Antioxidant activity in HepG2 cells,immunomodulatory effects in RAW 264.7 cells and absorption characteristics in Caco‐2 cells of the peptide fraction isolated from Dendrobium aphyllum

DA‐P, fraction of peptides with a molecular weight <1 kDa isolated from Dendrobium aphyllum, was analysed in three types of cell lines to verify its bioactivity and absorptivity. The cellular antioxidant activity of DA‐P in HepG2 cells was used and results revealed an EC50 of 2.88 ± 0.143 mg mL^?1 and a CAA unit of 63.46 ± 2.11 μm QE/100 g peptides. DA‐P treatment enhanced the secretion of cytokines in RAW 264.7 cells. After demonstrating the presence of tight junctions in Caco‐2 monolayers, the absorption was 25.57% ± 0.016% and 19.7% ± 0.012% from different sides. The relatively high absorption indicated that the antioxidant‐relevant immune functions of DA‐P had a greater possibility to be absorbed by Caco‐2 cells. Free amino acids and LC‐MS/MS analysis indicated the degradation and expulsion of components after the absorption of DA‐P, and Ser‐Ser‐Arg was able to come across the monolayers.     

Okra mucilage powder: a novel functional ingredient with antioxidant activity and antibacterial mode of action revealed by scanning and transmission electron microscopy

Okra mucilage powder (OMP) was firstly reported its antibacterial mode of action observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The reconstituted OMP or okra mucilage solution (OMS) with the concentration at 120 mg/mL was analysed for its total phenolic contents, total flavonoid contents and antioxidant activity reported as 11.33 ± 0.265 mg gallic acid/100 mL, 5.06 ± 0.197 mg catechin/100 mL and 176.18 ± 12.180 µmol Trolox equivalent/100 mL, respectively. The OMS exhibited strong antibacterial activities on Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes with more than 3 log reduction from bacterial inoculum. Nonetheless, mode of action of OMS studied via TEM revealed that cells treated with OMS showed broken cell walls, cell membrane separation and intracellular content leakage. SEM photography revealed furrowed bacterial cell wall surface for this OMS-treated cells when compared with untreated cells. Overall, our data suggested that the reconstituted OMP offered the greatest functional properties as antioxidant properties and antibacterial activities, aiding to its future application as a potential novel functional ingredient with health-promoting application.     

Influence of fermentation parameters on phytochemical profile and volatile properties of mulberry (Morus nigra) wine

In the present study Box–Behnken Design was employed to analyse the effects of fermentation parameters such as temperature (T _F), pH, inoculum size (I _S) and °Brix (B_X) on total phenolic concentration (TPC), total flavonoid concentration (TFC), total anthocyanin concentration (TAC), ethanol concentration (ETHC), total higher alcohol concentration (THAC) and total ester concentration (TESC) for the development of a phytochemical‐rich wine using mulberry as a substrate. The results demonstrated that fermentation parameters significantly alter the wine characteristics. Hence, a wine with excellent consumer preference (overall acceptability of 8.51) and high concentration of phytochemicals (TPC = 6014.03 ± 27.80 mg L⁻¹, TFC = 4791.35 ± 21.22 mg L⁻¹, TAC = 1480.72 ± 5.33 mg L⁻¹) as well as good aromatic properties (ETCH =82.85 ± 0.87 g L⁻¹, THAC =249.91 ± 0.31 mg L⁻¹ and TESC =52.55 ± 0.17 mg L⁻¹) with high antioxidant activity (DPPH =220.18 mmol·l⁻¹) was obtained at optimized fermentation conditions of T _F = 25°C, pH = 4.00, I _S = 10% (v /v) and B_X = 26. The results from the present study might contribute to strengthening the development of wine containing high concentrations of phytochemical compounds with attractive olfactory attributes. Copyright © 2017 The Institute of Brewing & Distilling     

Structural characterisation and immunomodulatory effects of polysaccharides isolated from Dendrobium aphyllum

