不同贮藏温度对冰淇淋品质及保质期的影响研究

通过测定产品在-12、-15、-18、-22℃及波动温度贮藏时的融化率、水分丢失和体积收缩的变化,对不同贮藏温度对冰淇淋品质的影响进行了研究。在此基础上结合Arrhenius关系式和Q10模型,选取-2、-5、-8℃进行加速试验,测定产品加速贮藏过程中水分丢失的变化,预测产品货架期。结果表明,贮藏期间冰淇淋的抗融性下降,表面水分丢失严重,且在恒温贮藏时出现严重的体积收缩。冰淇淋在-12、-15、-18、-22℃贮藏的货架期分别为45、79、233、601 d。     

High-Resolution NMR and Magnetic Resonance Imaging (MRI) Studies on Fresh and Frozen Cod ( Gadus morhua) and Haddock (Melanogrammus aeglefinus)

Changes in the fish muscle from cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) were investigated by high-resolution NMR and magnetic resonance imaging (MRI). Water- and salt-soluble extracts from fish stored at −20°C and −30°C were analysed by high-resolution proton NMR and enabled the identification of metabolites including trimethylamine oxide, trimethylamine (TMA) and dimethylamine. It was not possible to detect formaldehyde by NMR either in the stored fish samples or in spiked water or salt extracts even at high levels of formaldehyde addition, probably due to polymerisation. Systematic and controlled storage trials indicated the presence of dimethylamine at around 9 months for samples stored at −20°C, whereas no changes were detected at the control storage temperature of −30°C. A comparison of cod and haddock fillets stored for 1 year at −20 and −30°C confirmed the production of dimethylamine only in cod stored at −20°C. It was interesting to note that ‘fresh’ cod and haddock samples purchased from a local supermarket showed high levels of TMA indicating a breakdown of trimethylamine oxide to TMA by bacteria. TMA was not detected in the fish fillets especially obtained for the storage trials. MRI of fresh cod and fish stored at −8 and −30°C indicated that the fish half stored at −8°C exhibited dense lines or arches which are indicative of gaps in the tissue due to possible breakdown of the connective tissue. The images of fish stored at −30°C did not indicate any differences compared with the fresh fish. MRI also showed the presence of frozen and unfrozen areas in the fish non-destructively.     

The influence of additives and drying methods on quality attributes of fish protein powder made from saithe (Pollachius virens)

BACKGROUND: Fish protein powder (FPP) is used in the food industry for developing formulated food products. This study investigates the feasibility of increasing the value of saithe (Pollachius virens) by producing a functional FPP. Quality attributes of spray and freeze‐dried saithe surimi containing lyoprotectants were studied. A freeze‐dried saithe surimi without lyoprotectants was also prepared as a control sample. RESULTS: The amount of protein, moisture, fat and carbohydrate in the FPPs were 745–928, 39–58, 21–32 and 10–151 g kg^?1. Quality attributes of FPPs were influenced by the two drying methods and lyoprotectants. The highest level of lipid oxidation was found in the control and the second highest in the spray‐dried FPP. The spray‐dried fish protein had the lowest viscosity among all FPPs. Gel‐forming ability of samples with lyoprotectants was higher than that of the control. Water‐binding capacity, emulsion properties and solubility of the freeze‐dried fish protein containing lyoprotectants were significantly higher than spray‐dried and control samples. However, functional properties of spray‐dried FPP were higher than the control sample. CONCLUSION: It is feasible to develop value‐added FPP from saithe surimi using spray‐ and freeze‐drying processes, but freeze‐dried FPP containing lyoprotectant had superior functional properties and stability compared with spray‐dried sample. Both products might be used as functional protein ingredients in various food systems. Copyright © 2010 Society of Chemical Industry     

Effect of Ice Storage on the Physicochemical and Dynamic Viscoelastic Properties of Ribbonfish (Trichiurus spp) Meat

