Physicochemical characterization of chitosan extracted from Metapenaeus stebbingi shells

In this study, chitosan was extracted from Metapenaeus stebbingi shells. In order to determine physicochemical characteristics of the extracted chitosan, the yield, moisture and ash contents, degree of deacetylation, molecular weight, water and fat binding capacities, apparent viscosity and colour properties were measured using a variety of techniques including Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. In addition, the physicochemical characteristics of the chitosan extracted from M. stebbingi shells were compared to commercial chitosan. The degree of deacetylation was calculated by the titration method and elemental analysis. The molecular weight was determined by viscosimetric methods. The results of the study indicate that shrimp shells are a rich source of chitosan as 17.48% of the shell’s dry weight is consisted of this material. Extracted chitosan exhibited a lower molecular weight, higher degree of deacetylation, higher viscosity and higher water and fat binding capacities compared to the commercial chitosan.     

In vitro binding of bile acids and triglycerides by selected chitosan preparations and their physico-chemical properties

The selected 11 chitosan samples were evaluated for their fat- and bile acid-binding capacities, physico-chemical properties, and the correlations between each binding capacity and individual physico-chemical properties. The bile acid- and fat-binding capacities were estimated using in vitro assays, whereas the measured physico-chemical properties were deacetylation degree, swelling capacity, and solution viscosity. Chitosan samples might differ in their binding capacities against fat and/or individual bile acids. The bile acid-binding capacities were 0.20-0.61, 0.43-1.63, and 0.61-1.61 μmol/g chitosan for cholic, deoxycholic, and chenodeoxycholic acids, respectively. Stronger binding capacity of chitosan against a selected bile acid does not warrant greater binding capacity for other bile acid. The fat-binding capacity ranged from 1077-1239 g oil/g for the chitosan samples under the experimental conditions. No correlation was observed between any binding ability and individual physico-chemical properties, although the swelling capacity of chitosan was correlated to the solution viscosity (r=0.82, P=0.02) and deacetylation degree (r=-0.62, P=0.04), indicating that none of the measured physico-chemical properties can be used to predict the fat- or bile acid-binding ability of chitosan.     

Comparison of physicochemical,binding, antioxidant and antibacterial properties of chitosans prepared from ground and entire crab leg shells

Physicochemical, binding, antioxidant and antibacterial properties of chitosans prepared from ground and entire crab leg shells were compared. Chitosan prepared from ground shell (designated as g‐chitosan) had significantly higher nitrogen content, degree of deacetylation, solubility and viscosity, but lower ash content, bulk density and colour redness (a*) value than chitosan prepared from entire shell (designated as e‐chitosan). Compared with e‐chitosan, g‐chitosan had comparable water‐binding capacity, but higher fat‐binding and dye‐binding capacity, DPPH radical scavenging activity and antibacterial activity against two Gram‐negative (Salmonella Enteritidis and Escherichia coli) and two Gram‐positive (Listeria monocytogenes and Staphylococcus aureus) bacteria. This study demonstrated that chitosans prepared from ground and entire crab leg shell exhibited drastic differences in their physicochemical and functional characteristics. These differences were contributed by the particle size of the crab shell.     

脱乙酰魔芋葡甘聚糖性质及其脂类结合能力研究

采用红外及X-衍射等分析手段表征魔芋葡甘聚糖(KGM)与脱乙酰魔芋葡甘聚糖(Da-KGM)结构并比较其持水性和粘度,以纤维素为对照,采用体外模拟人体胃及肠道的pH环境,对比分析KGM及Da-KGM对脂肪及胆固醇的吸附能力。结果显示KGM脱乙酰基后1733 cm~(-1)处的乙酰基的特征吸收峰消失,结晶度增加,持水性下降83.7%,高粘度特性丧失;相比纤维素,KGM具有良好的脂肪及胆固醇吸附能力,其吸附总量随样品质量、吸附时间和胆固醇浓度的增加而增大,与天然KGM相比,Da-KGM的脂肪及胆固醇吸附能力降低,可能是因为KGM脱除乙酰基后KGM分子链间氢键作用加强致使与脂类结合位点减少,以及高粘度特性消失致使对脂类的直接包裹能力下降,提示KGM经脱乙酰加工成魔芋食品后在肠道与脂类的结合能力下降,其减肥降脂的生理功效可能受到影响。     

