寿命可靠性计算在食品货架期分析中的初步应用

以市售灭菌乳为研究对象,应用Weibull模型通过对食品非感官指标的分析,预测食品的货架期。灭菌乳分别在25、30、35、40℃环境下恒温储藏45d,并定期随机抽样进行感官检验和测定酸度。应用Weibull hazard analysis(WHA)方法分析非感官试验数据来预测样品货架期,并进行了寿命可靠性分析。     

寿命可靠性计算在食品货架期分析中的初步应用

以市售灭菌乳为研究对象,应用Weibull Hazard Analysis(WHA)方法,通过对食品品质指标的分析,预测食品的货架期;同时,探讨寿命加速试验线性无偏估计法在灭菌乳货架期可靠性分析方面的初步应用,分别在25、30、35、40℃环境下恒温贮藏,并定期随机抽样进行感官检验和测定酸度。     

威布尔分析法在青稞发酵酒货架期预测中的应用

利用威布尔危险值分析法(Weibull Hazard Analysis WHA),通过对不同贮存温度下青稞发酵酒跟踪感官评价,最终建立货架期预测数学模型,将预测货架期与实际货架期进行比较,预测数据的误差在-3.33%～4.86%,误差波动相对较小,预测模型应用效果较好。     

基于感官与理化指标的椪柑果酒货架期预测模型

通过对不同贮藏温度下椪柑果酒的感官、理化(挥发酸)和微生物(细菌总数)指标的变化分析,将感官威布尔危害分析(Weibull Hazard Analysis,WHA)模型和动力学模型分别结合Arrhenius方程,建立2种指标下椪柑果酒的货架期预测模型,并验证结果。研究结果表明,基于感官评价指标,在25,30,35,40℃温度下的货架期预测终点分别是620,436,310,222d,相对误差为-5.48%~5.52%;基于挥发酸评价指标,在25,30,35,40℃温度下的货架期预测终点分别是633,450,319,227d,相对误差为-2.74%~8.96%。椪柑果酒的贮藏温度与细菌总数相关性不显著,不作为具体参考指标。基于感官评价指标的货架期预测模型性能较优,可用于椪柑果酒的货架期终点预测。     

应用脂肪酶预测UHT乳货架期的研究

以市售UHT乳为研究对象,应用Arrhenius模型对脂肪酶进行分析,预测UHT乳的货架期.UHT乳分别在25、45℃环境下恒温储藏,并定期随机抽样,进行感官检验和脂肪酶含量测定.应用Arrhenius方法分析脂肪酶含量,来预测样品货架期,并建立了模型.     

应用游离氨基氮预测UHT乳货架期的研究

以市售UHT乳为研究对象,应用Arrhenius模型通过对游离氨基氮的分析,预测UHT乳的货架期.UHT乳分别在25℃和45℃环境下恒温储藏,并定期随机抽样进行感官检验和游离氨基氮质量浓度测定.应Arrhenius方法分析用游离氨基氮质量浓度来预测样品货架期,并建立了模型.     

速冻青稞鱼面贮运过程中货架期预测模型构建

通过对不同贮运温度下速冻青稞鱼面的感官、理化指标的变化分析,分别建立基于感官威布尔危害分析(Weibull Hazard Analysis,WHA)、化学动力学(Arrhenius)、BP神经网络(Back Propagation)的货架期预测模型,并验证结果。研究结果表明：在-18℃~25℃范围内,面条货架期随温度的升高逐渐缩短;根据国家标准确定速冻青稞鱼面在-18℃、-10℃、-5℃、0℃、5℃、10℃、25℃温度下货架期实际终点分别为94d、195d、100d、30d、24d、18d、3d;相关性分析显示,贮藏时间与TBA值呈极显著正相关,与POV值、pH值、感官评分相关性不显著。在-18℃、-10℃、-5℃、0℃、5℃、10℃、25℃温度下,基于感官评价指标的威布尔危害分析的货架期预测终点为296.21d 、206.89d、101.94d、29.92d、23.46d、19.15d、3.29d ,相对误差为0.27%~9.67%;基于TBA指标的Arrhenius方程,货架期预测终点为413.30d 、170.87d、101.05d、60.92d、37.40d、23.36d、6.26d,相对误差为1.05% ~108.62%。基于感官评价和理化指标(PH、TVB-N、TBA、POV)的BP神经网络模型货架期预测终点为281.45d 、190.07d、103.24d、31.46d、23.20d、17.17d、2.76d ,相对误差为4.60～7.96%。Weibull与BP神经网络预测模型性能较优,可用于速冻青稞鱼面的货架期终点预测。     