ABSTRACT: Changes in physicochemical and dynamic viscoelastic properties of ribbonfish ( Trichiurus spp) meat during different periods of ice storage were investigated. The differential scanning calorimetry profile of fresh ribbonfish meat revealed transitions at 33.17 °C, 48.85 °C, and 60.96 °C, indicating denaturation temperature of different protein fractions. The effect of cornstarch or tapioca starch at 9% level on the viscoelastic properties of ribbonfish meat stored in ice for different periods was also evaluated. Total volatile basic nitrogen (TVBN) increased significantly ( P < 0.05) during ice storage for 24 d. However, the myosin heavy chain concentration was unaltered during the ice storage period, as revealed by sodium dodecyl sulphate-polyacrylamide gel electrophore-sis (SDS-PAGE) pattern. A significant ( P < 0.05) decrease in protein solubility (in phosphate buffer 50 m M , pH 7.5, containing 1 M NaCl), calcium-activated adenosine triphosphatase (ATPase) activity, and an increase in reduced viscosity at a protein concentration of 5 mg/mL was observed after 10 d of ice storage indicating protein denaturation and aggregation. The addition of tapioca and cornstarch enhanced storage modulus values of fresh ribbonfish meat. The gelatinization temperature of tapioca starch solution was found to be in the range of 60 °C to 65 °C and for cornstarch 67 °C to 70 °C, as revealed by the differential scanning calorimetry (DSC) profile and dynamic rheological testing. The viscoelastic properties of ribbonfish meat was altered significantly ( P < 0.05), both due to the addition of starch and ice storage period as revealed by frequency sweep of prepared gels.     

货架期冷藏过程中鳝鱼肉理化指标及蛋白质变化规律

本研究目的是探讨鳝鱼货架期冷藏过程中品质变化规律及原因。首先测定了鳝鱼肌肉的挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、K值和硫代巴比妥酸反应产物（thiobarbituric acid reactive substances,TBARS） 值等指标,明确在冷藏条件下货架期为4 d。冷藏货架期内鳝鱼肉的pH值、色泽和持水率等理化指标测定结果显 示,随着贮藏时间的延长,pH值呈先下降后上升的趋势,肉色由鲜红变为褐红色,持水力逐渐下降。三氯乙酸- 可溶性氮含量和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE）的结果表明,货架期内随着冷藏时间的延长,肌球蛋白和肌动蛋白质逐渐发生降解。价键分析表明, 冷藏货架期内离子键和氢键总体呈下降趋势,二硫键和疏水作用含量呈现逐渐增加的趋势。红外光谱分析表明,冷 藏货架期内,酰胺A带吸收峰总体向高波数移动,这与氢键变化趋势一致。酰胺Ｉ带曲线拟合结果表明,冷藏前期 主要是β-组分间的相互转化,后期则由β-组分向α-螺旋和无规卷曲转化,蛋白无序程度增加。结合红外光谱和价键 分析表明氢键和离子键可能是冷藏初期维系鳝鱼蛋白二级结构的主要作用力,二者的破坏导致蛋白构象改变。     

冰衣对冷冻南美白对虾贮藏品质的影响

通过测定－20 ℃冷冻条件下无冰衣组、15%镀冰衣组和25%镀冰衣组南美白对虾的感官评分、解冻损 失、蒸煮损失、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、盐溶蛋白含量及肌苷酸（inosine-5’- monophosphate,IMP）关联物各比值,研究镀冰衣处理对冻藏南美白对虾品质的影响。通过分析IMP关联物各比值 （K、Ki、G、P、H及Fr）与主要鲜度指标间的相关性,探讨更适宜作为－20 ℃冷冻条件下镀冰衣南美白对虾品质评 价的指标。结果表明：随着贮藏时间的延长,3 组南美白对虾的解冻损失、蒸煮损失和TVB-N含量均呈明显上升趋势, 盐溶蛋白含量显著下降,25%镀冰衣组南美白对虾的品质始终优于无冰衣组和15%镀冰衣组;根据各指标间的Pearson相 关性分析,K、Ki、G、P、H及Fr值中,K值更适合用于评价该贮藏条件下南美白对虾的整体质量;无冰衣组、15%镀冰 衣组和25%镀冰衣组分别在贮藏第12、16、16周感官不可接受,镀冰衣能够有效延长冻藏南美白对虾的贮藏期。     

Influence of storage time and temperature on lipid deterioration during cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) frozen storage

