不同品种稻谷储藏期间品质变化的研究

通过研究1年储藏期内稻谷脂肪酸值、直链淀粉含量、粗蛋白含量的变化,探索储藏时间对7种稻谷品质的影响。结果表明:稻谷脂肪酸值在储藏期间逐渐升高,直链淀粉含量变化较小,而蛋白质含量呈现缓慢下降趋势。但不同品种在储存过程中的变化规律差异明显,仅以脂肪酸值作为稻谷新陈度的评价标准不合适。在所研究的稻谷中,中优208的品质最稳定属耐储藏品种。     

冻干甜椒贮藏过程中抗坏血酸及还原糖的变化

以冻干甜椒为材料,研究其在不同贮藏温度下抗坏血酸及还原糖含量的变化,揭示其品质变化的情况。分别采用斐林试剂比色法、固蓝盐B分光光度法测定抗坏血酸及还原糖的含量。结果表明,在贮藏期间,冻干甜椒中的抗坏血酸和还原糖含量逐渐减少,并且随储藏温度上升减少的速率增大。     

蛀食害虫对小麦淀粉酶及过氧化物酶活性的影响

探讨玉米象(Sitophilus zeamais)、米象(Sitophilus oryzae)和谷蠹(Rhyzopertha dominica)三种蛀食性害虫不同感染程度对小麦淀粉酶及过氧化物酶活性的影响及变化规律,为小麦科学储藏量化指标提供依据。选用河南产储藏2年的商用小麦,按不同虫种分组,设定不同的虫口密度和感染时间,检测小麦样品降落数值和过氧化物酶(POD)活性,并与虫口密度和感染时间作相关性分析。结果表明,随着虫口密度增加和感染时间延长,样品的降落数值呈波动上升趋势,POD活性呈下降趋势;三种害虫侵害后的样品降落数值与感染时间均存在极显著正相关,POD活性与感染时间均存在极显著负相关,降落数值与POD之间呈极显著负相关,而二者与虫口密度的相关性均不显著。     

不同品种柚子海绵层可溶性膳食纤维对酸奶储藏期品质的影响

目的 为探究不同柚子海绵层可溶性膳食纤维 (SDF) 对酸奶品质的影响。方法 以6种柚子 (西柚,琯溪蜜柚,文旦柚,坪山柚,梁平柚,沙田柚) 海绵层SDF和奶粉为主要原料制备柚子海绵层SDF酸奶,未添加柚子海绵层SDF的酸奶为对照组,解析储藏过程中酸奶理化指标和微生物指标的变化规律。结果 储藏15天后,琯溪蜜柚海绵层SDF (GSDF) 酸奶的乳杆菌活菌数 (9.34*10^7 CFU/mL) 和可滴定酸度最高 (107.3 °T),西柚海绵层SDF (XSDF) 酸奶的持水力 (67.8 g/g) 和嗜热链球菌活菌数最高。坪山柚海绵层SDF (PSDF) 酸奶的黏度比其他样品组更高,且其蛋白质下降程度最低。此外,添加柚子海绵层可溶性膳食纤维对酸奶的颜色也有较大影响,梁平柚 ( LSDF) 与沙田柚 (SSDF) 海绵层SDF酸奶色泽影响较小,其他柚子海绵层SDF对酸奶的色泽变化影响较大。结论 添加PSDF,XSDF和GSDF能提高酸奶的黏度,有益活菌数,持水力,是良好的功能性添加剂。     

