pH精制区带逆流色谱分离制备红曲中的酸式莫那可林K

建立了pH精制区带逆流色谱分离制备红曲中功能成分酸式莫那可林K的新方法。首先用体积分数95%乙醇提取红曲中的莫纳可林K,然后经过碱化处理使内酯式莫那可林K转化为酸式,最后采用溶剂系统V(石油醚):V(乙酸乙酯):V(甲醇):V(水)=5:5:4:6,上相添加HCl(10mmol/L)作为固定相,下相添加氨水(10mmol/L)为流动相进行pH精制区带逆流色谱分离。分离所得的酸式莫那可林K经HPLC检测纯度,并用UV,ESI-MS和~1H-NMR鉴定其化学结构。从2.0g粗提物一次分离得到纯度为93.4%的酸式莫那可林K147mg。     

Thermal degradation kinetics analysis of monacolin K in Monascus-fermented products

The objectives of this study were to investigate the thermal degradation kinetics of monacolin K in Monascus-fermented product (MP) solution. The results indicated that monacolin K content in MP solution remained fairly constant in the range of pH 3-9. However, heat treatment significantly decreased the content of monacolin K in MP solution, for example, from 75.8% under 100 °C, 60 min to 54.3% under 100 °C, 90 min at pH 9. Moreover, if the heating temperature was increased to 121 °C for 90 min at pH 9, the content of monacolin K rapidly decreased to 14.1%. The thermal degradation of monacolin K followed a first-order reaction kinetic. The temperature dependence of rate constants followed Arrhenius relationship, with an activation energy value of 126.64 kJ/mol (90-121 °C, r² = 0.99). Our results suggest that monacolin K is easily degraded when the MP solution is heated to a high temperature (such as 121 °C). However, more than 50% of monacolin K could be remained when the MP solution is heated under the pasteurization temperature used for food processing.     

添加葡萄糖及大豆源基质提高红曲monacolin K产量的研究

为探究大豆粉中促进红曲菌产莫纳可林K(monacolin K,MK)的关键组分,筛选替代大豆粉生产高MK含量功能性红曲的基质,以丛毛红曲菌(Monascus pilosus)MS-1为试验菌株,以大米为主要发酵基质,分析经典碳源葡萄糖及几种大豆源基质对红曲菌产MK的影响。结果表明,分别添加3%(质量分数)大豆异黄酮或5%(质量分数)大豆分离蛋白均可显著促进MK的产生(P<0.05)。添加3%(质量分数)葡萄糖对红曲菌产MK有显著抑制作用,但同时添加5%大豆分离蛋白和3%葡萄糖对红曲菌产MK有显著协同促进作用(P<0.05)。与添加大豆粉相比,同时添加5%大豆分离蛋白和3%葡萄糖更利于MK的产生,所得发酵产物MK的产量分别是添加豆粉和对照所得发酵产物MK产量的1.53倍和16.80倍。该研究结果可为生产高MK含量的功能性红曲提供理论和技术支持,还可为采用葡萄糖及大豆分离蛋白替代大豆粉生产高MK含量功能性红曲提供参考。     

红曲菌的复合诱变及其固态发酵条件的优化

通过紫外线和LiCl对一株红曲菌MP进行复合诱变,并通过响应面法对其固态发酵条件进行优化分析。结果表明：在前期温度为30℃,后期温度为24℃,初始含水量为60%的条件下,Monacolin K的产量最高可达5.33mg/g。     

红曲的生产工艺及Monacolin K和桔霉素的检测

综述红曲的生产工艺及Monacolin K和桔霉素的检测方法,指出采用新型生产工艺、优化发酵条件和应用菌种筛选等现代技术是生产既富含活性成分Monacolin K又不合桔霉素的功能性红曲的重要途径,同时预示Monacolin K和桔霉素检测技术的进展将为功能性红曲产品的质量、安全使用及国际市场的开拓提供技术支撑.     