Lean fish deterioration during frozen storage (−30 and −10 °C) for up to 1 year was studied by the assessment of lipid changes. Comparison between a formaldehyde (FA)-forming species (cod) and a non-FA-forming one (haddock) was carried out. Lipid damages were measured on the basis of free fatty acids (FFA), peroxide value (PV), thiobarbituric acid index (TBA-i) and fluorescent compounds. In both species at −30 °C, most lipid damage indices showed significant correlations with the storage time. However, at −10 °C, only the FFA and fluorescence detections provided significant correlations with the storage time. Comparison between the fish species showed higher lipid oxidation (PV and TBA-i) and hydrolysis (FFA content) in haddock than in cod at −10 °C; however, a higher fluorescence development was observed in cod at the same temperature. At −30 °C, little differences in lipid damage indices were detected between the two species. © 1999 Society of Chemical Industry     

A comparison of biochemical changes in cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) fillets during frozen storage

Changes in the muscle proteins of frozen cod fillets, which produce significant amounts of formaldehyde, and frozen haddock fillets, which produce negligible formaldehyde, were compared. Protein extractability and hydrophobicity and the amino acid contents of soluble and insoluble proteins, as well as formaldehyde formation, were investigated in matching pairs of cod and haddock fillets stored at ?10 and ?30 °C (control). Formaldehyde production in cod was much higher (845 and 1065 nmol g^?1 at 20 and 30 weeks respectively) than in haddock (93 and 101 nmol g^?1 after 20 and 30 weeks respectively) at ?10 °C. However, a rapid decrease in solubility of proteins, increase in hydrophobicity and decrease in the amino acid content of salt‐soluble proteins at ?10 compared with ?30 °C were observed in both species. The results showed that there were no significant differences in the nature of the protein changes between these two species, thus indicating that factors other than formaldehyde were involved in the denaturation of proteins and the formation of aggregates during frozen storage of cod and haddock fillets, especially at ?10 °C. © 2001 Society of Chemical Industry     

银杏叶提取液与竹醋液流化冰对鲳鱼冰藏期间品质变化的影响

研究银杏叶提取液流化冰与竹醋液流化冰对鲳鱼冰藏期间品质变化的影响。将新鲜鲳鱼运至实验室,清洗后随机分组,分别用体积分数1%银杏叶提取液与体积分数1%竹醋液制得的流化冰进行冰藏处理,以普通流化冰处理后的样品为对照组。贮藏期间,分别于第0、5、9、12、15、18天进行各组样品的感官、理化(质构、电导率、pH值、K值、硫代巴比妥酸值、挥发性盐基氮(total volatile basis nitrogen,TVB-N)含量)与微生物(菌落总数、假单胞菌总数和希瓦氏菌总数)指标分析,并结合低场核磁共振技术对冰藏鲳鱼品质变化的影响进行综合评价。结果得出:与对照组相比,银杏叶提取液和竹醋液流化冰处理组均能较好保持样品的感官品质与质构特性,延缓其电导率值、pH值、K值、TVB-N含量与微生物指标的上升,减慢鱼肉的氧化速率。银杏叶提取液与竹醋液流化冰处理能使鲳鱼的冰藏期从9~12 d分别延长至15~16 d和17~18 d。     

Shelf Life of Mature Green Tomatoes Stored in Controlled Atmosphere and High Humidity

Freshly harvested mature green tomatoes were washed, sorted and treated with 125 ppm chlorine water. The treated tomatoes were stored at 85% or 98% RH under controlled atmosphere (CA) storage for periods up to 8 wk. The controlled atmosphere was 2.5% O₂, 5.0% CO₂, and N₂ as the balance gas at 12°C. After storing 40 days, the tomatoes were allowed to ripen in air at 23°C. Samples of tomatoes were tested every 3 days to examine changes in quality as determined by visual observation, weight loss, titratable acidity, pH, color and firmness. Weight loss was reduced significantly by CA storage of tomatoes at 98% RH. Tomatoes remained green up to 40 days of storage and changed in color gradually during consecutive storage in atmospheric conditions. Appearance of the tomatoes was acceptable after ripening.     

