Kinetics of the ozone gas reaction in popcorn kernels

The objectives of this work were to determine the saturation times for popcorn kernels exposed to different concentrations of ozone gas (O₃) in a constant flow; to study the kinetics of the ozone gas decomposition in the grain mass; and to ascertain the ozone treatment effect on grain quality. In order to promote saturation and to study the decomposition reaction kinetics, samples of popcorn kernels were exposed to ozone gas or atmospheric air (control) at a specific flow rate of 0.33 m³ min⁻¹ t⁻¹, and concentrations of 500, 2200, and 4500 μg L⁻¹. The popping expansion volume, water content and electrical conductivity of the ozonized popcorn kernel samples were considered to investigate the effect of ozone treatment on popcorn quality. The effect of ozone treatment on insect mortality was also evaluated. The grain masses treated at ozone concentrations of 500, 2200, and 4500 μg L⁻¹ reached the saturation condition after 10, 3.1, and 2.1 h, respectively. At all concentrations considered, the decomposition kinetics of the ozone gas when in contact with the saturated grain mass was best explained by a first-order model. The decomposition rate constants were equal to 0.13, 0.11, and 0.12 min⁻¹, for the concentrations of 500, 2200, and 4500 μg L⁻¹, respectively. At these ozone levels, the quality analyses of the popcorn grains did not reveal alterations that could compromise the product commercially. Nevertheless, the concentrations of 500, 2200, and 4500 μg L⁻¹ proved to be lethal to the insects at the exposure times corresponding to the saturation in each case.     

可微波鸡米花预混粉层配料的研究

采用单纯形格子法实验设计优化鸡米花层预混粉的配方,以获得鸡米花微波后表层松脆的口感,通过对鸡米花的脆性、感官指标以及色差的分析,确定预混粉最优的配方为：小麦淀粉21％,变性淀粉25％,蛋清粉2．5％,大豆蛋白4．5％,其他成分占47％。结果表明,采用优化后的预混粉层配方生产出的鸡米花,可以使微波后产品脆性得到显著的提高,而且产品的感官质量较好。     

蔗糖对淀粉物料微波膨化的影响研究

研究了淀粉物料中添加蔗糖后微波加热效果、物料膨化效果的改变情况。结果表明,蔗糖的添加增强了微波对淀粉物料的加热效果,使得物料的温升速率大大提高,且随着蔗糖含量的增加,这种增强效应更明显。由于蔗糖对淀粉糊化的影响及加热后的特性,随着添加量的增加膨化率变小,膨化过程也相对迟缓;随着糖含量的增加,产品的孔隙状态发生变化,孔隙变形、回缩,产品硬度减小,脆度增大,孔隙率渐大,色泽加深。     

The effects of ingredients on popcorn popping characteristics

Response surface methodology was used to evaluate the effects of ingredients on popcorn popping characteristics. The effects of different ingredients on the expansion volume and unpopped kernel ratio of popcorn in a conventional popper and a microwave oven were evaluated and optimized by response surface methodology. The regression models were significant and had R² value in the range of 0.919–0.956. The optimum levels of ingredients for microwave popping were 4.4% salt, 5.9% vegetable oil, 0% sodium bicarbonate and 16.4% butter, this formulation giving an expansion volume of 33.1 mL g^?1. In the case of conventional popping, the maximum expansion volume of 37.3 mL g^?1 was obtained for 3.5% salt, 6% vegetable oil, 0.10% sodium bicarbonate and 12.9% butter.     

碘盐及发酵温度对低盐固态酱油质量的影响

实验室条件下考察了碘盐及发酵温度对低盐固态法酿造酱油的影响。试验分析表明微量碘对酱油的色泽有一定影响,使用碘盐的酱油色率略高于非碘盐的酱油,红色指数相近。而发酵温度按第1～7d,41～43℃;第8～18d,44～46℃;第19～20d,47～48℃模式控制,低盐固态酱油的色率及红色指数指标较好,氨态氮的生成率最高。     

低功率微波处理对板栗低温贮藏生理及品质的影响

采用不同强度的微波处理板栗3min,并于3℃条件下贮藏180d,研究低功率微波处理对板栗的呼吸强度、失重率、腐烂率、还原糖含量、淀粉酶活性、V_C含量、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性和丙二醛(MDA)含量的影响。试验结果表明:65 W/3min处理组对CAT活性增加抑制效果最好;130 W/3 min处理组对POD活性下降和MDA含量增加有较好抑制效果;260 W/3 min处理组能有效降低失重率、腐烂率;195 W/3min处理组对呼吸强度、淀粉酶活性、POD活性、还原糖含量的上升及VC的氧化有明显抑制作用,也能有效降低失重率、腐烂率。综合分析,低功率微波保鲜板栗的最佳处理条件为195 W/3 min,打孔PE袋包装,3℃低温冷藏180d,商品率93%~95%。     

