaemia, diabetes, etc.); therefore, how to modulate its digestion is an interesting topic. Previous studies have revealed that the microstructure and digestibility of starchy food of different botanical origin or from multiple processes are quite different; modulating starch digestion by retaining or altering its microstructure may be effective. In the present review, the current knowledge of the relationship between microstructural changes to starchy food and its digestibility at molecular, cell and tissue, and food processing levels is summarized. New technologies focused on microstructure studies and ways to manipulate food microstructure to modulate starch digestibility are also reviewed. In particular, some insights focusing on the future study of microstructure and the digestibility of starchy food are also suggested.
•Ultrasound induced fissures and pores on rice granule surface.•Amorphous region of starch was destroyed by ultrasound rather than crystalline region.•Ultrasound treatments improved the uniformity of ...starch particle size.•Ultrasound-treated starch showed a similar pasting profiles to the native starch.
To further investigate how controlled ultrasound treatments affect the morphology, physical property and fine structure of rice starch granules, the starch suspended in water was treated with different ultrasonic power levels (150, 300, 450 and 600 W) at 25 °C for 20 min. XRD, FT-IR and Raman spectroscopy were performed to characterise the long-range and short-range ordered structure of starch granules. Results indicated that ultrasound slightly destroyed the amorphous region of starch granules, while the A-type crystalline pattern remained unchanged. The result of chain length distributions showed that the fine structure of rice starch was not significantly changed by ultrasound treatment. SEM and particle size distribution demonstrated that ultrasound induced fissures and pores on the granule surface and elevated the homogeneity of granules, with minimum effect on the granule size. In addition, the thermal and pasting properties of rice starch were also measured by DSC and RVA. Results showed that after ultrasound treatments, the peak and breakdown viscosity increased, while the peak time, pasting temperature and gelatinisation enthalpy decreased. Overall, controlled ultrasound treatments dominantly modified the morphology and physical property of rice starch rather than the fine structure, providing additional information for the application of ultrasound on starch modification.
Microbial decontamination during the thawing process would offer an effective intervention step to ensure food safety. In this study, plasma-activated water (PAW) and slightly acidic electrolyzed ...water (SAEW) are proposed as the thawing media to assure microbiological safety and retain quality attributes of beef. Compared to the conventional air thawing (AT) and water thawing (WT), PAW thawing (PT) and SAEW thawing (ST) were found to efficiently inactivate the total bacteria, fungi and yeast in beef by 0.83 – 1.76 logs. In addition, PT and ST did not pose any detrimental effect on the physicochemical and sensory quality attributes of beef compared with AT, WT and microwave thawing (MT). The oxidation of lipid and proteins and the structure of proteins in beef was better retarded by PT and ST. PAW and SAEW as active thawing media provided thawed beef with higher microbial safety and maintained quality attributes compared with conventional thawing methods.
•PAW and SAEW were used as active beef thawing media.•PAW and SAEW effectively reduced the microbial loads of beef during thawing.•PAW resulted in non-detective levels of pathogens-S. aureus and Salmonella in beef.•PAW and SAEW retarded lipid oxidation of beef during thawing.•PAW and SAEW did not induce detrimental effects due to protein oxidation or changes on muscle micro-structure.
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•The antibacterial effect of US was in a time- and intensity-dependent manner.•US remarkably increased the sensitivity of E. coli cells to TEON.•US significantly increased the outer ...and inner membrane permeability.•US resulted in membrane fluidity reduction and membrane depolarization.•US caused conformational and compositional changes in some membrane components.
This study was aimed at providing new insights on the response of bacterial cell membranes to ultrasound exposure. Escherichia coli (E. coli) O157:H7 cells were exposed to different ultrasound treatments (power intensities of 64, 191, 372, and 573 W/cm2, frequency of 20 kHz, pulsed mode of 2 sec: 2 sec) and the dynamic changes in cell viability within 27 min were assessed. With an increase in ultrasonic intensity and prolonged duration, a 0.76–3.52 log CFU/mL reduction in E. coli populations was attained. The alterations in the sensitivity of ultrasound-treated cells to antimicrobial compounds were evaluated by exposure to thyme essential oil nanoemulsion (TEON). The treatment reduced the E. coli population by 2.16–7.10 log CFU/mL, indicating the effects of ultrasonic field on facilitating the antibacterial efficacy of TEON. Ultrasonic-treated E. coli cells also displayed remarkable morphological and ultrastructural damages with destroyed membrane integrity and misshaped cell structures, which was observed by electron microscopy analysis. Significant increase in outer and inner membrane permeability, along with the cytoplasmic leakage and membrane depolarization were assessed utilizing spectrophotometry. For the first time, significant reduction in the membrane fluidity in response to ultrasound exposure were investigated. Additional efforts in exploring the effect of ultrasonic field on some bacterial membrane compositions were performed with infrared spectroscopy. In this study, multiple lines of evidence effectively served to elucidate the alterations on cellular membrane structure and property during exposure to sonication that could extend our understanding of the antimicrobial molecular mechanisms of ultrasound.
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