A crude polysaccharide extract of Dendrobium aphyllum (cDAP, yield 38.15 ± 0.20%) was generated. The D. aphyllum polysaccharide (DAP, M_w 471.586 kDa), purified by DEAE‐Sepharose and Sephadex‐G200 Fast Flow, was composed of mannose (71.3%) and glucose (28.7%), according to GC–MS analysis. Its backbone was composed of β‐d ‐mannopyranose and β‐d ‐glucopyranose residues, as revealed by infrared spectroscopic analysis. Its glycosidic bond was mainly 1, 4‐linked, and the O‐acetyl groups were mainly linked to mannose residues, according to periodate oxidation and Smith degradation analysis. The DAP units polymerised into a filiform‐shaped spatial pattern, as characterised by atomic force microscopy and scanning electron microscopy. DAP treatment enhanced cytokine secretion (nitric oxide, interleukin‐6 and tumour necrosis factor‐α) and pinocytic and phagocytic capacities of RAW 264.7 mouse macrophages. The complement receptor 3 and mannose receptor were identified to be the receptors of DAP on RAW 264.7 cells, indicating that the Akt/mTOR/MAPK and IKK/nuclear factor‐?B pathways could be involved in DAP‐activated immunomodulation.     

Sugar beet pectin as a natural carrier for curcumin,a water-insoluble bioactive for food and beverage enrichment: Formation and characterization

Food and beverages enrichment with water-insoluble health-promoting nutraceuticals is important, but technologically challenging. Sugar beet pectin (SBP) is a natural dietary fiber with high emulsifying capacity. However, its potential as a natural encapsulator of hydrophobic nutraceuticals for beverage enrichment, has hardly been explored. Curcumin is a potent antioxidant with numerous attributed health benefits, but very low aqueous-solubility. We herein explored SBP as a carrier for solubilization and protection of curcumin (CUR). Using spectrofluorimetry, the CUR-SBP binding constant determined was (6.74 ± 0.5) ∙ 10⁵M⁻¹. As CUR:SBP molar ratio increased from 14:1 to 140:1, CUR encapsulation capacity increased from 14.5 ± 0.8 to 127.4 ± 0.4 mg _{CUR/g SBP}, and encapsulation efficiency moderately decreased from ~100% to 86 ± 7%. The encapsulation in SBP dramatically decreased CUR particle size, from >17 μm to <0.5 μm, in average, and conferred substantial protection to CUR during simulated shelf-life, decreasing the decay rate constant ~7 fold. Therefore, SBP is a potent natural encapsulator for hydrophobic nutraceuticals for food and even clear beverage enrichment.     

Decreasing effect of fluoride content in Antarctic krill (Euphausia superba) by chemical treatments

Decreasing effects of fluoride contents in Antarctic krill (Euphausia superba) as affected by chemical treatments with and without heating were investigated. The used chemicals were NaOH, Na₂CO₃, Na₂SO₃, citric acid, acetic acid, phosphoric acid, HCl, ethanol, lysine, aminoguanidine, arginine, carnitine, betaine, and creatine. Fluoride contents per dry weight were 788 ± 10 mg kg^?1 in the whole body of krill (WBK) and 294 ± 4 mg kg^?1 in the peeled krill meat (PKM) respectively. When WBK was treated with chemicals with and without heating or thawed, fluoride was not decreased. On the other hand, when the PKM was treated with chemicals without heating was remarkably decreased to less than 100 mg kg^?1, which is the criteria recommended by FDA. Particularly, the treatment of betaine without heating showed the best reduction effect of 30 ± 6 mg kg^?1, followed by carnitine (38 ± 17 mg kg^?1), acetic acid (52 ± 1 mg kg^?1), phosphoric acid (67 ± 2 mg kg^?1) and hydrochloric acid (68 ± 1 mg kg^?1).     

Effect of bioaugmentation on biochemical characterisation and microbial communities in Daqu using Bacillus,Saccharomycopsis and Absidia

Daqu, a saccharifying and fermenting agent for the production of Chinese vinegar and liquor, is manufactured through a spontaneous solid-state fermentation process (SSF). To investigate the influence of bioaugmentation with native microorganisms on Daqu SSF process, physicochemical properties, microbial biomass, volatile compounds and microbial communities were analysed in laboratory-scale Daqu. The results showed that the amylase activity of Daqu enhanced 6.35% ± 0.74% by inoculating Bacillus amyloliquefaciens, Saccharomycopsis fibuligera and Absidia corymbifera. Obviously higher microbial richness was found in the Daqu with bioaugmentation, although the microbial community structure remained relatively stable. Moreover, a total of twenty-two volatile compounds were detected in the mature Daqu. Slightly increase in the content of alcohols was found in the enhanced group by fungal inoculation, including ethanol (46.58 ± 1.36 mg kg⁻¹), isobutanol (0.19 ± 0.04 mg kg⁻¹) and isoamyl alcohol (1.55 ± 0.13 mg kg⁻¹). This study demonstrated that bioaugmentation had a positive effect on the amylase activity, main volatile compounds and microbial community richness.     