真空冷诱导对冰温贮藏罗非鱼片鲜度和滋味的影响

以罗非鱼片为实验原料,研究了3种真空冷诱导前处理对罗非鱼片冰温贮藏过程中鲜度和滋味的影响。真空冷诱导初始温度均为12℃,设置了3种不同的真空冷诱导速度:1℃/h(方式Ⅰ)、2℃/h冷诱导(方式Ⅱ)和快速冷诱导(方式Ⅲ)。当鱼片温度降低到冰温带时,真空冷诱导结束,取出鱼片装密封袋冰温贮藏。对比了不同的真空冷诱导方式对罗非鱼片鲜度指标K值、肌苷酸(IMP)和主要滋味游离氨基酸的影响。冷诱导速度越慢,冷诱导时间越长,冷诱导结束时去除的水分越多,12 h时K值略高,但在冰温贮藏过程中K值增长越缓慢,36 h后K值反而最低,鲜度最好。在呈味游离氨基酸总量和游离氨基酸总量(TFAA)方面,真空冷诱导方式Ⅱ优于方式Ⅰ和方式Ⅲ,方式Ⅰ和方式Ⅲ区别不明显。     

大菱鲆冷藏过程中的鲜度变化与货架期

以感官、化学和微生物为指标,对大菱鲆(Scophthalmus maximus)在0(冰藏)、3、7℃和10℃贮藏过程中的鲜度变化和货架期进行研究,并探讨菌落总数、嗜冷菌、假单胞菌、产H2S 菌、TVB-N、TMA-N 与感官评价的一致性。结果表明,在0 、3 、7 、10℃贮藏过程中,大菱鲆较好品质期分别为433、197、93h 和68h, 货架期分别为602、362、165h 和116h。各温度较好品质期终点和货架期终点时菌落总数分别为(5.74 ± 0.31)、(6.99 ± 0.39)lg(CFU/g),假单胞菌数分别为(5.48 ± 0.24)、(6.26 ± 0.71)lg(CFU/g),TVB-N 均值分别为(15.66 ± 1.93)、(31.81 ± 1.94)mg/100g,TMA-N 均值分别为(2.73 ± 0.12)、(10.71 ± 0.81)mg/100g,各温度下较好品质期终点和货架期终点时各指标均值均无显著差异(P ＞ 0.05),表明菌落总数、假单胞菌、TVB-N 和TMA-N 作为大菱鲆低温贮藏的鲜度指标与感官评价有较好的一致性。     

Color Change of the Snapper (Pagrus auratus) and Gurnard (Chelidonichthys kumu) Skin and Eyes during Storage: Effect of Light Polarization and Contact with Ice

Ten gurnard and 10 snapper were stored on ice. One side always contacted the ice; the other side was always exposed to air. At different intervals for up to 12 d, the fish were placed in a light box, and the images of both sides were taken using polarized and nonpolarized illumination. Image analysis resulted in average L*, a*, and b* values of skin, and average L* values of the eyes. The skin L* value of gurnard changed significantly over time while that of snapper was substantially constant. The a* and b* values of both fish decreased over time. The L* values of eyes were significantly lower for polarized images, and significantly lower for the side of fish exposed to air only. This may be a concern in quality evaluation methods such as QIM. The difference of colors between the polarized and nonpolarized images was calculated to quantify the reflection off the surface of fish. For accurate measurement of surface color and eye color, use of polarized light is recommended.     

草鱼冰藏期间新鲜度及热加工性质的变化

以草鱼（冰藏0、1、3、7 d）作为研究对象,探讨冰藏期间鱼肉新鲜度如pH值、挥发性盐基氮（totalvolatile base nitrogen,TVB-N）值、可溶性肌浆蛋白（soluble sarcoplasmic proteins,SSP）值、可溶性肌纤维蛋白（soluble myofibrillar proteins,SMP）值和色泽（L*、a*、b*）的变化规律,以及在巴氏杀菌条件下（80、90 ℃,10 min）蒸煮损失率、收缩面积比及色泽的变化。结果表明：草鱼冰藏过程中,TVB-N值由11.8 mg/100 g增加至16.87 mg/100 g,略低于淡水鱼上限值20 mg/100 g;pH值在前3 d由6.72降低到6.52,之后上升至6.56;SSP值无明显变化,SMP值在前3 d逐渐增加,之后轻微下降;鱼肉色泽变化值（ΔE）逐渐升高,表明鱼肉在冰藏7 d期间新鲜度逐渐下降。在热加工过程中,鱼肉逐渐变成白色,蒸煮损失率、收缩面积比和ΔE值随鱼肉冰藏时间的延长而缓慢下降。     

