Non-Volatile Organic Acids,pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

Effects of freezing and frozen storage on pH, titratable acidity and non-volatile organic acids of two pineapple fruit cultivars, Smooth Cayenne and Red Spanish, were studied. Pineapple fruit was frozen as slices in a cold room at −18°C and stored at this temperature for a 12 month period. A negative correlation was found between pH and titratable acidity in the two cultivars throughout frozen storage ( r =-0·67 for Smooth Cayenne and r =-0·71 for Red Spanish). Non-volatile organic acids were determined by high performance liquid chromatography. The major components were citric and L-malic acids. A high correlation was found between these two acids during frozen storage ( r =0·75 in Smooth Cayenne and r =0·78 in Red Spanish). There were significant differences ( P⩽ 0·01) in pH and titratable acidity between the two studied varieties after a year of frozen storage. Significant differences ( P⩽ 0·05) were found in pH values during frozen storage in cv Smooth Cayenne and in citric and L-malic acids in cv Red Spanish. Freezing preservation of pineapple fruit slices led to minimal chemical changes after a year of frozen storage.     

不同预处理方法对速冻菠萝贮藏品质的影响

以9成熟巴厘菠萝果实为材料,研究不同预处理方法(对照CK、柠檬酸、乳酸钙、NaCl、烫漂处理)对速冻菠萝贮藏品质的影响。结果表明:与对照相比,烫漂处理可使果实养分含量快速下降,严重影响果肉风味品质;而NaCl处理则延缓了可溶性固形物、VC、硬度的降低和细胞膜透性的上升,使得速冻菠萝保持较好的商品价值和食用品质。     

不同冻结温度对菠萝丁质量的影响

目的研究不同冻结温度对菠萝丁质量的影响。方法将菠萝丁分别放在-20℃、-25℃、-30℃下冻结,研究速冻前后菠萝细胞结构、质构和汁液流失率的变化。结果不同冻结温度下,细胞破坏程度不同,-30℃下速冻对细胞结构的破坏较小,解冻后产品不仅硬度损失小,而且汁液流失少。结论-30℃速冻可作为冻结菠萝果丁的适宜温度。     

不同冻结温度对菠萝丁质量的影响

目的研究不同冻结温度对菠萝丁质量的影响。方法将菠萝丁分别放在-20℃、-25℃、-30℃下冻结，研究速冻前后菠萝细胞结构、质构和汁液流失率的变化。结果不同冻结温度下，细胞破坏程度不同，-30℃下速冻对细胞结构的破坏较小，解冻后产品不仅硬度损失小，而且汁液流失少。结论-30℃速冻可作为冻结菠萝果丁的适宜温度。     

Thawing, Refreezing and Frozen Storage Effects on Muscle Functionality and Sensory Attributes of Frozen Cod (Gadus morhua)

Thawing and re-freezing of cod fillet blocks did not necessarily result in greater deterioration (relative to a ‘once frozen’ control) of cooked fish sensory attributes after 9 months frozen storage at –22°C. Thawed and refrozen fish muscle displayed a faster decline in myofibril protein solubility than once frozen controls and had reduced water-holding capacity but analysis of proton spin-spin relaxation times indicated no change in water location. The decline in protein solubility was not caused by complete protein unfolding. Long thawing times (30 hr) before re-freezing and storage resulted in cooked fish with more gray appearance and more stale flavor. Changes in fish muscle functionality did not enable direct inference of sensory attributes.     

Effect of Freezing and Frozen Storage on Chemical and Microbiological Characteristics in Sheep Milk Cheese

ABSTRACT: Most chemical components and water activity of an the Los Pedroches' brand ewes' milk cheese were not altered by frozen storage. Lactic acid concentration and pH were significantly different (p < 0.05) in control cheeses and those kept in frozen storage for 3 and 6 months from those stored for 9 months. Proteolysis continued slowly during frozen storage, with significantly higher rates of non protein nitrogen and amino acid nitrogen (p < 0.05) present at the end of the storage period. Counts of microorganisms, except for enterococci, tended to decrease during frozen storage. Freezing rates did not affect the chemical and microbiological characteristics studied.     

猪肉冰温贮藏过程中的品质变化与机理研究

研究表明浅度冻结、合理的贮藏条件及贮存期不会显著影响原料肉及肉制品的加工和食用品质.据此,本研究提出了“冰而鲜”的冰温保鲜的新技术:即将鲜肉经过预冷后,用尽快的降温速度使肉通过最大冰晶生成带(-5℃左右),并在-5℃的温度下进行贮藏的方法.同时系统研究了不同的降温温度(-36℃与-5℃)和不同的降温方式(风冷与浸渍)对...     