Partial purification of a polygalacturonase from a new Aspergillus sojae mutant and its application in grape mash maceration

The use of polygalacturonase (PG) preparations in winemaking promotes the release of phenolic compounds. A PG from a new source, Aspergillus sojae mutant, was semi‐purified and tested for grape mash maceration. Crude extract (CE), a commercial pectinase, and two high PG activity semi‐purified preparations, F_I and F_II, were applied for maceration at PG activity of 3.5 U g^?1 of grape for 46 h. Enzyme‐assisted maceration significantly (P < 0.05) increased the total phenolic content from 255.8 to 916.3 ± 5.2, 5732.9 ± 9.9, 563.4 ± 6.7 and 620.6 ± 18.4 mg L^?1 for CE, commercial pectinase, F_I and F_II, respectively. The content of individual phenolics such as gallic, protocatechuic, chlorogenic and p‐coumaric acids was improved. Principal component and hierarchical clustering analyses suggested that CE has a better performance upon the release of phenols. Semi‐purified preparations acted similar to commercial pectinase. These findings open an opportunity for the potential use of PG from the mutant strain as an alternative macerating enzyme.     

Effect of limited enzymatic hydrolysis on physico‐chemical properties of soybean protein isolate‐maltodextrin conjugates

The effect of limited hydrolysis was investigated on the physico‐chemical properties of soy protein isolate–maltodextrin (SPI‐Md) conjugate. The hydrolysates at a degree of hydrolysis (DH) of 1.8% showed much higher surface hydrophobicity (H₀; 71.39 ± 3.60) than that of the SPI control (42.09 ± 2.17) and SPI‐Md conjugates (53.46 ± 2.74). Intrinsic fluorescence analysis demonstrated the unfolding of protein molecule and exposure of hydrophobic groups of SPI‐Md conjugate hydrolysates. As evidenced by far‐UV circular dichroism (CD) spectroscopy, the limited hydrolysis increased the unordered secondary structures of SPI‐Md conjugates. The denaturation temperature (T_d) of SPI‐Md conjugate was significantly increased by subsequent limited hydrolysis from 102.53 ± 0.60 °C to 108.11 ± 0.61 °C at DH 1.8%. In particular, the emulsifying activity index (EAI) was improved notably after limited hydrolysis of DH 1.8% (147.76 ± 4.39 m² g^?1) compared with that of native SPI (88.90 ± 1.44 m² g^?1) and SPI‐Md conjugate (108.97 ± 1.45 m² g^?1).     

Yogurt and Streptococcus thermophilus metabolites ameliorated telomere attrition in D-galactose-induced ageing mice and t-BHP-challenged HepG2 cells

Antioxidant-rich diets affect telomere length, an integrative marker associated with age-related diseases. Yogurt exerts antioxidative capacity and is speculated to support healthy ageing. However, direct experimental evidence is missing. Here, the effects of yogurt and dairy-fermenting bacteria on D-galactose-induced ageing mice and chemically challenged HepG2 cells were evaluated. Relative telomere length (RTL) in leucocyte and liver were significantly longer in yogurt (1.21 ± 0.07; 1.23 ± 0.11) and Streptococcus thermophilus group (1.18 ± 0.15; 1.13 ± 0.12). When t-BHP-challenged HepG2 cells were treated with digested yogurt and S. thermophilus, the senescence index (13.67 ± 3.30; 19.67 ± 2.87) were lower and RTL (1.25 ± 0.11; 1.18 ± 0.10) were longer than the model. Antioxidative effects were observed for yogurt and S. thermophilus metabolites, whereas milk and Lactobacillus rhamnosus metabolites showed minimal influence on RTL and oxidative stress. In conclusion, this study showed that yogurt and S. thermophilus metabolites ameliorated telomere attrition in ageing mice and t-BHP-challenged HepG2 cells, possibly by reducing oxidative stress.     

