基于空气(普通包装)和真空包装条件下鲈鱼片脂肪氧化指标建立鲈鱼货架期预测模型

建立鲈鱼片在空气和真空包装条件下基于脂肪氧化指标的货架期预测模型。将鲈鱼片经空气和真空包装后分别置于微冻(-2 ℃)、冰温(0 ℃)和冷藏(4 ℃)下贮藏,测定各温度下鱼片的酸价(AV)、过氧化值(POV)和硫代巴比妥酸(TBA)值,并进行感官评价。结果表明:真空包装可以有效的延缓鱼片在贮藏期间脂肪的氧化,且腹部鱼片比背部氧化更显著。基于空气和真空包装条件下鱼片脂肪氧化指标建立的鲈鱼货架期预测模型具有较高的拟合精度,预测值和实测值之间的相对误差均在±10.60%以内,且真空包装组所建立的三个值的预测模型平均相对误差较小,但普通包装组所得的货架期模型平均相对误差也在允许的范围内,这表明该模型能够很好地预测鲈鱼的剩余货架期。本研究结果为不同包装方式下鲈鱼剩余货架期的预测提供了理论依据。     

Estimating the Shelf Life of Brown Pan Bread, Suitability of Survival Analysis Methodology

ABSTRACT:  This paper uses survival analysis methodology to estimate the shelf life of brown pan bread. The key concept of survival analysis is to focus the shelf-life estimation on consumer rejection rather than on product deterioration. The likelihood function, which corresponds to the joint probability of the consumers' observations, is established for a suitable parametric model. The parameters of the model are estimated via the maximization of the likelihood function. From these, the survival function, as well as other quantities of interest is estimated. Different models were applied to the brown pan bread data and used to predict, and compare, the shelf life of brown pan bread for F(t) = 0.25 and 0.50 (25% and 50% consumer rejection). The variation in consumer's global acceptability of the product throughout its shelf life was studied.     

食品感官货架期确定的一般原则与方法

感官品质是描述和判断食品质量最直观的指标,将此品质作为货架寿命的评价指标而确定的货架期为感官货架期,则对应的感官评价方法是确定感官货架寿命的关键技术之一。由此,结合感官评价方法与货架期预测原理,提出了食品感官货架期确定的一般原则与方法,旨在指导构建我国不同类型食品感官品质的货架期确定指南,完善食品货架期检测标准,为我国食品质量与控制的保障提供标准化支撑。     

H2O2喷雾处理对馒头品质及保质期的影响

采用H2O2喷雾处理的方法对馒头品质及保质期进行研究。结果表明:H2O2喷雾浓度和喷雾时间能明显影响其延长馒头保质期的效果。在H2O2喷雾浓度为20%、喷雾时间为5 s、静置时间为60 min时,馒头的保质时间从20 h延长至43 h,未检测出有残留的过氧化氢。     

月饼品质指标变化规律研究和保质期预测模型的建立

本实验以航天月饼为研究对象,研究其在4、22、37、47 ℃下贮藏过程中感官、理化和微生物指标变化特点。采用零级或一级动力学模型结合Arrhenius方程建立基于月饼品质指标的保质期预测模型。结果表明：航天月饼的感官评分、pH值、色调角h、亮度（L*值）随贮藏时间延长呈下降趋势;在月饼接近保质期终点时,电子舌分析结果显示酸味响应增强,电子鼻分析结果表明硫化物、氮氧化合物、有机硫化物、甲烷、乙醇等化合物响应增加;酸价、过氧化值、羰基价、a*值、菌落总数、霉菌与酵母菌数随时间延长呈上升趋势,大肠菌群在贮藏期间未检出。相关性分析表明酸价预测模型精度最高,活化能（Ea）为44.76 kJ/mol,指前因子k0为2.91×106,且预测值与实测值相对误差的绝对值在10%以内。航天月饼在不同贮藏温度和时间下油脂氧化是影响其品质的主要因素,这种品质变化规律可以通过Arrhenius方程进行预测。本研究可为航天食品保质期预测提供参考。     

