Effects of atmospheric composition on respiratory behavior, weight loss, and appearance of Camembert-type cheeses during chamber ripening

Respiratory activity, weight loss, and appearance of Camembert-type cheeses were studied during chamber ripening in relation to atmospheric composition. Cheese ripening was carried out in chambers under continuously renewed, periodically renewed, or nonrenewed gaseous atmospheres or under a CO₂ concentration kept constant at either 2 or 6% throughout the chamber-ripening process. It was found that overall atmospheric composition, and especially CO₂ concentration, of the ripening chamber affected respiratory activity. When CO₂ was maintained at either 2 or 6%, O₂ consumption and CO₂ production (and their kinetics) were higher compared with ripening trials carried out without regulating CO₂ concentration over time. Global weight loss was maximal under continuously renewed atmospheric conditions. In this case, the airflow increased exchanges between cheeses and the atmosphere. The ratio between water evaporation and CO₂ release also depended on atmospheric composition, especially CO₂ concentration. The thickening of the creamy underrind increased more quickly when CO₂ was present in the chamber from the beginning of the ripening process. However, CO₂ concentrations higher than 2% negatively influenced the appearance of the cheeses.     

Kinetics of moisture loss and fat absorption during frying for different varieties of plantain

This study compares the behaviour of four varieties of green plantain at their initial stage of maturity during the frying process. A variety traditionally used for the manufacture of thin plantain chips (Dominico Hartón commun) and three other varieties found in Latin America (Bouroukou, Bluggoe and FHIA 21) were used. The varieties were characterised by measuring initial moisture content, total sugar content, reducing sugar content, starch content and apparent density. Moisture loss and fat uptake kinetics during frying were assessed at different temperatures (145, 165 and 185°C). With all four varieties, the time required to produce a final moisture content of 40 g kg⁻¹ (wb) was about 90 s at 165°C and 185°C. Use of a lower temperature (145°C) extended the processing time to 150 s. On the other hand, temperature had very little effect on fat content, which proved to be essentially determined by the variety of plantain. Fat content for final water content levels of 40 g kg⁻¹ (wb) ranged from 300 g kg⁻¹ (wb) for Bouroukou to 450 g kg⁻¹ (wb) for Bluggoe regardless of the processing temperature. © 1999 Society of Chemical Industry     

Biochemical changes during ripening of some sudanese date varieties

Changes in the chemical composition of three popular Sudanese varieties of date (Jawa, Bentamoda and Mishrig Wad Laggai) during ripening are described and are related to changes in texture and in the activities of various degradative enzymes in the fruit. Total invertase levels were high throughout maturation of the three varieties. Although the proportion of soluble enzyme increased during ripening solubilisation did not appear to influence the relative amounts of sucrose and reducing sugars in the ripening fruit. Both cellulase and polygalacturonase were absent or at low levels in the green fruit but displayed large increases in activity during ripening. This enhancement was reflected in a reduction in fruit firmness although little change in cellulose or pectin levels was apparent analytically until the final stage of ripening. Despite a considerable rise in pectinesterase activity during ripening no significant trend could be discerned in the degree of esterification of pectin suggesting that the enzyme is of minor importance in softening of these fruit.     

油橄榄鲜果中主要化合物随成熟度的变化

为阐明油橄榄果实成熟过程中主要化合物的变化,探索最佳成熟度,本试验以不同成熟度的皮瓜尔鲜果为材料,测定其蛋白质、还原糖、粗脂肪、总多酚的含量,以及果油中主要的脂肪酸和角鲨烯的相对含量。结果表明,随着成熟度的增加,蛋白质含量无较大差异,还原糖先降低后略有升高,粗脂肪先升高后趋于平稳,总多酚先降低后趋于平稳;各种脂肪酸相对含量在整个成熟过程中变化不一致;油酸、棕榈酸、亚油酸、亚麻酸、硬脂酸是橄榄油中含量较高的脂肪酸;角鲨烯先升高后降低。利用主成分分析对油橄榄果实品质进行综合评价,第四成熟度为油橄榄果的最佳成熟度。     

Effects of raw materials,processing conditions and packaging on the quality of plantain chips