Preparation and characterisation of selected physicochemical and functional properties of β‐chitosans from squid pen

Squid pen β‐chitosans prepared under various deacetylation conditions (30%, 35%, 40% and/or 45% NaOH for 15, 30 and/or 60 min) were characterised. β‐Chitosans (deacetylated with 35–45% NaOH for 15–60 min) had 87.1–96.2% degree of deacetylation (DD), 93.5–96.7% solubility and 120.5–654.9 mPa s viscosity. Treatment with 30% NaOH for 15–60 min yielded inadequately deacetylated β‐chitosans (DD = 51.9–80.2%). Two chitosans prepared under 35% NaOH for 15 min and 45% NaOH for 30 min (designated as 35%–15 and 45%–30, respectively) were further compared. Drying (sun‐drying vs. oven‐drying) methods did not affect DD. 35%–15 chitosan exhibited lower nitrogen, DD and bulk density, but higher viscosity compared with 45%–30 chitosan. Higher water‐ and fat‐binding capacity but lower DPPH radical scavenging activity were observed for 35%–15 chitosan compared with 45%–30 chitosan. Compared with 45%–30 chitosan, 35%–15 chitosan exhibited higher antibacterial activity against Salmonella Enteritidis and Listeria monocytogenes, but lower antibacterial activity against Escherichia coli.     

The preparation of chitosan nanoparticles by wet media milling

Three different molecular weights of chitosan were pulverised to nanoparticles by wet media milling. The effects of the milling on properties of chitosan, such as viscosity average molecular weight (Mv), ash content, the degree of deacetylation (DD), particle size, chemical structure, colour, swelling power and apparent viscosity, were investigated. Our results showed that high (578.3 kDa), medium (181.6 kDa) and low (66.3 kDa) molecular weight chitosan with particle size of 342.7, 358.1 and 346.2 μm were milled to nanometre range after 1, 1.5 and 2.5 h of milling, respectively. After 5 h of milling, the particle sizes of the three samples were decreased to 543.8, 366.6 and 308.4 nm, respectively. Chitosan did not show significant increase in ash contents after milling. The milling decreased the Mv of chitosan, but did not change DD and the chemical structure. The suspension of chitosan nanoparticles was of cream‐white colour. The swelling powder and apparent viscosity of chitosan increased after the milling treatment.     

Studies on kolanut and cashew kernels: moisture adsorption isotherm,proximate composition,and functional properties

Kolanut (Cola nitida) and cashew (Anacardium occidentale) kernels were analysed and their moisture adsorption isotherms, proximate composition, and functional properties were compared. The dried powdered sample of kolanut contained 69% carbohydrate, 18% crude fat and 3.1% ash by weight, while the cashew sample had 51% crude fat, 36% crude protein, 0.3% ash and 3.4% carbohydrate. These differences significantly affected their relative water and oil absorption capacities, least gelation concentration, bulk density, and emulsion properties. However, both samples would retain nutritional integrity when stored in atmospheres with water activities of up to 0.68 for kolanut and 0.85 for cashew kernels. The Brunauer–Emmett–Teller (BET) and Henderson mathematical models described both isotherms with less than 2% mean relative deviation.     

Functional properties of raw and precooked taro (Colocasia esculenta) flours

Functional properties such as bulk density, water and oil absorption, foam capacity and stability, and viscosity of five raw and precooked taro ( Colocasia esculenta ) flours were studied. Proximate analyses of the taro flours indicated they were low in fat, protein and ash, but rich in starch and total dietary fibre. Heat processing affected the functional properties of taro flour. the raw taro flours were slightly different from each other for the tests on bulk density, water retention, and viscosity. On the other hand, the cooked flours showed no significant differences for the tests on oil retention, gelation and foaming.     