溴甲烷熏蒸对不同苹果品种贮藏品质的影响

不同温度条件下溴甲烷熏蒸处理5个不同品种的苹果,以明确溴甲烷熏蒸对中国生产的苹果的呼吸强度、果皮色泽、硬度、可溶性糖、总酸度等品质指标的影响,为建立苹果溴甲烷检疫熏蒸处理技术标准提供依据。结果表明,溴甲烷熏蒸在30℃下对5个品种苹果呼吸无显著影响,在15、20℃下能降低富士、青冠、金冠、青苹果在熏蒸期间的呼吸速率,其他温度无明显规律;15℃以下熏蒸处理的富士、金冠在贮藏期间呼吸强度较对照显著提高,20℃以上5个品种苹果在贮藏期间呼吸强度较对照无明显变化;各处理温度下对富士、青苹果色泽有显著影响,富士、青冠在20℃以上处理后硬度显著提高,对5种苹果可溶性糖无显著影响,富士的总酸度在15℃以上显著提高,其他品种无显著影响。可以用于这5个苹果品种溴甲烷熏蒸处理条件为:10℃、64g/m3可用于青冠、青苹果,15℃、48g/m3可用于青冠、青苹果,20℃、40g/m3,可用于青冠、花牛、青苹果,25℃、32g/m3,适用于富士、青冠、花牛、青苹果,30℃、24g/m3可用于5个品种的处理。     

Drip loss,peroxidase and sensory changes in kiwi fruit slices during frozen storage

The biochemical, sensory and drip loss changes that occur during processing and prolonged frozen storage of kiwi fruit slices (cvs Abbott and Hayward) were studied. Fruit slices were frozen at ?40°C, packed in polyethylene bags and stored at ?18°C for 11 months. Maturity characteristics (pH, acidity, dry matter, soluble solids) were determined on raw fruit. Objective (proteins, peroxidase (EC 1.11.1.7) activity, drip loss) and subjective (sensory tests) analyses were carried out during processing and storage, and indicated a good quality of the frozen kiwi fruit slices after 11 months of storage. There were significant differences (P < 0.05) between the studied varieties with respect to drip loss during frozen storage and colour after 11 months. Best results were obtained with cv Hayward. This variety showed less drip loss after thawing and after 11 months storage presented the same green colour as after freezing, while cv Abbott became yellowish-green.     

Variations in the soluble sugar and organic acid contents in radish (Raphanus sativus L.) cultivars

The radish is a root vegetable of the Brassicaceae family that is mainly consumed in Far Eastern Asian countries. Because chemical indexes indicating the quality of a radish have not been established, we investigated the variations in the contents of the soluble sugars and organic acids that influence taste among seven radish cultivars. In terms of the total soluble sugar content, which is a strong index of sweetness, Koshin, Kouto, and Shogoin were the three highest among the seven cultivars. Sobutori, which is the most common radish cultivar in Japan, was the lowest. The total organic acid contents varied among the seven cultivars, although they were five to thirteen times lower than the total soluble sugar contents. These results indicate that there are variations in the soluble sugar and organic acid contents among radish cultivars; therefore, these contents may be used as chemical indexes for the quality of radishes.     

兰州百合鳞茎冷藏保鲜过程中碳水化合物含量及淀粉酶活性的变化

以兰州百合为试材,采用紫外-可见分光光度法测定了-2 ℃冷藏保鲜过程中百合鳞茎内可溶性糖、还原糖、淀粉的含量与淀粉酶活性的动态变化,分析了碳水化合物含量与淀粉酶活性之间的关系。结果表明,在-2 ℃、60 d的冷藏保鲜期内,随着冷藏时间的延长,兰州百合鳞茎内淀粉含量明显下降,其下降幅度达62.29%,可溶性糖与还原糖含量呈上升趋势,分别上升了2.22%和1.39%。β-淀粉酶是兰州百合鳞茎中的主要淀粉酶,其活性随冷藏时间的延长而有所降低,α-淀粉酶的活性随冷藏时间的延长先降低后升高,总淀粉酶在高活性的基础上整体呈现降低的趋势。相关性分析表明,鳞茎中碳水化合物含量及淀粉酶活性之间的相关性差异水平有所不同。总淀粉酶、β-淀粉酶活性与可溶性糖、还原糖含量具有极显著负相关性,而与淀粉含量具有极显著正相关性。可溶性糖和还原糖含量的增加与低温诱导下淀粉在β-淀粉酶的作用下分解有关。     