Changes in lipoxygenase isozymes and trypsin inhibitor activity in soybean during germination at different temperatures

Influence of germination temperature on lipoxygenase isozymes and trypsin inhibitor activity, the two undesirable components in soybean for human consumption, is not yet reported in soybean sprouts. Two Indian soybean genotypes were incubated for 144 h in a seed germinator at two different temperatures (25 and 35 °C) and the activities of lipoxygenase isozymes and trypsin inhibitor were monitored in the germinating seedlings every 24 h. Lipoxygenase-I as well as lipoxygenase-II + III were degraded continuously over the 144 h and the rate of degradation, of both the classes of lipoxygenase, was faster at the higher germinating temperature (35 °C) in both the genotypes. Trypsin inhibitor was also degraded continuously during germination upto 144 h and the degradation was faster at higher germination temperature. Protein extracts of seedlings of different periods, developed at different temperatures, and analyzed using polyacrylamide gel electrophoresis, indicated that the original Kunitz inhibitor band (R_f = 0.75) declined continuously in intensity during germination at both temperatures in both genotypes, and a new band (R_f = 0.72) possessing trypsin inhibitor activity appeared at 48 h at 35 °C, while it appeared at 72 h at 25 °C. Early appearance of a modified form of Kunitz inhibitor, a degraded product of native form, at 35 °C as compared to 25 °C, confirms that the faster quantitative reduction at higher temperature is due to faster degradation of the original Kunitz inhibitor form at higher temperature.     

Drying kinetics and quality changes during drying of red pepper

A mathematical model is proposed to simulate the process of drying of individual pieces of red pepper under constant external conditions and to predict changes in some nutritional and organoleptic attributes of the product. The model was solved numerically to obtain moisture content and temperature as well as ascorbic acid and carotenoids concentration in the product as a function of time. A good agreement between predictions and experimental data at different drying temperatures was obtained.Water sorption isotherms of red pepper were determined in the range 20-50 °C and represented by two different sorption equations. Drying kinetics were represented by a diffusive model, the effective moisture diffusivity ranging from 5.01 to 8.32×10⁻¹⁰ m²/s with an activation energy of 23.35 kJ/mol. Degradation kinetics for ascorbic acid and total carotenoids were measured in the range 50-70 °C and modelled as first-order reactions. The rate constants increased with temperature and product moisture content. Average activation energies for carotenoids and vitamin C degradation were 50.1 and 26.9 kJ/mol, respectively.     

TLC薄层色谱法同步检测功能红曲中酸型和内酯型莫那呵啉K(MonacolinK)

功能红曲产品中的Monacolin—K包括酸型和内酯型两种成分。采用TLC法，以60％乙腈溶液作为提取剂，V（氯仿）：V（甲醇）：V（氨水）=25：3：1作为展开剂，以10％硫酸-乙醇溶液显色，紫外检测波长为365nm，可同步检测酸型和内酯型莫奈呵啉K。该法适用于任何含莫奈呵啉K的样品的检测，特别适用于大批量经常性的定性或半定量检测莫奈呵啉K。     

Kinetics of ascorbic acid degradation in fruit-based infant foods during storage

The kinetics of ascorbic acid (AA) degradation in a fruit-based beikost product added with AA were determined after storage at 4, 25, 37 and 50 °C during 4, 8, 12, 16 and 32 weeks in plastic polypropylene/ethylene–vinyl alcohol vacuum packaging. It was confirmed that AA degradation followed an Arrhenius first-order kinetics, with an activation energy of 20.11 ± 0.33 kcal mol⁻¹. No AA losses at 4 °C were recorded during the entire storage period. In contrast, a time- and temperature-dependent decrease (p < 0.05) in AA was observed at the other tested temperatures – the degradation rate decreasing from 50 °C to 25 °C, as expected. AA percentage retention at the end of storage ranged between 6.4% (50 °C/16 weeks) and 100.9% (4 °C/32 weeks).     