Physicochemical characterisation of β-chitosan from Sepioteuthis lessoniana gladius

β-Chitin and its chitosan from the gladius of Sepioteuthis lessoniana have been isolated, purified, characterised and compared with the commercial chitosan. Ash, moisture, mineral, metal and elemental content were analyzed using standard techniques. The optical activity of chitin was found to be levorotatory. The degree of deacetylation was calculated by potentiometric titration and ¹H NMR. Viscosity average molecular weight of β-chitosan was calculated by viscometry and size average molecular weight by GPC. The structure of β-chitosan was elucidated with FT-IR and NMR. Thermal nature, crystalline structure and morphology of β-chitosan were characterised through DSC, XRD and SEM, respectively. The water and fat binding capacity of β-chitosan presently studied was significantly higher than that of the commercial chitosan. The result of the present study adds that S. lessoniana gladius is also an additional source of β-chitin and chitosan of higher yield, lower molecular weight and higher degree of deacetylation.     

Physicochemical and functional properties of chitosans affected by storage periods of crab leg shell

Effects of storage period (0, 1, 2, 3 and 4 months) of crab leg shell at room temperature on selected physicochemical and functional properties of E‐ and G‐chitosans, respectively, prepared from entire (E) and ground (G) shells were evaluated. Increased storage period of crab shell generally increased degree of deacetylation (DD) and viscosity, but decreased DPPH radical scavenging activity of both chitosans. Water‐binding (WBC) and fat‐binding (FBC) capacities of E‐chitosan were not affected by storage period of crab shell; however, those of G‐chitosan significantly increased when crab shell was stored for more than 1 month. Dye‐binding capacity (DBC) of both chitosans decreased when crab shell was stored for 1 month, but further decrease was not observed with increased storage period to 4 months. Prepared with 4‐month stored crab shell, E‐chitosan exhibited comparable viscosity, colour whiteness index, DPPH radical scavenging activity and DBC, but lower DD, WBC and FBC than G‐chitosan.     

Denaturation of soybean proteins related to functionality and performance in a meat system

The effect of heat treatment on the functional properties of a soybean protein isolate was studied; heat affected the nitrogen solubility and gel properties of the isolate as well as its water absorption ability and viscosity. Significant correlations were found between protein solubility and gel viscosity. The viscosity of dispersions correlated to solubility or to water absorption depending on the protein concentration. Significant correlations were found between the functional properties of the protein and moisture loss from a model system in which the meat protein was partially replaced with soya. Protein solubility and gel properties were found to be the best predictors of moisture loss from the meat system. Viscosity of raw meat systems correlated with the solubility and water absorption of the added soya protein.     

壳聚糖溶液的流变学性质及应用研究

对壳聚糖稀溶液的流变学性质进行了研究,探讨了分子量和脱乙酰度结构参数以及温度、浓度、剪切速率、pH、离子强度等环境因素对壳聚糖稀溶液流变性质的影响。结果表明:壳聚糖溶液的黏度随分子量的增大而增大;随着脱乙酰度的增大和pH的增大,壳聚糖溶液的黏度先减小后增大,分别在脱乙酰度70.8%和pH4.9时黏度达到最小;离子强度的增大导致壳聚糖溶液的黏度降低。壳聚糖溶液是剪切变稀的假塑性流体,其黏度随浓度的增加逐渐增加,随温度的升高而减小,在0~80℃范围内,温度对壳聚糖溶液的黏度的影响符合Arrhenius模型,活化能为32.60kJ/mol。因此当作为食品增稠剂时,应该选用高分子量、高脱乙酰度的壳聚糖,添加到酸性低盐食品体系中。     