Spectroscopic and molecular docking studies of the interactions of sunset yellow and allura red with human serum albumin

Binding interactions of human serum albumin (HSA) with sunset yellow (SY) and allura red (AR), two food colorants, were investigated at the molecular level through fluorescence and UV absorption as well as molecular docking. The collective results of the study under the simulated physiological conditions proposed a static type of binding occurring between the two dyes and HSA. When compared with AR (293 K: Ksv = (4.21 ± 0.36) × 10⁴ L·mol⁻¹; K_b = (0.30 ± 0.23) × 10⁶ L·mol⁻¹), SY (293 K: Ksv = (6.80 ± 0.10) × 10⁴ L·mol⁻¹; K_b = (3.11 ± 2.01) × 10⁶ L·mol⁻¹) had stronger quenching ability and higher affinity for HSA due to less steric hindrance. It can be deduced that the energy transfer from HSA to the two dyes occurred with high probability based on the Förster resonance energy transfer theory (r < 7 nm, 0.5 R₀ < r < 2.0 R₀). The spectral analysis suggested that the formation of the dye-HSA complex resulted in the change in microenvironment around Tyr and Trp residues and in the secondary structure of the protein. According to molecular docking simulation, the two structural analogs almost bound to the same site of HSA, near Sudlow's Site I, but significant difference existed in the number and location of hydrogen bond (H-bond) formed between the dyes and HSA. From the molecular docking along with the thermodynamic parameters (AR: ΔH^o = −(58.79 ± 15.24) kJ·mol⁻¹, ΔS^o = −(115.1 ± 31.10) J·mol⁻¹·K⁻¹; SY: ΔH^o = −(52.24 ± 3.15) kJ·mol⁻¹, ΔS^o = −(50.07 ± 11.14) J·mol⁻¹·K⁻¹), it could be inferred that H-bond and van der Waals forces were the major binding forces involved in formation of the dye-HSA complexes.     

Kinetics of Crude Peroxidase Inactivation and Color Changes of Thermally Treated Seedless Guava (Psidium guajava L.)

Thermal treatment of seedless guava (Psidium guajava L.) cubes was carried out in the temperature range of 80–95 °C. The kinetics of peroxidase inactivation and color changes due to thermal treatments were determined. Peroxidase inactivation followed a first-order kinetic model, where the activation energy was 96.39 ± 4 kJ mol⁻¹. Color was quantified in terms of L, a, and b values in the Hunter system. The color changes during processing were described by a first-order kinetic model, except total color difference which followed a zero-order kinetic model. The temperature dependence of the degradation followed the Arrhenius relation. The activation energies (E _a) for L, a, b, and total color difference (ΔE) were 122.68 ± 3, 88.47 ± 5, 104.86 ± 5, and 112.65 ± 5 kJ mol⁻¹, respectively. The results of this work are a good tool to further optimize seedless guava thermal treatment conditions.     

Thermal Inactivation Kinetics of Tulane Virus in Cell‐Culture Medium and Spinach

Human noroviruses (HNoVs) cause significant gastrointestinal disease outbreaks worldwide. Tulane virus (TV) is a cultivable HNoV surrogate widely used to determine control measures against HNoVs. The objective of this study was to determine the heat inactivation kinetics (D‐ and z‐values) of TV in cell‐culture media and on spiked homogenized spinach using the first‐order and Weibull models. TV in cell‐culture media at approximately 7 log PFU/mL (PFU—plaque forming unit) in 2‐mL glass vials was heated at 52, 54, and 56 °C for up to 10 min in a circulating water bath. Survivors were enumerated using confluent host LLC‐MK2 cells in six‐well plates by plaque assay. Data from three replicate treatments assayed in duplicate were analyzed statistically. D‐values by the first‐order model for TV in cell‐culture media at 52, 54, and 56 °C were 4.59 ± 0.05, 2.91 ± 0.05, and 1.74 ± 0.07 min, respectively, with a z‐value of 9.09 ± 0.01 °C (R² = 0.997). The Weibull model showed t_d = 1 values of 2.53 ± 0.08, 1.99 ± 0.10, and 0.57 ± 0.64 min, respectively, at the same temperatures. The D‐values for TV in spinach were 7.94 ± 0.21, 4.09 ± 0.04, and 1.43 ± 0.02 min and the z‐value was 10.74 ± 0.01 °C (R² = 0.98) by the first‐order model and 4.89 ± 0.02, 3.21 ± 0.45, and 0.25 ± 0.38 min for the Weibull model at 50, 54, and 58 °C, respectively. In comparison to previously reported results for the cultivable HNoV surrogate, murine norovirus ‐1, TV in cell‐culture media and spiked on spinach homogenates showed lower D‐ and z‐values. TV may not be an ideal HNoV surrogate for heat inactivation studies in cell‐culture media or homogenized spinach in vacuum bags.     