Shelf life of powdered Campomanesia adamantium pulp in controlled environments

The objective of this study was to evaluate the shelf life of powdered guavira pulp obtained by a foam mat drying process. The dehydrated guavira pulp was packed into low density polyethylene (LDPE) bags and stored under two controlled conditions: environmental (25 °C, RH 75%) and accelerated (35 °C, RH 90%) for 90 days. The shelf life was accompanied by carrying out the following analyses every 10 days: moisture content, water activity, vitamin C content, pH and titratable acidity. Vitamin C was the quality attribute used to determine the shelf life of the product, by determining its degradation kinetics as a function of storage time. The linear regression data showed that the vitamin C degradation reaction fitted the zero and first order kinetic models. The shelf life of the powdered guavira pulp under environmental conditions was approximately 49 days, and under accelerated conditions (35 °C) 45 days. The Q10 was equal to 1.09, predicting a shelf life similar to that found under environmental conditions. The moisture content for these conditions was 10.0% e 5.4% for 35 °C and 25 °C, respectively. The above demonstrate the efficiency of the accelerated test in predicting the shelf life of the product.     

高产开环型monacolin K红曲霉菌株的筛选及其在红曲酒酿造中的应用

该研究采用38株红曲霉菌株固态发酵制备功能红曲米,采用高效液相色谱法测定红曲米中monacolin K和桔霉素含量,筛选高产开环型莫纳可林K(monacolin K)红曲霉菌株,通过形态观察及分子生物学技术对筛选菌株进行鉴定,并将其应用于红曲酒酿造,分析红曲酒的品质。结果表明,筛选得到1株高产开环型monacolin K、不产桔霉素的菌株ABQ2,经鉴定,其为丛毛红曲霉（Monascus pilosus）。采用该菌株发酵制备功能红曲米中的monacolin K含量达到25.10 mg/g,开环率为90.5%,且桔霉素未检出。采用菌株ABQ2酿造的红曲酒酒精度为12%vol,酸度为1.91 g/100 mL,monacolin K含量为0.48 mg/mL,其理化指标均符合相关行标要求;与小曲酒相比,红曲酒中总酯含量（433.65 mg/L）极显著增加（P<0.01）,其中乳酸乙酯和乙酸乙酯含量最高,高级醇类含量（145.52 mg/L）略低,主要为正丙醇、异丁醇、正戊醇、β-苯乙醇等。     

Oxidative stability of fried dough from rice flour containing rice bran powder during storage

The aim of this study was to evaluate the efficiency of rice bran powder on lipid peroxidation inhibition of fried dough from rice flour during storage. Rice flour dough containing rice bran powder at 5, 10 and 15 g rice bran powder/100 g mixed rice flour were fried in soybean oil at 160 °C for 1 min and stored in dark at 60 °C for 10 days. Lipid peroxidation of fried dough was determined by change of fatty acid compositions, oxygen absorption in vial headspace, lipid hydroperoxides, TBA values including decreasing tocopherol and gamma-oryzanol contents during storage. Polyunsaturated fatty acid decreased rapidly in fried dough without rice bran powder, while an increase of oxygen absorption in vial headspace, lipid hydroperoxide and TBA values were significantly lower (p?0.05) in fried dough containing rice bran powder. In addition, tocopherol degradation was significantly lower in fried dough containing rice bran powder during storage (p?0.05). However, there was no significant difference in gamma-oryzanol contents among fried dough during storage (p>0.05). These results demonstrated that rice bran powder shows the antioxidative effects on fried dough during storage.     