Physicochemical property changes in germinated brown rice flour from different storage periods of paddy rice

This study revealed that the storage duration (2, 4, 6, 8, 10 and 12 months) of paddy rice and pH (3 and 6.8) of steeping water during germination were significantly influenced the physicochemical properties of germinated brown rice flour (GBRF). GBRF obtained at pH 3 vs. 6.8 provided the highest both reducing sugar content and free gamma‐aminobutyric acid (GABA) content (99.8 vs. 54.2 mg per 100 g flour respectively) as the paddy rice was stored for 8 months. The peak viscosity of GBRF obtained at pH 3 and 6.8 exhibited the lower values than that of non‐GBRF throughout the storage. From the principal component analysis, reducing sugar had a positive correlation with α‐amylase activity whereas a negative correlation was found with peak viscosity. GBRF from paddy rice stored for 8 months and germinated at pH 3 possessed the highest free GABA content, 50 times of the non‐GBRF, which can be further utilised in functional and healthy foods.     

Effect of enzymes on strawberry volatiles during storage, at different ripeness level, in different cultivars, and during eating

Strawberry samples with enzyme activity and without enzyme activity (stannous chloride added) were measured for real-time formation of lipoxygenase (LOX) derived aroma compounds after 5 min pureeing using selected ion flow tube-mass spectrometry (SIFT-MS). The concentration of (Z)-3-hexenal and (E)-2-hexenal increased immediately after blending and gradually decreased over time, while hexanal concentration increased for at least 5 min in ground strawberries. The formation of hexanal was slower than the formation of (Z)-3-hexenal and (E)-2-hexenal in the headspace of pureed strawberries. The concentration of LOX aldehydes and esters significantly increased during refrigerated storage. Damaging strawberries increased the concentration of LOX aldehydes but did not significantly affect the concentration of esters. The concentrations of many of the esters were strongly correlated to their corresponded acids and/or aldehydes. The concentration of LOX-generated aldehydes decreased during ripening, while fruity esters increased. Different varieties had different aroma profiles and esters were the greatest percentage of the volatiles. The aroma release of some of the LOX-derived aldehydes in the mouthspace in whole strawberries compared to chopped strawberries showed that these volatiles are formed in the mouth during chewing. The persistence of LOX-derived compounds was higher than esters after swallowing. The mouthspace after and before swallowing persistence ratio of esters decreased as the chain length of the acid part of the ester compounds increased in whole strawberries. PRACTICAL APPLICATION: The storage studies showed that the concentrations of fruity and fresh volatiles increased during ripening and storage while damaging only increases the fresh volatiles. The nose, mouth, and headspace information can be used in the flavor industry to improve the formula of natural strawberry flavor by considering human perception during eating.     

茶籽在贮藏过程中主要成分的变化

介绍了茶籽中主要成分在近6个月的贮藏过程中的变化情况。经过测定茶籽仁中的水分、蛋白质、脂肪、游离脂肪酸、淀粉和总糖的含量,得知在贮藏过程中茶籽仁中的水分和总糖的含量呈逐步下降的趋势,蛋白质含量呈波浪状缓慢下降,脂肪含量略有上升,淀粉的含量变化亦不大,而游离脂肪酸含量随贮藏时间的增加呈直线上升状态。实验表明,在11月至来年3月这一段时间内,在室温条件下贮藏干茶籽是一种经济有效的方法。     

Differences in accumulation of storage proteins between wheat cultivars during development