冻结速率和冻藏温度对文蛤蛋白质冷冻变性的影响

利用IMP热电偶测温系统，对文蛤分别在-18℃和-30℃冻结温度下的冻结过程进行了测量，对-18℃和-30℃下3种贮藏形态的贝肉冻结样品和冻藏样品肌原纤维蛋白的Ca~(2+)-ATPase活性、Mg~(2+)-ATPase活性、盐溶性蛋白溶解度及添加抗冻剂后防止其冷冻变性的影响进行了研究。结果发现，冻结对贝肉蛋白质变性影响不大，冻藏使蛋白质发生显著的变性，温度低的变性小；在贮藏贝肉的3种形态中，无完整细胞形态的贝糜的变性幅度最大，碎贝肉次之，贝肌肉形态的保持得较好；添加抗冻剂能有效防止贝肉蛋白质冷冻变性，尤其能使贝糜形态贝肉蛋白质的稳定性大大提高。     

Effects of Elevated Temperature Postharvest on Color Aspect,Physiochemical Characteristics,and Aroma Components of Pineapple Fruits

In this work, 2 separate experiments were performed to describe the influence of elevated temperature treatments postharvest on the color, physiochemical characteristics and aroma components of pineapple fruits during low‐temperature seasons. The L* (lightness) values of the skin and pulp of pineapple fruits were decreased. The a* (greenness‐redness) and b* (blueness‐yellowness) values of the skin and pulp were all markedly increased. The elevated temperature significantly increased the contents of total soluble solids (TSS) and slightly affected contents of vitamin C (nonsignificant). Titratable acidity (TA) of pineapple fruits were notably decreased, whereas the values of TSS/TA of pineapple fruits were significantly increased. The firmness of the pineapple fruits decreased and more esters and alkenes were identified. The total relative contents of esters were increased, and the total relative contents of alkenes were decreased.     

Blanching, Freezing and Frozen Storage Influence Texture of White Asparagus

We studied effects of three methods of blanching in conjunction with freezing, on texture of white asparagus as defined by three measures: maximum shear force, cutting energy, and total fiber content. We also assessed shelf life of asparagus kept in frozen storage at -22°C. Methods of blanching were total immersion in hot water, progressive immersion in hot water and steam. An increase in total fiber content was found throughout frozen storage. This increase correlated with lignification of vascular bundles in the basal segment of spears, even during frozen storage. This was reflected in an increase in maximum shear force and cutting energy required. The shelf life of frozen asparagus was 12 mo using total fiber content as a criterion.     

不冻液冻结乌鳢块冻藏过程中品质变化

为了研究不冻液冻结对乌鳢块冻藏过程中冰晶及品质的影响,采用不同冻结温度（－20、－30、－40 ℃）的不冻液和空气冻结乌鳢块,以冰晶大小、盐溶性蛋白含量、pH值、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、硫代巴比妥酸（thiobarbituric acid,TBA）值和持水性等为指标,考察了乌鳢块冻藏（－18 ℃）过程中的品质变化。结果表明：采用－20、－30、－40 ℃不冻液冻结的乌鳢块通过最大冰晶生成带的时间分别为310、226 s和125 s,生成冰晶的面积分别为308.8、142.4 μm2和86.5 μm2,分别显著短于和小于空气冻结方式下乌鳢块通过最大冰晶生成带的时间（3 412 s）和生成冰晶的面积（939.6 μm2 ）（P＜0.05）。另外,在－18 ℃冻藏过程中,经不冻液冻结的乌鳢块的盐溶性蛋白含量均明显高于空气冻结组,而形成冰晶大小、pH值、TBA值、TVB-N含量、汁液流失率和蒸煮损失率均明显低于空气冻结组,其中－40 ℃不冻液冻结后的乌鳢块在冻藏过程中品质变化最小。综合以上结果,不冻液冻结比空气冻结能够更好地保持冻藏过程中乌鳢块的品质,且不冻液的冻结温度越低,冻结速率越高,形成冰晶越小,越有利于鱼肉品质的保持。     