Chemical and biological characteristics of protein hydrolysates from fermented shrimp by-products

Protein hydrolysates were prepared through lactic acid fermentation of the inedible portions of shrimp (cephalothorax and exoskeleton), the by-products of shrimp processing operations. The protein-rich liquid hydrolysate was further processed into a concentrated paste via vacuum evaporation at 80 °C or was also processed into a dry powder using a spray drying method at 180 °C/140 °C (inlet/outlet temp). The laboratory compared the composition of the three forms of shrimp protein hydrolysates. The protein and ash content of the hydrolysates ranged from 8.43 ± 0.22 to 46.73 ± 1.29 and 2.03 ± 0.52 to 8.25 ± 0.14 g/100 g of wet weight. All the samples were analyzed for fifteen amino acids; the powder form was analyzed for colour, microbial content, and for heavy metal occurrence. The shrimp by-products were successfully converted into micro-nutrient by-products rich in amino acids for potential recommendations in the supplementation of animal and human diets.     

Comparison between atmospheric and vacuum frying of apple slices

Vacuum deep-fat frying is a new technology that can be used to improve quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper atmospheric and vacuum frying of apple slices were compared, in terms of oil uptake, moisture loss and color development. In addition, some apple slices were pre-dried (up to 64% w.b.) before vacuum frying to determine the overall effect. To carry out appropriate comparisons between both technologies equivalent thermal driving forces were used in both processes (ΔT = 40, 50, 60 °C), keeping a constant difference between the oil temperature and the boiling point of water at the working pressure. Vacuum frying was shown to be a promising technique that can be used to reduce oil content in fried apple slices while preserving the color of the product. Particularly, drying prior to vacuum frying was shown to give the best results. For instance, when using a driving force of ΔT = 60 °C, pre-dried vacuum fried slices absorbed less than 50% of the oil absorbed by atmospheric fried ones. Interestingly, a strong relationship between water loss and oil content was observed in both technologies, allowing the extension of observations that have been made for atmospheric frying.     

Influence of temperature on heat transfer coefficient during moderate vacuum deep-fat frying

The objective of this study is to analyze the influence of temperature and reduced pressure on the convective heat transfer coefficient, h, during frying of products with different area/volume ratio. h was determined from surface temperature and moisture loss experimental data during frying of potato cylinders and “churros”, at different oil temperatures (100, 120 and 140 °C) and moderate vacuum (19.5–25.9 kPa). The results obtained during vacuum frying were compared with those obtained at atmospheric pressure, both for the same oil temperature (140 °C) and for the same thermal gradient (40 °C). During frying, h changes considerably, reaching a maximum between 700–1600 Wm⁻² K⁻¹ in vacuum frying and 800–2000 Wm⁻² K⁻¹ in atmospheric frying. To quantify the effect of oil temperature, pressure and size of the product on h, a parameter called “bubbling efficiency”, BE, was defined. BE relates the bubble departure radius and the area/volume ratio of the product. An equation (the derivative of the Gompertz function) was proposed to estimate the mean heat convective coefficients for each frying condition as a function of BE (R² = 0.957). The relation between h and BE shows a maximum corresponding to an optimal bubbling pattern. Most of the vacuum frying settings are outside this optimum, being affected by the insulation effect of bubbles covering the surface.     

Quality of superchilled vacuum packed Atlantic salmon (Salmo salar) fillets stored at −1.4 and −3.6 °C

The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6 °C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were investigated during storage and compared to ice chilled and frozen references. Drip loss was not a major problem in superchilled salmon. Textural hardness was significantly higher in superchilled salmon fillets stored at −3.6 °C compared to those stored at −1.4 °C, ice chilled and frozen references. Cathepsins B and B + L were not deactivated at the selected storage temperatures. The storage time of vacuum packed salmon fillets can be doubled by superchilled storage at −1.4 °C and −3.6 °C compared to ice chilled storage.     