The effects of raw material, processing conditions and packaging on the quality of plantain chips were investigated. Two cultivars of plantain Musa spp—Agbagba and Obino lewai—as well as cooking banana were used for the study. The fruits were at stages 1 to 4 of the banana ripening chart. The study started with a consumer survey aimed at product definition. This was followed by series of experiments to determine the effects of raw material, processing conditions and packaging on the quality of plantain chips. A correlation analysis was also carried out on the physical and chemical characteristics of raw plantain. The work revealed that the stage of ripeness of raw material had some effect on the quality of chips as there was gradual increase in pulp/peel ratio and sugar was significantly different (P < 0·05). Moisture content of pulp/texture of pulp, texture of pulp/sugar content of pulp and texture of pulp/ripening stages were negatively correlated, while pulp/peel ratio and moisture content of pulp were positively correlated. Chips packed in 80 μm high-density polyethylene pouches and stored at various relative humidities had extended shelf-life compared with the low-density polyethylene packed chips stored at the same relative humidities. This was due to the inadequacy of the low-density polyethylene in giving the required protection against moisture transmission thereby resulting in soggy chips in shorter periods. The implication of the findings on the formulation of a guideline for the processing of a good-quality plantain chips for the marketing system is discussed.     

香蕉皮化学成分的预试验及抑菌初探

采用水提法和醇提法在常温下浸泡香蕉皮24h,然后采用试管法和圆形滤纸层析法分析鉴定其化学成分。结果表明:香蕉皮中含有酚类、油脂类、有机酸、缩合鞣质、蛋白质和糖类等化学成分。为进一步研究其抑菌的有效成分,用丙酮提取香蕉皮中的鞣质和酚性成分,用乙醚提取香蕉皮中的总有机酸,以几种常见细菌为供试菌做了初步抑菌试验(测抑菌圈直径大小)。结果表明:香蕉皮中的抑菌成分主要是有机酸。     

薏米预熟化工艺研究

针对粮食的熟化时间不同,采用常压蒸煮、高温高压蒸煮和微波熟化技术分别对薏米进行预熟化研究,并对比分析3种预熟化工艺对薏米营养成分、质构和色泽的影响。结果表明:常压蒸煮工艺条件为40℃恒温浸泡2.5 h,物料厚度0.7 cm,蒸煮时间15 min;高温高压蒸煮工艺条件为40℃恒温浸泡1 h,蒸煮温度115℃,蒸煮时间3 min;微波预熟化工艺条件为40℃恒温浸泡1.5 h,微波功率539 W,物料厚度2.8 cm,时间5 min。与原料薏米相比,3种预熟化方式制得预熟化薏米中脂肪含量均明显升高,常压蒸煮和高压蒸煮的蛋白质含量升高,而微波预熟化蛋白质含量与原料接近;沸水中煮15 min,焖5 min后,预熟化后薏米的弹性、胶黏性和咀嚼性均明显升高,能与小米共煮同熟;3种预熟化工艺均不同程度改变薏米的色泽。     

香蕉花多糖抗氧化活性及稳定性研究

目的：以香蕉花多糖为研究对象,研究其抗氧化活性及稳定性。方法：采用热水提醇沉法从香蕉花中制备活性多糖,首先分析香蕉花多糖的化学组成成分,并以总抗氧化能力和DPPH、羟基、超氧阴离子等自由基清除能力为评价指标,探索香蕉花多糖的抗氧化活性;在此基础上进一步以羟基自由基清除能力为评价指标,通过模拟光照、pH、温度、金属离子、食品配料以及灭菌方式等常见食品加工条件,系统地研究香蕉花多糖的抗氧化稳定性。结果：香蕉花多糖的得率为14.56%,多糖中总糖、糖醛酸、蛋白、多酚和黄酮含量依次为515.61、287.88、53.46、2.23和7.94 mg/g。香蕉花多糖具有较强的还原铁离子能力和自由基清除活性。光照条件会快速降低香蕉花多糖的抗氧化活性,而强酸性和碱性条件对香蕉花多糖的抗氧化稳定性影响较小。香蕉花多糖耐热性较好,尤其是温度在60～80 ℃、加热时间2～3.5 h的条件下,其抗氧化稳定性较强。金属钠离子的添加几乎不影响香蕉花多糖的抗氧化活性,但随着金属钾离子、铁离子、铜离子浓度的增大,香蕉花多糖的抗氧化活性会明显下降。此外,添加柠檬酸、苯甲酸钠有利于提高香蕉花多糖的抗氧化活性,但蔗糖、葡萄糖的添加对香蕉花多糖的抗氧化稳定性影响较大。灭菌方式对香蕉花多糖的抗氧化活性有一定的影响,因此对香蕉花加工产品进行灭菌时可优先选择高压杀菌。结论：香蕉花多糖具有较强的抗氧化活性,长期光照、金属铁离子和铜离子、食品配料蔗糖和葡萄糖会影响其抗氧化稳定性,在香蕉花的加工贮藏中应避免与此类条件或物质直接接触。     