液体浸渍冷冻对鲟鱼贮藏过程中品质的影响

研究新兴低温冻结技术液体浸渍冷冻对鲟鱼贮藏期品质的影响,分析比较液体浸渍冷冻和传统空气冷冻处理后的鲟鱼在贮藏期的品质变化,并对多个指标进行了检测分析。结果表明,液体浸渍冷冻处理的鲟鱼冷冻速率是传统空气冷冻的12.47倍,经过液体浸渍冷冻的鲟鱼其肌纤维受到的破坏较空气冷冻小,贮藏过程中鲟鱼的回复性与L*值均较空气冷冻高(P0.05),二者挥发性盐基氮值和过氧化值的变化趋势也具有显著性差异(P0.05)。因此,液体浸渍冷冻能够更好地保持鲟鱼原有的品质,可在鲟鱼贮藏保鲜过程中加以利用。     

微波干燥工艺对月柿果片色泽质构及感官品质的影响

采用微波干燥技术对月柿果片进行干燥,考察微波功率、切片厚度、装载量对月柿片色泽、硬度、咀嚼性、复水比、感官评分等品质特性的影响。结果表明：随着微波功率增加,月柿果片的L*值、b*值显著减小（p<0.05）,而a*值、色差值（ΔE）、硬度、咀嚼性的趋势相反;复水能力与感官评分出现先升高后下降的变化,均在280 W时达到峰值。当切片厚度不断提升,月柿果片由焦黑色逐渐转变为亮黄色,柿片的硬度、咀嚼性显著提高（p<0.05）,复水能力不断减弱,感官评分升高,但当厚度超过2.00 cm,干制品呈红褐色,L*值、b*值下降,柿片偏硬,难以咀嚼,易粘牙,感官评分降低。随着装载量的提高,干燥样品色泽越接近鲜柿,硬度变小、韧性下降,而复水比、感官评分呈现先增加后减少的趋势。综合而言,在微波功率280 W、切片厚度2.00 cm、装载量1.60 kg/m2的条件下,柿片L*值48.39,a*值12.89,b*值33.61,ΔE值24.94,硬度值2316.23 g,咀嚼性1106.97 g,复水比达1.77,感官评分为87.80分,此时产品色泽亮丽,软硬适中,富有嚼劲,复水性好,具有月柿风味浓郁和感官品质优良的优点。     

冻结及冻藏温度对小龙虾冻藏过程中脂质氧化的影响

本研究将小龙虾热烫后置于真空包装盒内,灌水并抽真空,分别于3 种冻结温度（－20、－40 ℃和－55 ℃）的冰柜内冻结至中心温度为－15 ℃,再于2 种冻藏温度（－20 ℃和－40 ℃）的冰柜中冻藏24 周,测定不同温度冻结和冻藏小龙虾肉的脂肪质量分数、游离脂肪酸（free fatty acids,FFAs）含量以及脂肪酸组成、过氧化值（peroxide value,POV）和硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）值,探讨冻结及冻藏温度对小龙虾脂质氧化的影响。结果表明：随着冻藏时间的延长,6 组小龙虾的脂肪质量分数、不饱和脂肪酸（unsaturated fatty acids,UFAs）和多不饱和脂肪酸（polyunsaturated fatty acids,PUFAs）相对含量显著下降（P＜0.05）,FFAs含量和饱和脂肪酸（saturated fatty acids,SFAs）相对含量、POV、TBARS值总体显著上升（P＜0.05）。冻藏温度相同时,－20 ℃冻结的小龙虾肉的POV、TBARS值高于－40 ℃和－55 ℃,而FFAs含量和脂肪酸组成无明显差异;冻结温度相同时,－20 ℃冻藏小龙虾肉脂肪和FFAs含量、POV、TBARS值均明显高于－40 ℃冻藏组,UFAs和PUFAs含量低于－40 ℃冻藏组,SFAs含量高于－40 ℃冻藏组。结论：冻结温度－40、－55 ℃和冻藏温度－40 ℃均减轻了小龙虾肉脂质的水解和氧化程度。     

浸渍冻结对凡纳滨对虾冻藏过程中肌肉组织的影响

本文以肌纤维轮廓、细胞间隙、肌丝、肌节以及肌纤维间隙等为指标,研究浸渍冻结和静止空气冻结对凡纳滨对虾冻藏过程中肌肉组织结构的影响。结果发现,浸渍冻结对虾的肌纤维排列更加致密,形成的冰晶间隙更加细小,分布均匀,肌原纤维直径变短的程度比静止空气冻结的小;而静止空气冻结的肌纤维排列疏松,形成的冰晶间隙宽大。随着贮藏时间的增加,浸渍冻结对虾的冰晶逐渐增大,间隙逐渐变大,细胞核也逐渐分解变少。冻藏90 d后,静止空气冻结对虾中很难发现细胞核的存在,肌丝结构大部分消失,明暗带难分辨,肌节长度变短程度严重,肌节消失,且没有完整结构的线粒体。但是浸渍冻结对虾中肌丝结构及明暗带依然存在,肌节长度变短程度比静止空气冻结的小,部分线粒体结构完整。结果表明,浸渍冻结更有利于对虾的肌肉结构的保持,能更好地保持对虾的品质。     