Shelf life estimation of brown pan bread: A consumer approach

In this study three different approaches—acceptability limit, failure cut-off point methodology, and survival analysis—to estimate the sensory shelf life of brown pan bread elaborated with different enzymes using consumer data were compared. The study was carried out in Spain and Uruguay independently, where four batches of bread were produced, with the same base formulation, one without enzyme, the others with the addition of maltogenic amylase, xylanase, and a mixture of both. The results showed that for Uruguayan consumers the mixture of enzymes provided better results in extending shelf life than the addition of amylase alone. For the Spanish consumers only the addition of amylase provided the desired results, and for consumers of both countries the use of xylanase did not extend the shelf life of bread. Among the methodologies used for the estimation, survival analysis provided the most adequate predictions considering consumer rejection of the product. Hedonic scales do not always reflect consumer behaviour when deciding whether to accept or reject a certain product for its consumption.     

鸡毛菜的品质动力学分析及货架期预测模型

为探讨鸡毛菜贮藏过程中的品质变化,测定贮藏在278、283、288 K和293 K 4 个温度条件下的鸡毛菜的叶绿素和还原型抗坏血酸含量,进行动力学分析、货架期预测和感官评价,并采用Arrhenius 方程对速率常数k和温度进行非线性拟合,建立包含有货架期、温度和品质指标的鸡毛菜货架期预测模型。结果表明,在研究的温度范围内,鸡毛菜贮藏的温度越低,叶绿素和还原型抗坏血酸降解速率越慢,零级规律比一级动力学分析更适合描述叶绿素和还原型抗坏血酸的降解,还原型抗坏血酸和叶绿素降解的活化能Ea分别为85.27、93.27 kJ/mol。以叶绿素损失20%为终点得到的货架期更接近感官评分终点为3.5 分得到的货架期,此时还原型抗坏血酸损失超出20%。因此应根据实际情况综合选择货架期判定特征指标和终点值,从而获得较高的货架期预测精度。     

Bromate Determination by X-Ray Fluorescence (XRF) to Identify Pre-Baking Potassium Bromate Addition in Bread

Wavelength-dispersive x-ray fluorescence (WDXRF) was applied to determine bromate (Br) as an indication of pre-baking bromate addition in bread. The proposed methodology needed a minimum sample preparation procedure because it was carried out directly on solid samples. The calibration of Br in bread obtained showed low detection limit and high sensitivity to distinguish precisely Br concentrations greater than natural Br. The excellent performance of the present methodology would be useful to identify pre-baking bromation in bread, which can be used to help set up a programme to control bromation in bread. Application of this methodology to bakery control caused an important reduction of bromate use in province of Córdoba, Argentina.     

Multiparametric investigation of mould‐free shelf life of bread via factorial design

The investigation of a complex process, such as the bread making process, can be greatly favored by the approach of statistical design of experiments. Using simple first order factorial designs, reliable models were constructed investigating the effects of salt, sugar, sorbic acid, calcium propionate, vegetable fibers, fat and emulsifier on the shelf life of bread (optimization parameter). These effects were in general linear. An exception was observed in the case of use of calcium propionate where an interaction between salt and sugar was determined. The effects of all significant factors on optimization parameter were reasonable. Sorbic acid and calcium propionate proved to be more effective preservatives than salt and sugar by an order of magnitude. Antifungal efficiency of sorbic acid was found to be about three times that of calcium propionate. Prolongation of shelf life reached 117% for sorbic acid and 63 % for calcium propionate, when salt and sugar were fixed to their basic levels. Vegetable fibers had a detrimental effect on shelf life greatly decreasing it by as much as 65 % of the control samples (without fibers). Addition of fat and emulsifier in the dough showed a slightly negative effect on the mould‐free shelf life of bread.     

