Sensory,microbial and chemical effects of a slurry ice system on horse mackerel (Trachurus trachurus)

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater, was evaluated in parallel with flake ice for the storage of horse mackerel (Trachurus trachurus). Storage in slurry ice led to a significant enhancement of shelf life (5 days for flake ice to 15 days for slurry ice), better control of pH and lower counts of total aerobes and proteolytic and lipolytic bacteria, these reaching an average difference between batches of 2, 1.43 and 1.98 log units respectively after 8 days of storage. Storage in slurry ice also involved a significantly slower formation of total volatile basic nitrogen and trimethylamine after 8 days of storage. Staphylococcus xylosus and Proteus penneri were identified as the leading proteolytic and lipolytic organisms in horse mackerel muscle. Storage of horse mackerel in slurry ice enhances the shelf life of this medium‐fat fish species through better maintenance of sensory and microbiological quality. Copyright © 2004 Society of Chemical Industry     

Effect of previous gutting on rancidity development in horse mackerel (Trachurus trachurus) during frozen storage at −20 °C

Gutting was applied to fresh horse mackerel (Trachurus trachurus) to study its effect on rancidity development during a prolonged frozen storage (up to 12 months at −20°C). To do so, chemical (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence ratio, FR) and sensory (odour and taste) analyses were carried out. The results showed that the gutting of horse mackerel led to a higher degree of oxidation in the frozen product, according to the chemical (PV, TBA-i and FR) and sensory (odour and taste) analyses. However, a lower extent of lipid hydrolysis (FFA formation) was detected at the end of the storage (twelfth month) as a result of gutting. It is concluded that the gutting of a medium-fat fish species such as horse mackerel is not recommended as previous treatment to frozen storage.     

不同解冻方式对智利竹筴鱼船上冻品贮藏品质的影响

以挥发性盐基氮（TVB-N）、三甲胺氮（TMA-N）、组胺以及硫代巴比妥酸（TBA）含量为指标,研究了不同解冻方式对智利竹筴鱼在-18℃下冻藏6个月品质的变化。结果表明,流水解冻相对于室温解冻和4℃解冻,在TBA和组胺含量上有显著性差异（p<0.05）,而室温解冻和4℃解冻在TVB-N,TMA-N,TBA和组胺上组间差异不显著（p>0.05）。结果表明,4℃解冻对于鱼体品质变化的控制较为理想。      

The effect of frozen storage of mackerel (Scomber scombrus) on its quality when hot-smoked

Whole mackerel (Scomber scombrus) were frozen using a horizontal plate freezer, wrapped in plastic bags and frozen stored at - 20°C. At suitable intervals (11, 22 and 33 weeks) the fish were removed from the cold store and subsequently hot smoked (in gutted from) using an AFOS-Torry Mini Kiln. All smoked mackerel samples, despite their different previous histories, were assessed by the panellists as moderately acceptable products in- terms of their texture and flavour, even after 33 weeks frozen storage prior to smoking. Protein denaturation, as related to salt-soluble protein, was influenced by the frozen storage history (24% drop after 33 weeks frozen storage) and seemed to be affected by the free amino acids formed during frozen storage. After smoking the denaturation was extensive (above 80%) in all mackerel samples. Lipid oxidation was quite extensive (PV 108 meq kg^?1) in the 22 and 33 weeks frozen stored mackerel samples. However, no rancid flavour in the latter smoked mackerel samples was detected by taste panellists. A 58% increase in free amino acids during frozen storage was observed. Extensive losses of 74% in available lysine were observed in the 22 and 33 weeks frozen stored mackerel samples after smoking which could be due to aminocarbonyl reactions with the products of lipid oxidation. A 40% loss of thiamine was observed in the 33 weeks frozen stored samples after smoking. The histamine contents did not exceed 94 mg kg^?1 and would not be expected to cause symptoms of scombrotoxin poisoning.     

Effect of frozen storage on the quality of whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus)

 Whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus) were assessed for quality (physical, chemical and sensory attributes) changes throughout 12 months of frozen storage at −18 °C. The pH, expressible water (EXW), quantities of trimethylamine (TMA), dimethylamine (DMA), formaldehyde (FA), the total volatile base nitrogen (TVB-N) the thiobarbituric acid number (TBA), peroxide value (PV) and amount of free fatty acids (FFA) increased, while sensory attributes (odour, taste, texture) decreased during the frozen storage period. A comparison of quality scores between whole fish and fillets of horse mackerel and mediterranean hake showed that there were no significant differences (P>0.05) in attribute scores. There were, however, significant differences (P<0.05) in pH, EXW, TMA, DMA, FA, TVB-N, TBA, FFA and PV. Received: 19 April 1996/Revised version: 7 September 1996     

茶多酚对面团中面筋蛋白结构的影响

本研究通过对面团面筋中自由氨基和二硫键含量的检测,并采用拉曼光谱和扫描电镜对面团结构的分析,探究茶多酚对面筋蛋白结构的影响。结果表明,茶多酚在面团中添加量为0.5%、1.0%、2.0%时,面团中湿面筋的含量分别降低了17.8%、66.3%和93.3%;游离氨基含量分别增加了57%、151%和313%;自由巯基含量分别增加了48%、69%、111%。拉曼光谱分析表明茶多酚的添加使得面团中的氢键作用有所增强;蛋白质二级结构的分析表明,2.0%的茶多酚降低了α-螺旋的相对含量(21.9%),而β-折叠和无规则卷曲结构则分别增加了17.2%和5.1%;随着茶多酚添加量的增加,色氨酸残基I₇₅₇相对强度逐渐降低,并且二硫键的扭-扭-反结构分别增加了3.0%、6.0%、13.4%。综上所述,茶多酚的添加破坏了面筋蛋白网络结构,与扫描电镜和激光共聚焦显微镜的结果一致。因此,防止茶多酚与面筋蛋白的相互作用是开发含有多酚类功能性面制品的基础。     