不同冻藏温度对金枪鱼肉肉色变化的影响

以黄鳍金枪鱼背部肌肉为研究对象,测定不同的冻藏温度(-18℃,-25,-55℃)对肌肉颜色(a*值)、高铁肌红蛋白的含量、脂肪氧化的影响。结果表明:随着冻藏时间的延长,a*值呈下降趋势;高铁肌红蛋白含量增加、脂肪氧化值增加;在不同的冻藏温度下,肌肉a*值变化显著(p<0.05);冻藏温度越低,a*值,脂肪氧化值变化越小,肌红蛋白氧化成高铁肌红蛋白的量越少。     

贮藏温度对鲜切菠萝生化品质的影响

为了保持和改善鲜切菠萝的贮藏品质,研究不同贮藏温度(0、4、6、8和12℃)对鲜切菠萝的品质及理化特性的影响.结果表明:0～4℃贮藏能够显著抑制鲜切菠萝的硬度下降现象以及含糖量(TSS)、含酸量(TA)和VC含量的降解损失,维持鲜切果实较低的多酚氧化酶(PPO)活性和过氧化物酶(POD)活性,延缓果实细胞膜透性的上升和丙二醛(MDA)含量的积累,使鲜切果实的感官和综合品质好,贮藏寿命长于6、8和12℃的果实.在0、4、6、8和12℃条件下,温度越高,鲜切菠萝的品质劣变越快.建议04℃为九成熟菠萝鲜切产品保鲜的适宜温度.     

液氮间歇式浸渍冻结对饺子冻裂率及感官品质特性的影响

为探究液氮间歇式浸渍冻结对饺子色差、质构、感官品质和微观结构的影响,本文以冻裂率为指标分别研究液氮浸入时间、间隔时间、浸入次数对饺子的影响;以低温冰箱冻结、螺旋隧道式冻结为对比,采用色差仪、质构仪、扫描电镜等分别研究液氮间歇式浸渍冻结对饺子色泽、质构、感官特性及微观结构等品质特性的影响。结果表明,当液氮单次浸入时间为2 s,间隔时间为10 s,浸入8次,总时间为86 s时,用时最短,同时中心温度达到-18℃以下,且饺子冻裂率为零。与传统的低温冰箱冻结、隧道式冻结方式相比,液氮间歇式浸渍冻结后饺子L^*显著性提高（P<0.05）,色泽外观明显改善,硬度、胶着性、咀嚼性显著降低（P<0.05）,口感更接近于新鲜未处理组饺子品质。扫描电镜观察结果表明液氮冻结处理组饺子皮内部形成孔洞最小且最多,过多的孔洞可能破坏了面筋网络结构,导致饺子耐煮性较差。本研究为液氮冻结在米面制品中的应用提供了一定的理论基础和技术支撑。     

Color and Its Stability in Restructured Beef Steaks during Frozen Storage: Effects of Various Binders

Color and its stability were evaluated in restructured steaks made with various binders (calcium alginate, crude myosin extract, whey protein concentrate, wheat gluten, soy isolate or surimi) vs controls (intact ribeye muscle, restructured steaks with no additives or with NaCl and sodium tripolyphosphate). Steaks made with various binders showed similar effects on initial surface metmyoglobin concentration and sensory color attributes, except steaks made with calcium alginate or soy isolate protein. During 12-wk frozen storage, steaks made with various binders (except soy protein isolate) had similar color stabilities.     

Color Changes of Tomato Purees During Storage at Freezing Temperatures

ABSTRACT: The changes in color of unblanched and blanched tomato purees during storage at −7 and −18 °C were studied. They showed the typical sigmoidal-shape of radical reactions and were well described by the Logistic equation (R > 0.95; P < 10⁻³). After an initial induction time, a progressive increase in the bleaching rate was found for both unblanched and blanched frozen tomato purees. The color changes for the unblanched sample were statistically higher than those for the heated one. In the former case, the bleaching of carotenoids was attributed to both chemical and enzyme-catalyzed oxidation reactions. The effect of storage temperatures on color changes was appreciable only in the case of the unblanched tomato samples.