发酵方式对馒头在冷藏过程中品质及其货架期的影响

将一次发酵、快速二次发酵和老面发酵的馒头进行冷藏贮存,测定冷藏过程中馒头的pH、水分含量、比容、菌落总数、霉菌的变化趋势,以及将馒头复蒸之后的感官评分变化。结果表明:馒头的水分含量、pH、感官评价均呈现总体下降趋势;馒头的比容在冷藏过程中略有波动比较稳定;三种馒头的菌落总数14 d时未达到10⁶CFU/g,低温有效地抑制了微生物的生长;0~2 d未检测到霉菌,随着贮存时间延长霉菌超出标准范围。老面发酵馒头在0~4 d时稳定性最好,各项指标变化幅度最小,8~14 d时霉菌生长迅速,加快了变质,一次发酵馒头微生物生长最快,水分含量下降最快,二次发酵馒头水分含量变化最为稳定。综合霉菌和感官评分,将冷藏馒头分别划分成三个食用阶段。一次发酵馒头最佳食用阶段为0~4 d,可食用阶段为5~11 d,不可食用阶段为12 d以上;快速二次发酵馒头最佳食用阶段为0~2 d,可食用阶段为3~11 d,不可食用阶段为12 d以上;老面发酵最佳食用阶段为0~4 d,可食用阶段为5~9 d,不可食用阶段为10 d以上。     

Shelf life of shrimp (Penaeus merguiensis) stored in ice (0°C) and partially frozen (—3°C)

Sensory, biochemical and microbiological changes and changes in SDS-PA GE patterns of myofibrillar and sarcoplasmic proteins were studied in shrimp (Penaeus merguiensis) muscle during storage at partial freezing temperature (—3°C; PFS) and in ice (0°C; IS). During PFS up to 20 days there were slight changes in biochemical parameters, apparently no changes in microbiological populations, and no changes in electrophoretic protein patterns. Rapid changes in these parameters occurred in IS over the same period. Sensory assessment of shrimps stored at PFS showed that a considerable increase in prime quality life was possible at this temperature over shrimps in IS. Prime quality life of shrimps in PFS was found to be 16 days, compared with 8 days in IS. Extension of prime quality life was attributed to the significantly slower rate of biochemical and microbiological changes at PFS compared with IS. Changes in sensory properties were associated with changes in some of the chemical properties.     

流化冰处理对南美白对虾冰藏期间品质与水分迁移变化的影响

为研究流化冰对南美白对虾冰藏期间品质与水分迁移变化的影响,将新鲜样品分别进行流化冰（slurry ice,SI）与碎冰（crush ice,CI）处理后于4 ℃条件下贮藏,每天对对虾的质构、色差、总挥发性盐基氮（total volatile base-nitrogen,TVB-N）含量、硫代巴比妥酸反应物（thiobarbituric acid-reactive substances,TBARS）值、多酚氧化酶（polyphenol oxidase,PPO）活力、菌落总数进行测定,并结合低场核磁共振（low-field nuclear magnetic resonance,LF-NMR）与核磁成像技术比较两种方式对南美白对虾贮藏期间品质与水分迁移的影响。结果显示：SI组样品的弹性与咀嚼性均优于CI组,其与L*、a*值和PPO活力均显著相关（P＜0.05）;SI组样品经10 d贮藏,其TVB-N含量、TBARS值与菌落总数始终维持在较低水平,品质明显优于CI组。LF-NMR结果显示,两组样品在贮藏期内的水分迁移均有所增强,不易流动水含量A22从贮藏第3天开始显著变化（P＜0.05）;而T22和自由水含量A23则在整个贮藏期间呈现明显增长趋势,但SI能较好减缓样品的水分迁移与流失。可见,流化冰对南美白对虾的冰藏保鲜效果优于碎冰,其效果在贮藏中后期（3～5 d）更明显。与CI组样品对比,SI处理能使南美白对虾的冰藏货架期延长至少2 d。