乙醇体积分数和贮存时间对乙醇溶液物理特性的影响

利用密度声速仪、水分活度仪、电导率仪和近红外光谱仪,测定了不同乙醇体积分数和贮存时间下乙醇溶液的部分物理特性。结果表明,不同体积分数乙醇溶液的声速值、水分活度和电导率均存在差异,且同一种体积分数乙醇溶液在贮存不同时间,声速、水分活度和电导率也分别发生变化;近红外光谱（NIR）结果表明,低体积分数乙醇溶液（5%和14%）自由羟基吸收峰强于高体积分数乙醇溶液（38%和45%）,猜测是高体积分数乙醇溶液中大部分羟基与乙醇分子或水分子形成了氢键,这种氢键随着乙醇体积分数变化发生改变,且变化速度比较缓慢,从而影响不同体积分数或不同贮存时间乙醇溶液的物理特性。该结论提出了乙醇-水微观结构对乙醇溶液物理特性的影响,为乙醇产品质量的分析和监测奠定了理论基础。     

改性大豆分离蛋白对微波复热鸡米花品质的影响

为解决微波复热后鸡米花表皮由于浸湿而失脆的问题,本研究向面糊层中添加了超高压均质-酶解复合改性大豆分离蛋白(UESPI),测定了鸡米花微波复热后外层的水分、油分,并分别以色差值,TPA分析中的正向峰数,面糊层孔洞结构为指标研究了面糊层中添加大豆分离蛋白对鸡米花色泽,脆度,表层微观结构的影响。结果表明,面糊中添加20%UESPI的鸡米花微波复热后,表层水分、油分显著下降(p<0.05),鸡米花呈金黄色泽,其微波复热后脆度与新鲜油炸鸡米花脆度相近(p>0.05)。SEM结果则显示面糊层结构致密、几乎无孔洞,有效的阻止了内芯水分、油分的外溢。本研究采用UESPI作为鸡米花面糊层配料,有效的提高了鸡米花微波复热后的脆性,极大的改善了鸡米花的感官特性。     

Effects of storage at chilling temperature on ion absorption,salt retention capacity and respiratory pattern in yam tubers

Yams, like most tropical crops, are subject to chilling injury when stored at temperatures below 10°C. Membrane permeability changes are considered to be among the causative factors. Some physiological parameters associated with the cell membranes were therefore examined in yam tuber tissue. It was established that incipient chilling injury could be rapidly detected by changes in ion absorption and salt retention capacities of tuber disks. Chilling effects were also reflected by changes in respiratory rate. It is proposed that these techniques can be used for rapid screening of tubers of a wide range of yam varieties, to establish optimum and minimum safe storage temperatures.     

蒸汽—微波协同膨胀设备研发与应用评价

针对现有烟梗微波膨胀设备存在的缺陷和不足,研发了蒸汽—微波协同膨胀设备。该设备主要由物料传输系统、微波系统、蒸汽循环系统和加热腔体组成,采用蒸汽和微波复合加热能源,降低了获得高膨胀度所需的微波功率,既充分发挥了微波膨胀的质量优势,又有效防止了微波打火现象发生。与纯微波膨胀设备相比,烟梗膨胀度平均提高57.8%,有效膨胀率平均提高4.06%;制得梗丝的填充值平均提高0.46cm3/g,整丝率平均提高2.03%,碎丝率平均降低0.95%,感官质量明显提升。     

微波对稻谷储藏过程脂肪酶和脂肪酸的影响

为研究微波对稻谷储藏品质的影响,采用2 450 MHz微波处理稻谷,于不同温度(8、20、30℃)下储藏180天,研究储藏过程稻谷脂肪酶活性、游离脂肪酸含量及其组成。结果表明,经低强度的微波条件处理后,稻谷脂肪酶活力和游离脂肪酸的含量均有提高,不饱和脂肪酸含量降低。稻谷储藏过程中,脂肪酶活力逐渐降低,游离脂肪酸含量增加,脂肪酸组成发生变化,低强度微波处理对稻谷的储藏品质影响不大。     

Combined effects of freezing rate, storage temperature and time on bread dough and baking properties