南极磷虾壳聚糖、壳寡糖的制备与品质鉴定

本研究以南极磷虾壳为原料,制备较高品质的壳聚糖与壳寡糖,并对二者的品质进行鉴定。南极磷虾壳经脱钙、脱蛋白处理,探索脱乙酰反应条件（碱溶液浓度、反应温度与反应时间）,制备具有较高脱乙酰度的南极磷虾壳聚糖,并对壳聚糖的理化指标进行鉴定;探索酶法降解条件（壳聚糖酶添加量、酶解时间）,制备较高纯度的南极磷虾壳寡糖,并对壳寡糖的结构特征进行鉴定。结果表明,使用60%的氢氧化钠于110 ℃脱乙酰处理4 h制备的南极磷虾壳聚糖脱乙酰度为85.74%,粘均分子量为 305.65 kDa,水分含量4.66%,灰分含量0.98%,酸不溶物含量0.40%,各项理化指标均符合食品级壳聚糖的要求;使用壳聚糖酶水解南极磷虾壳聚糖制备壳寡糖,在壳聚糖酶添加量为0.2% （m/V）,酶解16 h条件下,南极磷虾壳寡糖产品得率为46.0%,红外光谱与NMR谱图显示了表征壳寡糖结构的全部特征峰,质谱结果显示南极磷虾壳寡糖主要由二糖(GlcN)₂、三糖(GlcN)₂-GlcNAc与四糖(GlcN)₃-GlcNAc构成。本研究通过制备较高品质的壳聚糖与壳寡糖,为南极磷虾壳的高值综合利用与南极磷虾新产品开发提供了技术支持。     

Processing and formulation effects on rheological behavior of barley β-glucan aqueous dispersions

A freeze–thaw cycling process applied to barley β-glucan aqueous dispersions resulted in network structure development, which remained intact after thawing in both acidic and neutral conditions. The effects of freeze–thaw cycling were milder in the presence of sucrose where β-glucans were less prone to cryogel formation, giving weaker cryostructurates. The effect of three operating factors (β-glucan content, sucrose content and salt content) and their interactions on viscosity at shear rates of 10, 50 and 125 s⁻¹ was studied using response surface methodology. Significant positive linear effects were identified for all the factors on the first two models, while salt was not significant for the response at 125 s⁻¹. The β-glucan also exhibited significant negative quadratic effects for all three responses. Significant negative interactions were observed between β-glucan and sucrose, and β-glucan and salt for the viscosity at 10 and 50 s⁻¹, while for the viscosity at 125 s⁻¹, only the interaction between β-glucan and sucrose was significant. Response surface methodology and a second order regression model were used for the study of three factors (pH, temperature and time) influencing the viscosity of β-glucan dispersions of a low and a high molecular weight sample, following acid hydrolysis. Significant linear effects on viscosity of the low and high molecular weight samples were obtained for all the factors. A significant positive interaction effect was observed between pH and time for the viscosity of the lower molecular weight sample, while time exhibited a significant negative quadratic effect for the response of the high molecular weight sample. Acid hydrolysis had a stronger impact on viscosity reduction of the high molecular weight sample.     

Deteriorative changes in pink perch mince during frozen storage

Frozen storage of mechanically deboned pink perch mince for 180 days resulted in a decrease in emulsifying capacity, protein solubility, and relative viscosity while, cook-loss, water binding capacity in terms of absorbed moisture, and drip-loss increased. Alteration in protein fractions were observed by polyacrylamide gel electrophoresis and protein break down products (volatile bases) were increased. There was little change in lipid oxidation products (peroxide value and thiobarbituric acid) but a very large increase in free fatty acids. Significant (P < 0.05) correlations existed between several of these changes. Sensory attributes of the cooked mince deteriorated after 90 days. Mechanical deboning and freezing of the pink perch mince could offer a potential means of processing currently wasted by-catch fish for human food.     

Nutritional and sensory properties of a maize‐based snack food (kokoro) supplemented with treated Distillers’ spent grain (DSG)

The effect of treated Distillers’ spent grain (DSG) supplementation on the nutritional and sensory properties of kokoro, a maize‐based snack, was investigated. Treated DSG was used to replace 5%, 10%, 15%, 20%, 25%, 30% and 35% of maize flour. Mean water absorption capacity of DSG was 291%, swelling capacity 2.27 bulk density was 58%, oil absorption capacity 216, protein content of 27% and a total dietary fibre content 24.2%. The swelling, water and oil absorption capacities of the flour blends increased while bulk density decreased significantly. The ash, fat, protein, insoluble and total dietary fibre and total nonessential and essential amino acids contents of the flour blends increased with DSG inclusion. Processing the flour blends to kokoro slightly increased the ash, fat and protein contents, while the total nonessential and essential amino acids, total sugar and total dietary fibre decreased. The addition of DSG increased the lysine and tryptophan contents of kokoro. Although the sensory evaluation results indicate that kokoro with 5%, 10% and 15% DSG were well accepted and compared favourably with those made from whole maize for overall acceptability, it was observed that generally, there is a consumer dislike of the new product as the amount of DSG added increased.     