The potential application of the protein hydrolysates of three medicinal plants: cytotoxicity and functional properties

Functional evaluation of encrypted bioactive peptides in protein structure helps to better understand those for using in pharmacy and food sciences. For this purpose, the total protein was extracted from Matricaria chamomilla, Ziziphora clinopodioides, and Cressa cretica, and partially purified with ammonium sulfate. Protein hydrolysates were obtained from pancreatin hydrolysis for 240 min and the enzyme hydrolysis was confirmed using the determination of hydrolysis degree and Fourier transform infrared (FT-IR) followed by the physicochemical and sensory properties were investigated. The results showed that all hydrolysates had both cytotoxic and antioxidant activities. Specifically, C. cretica hydrolysates represented cytotoxic activity against the MCF-7 cell line with the IC₅₀ of 135.21 µg/mL, while showed no significant growth inhibition effect on the HEK293 cell line. Besides, M. chamomilla hydrolysates showed the lowest bitterness value (1.125 ± 0.52). From the perspective of color investigation, M. chamomilla hydrolysates indicated the highest L^* and the lowest a^* factors. The highest turbidity and surface tension, and 10-fold more cancer cell killing effect under gastrointestinal digestion conditions were observed for M. chamomilla hydrolysates. Therefore, bioactive peptides might be formulated in designing of novel anticancer drugs or could be used in promising protocols for the production of food products with beneficial health effects.     

Modeling of Enzymatic Hydrolysis of Whey Proteins

The aim of this work was to emphasize the limitations of modeling complex phenomena under unrealistic model assumptions. As a case study, the whey protein hydrolysis mechanism was modeled. A stirred batch reactor was used to study the degree of hydrolysis of sweet whey protein concentrate by using the protease alcalase. A completely random two-factorial experimental design was used, three levels of initial enzyme concentrations (E ₀) (1.58, 3.18, 6.36 AU (Anson units)/L) times three levels of initial substrate concentrations (S ₀) (18.73, 38.45, 81.16 g/L). All treatments were carried out at optimal alcalase—activity conditions: pH 8 and 50 °C. Reactions were monitored for 180 min. The degree of hydrolysis (h) curves was finally adjusted for each treatment to the exponential model using nonlinear regression techniques but not assuming a Michaelis–Menten relationship. From the estimation process, the coefficient b was constant (27.26 ± 1.37) and independent of E ₀ and S ₀, while coefficient a depended directly on the ratio E ₀/S ₀, ranging from 0.0017 to 0.0497. A noncritical strategy of forward modeling based on unrealistic assumptions was misleading in the face of complex phenomena; instead, a modeling strategy moving from data to the identification and estimation of parameters of practical interest must be considered.     

Modelling osmotic dehydration of lemon slices using new sweeteners

Lemon slices were osmotically dehydrated using the following healthy sweeteners as osmotic agents: tagatose, isomaltulose, oligofructose and aqueous extract of stevia. A kinetic study using a Fickian approach was performed, which also analysed the changes in water activity, total mass, mass of water and mass of soluble solids in lemon slices. The results showed that the greatest value of effective diffusivity (D_e) in osmodehydrated lemon slices was obtained from a combination of oligofructose and stevia [D_e = (10.2 ± 0.3) × 10^?9 m²·s^?1]. However, the level of water activity (a_w) reached with this syrup was the highest (a_w = 0.978 ± 0.004 after 1440 min) meaning that the product might be less stable. Additionally, isomaltulose favoured the total mass loss, whereas tagatose did the opposite. Finally, the syrup recommended for dehydrating lemon slices would be a combination of tagatose, oligofructose and aqueous extract of stevia as its D_e was similar to the value obtained when only oligofructose and stevia were used, but a_w values were lower.     

The effect of hydrogen peroxide bleaching of canola meal on product colour,dry matter and protein extractability and molecular weight profile

The aim of this study was to bleach canola meal by hydrogen peroxide to understand the treatment effect on product colour, dry matter and nitrogen extractability. Meal suspensions at 2.5%, 5% and 10% (w/v) were treated in 3, 6 and 10% H₂O₂ at pH 3, 7 and 10. The bleached meal was extracted under acidic and alkaline conditions. The results showed a high bleaching effectiveness of canola meal by H₂O₂. The L* parameter was increased from 47.18 ± 0.56 up to 86.80 ± 1.05. Effect of pH was significant and the highly bleached meal was obtained at pH 10. Extractability of dry matter was increased when the meal was treated with H₂O₂, from 26.87 ± 0.10% for the control meal up to 83.20 ± 0.59% for the meal treated in 10% H₂O₂ in a 2.5% (w/v) suspension. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis showed a depolymerisation effect of H₂O₂ on the high molecular weight proteins.     