This study compares the effects of freezing temperature and rate as well as storage temperature and time on the quality of frozen dough. Yeasted bread dough was frozen using four freezing rates (19-69 °C/h), then stored at −10, −20, −30, or −35 °C for up to 180 days. Dough strength diminished with longer storage time and higher storage temperatures. Cryo-SEM showed that dough stored at −30 and −35 °C had the least damaged gluten network. NMR studies showed that more rapidly frozen dough, and that stored at lower temperatures had lower transverse relaxation (T₂) times (9-10 ms). However, dough stored at −20 °C displayed the highest yeast activity among samples. Bread loaf volume decreased with storage time, and bread made from dough stored at −20 °C showed the highest loaf volume. Breads produced from −30 and −35 °C stored dough displayed less change in the texture profile during storage as well as less change in T₂ values. Response surface analysis showed that optimal properties occurred at freezing rates of around 19-41 °C/h and storage temperatures of −15 to −20 °C.     

食用胶复配对微波复热鸡米花品质的影响

针对微波复热鸡米花的加工工艺,在预实验基础上选用黄原胶、卡拉胶以及魔芋胶以不同比例复配,研究其对最终产品品质的影响。微波复热后以鸡米花的脆性作为主要评定指标,同时对制品进行物理性质分析及感官评价,筛选出微波复热后品质最优的胶体复配比例。结果表明,向浸蘸溶液中添加三种食用胶中的任意一种或任意两种食用胶复配添加时,均可以显著改善微波复热后鸡米花的脆性(p<0.05)。而三种食用胶等比例复配对微波复热鸡米花品质则没有明显改善作用。卡拉胶1.00%的添加量会对产品风味产生不良影响。其中0.50%黄原胶和0.50%卡拉胶复配时,微波复热后鸡米花的脆性显著提高,外壳水分和油分含量显著降低(p<0.05),感官质量也较高。这表明向浸蘸溶液中添加0.50%黄原胶和0.50%卡拉胶复配食用胶可以很大程度上改善微波复热鸡米花的食用品质。     

微波处理真空包装对葡萄贮藏品质和生理变化的影响

研究了微波、真空包装以及微波处理真空包装对葡萄贮藏过程中果实的耐压力、可溶性糖、VC、多酚氧化酶(PPO)活性的影响以及感官评定分析。研究结果表明:采用微波真空包装的葡萄果实耐压力、可溶性糖、VC的变化均小于其他处理方式且变化最小,多酚氧化酶(PPO)活性降低最大,感官评定最好。微波处理真空包装可以有效地降低多酚氧化酶(PPO)活性和果实的呼吸强度,提高了抗氧化酶的活性,有利于果实的贮藏保鲜。      

微波干燥温度和物料厚度对铁棍山药片品质的影响

以新鲜铁棍山药为材料,采用光纤插入物料中心在线控制微波干燥的物料温度、厚度的方式进行干燥,通过单因素试验法进行干燥加工处理,采用索氏提取法提取样品中的多糖,同时采用苯酚硫酸比色法测定经不同干燥参数制备的样品的多糖得率,以自制作微波干燥系统进行重量记录以及物料的温度控制,色差计测样品色泽进而评价干燥的效果。结果发现:在控制不同的物料温度且厚度为5 mm时,最高的多糖得率的物料温度为50℃且此时白度值最大,但所需干燥时间最长;物料温度为60℃时改变物料的厚度,得到最高的多糖得率的物料厚度为5mm。综合比较可知,实际微波干燥生产时以温度60℃且物料厚5mm干燥的效果更好。     