Effects of vacuum frying on structural changes of bananas

Effects of oil temperature, frying time, and ripeness on dimensional changes of vacuum fried bananas were studied. Banana slices with cross section diameters of 25-30 mm and a thickness of 3.5-4.5 mm were fried at temperatures of 100, 110, and 120 °C and 8 kPa for 20 min to determine which temperature produced the highest degree of expansion. Using this temperature, the width and thickness of the product were measured at 0, 5, 10, 15, and 20 min to model the dimensional changes as a function of moisture ratio. Sensory evaluation was conducted using a 7-point hedonic scale test to determine the effect of ripeness on acceptability of the product. Scanning electron microscopy (SEM) was used to analyze the structure of the vacuum fried bananas.The experimental results under this vacuum pressure revealed that frying temperature of 110 °C on bananas at the second day of ripeness yielded the highest volume expansion. Sensory evaluations did not unveil any significant difference (p > 0.05) in acceptability of the products based on ripeness. Results from SEM exhibited, as a function of frying time, a dramatic increase in the pore size of the bananas, while the Heywood shape factor indicated an overall increase in the product volume.     

Comparison of the crystalline properties and structural changes of starches from high-amylose transgenic rice and its wild type during heating

A transgenic rice line (TRS) enriched amylose and resistant starch has been developed by antisense RNA inhibition of starch branching enzymes. In this study, gelatinisation and crystalline properties, swelling power, water solubility, morphological and structural changes of starches from TRS and its wild-type Teqing (TQ) were carefully investigated during heating. Compared to TQ, TRS starch showed higher gelatinisation temperatures, lower gelatinisation enthalpy and swelling power. Morphological and structural changes showed that TQ starch drastically swelled after 70 °C, then gradually disrupted with increasing heating temperature. The surrounding band of TRS starch restrained granule swelling, though the subgranules disrupted to form the cavity. The results of spectroscopic analyses indicated that A-type crystalline of TQ changed to amorphous starch after 75 °C, while C-type crystalline of TRS gradually changed to B-type crystalline after 75 °C, then became amorphous starch at 95 °C. These results add to our understanding of the effect of heating on the high-amylose rice starch.     

Free radical interactions between raw materials in dry soup powder

Interactions at the free radical level were observed between dry ingredients in cauliflower soup powder, prepared by dry mixing of ingredients and rapeseed oil, which may be of importance for quality deterioration of such dry food products. The free radical concentrations of cauliflower soup powder, obtained by electron spin resonance (ESR) spectroscopy, rapidly become smaller during storage (40 °C and relative humidity of 75%) than the calculated concentrations of free radicals based on the free radical concentrations of the powder ingredients used to make the soup powder and stored separately under similar conditions. Similarly, free radical concentrations decreased faster when any combination of two powder ingredients (of the three major ingredients of the soup powder) were mixed together and stored at 50 °C for 1 week than when each powder component was stored separately. Furthermore, yeast extract powder was found to play a key role when free radical interactions between powder ingredients occurred. The incubation of rapeseed oil with powder ingredients at 45 °C for 24 h, indicated the ability of cauliflower powder to increase the concentration of hydroperoxides in rapeseed oil, while yeast extract powder was found to prevent this hydroperoxide formation.     

Shelf life prediction of aluminum foil laminated polyethylene packed vacuum dried coconut milk powder

Shelf life of vacuum dried coconut milk powder packed in aluminum foil laminated polyethylene packages was predicted using developed mathematical models based on two limiting criteria viz., onset of caking and lipid oxidation. Accelerated storage studies for coconut milk powder packed in aluminium foil laminated polyethylene pouches were conducted at 90 ± 1% relative humidity and 38 ± 2 °C temperature. Threshold value for the shelf life prediction based on moisture migration was taken as the critical moisture content at which lump formation was observed. Shelf life prediction based on lipid oxidation involved establishing relationships between rate of oxygen absorption, package oxygen concentration, volume of O₂ absorbed, peroxide value of the powder and storage time. A peroxide value of 10 mEq. of O₂ per kg fat was considered as the threshold limit for oxidative rancidity. A good fit between experimental and predicted data with relative deviation percent below 10% was observed during storage studies.