Effect of sourdough at different concentrations on quality and shelf life of bread

The objective of this work was to study the effect of sourdough obtained with selected exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) strains on the quality of bread and its shelf life. Two sourdough concentrations were used in order to ascertain the best bread composition. Fresh bread quality was studied by means of microbiological, physical, chemical and mechanical analysis, whereas physical, thermal and mechanical properties were investigated to study the product shelf life. The results showed that dough prepared with 30 g/100 g of sourdough had a negative impact on bread quality properties in the absence of EPS-producing LAB strains, whereas the opposite was observed in the presence of EPS-producing strains: bread samples at 30 g/100 g of sourdough showed higher volume, higher moisture content and better mechanical properties during storage than samples at 20 g/100 g of sourdough. Moreover, 30 g/100 g of sourdough showed a protective effect on bread staling, thus confirming the effect of sourdough concentration and the positive role of EPS on functional properties.     

应用Schaal耐热试验法预测软包装风味鱼的货架期

采用高温"Schaal耐热试验法"预测风味鱼的货架期。选取40、60℃2个温度进行加速实验,以加速贮藏过程中产品酸价、过氧化值及微生物的变化为指标,结合产品感官评定,依据温度与油脂货架寿命系数的关系,预测产品货架期。结果表明不添加防腐剂的产品货架期为80d,添加0.0075%山梨酸钾的产品货架期为160d。     

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.     

Quality and storage life of par-baked frozen breads

During storage of frozen par-baked breads for a prolonged period of time, bread quality may undergo changes such as increased firmness, moisture and flavour losses resulting in product deterioration. Four categories of par-baked breads namely—variety, white, multi-grain and rye were stored at −18°C for 9 months to evaluate the effects of storage period on product quality, and to develop prediction models that describe kinetics of deterioration of selected quality parameters. The quality was evaluated based on sensory, chemical and physical attributes and properties. Storage life was determined based on the changes in bread quality below certain level. The principal component analysis indicated that approximately 90% of the total variability of 19 quality parameters can be explained with only two principal components. The zero-order kinetic reaction showed good agreement (R²>80%) with quality changes observed by the sensory panel over the storage period. A prediction model, based on the bread quality at zero time and the quality at the time when the bread was rejected by the sensory panel, was developed. The proposed prediction model would provide a useful means of estimating storage life of par-baked breads made with similar formulations.     

基于Arrhenius模型预测无乳糖超高温乳的货架期

采用电子眼、电子鼻、电子舌等感官评价技术,结合货架期加速实验(ASLT)的阿伦尼乌斯公式(Arrhenius)模型,建立无乳糖超高温灭菌乳(UHT乳)的货架期预测模型。将无乳糖UHT乳分别贮存于37、27、4℃下,以色泽、气味、滋味为主要指标,在不同的贮存温度下,综合分析无乳糖UHT乳品质与贮存时间之间的变化,并应用Arrhenius公式建立货架期模型。结果表明:37、27℃下贮存的无乳糖UHT乳色泽的发生显著性变化(P<0.05)的时间为24、33 d;苦味发生显著性变化(P<0.05)的时间为24、27 d;而贮存60 d气味无显著性变化(P>0.05)。4℃下贮存60 d的无乳糖UHT乳色泽、气味、滋味均无显著性差异(P>0.05)。以苦味为指标,利用Arrhenius公式拟合的货架期模型为:t=0.109×e-5.1882。选取37、27℃验证模型准确性,与实际货架期之间的误差分别为9.5%、12.5%,误差较小。用此公式计算4℃下无乳糖UHT乳货架期为71 d。因此,以感官指标为依据建立货架期预测模型可预测无乳糖UHT乳的货架期。     

Oxidative stability of whole wheat bread during storage

The oxidative stability was examined in whole wheat bread packed in modified atmosphere (nitrogen) using vacuum grade plastic bags and stored for up to 5 weeks. Small, but significant, differences in oxidative stability developed with time for whole wheat bread crumb and crust. The samples were evaluated by direct electron spin resonance (ESR) spectroscopy for detection of free radicals, peroxide value (POV), overall antioxidative capacity using Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays, and by the content of tocopherols as determined by HPLC. The overall antioxidative capacity was reduced during storage with an accumulation of lipid hydroperoxides peaking after 2-3 weeks of storage. Bread crust was generally found to be more oxidative stable when compared to crumb. Quality of bread with extended shelf life may accordingly be improved minimising oxidation.     