淀粉老化对微波膨化影响的研究

采用Ｘ－ 衍射方法确定了淀粉物料的老化程度,并研究了淀粉的老化对其微波膨化的影响,探讨了淀粉老化对微波膨化影响的机理。     

Influence of the temperature of salt brine on salt uptake by Ragusano cheese

The influence of temperature (12, 15, 18, 21, and 24 degrees C) of saturated brine on salt uptake by 3.8-kg experimental blocks of Ragusano cheese during 24 d of brining was determined. Twenty-six 3.8-kg blocks were made on each of three different days. All blocks were labeled and weighed prior to brining. One block was sampled and analyzed prior to brine salting. Five blocks were placed into each of five different brine tanks at different temperatures. One block was removed from each brine tank after 1, 4, 8, 16, and 24 d of brining, weighed, sampled, and analyzed for salt and moisture content. The weight loss by blocks of cheese after 24 d of brining was higher, with increasing brine temperature, and represented the net effect of moisture loss and salt uptake. The total salt uptake and moisture loss increased with increasing brine temperature. Salt penetrates into cheese through the moisture phase within the pore structure of the cheese. Porosity of the cheese structure and viscosity of the water phase within the pores influenced the rate and extent of salt penetration during 24 d of brining. In a previous study, it was determined that salt uptake at 18 degrees C was faster in 18% brine than in saturated brine due to higher moisture and porosity of the exterior portion of the cheese. In the present study, moisture loss occurred from all cheeses at all temperatures and most of the loss was from the exterior portion of the block during the first 4 d of brining. This loss in moisture would be expected to decrease porosity of the exterior portion and act as a barrier to salt penetration. The moisture loss increased with increasing brine temperature. If this decrease in porosity was the only factor influencing salt uptake, then it would be expected that the cheeses at higher brine temperature would have had lower salt content. However, the opposite was true. Brine temperature must have also impacted the viscosity of the aqueous phase of the cheese. Cheese in lower temperature brine would be expected to have higher viscosity of the aqueous phase and slower salt uptake, even though the cheese at lower brine temperature should have had a more porous structure (favoring faster uptake) than cheese at higher brine temperature. Therefore, changing brine concentration has a greater impact on cheese porosity, while changing brine temperature has a larger impact on viscosity of the aqueous phase of the cheese within the pores in the cheese.     

The effect of multiwall Kraft paper or plastic bags on physico-chemical changes in milk powder during storage at high temperature and humidity

Plastic bags have recently been introduced as an alternative to multiwall Kraft paper bags in packaging milk powder in 25-kg sizes as it is thought that plastic bags are more durable and would preserve the quality of milk powders during storage better than paper bags. However, there is little scientific information available on the performance of plastic bags for milk powder storage. The aim of this study was to compare the properties of skimmed milk powder (SMP) packaged in plastic or paper bags. Commercially produced and packaged SMP in 25-kg plastic or paper bags was stored at 37°C and 90% relative humidity. Samples were analysed at intervals (0, 45, 90 and 135 days) for moisture, water activity, lactic acid content, pH, insolubility index, bulk density, flowability, dispersibility and particle size. The magnitude of change in the majority of SMP properties measured during storage suggests that plastic bags are similar to paper bags in maintaining milk powder quality during storage.     

Effect of fish,starch and salt contents on the microstructure and expansion of fish crackers (‘keropok’)

Light microscopy studies on the fish cracker gel and expanded product (‘keropok’) emphasised the role of fish proteins in the starch expansion process. The addition of salt (20 g kg⁻¹) in the ‘keropok’ helped to distribute evenly the starch in the fish protein. Formation of thin fish muscle bundles assisted the expansion of ‘keropok’. At 700–900 g kg⁻¹ fish content, the fish muscle bundles formed a continuous network that caused a drop in the ‘keropok’ expansion. From the scanning electron microscopy study, ridges were found in samples (containing 600–900 g kg⁻¹ fish content) with 20 g kg⁻¹ salt at high magnification. © 1999 Society of Chemical Industry     

Impact of storage environment on the efficacy of hermetic storage bags

Small hermetic bags (50 and 100 kg capacities) used by smallholder farmers in several African countries have proven to be a low-cost solution for preventing storage losses due to insects. The complexity of postharvest practices and the need for ideal drying conditions, especially in the Sub-Sahara, has led to questions about the efficacy of the hermetic bags for controlling spoilage by fungi and the potential for mycotoxin accumulation. This study compared the effects of environmental temperature and relative humidity at two locations (Indiana and Arkansas) on dry maize (14% moisture content) in woven polypropylene bags and Purdue Improved Crop Storage (PICS) hermetic bags. Temperature and relative humidity data loggers placed in the middle of each bag provided profiles of environmental influences on stored grain at the two locations. The results indicated that the PICS bags prevented moisture penetration over the three-month storage period. In contrast, maize in the woven bags increased in moisture content. For both bag types, no evidence was obtained indicating the spread of Aspergillus flavus from colonized maize to adjacent non-colonized maize. However, other storage fungi did increase during storage. The number of infected kernels did not increase in the PICS bags, but the numbers in the woven bags increased significantly. The warmer environment in Arkansas resulted in significantly higher insect populations in the woven bags than in Indiana. Insects in the PICS bags remained low at both locations. This study demonstrates that the PICS hermetic bags are effective at blocking the effects of external humidity fluctuations as well as the spread of fungi to non-infected kernels.