Starch hydrogels from discarded chestnuts produced under different temperature-time gelatinisation conditions

It is essential to know the temperature-time dependence on the chestnut starch gelatinisation process. With this aim, physicochemical and thermomechanical properties of native chestnut starch and with different gelatinisation degrees, isolated from discarded chestnut fruits under environmental friendly aqueous procedures, were studied. Isolated starch (144.96 ± 1.74 μm) presented high total starch (91.83 ± 0.24%), low damage starch (0.10 ± 0.04%), apparent amylose content of 20.31 ± 1.48% and relative crystallinity of 15.7 ± 0.4% with a C-type pattern. Chestnut starch dispersions were formulated at 40% (w/w). Rheological measures indicated that temperatures below 60 °C were not able to form a hydrogel. The hydrogels formed between 62.5 and 65 °C (peak and final gelatinisation temperature, respectively) developed a stable and strong network with short maturation times and full thermoreversibility. Finally, hydrogels prepared above 65 °C were weaker and no completely thermoreversible. A linear relationship was identified between elastic features determined by rheology (G′_gel,1 Hz) and texture (springiness, D₁/D₂).     

Bifurcaria bifurcata: a key macro‐alga as a source of bioactive compounds and functional ingredients

The aim of this work was to study the proximate composition and the bioactive profile of Bifurcaria bifurcata. It contains 73.31 ± 0.69% of moisture, 8.57 ± 0.11 g per 100 g dry weight (d.w.) of protein, 5.81 ± 0.14 g per 100 g d.w. of lipid content and 30.15 ± 0.00 g per 100 g d.w. of ash. The polyunsaturated fatty acids were the most abundant fatty acid (FA), accounting for 2426.56 mg per 100 g which represents 41.77% of the total FA. The methanolic fraction showed high quantity of polyphenols (220.01 ± 0.010 phloroglucinol equivalents g^?1 extract), DPPH radical reduction capacity (EC₅₀:58.82 μg mL^?1) and oxygen radical absorbent capacity (3151.35 ± 119.33 μmol Trolox equivalents g^?1 extract). The highest antimicrobial effect was observed against Pseudomonas aeruginosa (11.3 ± 1.5 mm) and Saccharomyces cerevisiae (IC₅₀:17.07 μg mL^?1) induced by methanolic and dichloromethane fractions, respectively. Dichloromethane fraction revealed the highest antitumor activity on Caco‐2 and HepG‐2 cells. Bifurcaria bifurcata can be a promising source of bioactive compounds and functional ingredients.     

Microwave‐assisted degradation of chitosan with hydrogen peroxide treatment using Box‐Behnken design for enhanced antibacterial activity

Low molecular mass (MM) chitosan with high degree of deacetylation (DDA) has excellent bioactivity including antioxidant, antibacterial and encapsulation properties. In this work, to reduce the MM of chitosan, microwave‐assisted heating treatment (MAHT) conditions were investigated using three factors at three levels Box‐Behnken design (BBD). Microwave heating (MH) time, H₂O₂ concentration and solid‐to‐liquid ratio significantly affected the DDA and MM of chitosan. The antibacterial activities of chitosan before and after degradation were investigated based on minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The results showed that a second‐order polynomial equation fitted the observed values using multiple regression analysis and had a high coefficient of determination (R² = 0.9591 and 0.9161 for the DDA and MM of chitosan, respectively). An optimisation study was performed using Derringer's desirability function methodology, and the optimal conditions were 80‐s MH time, 1.5% H₂O₂ concentration and 1:40 solid‐to‐liquid ratio. The MIC and MBC of chitosan before and after degradation against Escherichia coli and Salmonella typhimurium were 0.031 and 0.063 mg mL^?1, and 0.25 and 0.125 mg mL^?1, respectively. The optimised DDA and MM of chitosan were 90.58 ± 2.04% and 124.25 ± 14.36 kDa, respectively, which significantly reduces the use of oxidant reagent.