Ochratoxin A reduction in meat sausages using processing methods practiced in households

The aim of this study was to investigate the possibilities of ochratoxin A (OTA) reduction in home-made meat products. Meat sausages (n = 50) produced from raw materials coming from pigs exposed to OTA-contaminated feed, were subject to common heat processes practiced in households (cooking, frying and baking). Concentrations of OTA in pre- and post-processed products were quantified using a validated immunoassay method, enzyme-linked immunosorbent assay, and confirmed using a high-performance liquid chromatography with fluorescence detection. In line with the differences in recipes used and the degree of OTA accumulation in raw materials, OTA concentrations established in Mediterranean and roast sausages were lower than those found in liver and blood sausages. Baking of contaminated sausages at the temperatures of 190–220°C (for 60 min) resulted in significant reduction of OTA levels (75.8%), while 30-min cooking (at 100°C) and frying (at 170°C) proved to be significantly less effective (e.g. yielding OTA reductions of 7.4% and 12.6%, respectively). The results pointed out that despite high OTA stability, heat processes are capable of reducing its concentration in home-made meat products, depending on the processing modality used.     

Cooking characteristics,chemical composition and protein quality of newly developed genotypes of pigeonpea (Cajanus cajan L)

Eight newly developed pigeonpea genotypes (ICPL 87, ICPL 151, ICPL 270, ICPL 366, ICPL 87051, ICPL 87063, ICPL 87067, and ICPV 1), and the two controls (BDN 2 and C 11) were analysed for cooking quality parameters and chemical composition, including amino acids and minerals. Protein quality was evaluated by determining the true protein digestibility, biological value, net protein utilisation (NPU), and utilisable protein. These genotypes differed significantly (P < 0–01) in the dhal cooking time. Sensory properties of dhal of these genotypes were found to be within the acceptable range, even though there were considerable differences among genotypes. Dhal protein, calcium, magnesium, zinc, and iron contents of these genotypes showed noticeable differences. Calcium content of ICPL 87067 was the highest (85-6 mg per 100 g) and of ICPL 87 the lowest (54-4 mg per 100 g) indicating large differences among the newly developed genotypes. No noticeable differences in sulphur-containing amino acids of these genotypes were observed. NPU was the highest (65–4%) for ICPL 366 and the lowest (56–6%) for ICPL 270 and ICPL 87067 indicating significant (P < 0–01) differences among genotypes studied.     

Volatile and non-volatile chemical composition of the white guava fruit (Psidium guajava) at different stages of maturity

The effect of the maturation stages on the chemical composition and volatile compounds of the white Guava (Psidium guajava) Cv. Cortibel was investigated during three different stages. The stages were characterized by evolution of color, pH, titratable acidity, sugars, soluble solids, vitamin C and volatile components. The fruits were stored at 24 °C and air humidity of 74% for 13 days. The volatile extracts were obtained using headspace technique and analyzed using gas chromatograph/mass spectrometry (GC/MS) system. The titratable acidity and sugars decreased. The pH level and amount of vitamin C increased throughout progress of maturation. The behavior of volatile compounds of fruits in the three stages of maturation was: in immature fruits and those in their intermediate stage of maturation, were predominantly the aldehydes such as (E)-2-hexenal and (Z)-3-hexenal. In mature fruits, esters like Z-3-hexenyl acetate and E-3-hexenyl acetate and sesquiterpenes caryophyllene, α-humulene and β-bisabollene are present.     

Changes in chemical composition and nutritional quality of fried sardine (Clupea pilchardus) produced by frozen storage and microwave reheating

Modifications in proximate composition, fatty acids, amino acids and –SH groups content, as well as changes in solubility and nutritional quality of protein, were studied in fillets of sardine (Clupea pilchardus) that had been successively pan-fried, frozen stored and reheated by two different means, namely conventional oven and microwave oven. Upon pan-frying in olive oil the sardine absorbed C18: 1(n-9) and C18: 2(n-6) and lost saturated (SFA) and polyunsaturated fatty acids (PUFA); this loss continued upon reheating, and as a consequence the percentage of MUFA increased compared to the just-fried sardine. A loss of water was observed during all processes. Upon frying there was a decrease of cyst(e)ine. Upon reheating by both microwave and conventional oven, methionine decreased; however, cyst(e)ine only decreased with the use of a conventional oven. A loss of –SH groups was recorded during frying and this phenomenon continued upon reheating. Biological value (BV) together with net protein utilisation (NPU) decreased upon both frying and reheating. © 1997 SCI.     