Effect of Defatted Maize Germ Addition on the Functional and Textural Properties Of Wheat Flour

The objective of this study was to assess functional properties of wheat flour blends with defatted maize germ flour (DMGF), a byproduct of the corn oil industry, at 5–25% levels. The bulk density, oil, and water absorption capacities, emulsion/foaming capacity and stability, objective color, least gelation concentration, and rheological properties (apparent viscosity and dough compression) were determined in control and flour blends. With DMGF addition, bulk density and foaming capacity decreased from 0.62 g/mL to 0.55 g/mL and 33.7% to 25.7%, respectively, both at 25% level. In general, when compared to control, oil and water absorption and emulsion capacities increased significantly in flour blends with >10% DMGF. Overall, regardless of the DMGF level, complete or partial gelling was observed at ≥ 8% gelation concentration. The apparent viscosity increased with increasing DMGF levels (0–25%) in all flour blends and also at all 4 concentrations from 5% to 20%. The control flour dough had a hardness value of 7.56 N, which increased significantly to 84.6N, when the DMGF level increased to 25% in the flour blend. These results indicate that most of the functional properties of wheat flour blends improved with DMGF addition, thus DMGF has a great potential to be used in a variety of food products.     

脱乙酰化反应条件对壳聚糖性能的影响

本文研究了甲壳素在脱乙酰化反应时不同反应条件,如碱浓度、反应时间、反应温度和处理方法对壳聚糖性能,如分子量、脱乙酰化度的影响,探讨了分子主链降解反应与脱乙酰化反应之间的关系。结果表明:随着碱浓度和反应时间的增加,壳聚糖脱乙酰化度提高,而分子量降低;脱乙酰化越高,主链降解程度增加;反应温度升高,脱乙酰化反应速度加快;而采用短时重复多次反应的处理方法,则可增加壳聚糖的脱乙酰化度,并减少主链降解程度。     

新鲜与干制柑橘皮果胶物化特性比较分析

以柑橘皮为原料,分析、比较新鲜柑橘皮果胶（fresh citrus pectin,FCP）与干制柑橘皮果胶（dried citruspectin,DCP）的物化特性差异。采用传统酸法结合金属螯合剂（六偏磷酸钠）分别从新鲜、干制柑橘皮中提取得到果胶FCP、DCP,测定FCP和DCP的物化特性参数,包括水分、灰分、酸不溶灰分和蛋白含量等基本理化指标,以及半乳糖醛酸含量、酯化度、胶凝度、分子质量和表观黏度等果胶品质评价指标。结果表明：FCP与DCP的基本理化性质相差不大,FCP半乳糖醛酸含量、酯化度、胶凝度和分子质量分别为77.29%、67.5%、179.8和158.8 kD,而DCP对应的值依次为74.98%、66.7%、153和109.1 kD,FCP表观黏度值高于DCP。新鲜和干制柑橘皮果胶品质存在一定差异,特别是作为果胶品质重要参考指标的胶凝度,FCP要高于DCP,而这可能与FCP的分子质量较高有关,但两者的半乳糖醛酸含量和酯化度均符合果胶品质的国家标准GB25533-2010《食品安全国家标准 食品添加剂》要求。     

豆渣膳食纤维对酥性饼干特性的影响

将豆渣中酶法提取的可溶性膳食纤维(豆渣SDF)、不溶性膳食纤维(豆渣IDF)以及商业菊粉,分别添加到酥性饼干中,研究其对饼干的物理化学特性和感官品质的影响。结果表明:添加豆渣IDF的饼干持水性和硬度较高,添加豆渣SDF和菊粉的饼干松密度值和过氧化值较低,且两者的松密度值没有较大差异,而添加豆渣IDF的饼干与之相反,添加4%豆渣SDF的饼干感官评定结果最优,且总膳食纤维、水分和脂肪含量较空白高,而蛋白质和灰分含量没有明显变化。