速冻青稞鱼面储运过程中货架期预测模型构建

通过对不同储运温度下速冻青稞鱼面的感官、理化指标的变化分析,分别建立基于感官威布尔危害分析(Weibull Hazard Analysis, WHA)、化学动力学(Arrhenius)、BP神经网络(Back Propagation)的货架期预测模型,并验证结果。研究结果表明:在-18～25℃范围内,面条货架期随温度的升高逐渐缩短;根据国家标准确定速冻青稞鱼面在-18、-10、-5、0、5、10、25℃下货架期实际终点分别为294、195、100、30、24、18、3 d;相关性分析显示,储藏时间与TBA值呈极显著正相关,与POV值、pH值、感官评分相关性不显著。在-18、-10、-5、0、5、10、25℃温度下,基于感官评价指标的威布尔危害分析的货架期预测终点为296.21、206. 89、101. 94、29.92、23. 46、19. 15、3. 29 d,相对误差为0.27%～9. 67%;基于TBA指标的Arrhenius方程,货架期预测终点为413. 30、170. 87、101. 05、60. 92、37. 40、23. 36、6. 26 d,相对误差为1. 05%～108. 62%。基于感官评价和理化指标(pH、TVB-N、TBA、POV)的BP神经网络模型货架期预测终点为281.45、190.07、103.24、31.46、23.20、17. 17、2.76d,相对误差为4.60%～7.96%。Weibull与BP神经网络预测模型性能较优,可用于速冻青稞鱼面的货架期终点预测。     

Weibull模型在板鸭货架寿命预测中的应用

以重庆白市驿板鸭为研究对象,应用Weibull模型通过消费者对食品的接受性分析,来预测板鸭的货架寿命。板鸭分别在20、25、30℃下恒温连续贮藏,定期随机抽样进行感官和理化检验,应用危害分析对实验数据处理来得到预测模型,并对板鸭的货架寿命进行了预测。     

压缩饼干硬度临界值的确定以及加速试验条件下硬度的变化规律

压缩饼干是一种长货架期食品,理化指标和感官指标变化缓慢。为了阐明压缩饼干在贮藏过程中硬度变化规律,通常采用加速试验的方法。首先在50℃条件下采用感官可接受性评价和WHA(Weibull Hazard Analysis,威布尔危险分析)方法确定出压缩饼干硬度的感官可接受终点值以及以硬度作为指标的货架寿命预测模型。其次,分别将压缩饼干贮藏在40、60℃和70℃下进行加速试验,研究样品硬度变化与温度和贮藏时间之间的关系。结果表明:压缩饼干硬度的可接受临界值为290～330N;温度的增高明显地加快了压缩饼干变硬,温度越高压缩饼干达到硬度终点的时间越短。继续贮藏,硬度在一定范围内波动。     

Survival analysis,consumer perception and physico-chemical analysis of low fat UHT milk stored for different time periods

Survival analysis based on consumers' acceptance or rejection of milk of different storage ages, was used to validate the shelf-life of low fat ultra-high temperature treated (UHT) milk in high density polyethylene bottles, as previously determined by a multivariate accelerated shelf-life test (MASLT). UHT milk between 120 and 290 d of storage were evaluated. Based on 50% of consumers rejecting the product, the shelf-life was estimated to be 214 d, validating the shelf-life of 211 d estimated by the MASLT. In addition, consumers completed check-all-that-apply attribute questions and rated the acceptability of the milk. The consumers noted positive sensory attributes more frequently in fresher milk samples with an increase in negative attributes with storage. Along with this, hedonic scores for the milk decreased and physicochemical and enzymatic reactions associated with the deterioration of UHT milk increased with storage.     

酱香型蓝莓利口酒贮存过程中品质稳定性研究

采用食品加速货架期测试法（ALST）对酱香型蓝莓利口酒的货架期进行预测,首先通过对其理化指标、微生物指标和感官品质的检测,得到了产品在55 ℃条件下的货架期为6 d,在45 ℃条件下的货架期为20 d。再利用Q10模型计算出Q10值为10/3,预测酱香型蓝莓利口酒在商业贮存温度（20 ℃）条件下的货架期约为406 d。     

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。     

保藏温度及时间对UHT 灭菌乳品质的影响

以复合塑料袋装UHT 灭菌乳为研究对象,考察保藏温度和时间对UHT 灭菌乳品质的影响。研究表明,保藏温度和时间对UHT 灭菌乳的蛋白质、乳脂肪、乳糖、滴定酸度及感官指标均有显著影响。具体而言,随保存时间延长,蛋白质、乳脂肪、乳糖含量及感官品质降低,而滴定酸度升高。保藏温度越高,以上变化明显加剧。4℃条件下,保藏时间范围内,样品的感官评分均保持在98 分以上,说明具有优良的感官品质;而保存在22℃和37℃条件下,感官品质下降,且保藏温度越高,感官品质降低越明显。     