The concentration and composition of storage proteins in the developing kernels of five different wheat cultivars were investigated. The plants were grown in solution culture under strictly controlled conditions in climatic chambers and with long-term limitation of external nitrogen availability. Thus, by growing these cultivars under the same defined treatments, reliable differences in the storage protein development could be determined. The total protein concentration was assayed using an automatic nitrogen analyser. The storage protein composition was examined by acidic polyacrylamide gel electrophoresis and sodium dodecyl sulphate polyacrylamide gel electrophoresis from 6 to 58 days after anthesis. The results showed that, in all stages of plant development, the ranking of the cultivars as to the storage protein concentration was the same as for mature field-grown kernels. The differences in the storage protein concentration between the cultivars could not be explained by differences in protein composition. The start of storage protein formation during plant development did not differ between the tested cultivars, as determined by the electrophoresis pattern. The differences in the storage protein concentration between cultivars most likely depends on the relative balance between starch and nitrogen deposition in the grain, during the whole grain filling period.     

Efficient expression and secretion of recombinant alpha amylase in Pichia pastoris using two different signal sequences

We have cloned and expressed a bacterial thermostable alpha amylase gene in Pichia pastoris using the methanol-controlled alcohol oxidase (AOX1) promoter. Two integrative vectors were constructed with two different secretion signal sequences in order to obtain efficient secretion of the protein. One vector contains the structural gene encoding the mature alpha amylase fused to the SUC2 gene signal sequence from Saccharomyces cerevisiae. In the other vector, the alpha amylase is expressed with its own signal sequence. In both cases, the alpha amylase were secreted into the culture medium with high efficiency, around 2·5 and 0·9 g/l respectively.     

不同树莓品种冻藏品质变化及适宜冻藏品种筛选

针对8个树莓品种冻藏后贮藏品质变化进行研究,并筛选出适宜冻藏的品种。结果表明:树莓鲜果细胞膜紧贴细胞壁,速冻后胞内失水,细胞膜萎缩,细胞膜与细胞壁分离;在-18℃条件下,随着贮藏时间延长,细胞膜渗透率、汁液流失率升高;硬度下降;可溶性固形物在整个贮藏期中变化都不大;贮藏前30d,总酚和花色苷含量下降较快,贮藏30¹20d,总酚和花色苷含量下降缓慢。其中米克、美国22号、胜利在冻藏后能保持较高的细胞完整性,可溶性固形物、花色苷和总酚的保持率均有较好表现,汁液流失率变化较小,为适宜加工速冻树莓的品种。      

对比PE膜与微孔膜对冷藏青萝卜品质的影响

为探讨包装材料对青萝卜采后贮藏品质的影响,以卫青萝卜为试材,在(2.0±0.5)℃冷藏条件下,分别采用PE膜、微孔膜对卫青萝卜进行包装,比较了卫青萝卜主要理化及感官指标变化。结果表明:贮藏期间PE膜组和微孔膜组的VC、酸度、可溶性固形物、亚硝酸盐以及还原糖含量变化基本一致,均为先上升后下降。微孔膜组的VC含量、酸度、可溶性固形物含量和失重率均比PE组高;PE组的淀粉酶活性、还原糖和亚硝酸盐含量高于微孔膜组;微孔膜组的质构指标和感官指标优于PE组;二者色差指标差异不明显。微孔膜包装处理的卫青萝卜最佳食用期为5周,最佳贮藏期为11周。PE组包装处理的卫青萝卜品质随着贮藏时间的延长而逐渐下降,最佳贮藏期为9周。微孔膜组的卫青萝卜品质更佳。     