Compositional and quality characteristics of paneer made from soya beans and buffalo milk under different heat treatments

Soya—buffalo milk (SBM) paneer was prepared from an admixture (1: 1 w/w, wet basis) of buffalo milk and tofu, the latter made by two methods (boiling and pressure cooking). Calcium sulphate (20 g litre^?1) and citric acid (100 g litre^?1) were used as coagulants for tofu and SBM-paneerpreparations, respectively. Significant differences (P0.05) were observed in the yield of okara and hulls of soya beans in the two methods. However, no significant differences were observed in the yield and composition of tofu. SBM-paneer( unfried and fried) showed no significant difference in composition between the methods, excepting the moisture and fat levels in the unfried SBM-paneer. Fried SBM-paneer prepared by pressure cooking showed a significant difference in the sensory score. Comparative appraisal of the composition of tofu, SBM-paneer ( fried and unfried) and whey obtained in the two methods are presented.     

高温水煮和酸煮对猪骨硬度及化学成分的影响

为研究高温水煮和酸煮对猪骨硬度及化学成分的影响。以猪骨为实验对象,研究120℃条件下猪骨在水中煮制不同时间(40、50、60、70、80 min)和不同体积分数(0.0%、0.2%、0.4%、0.6%、0.8%、1.0%)的醋酸溶液中煮制80 min后猪骨硬度的变化。用凯氏定氮法和电感耦合等离子体原子发射光谱法测定未煮制猪骨、120℃条件下水中和1.0%醋酸溶液中煮制80 min后猪骨蛋白含量、钙、磷元素含量和钙、磷元素溶出量,用扫描电子显微镜观察猪骨粉碎后微观结构,测定猪骨红外吸收光谱,探究煮制后猪骨成分和结构的变化。结果表明,高温煮制能使猪骨硬度下降,水煮时间从40 min延长到80 min,猪骨硬度从(16 445±867)g下降到(10 995±546)g,醋酸溶液体积分数从0.0%增加到1.0%,猪骨硬度从(10 995±546)g下降到(6 003±153)g。高温煮制能使猪骨蛋白含量降低,猪骨表观钙、磷含量增加,钙、磷溶出量增加。水煮后猪骨蛋白含量为(28.5±2.3)g/100 g,降低了7.4%;猪骨表观钙、磷元素含量分别为(210.0±8.2)mg/g和(96.0±4.0)mg/g,分别增加了11.8%和8.9%;猪骨钙、磷含量溶出量分别为(0.57±0.04)mg/g和(0.17±0.01)mg/g。1.0%醋酸煮后猪骨蛋白含量为(25.9±0.9)g/100 g,降低了10.0%;猪骨表观钙、磷元素含量分别为(230.0±6.4)mg/g和(100.0±2.3)mg/g,分别增加了18.3%和14.8%;猪骨钙、磷元素溶出量分别为(1.73±0.01)mg/g和(0.75±0.01)mg/g。经扫描电子显微镜观测发现,煮制后的猪骨易粉碎,1.0%醋酸煮后的猪骨最容易粉碎。红外光谱发现,煮制后猪骨成分发生了变化,图谱的峰比未煮制简单,成分比未煮制猪骨单一,而加水煮制和加酸煮制后猪骨图谱的峰相似,煮制后猪骨红外光谱图更接近人工合成的羟基磷灰石晶体。高温水煮和酸煮均能引起猪骨蛋白、钙元素和磷元素等化学成分含量的变化,导致猪骨硬度显著下降(P0.05)。     

香蕉MaWRKY31转录因子的特性及对MaACS1、MaACO1和MaSAG1的调控

从香蕉果实中克隆得到1个WRKY转录因子,命名为Ma WRKY31。氨基酸序列比对及进化树分析发现Ma WRKY31具有一个典型的WRKY结构域,与拟南芥WRKY31和番茄Sl WRKY6同源性较高,且同属于第Ⅱ类b亚族。实时荧光定量聚合酶链式反应表明外源乙烯处理诱导了Ma WRKY31的表达,并且随着香蕉果实的成熟衰老,其表达明显增强。亚细胞定位和转录活性分析显示Ma WRKY31定位于细胞核,是一种核蛋白,并且具有转录激活活性。双荧光素酶瞬时表达分析显示,Ma WRKY31可以激活乙烯合成基因Ma ACS1和Ma ACO1,以及成熟衰老相关基因Ma SAG1的启动子活性。这些结果表明Ma WRKY31可能通过调控乙烯合成和成熟衰老相关基因的表达来参与香蕉果实成熟衰老过程,加深了对香蕉果实成熟衰老转录调控机制的认识。