响应面法优化汉堡面包的种面发酵工艺

为优化选出抑青霉菌效果最好的汉堡面包种面发酵基质及工艺,本文通过单因素实验结合Box-behnken响应面试验进行优化,以种面对青霉菌的抑菌率作为评价指标,选出最优的发酵剂和糖种类等发酵工艺,并对最优条件下制作的汉堡面包的理化性质、微生物数量、感官、质构以及保质期等指标进行测定。结果表明,最优发酵工艺为种面中添加乳酸菌发酵剂B和蔗糖,蔗糖浓度选择4.1%,发酵时间及温度分别选择20 h和30℃。此条件下发酵后的种面对青霉菌的抑菌率为32.67%,与理论预测值相比,其相对误差约为4.41%。最优发酵工艺下制作的汉堡面包抑菌效果较好且具备良好的理化特性,其中酸价2.68 mg/g、比容3.07 mL/g、过氧化值0.15 g/100 g、硬度1158.65 g、弹性0.88 mm。冷却包装2 h后菌落总数及霉菌均未检出,在20℃室温下保质期长至15 d。     

黑芝麻复合蜜丸货架期预测及包装方式对其贮藏品质的影响

以黑芝麻复合蜜丸为研究对象,以酸价和过氧化值为评价指标,考察不同储藏温度对其品质的影响;在此基础上,通过构建Arrhenius模型对裸包装条件下的黑芝麻复合蜜丸的货架期进行预测。为进一步延长货架期,设置4种不同包装形式对黑芝麻复合蜜丸进行包装,同时考察不同包装方式对其水分、质构、理化特性等贮藏品质的影响。结果表明：与对照组相比,充氮、包壳、蜡封对阻止黑芝麻复合蜜丸水分下降、硬度和酸价上升均有一定的作用,其中以蜡纸+药丸壳+蜡封+锡箔纸+聚乙烯塑料袋这种包装形式效果最佳。该研究结果为蜜丸类产品的储存提供参考。     

温度对李果实采后品质的影响及货架期预测模型建立

目的 研究李果实采后品质变化及建立李果实采后货架期预测模型。方法 本试验设置了3种温度（4、15、25℃）,并定期测定生理生化指标。采用零级动力学模型和一级动力学模型结合Arrhenius方程建立基于品质变化的李果实采后货架期预测模型,并验证模型的预测精确度。结果 低温明显延缓了果皮强度和果肉硬度的下降和果实失重率的上升,同时也延缓了花色苷含量的积累,对总酸含量影响不明显。根据果皮强度、果肉硬度和失重率变化建立货架期预测模型,通过验证发现基于失重率变化的货架期预测模型具有最好的精确度,相对误差值低于10%。结论 货架期预测模型的建立,可快速预测果实剩余货架期,为贮藏和货架提供技术指导。     

油脂对馒头品质的影响

本文研究了不同类型油脂对馒头品质及老化的影响.发现,固态油脂（起酥油和精制猪油）的适量添加能够改善馒头的表面色泽和内部质构,增大了馒头的体积和延缓了馒头的老化.而液体油（一级豆油）不能对馒头的品质起到改良作用.     

EFFECT OF NATIVE AND LYOPHILIZED KEFIR GRAINS ON SENSORY AND PHYSICAL ATTRIBUTES OF WHEAT BREAD

Native and lyophilized kefir grains were added directly to bread dough or as a starter in sourdough. Because of inadequate leavening activity of kefir, yeast‐leavened breads were prepared. Kefir addition influenced the quality attributes and the shelf life of wheat bread. The pH of bread containing kefir decreased as compared to that in the control bread. The acidity of bread with kefir increased as compared to that in the control bread. An addition of kefir grains, regardless of the form, lowered the bread volume and increased the mold‐free shelf life from 4 (control) to 5–7 days. The addition of kefir grains in bread dough contributed to a milder taste, a more delicate yogurt‐like or dairy aroma. The breads made with sourdoughs containing native or lyophilized kefir grains scored higher for crumb quality number than breads made by directly adding kefir grains.