花生贮藏蛋白质亚基构成、缺失与品质间关系研究

对208个花生品种(系)籽仁中蛋白质、可溶性糖、淀粉、脂肪含量、贮藏蛋白组分亚基组成及其相互间的相关性进行了分析。结果表明:1)花生籽仁主要营养成分以脂肪为主,其含量在39.6~59.0 g/100 g,其次为粗蛋白质含量,平均为27.6 g/100 g;籽仁中可溶性糖平均含量为9.3 g/100 g;可溶性淀粉含量最大值为16.3 g/100 g。2)花生籽仁淀粉含量与蛋白质、脂肪和可溶性糖间均表现极显著的负相关关系,可溶性糖与蛋白质含量间呈极显著的正相关而脂肪含量与蛋白质和可溶性糖含量间均无明显相关关系。3)SDS-聚丙烯酰胺凝胶电泳分析发现,花生贮藏蛋白各亚基分子质量在14.4~97.4 ku之间,共有14~17条条带,部分品种贮藏蛋白在34.2 ku处有明显的条带缺失,条带缺失品种占供试品种材料总数的21.7%;在26.8、25.6 ku处或表现条带缺失或表现明显的颜色、面积和含量差异。4)对缺失蛋白亚基进行SHOTGUN测试,共检测得到112个肽段,其中18个蛋白质为可信蛋白,其功能涉及生物细胞代谢/能量代谢、免疫调节、信号传递等细胞过程。缺失蛋白涉及花生各个生长发育过程,可能与花生生物产量的提高和品质的改善有密切关系。     

The effects of low‐temperature potato storage and washing and soaking pre‐treatments on the acrylamide content of French fries

BACKGROUND: Since the discovery in 2002 of acrylamide in a wide range of foods, there has been much work done to explore mechanisms of formation and to reduce acrylamide in commercial products. This study aimed to investigate simple measures which could be used to reduce acrylamide formation in home‐cooked French fries, using potatoes from three cultivars stored under controlled conditions and sampled at three time points. RESULTS: The reducing sugar content for all three cultivars increased during storage, which led to increased acrylamide levels in the French fries. Washing and soaking (30 min or 2 h) raw French fries before cooking led to reductions in acrylamide of up to 23, 38 and 48% respectively. Pre‐treated fries were lighter in colour after cooking than the corresponding controls. CONCLUSION: Pre‐treatments such as soaking or washing raw French fries in water reduce acrylamide and colour formation in the final product when cooking is stopped at a texture‐determined endpoint. Copyright © 2008 Society of Chemical Industry     

萝卜籽粕中蛋白质的提取及抗氧化活性研究

采用碱溶酸沉法提取萝卜籽粕中的蛋白质,通过单因素试验和正交试验确定最佳的提取条件;对蛋白质的抗氧化活性进行研究;采用SDS-PAGE法测定各蛋白质组分相对分子质量分布。结果表明:萝卜籽粕中蛋白质的最佳提取条件为料液比1∶50、碱溶pH 10、提取温度60℃、提取时间90 min、酸沉pH 4.5,在此提取条件下,蛋白质提取率可达80.2%,蛋白质纯度为89.5%;萝卜籽粕中蛋白质对DPPH·、NO_2~-、H_2O_2、·OH具有很好的清除能力;萝卜籽粕中蛋白质约有5种亚基分离组分,其中4种亚基分离组分相对分子质量由小到大分别约为22.0、31.0、43.0、66.2 k Da,1种亚基分离组分的相对分子质量在66.2~97.4 k Da之间。     

Influence of storage conditions on pigment degradation in paprikas from different greenhouse pepper cultivars

A comparative study was made of the pigments and kinetics of pigment degradation in paprika from Ocal, Datler, Belrubí and L T Datler varieties of pepper cultivated in greenhouse conditions during storage in darkness and at different temperatures and degrees of humidity. Differences were established after fitting the experiment data to a first- or second-order kinetic model. The pigment degradation rate constants and half-lives were obtained for each variety and each storage condition. As expected, the speed of pigment degradation increased for all the paprika types at higher storage temperatures and decreased as relative humidity rose. The data obtained allowed the determination of the parameters involved in the respective Arrhenius equations which equate the pigment degradation rate constant (supposed first or second order) with absolute temperature in cases of zero humidity. Significant differences with respect to degradation rate and pigment content were found between the cultivars in most of the storage conditions assayed. © 1998 Society of Chemical Industry.