嗜酸乳杆菌细菌素对鲜乳保质期的影响及防腐技术体系的建立

研究嗜酸乳杆菌（Lactobacillus acidophilus）产细菌素lactobacillin XH1对鲜乳保质期的影响。将0.5 g/kg嗜酸乳杆菌细菌素lactobacillin XH1分别添加到鲜乳和消毒鲜乳中,分析其在4 ℃贮藏期间抑菌活性、酸度、感官特性的变化趋势。通过在消毒鲜乳中添加嗜酸乳杆菌细菌素lactobacillin XH1,建立消毒鲜乳防腐应用中的危害分析和关键环节控制点（HACCP）技术体系。结果表明,4 ℃条件下贮藏,添加细菌素lactobacillin XH1的乳样的抑菌活性显著大于未添加细菌素lactobacillin XH1的乳样,且酸度变化趋势平缓,仍保持产品原有的风味、色泽、质构等感官特性,有效地延长鲜乳保质期2 d,消毒鲜乳保质期4～6 d。并建立了嗜酸乳杆菌细菌素lactobacillinXH1在消毒鲜乳防腐应用中的HACCP体系,确保产品的安全性。     

Effect of green tea catechins on physical stability and sensory quality of lactose-reduced UHT milk during storage for one year

Ultra-high temperature (UHT) processed lactose-reduced milk containing added green tea extract (GTE) at two concentrations (0.1% and 0.25%) was stored at 22 ± 2 °C for one year. The effect of GTE addition on physical stability, protein binding, and sensory quality was evaluated. Sedimentation in skim milk and creaming of full fat milk were inhibited by addition of GTE. The formation of Maillard-related flavour compounds was inhibited during storage as determined by dynamic headspace GC–MS. Using Western blot analysis, milk proteins were found to be highly conjugated to polyphenols. Addition of GTE before UHT treatment resulted in increased bitterness and astringency in UHT milk and this remained during storage. Even though GTE addition improved the physical stability and inhibited Maillard reactions in the milk, the taste and flavour contribution from GTE was dominating throughout storage, and alternative sources of polyphenols should be explored for increasing shelf-life stability of long-life milk.     

Fluorometric determination of chemically available lysine: adaptation, validation and application to different milk products

A spectrophotometric method based on the reaction between available lysine and ortho-phthaldialdehyde (OPA) was adapted and validated for fluorometric determination of the chemically available lysine contents in milk matrices (UHT and conventional in-bottle sterilized cow milk, milk-based infant formulas and infant formula ingredients). The values of the analytical parameters show its usefulness as a routine method (linearity, r = 0.9992; detection limit, 0.0066 mg/mL assay; accuracy, 99-108%; precision, intra-day 2.1-5.9% and inter-day 3.5 10.2%). No statistically significant differences (p < 0.05) were found between the values obtained with the adapted method and those obtained applying the 1-fluoro-2,4-dinitrobenzene (FDNB) (Carpenter) technique. The OPA method was used to measure the chemically available lysine contents in UHT and sterilized milk marketed in Spain, to study the evolution of chemically available lysine during the shelf-life of UHT milks, and finally the quality of name- and store-brand UHT milks was also compared. No statistically significant differences (p < 0.05) were found between either the available lysine contents of the same type of UHT or sterilized milk or between store- and name-brand UHT milks. Statistically significant differences (p < 0.05) were found between the chemically available lysine contents in UHT and sterilized milk. Losses of chemically available lysine ranging from 2.7 to 29% were obtained during the shelf-life of UHT milk.     

Changes in flavour and volatile components during storage of whole and skimmed UHT milk

Six batches of commercial UHT milk, submitted to direct treatment, three whole and the other three skimmed milk, were stored at 25±2°C for 4 months. Non-casein nitrogen (NCN) and sensorial analysis were carried out on packs opened every month. Volatile composition was analysed every 15 days, using a purge-and-trap concentrator coupled on-line to a GC–MS instrument. NCN increased during storage; the increase was greater in skimmed milk samples. Sensory characteristics were slightly better in the whole samples, although the scores decreased for both groups in the third month. Quantification of about 40 volatile components in whole milks showed no changes until 90 days (the legal shelf-life in Spain); the main change was the increase of methyl ketones. New components appeared in skimmed samples after 65 days storage; they could be related to both proteolysis and Maillard reaction. This is consistent with the poorer sensory quality found in skimmed milk samples.