惰性粉对嗜卷书虱的致死效果及机理研究

本研究采用拌粮法研究了不同浓度和粒径的硅藻土、沸石粉、蒙脱石和高岭土等四种惰性粉对嗜卷书虱的作用效果。研究结果表明,与其他3种惰性粉相比,沸石粉对嗜卷书虱的作用最好,处理时间为7 d时,在处理浓度为1 000 mg/kg条件下,校正死亡率即达到了76.32%。而在所研究的粒径范围内,不同粒径对嗜卷书虱的作用除在处理7 d时,100目高岭土的作用效果显著优于400目的外,其他处理并没有显著差异。利用X射线衍射(XRD)、扫描电子显微镜(SEM)和Brunauer-Emmett-Teller(BET)3种检测手段研究4种惰性粉的组成、形貌和吸附特性,以分析不同惰性粉对嗜卷书虱作用效果存在差异的原因,为后期选择或改性出杀虫效果更好的惰性粉提供参考。     

The effect of filleting and ice application on the quality and safety of Atlantic bonito (Sarda sarda) at refrigerated storage

Filleting effect of refrigerated bonito with and without ice on the quality changes and food safety was investigated. Significant variations occurred (P < 0.05) in sensory, chemical and microbiological values amongst groups. The best sensory results were found for filleted bonito with ice (FBRI) with a shelf‐life of 13 days. While sensory values decreased significantly during storage, opposite situation occurred for both chemical and microbiological results (P < 0.05). The lowest total volatile basic nitrogen value was also observed with FBRI and was within the acceptable levels for 15 days as 17.86 mg 100 g^?1. All samples contained acceptable trimethylamine levels for 15 days despite unacceptable sensory values after certain days. Although filleting seemed to increase the lipid oxidation, ice application resulted in lowering thiobarbituric acid content. Histamine results closely supported sensory values in terms of legally permitted levels usually by set FDA. While WBR contained histamine value over EU permitted level as 113.78 ppm on the 7th day, the value for FBRI was 56.13 ppm on the 15th day. Histamine‐forming bacteria counts supported histamine formation in most groups, while total bacteria counts were in agreement with sensory results. This study suggests that using ice and filleting can improve shelf‐life of bonito stored at refrigerated temperatures in terms of food quality and safety.     

冻结方式对凡纳滨对虾贮藏中组织冰晶及品质的影响

新鲜凡纳滨对虾采用液氮、平板及冰柜冻结结合-20 ℃贮藏,研究不同贮藏时间内其组织冰晶形态与品质变化,以评价出最优的冻结方式。结果显示,随着贮藏时间的延长,平板及冰箱冻结的盐溶性蛋白含量、持水性、感官评分显著降低(p<0.05);而液氮冻结形成的冰晶直径比平板速冻小1/3,比冰箱小1/2;冻结后贮藏180 d其挥发性盐基氮(TVB-N值)≤25 mg/100 g,硫代巴比妥酸值(TBA)仅为0.72 mg/100 g,有效抑制了虾肉肌原纤维蛋白变性及脂肪氧化,能较好维持肌肉组织形态和品质,从而使虾肉的货架期延长至180 d以上。     

冻藏温度对罗氏沼虾冻藏品质的影响

以解冻汁液流失、蒸煮损失、TVB-N、K值、硬度、剪切力和色差为指标,研究不同冻藏温度对速冻罗氏沼虾冻藏品质的影响。试验结果表明:经液氮速冻后的罗氏沼虾,在-50,-18℃2种条件下冻藏,随着冻藏时间的延长,罗氏沼虾的持水能力和质构特性均变差,冻藏20周后,硬度分别下降了55.79%和59.45%。2种冻藏条件下的罗氏沼虾TVB-N和K值均随时间的延长而增加,而-50℃下冻藏的罗氏沼虾TVB-N和K值增加缓慢,说明较低的冻藏温度,有利于罗氏沼虾冻藏品质的保持。     

甜橙果肉粉对橙油风味物质的吸附性能研究

为探究柑橘果肉在风味吸附方面的机制,测定了甜橙果肉粉的成分构成、氮气吸附-脱附等温线,采用扫描电子显微镜（scanning electron microscope, SEM）观察了其微观结构,采用气相色谱-质谱法（gas chromatography-mass spectrometry, GC-MS）测试分析了其对橙油风味物质的吸附性能。成分分析结果表明甜橙果肉粉主要由膳食纤维（51.87%±3.12%）、蛋白质（20.47%±0.58%）、脂肪（11.33%±1.60%）、淀粉（4.06%±0.59%）构成。SEM观察结果及氮气吸附-脱附等温线分析结果表明,甜橙果肉粉复合物中存在丰富的褶皱和缝隙等不规则结构,比表面积达2.98 m2/g。GC-MS测试分析结果表明,甜橙果肉粉对橙油典型香气成分例如柠檬烯、γ-萜品烯、β-月桂烯、β-水芹烯、芳樟醇、辛醛、壬醛等有明显的吸附作用,尤其与直链脂肪醛、含氧萜类衍生物的相互作用较明显,而对α-蒎烯、桧烯等双环单萜类成分的吸附作用相对较弱。综上,甜橙果肉粉中各组成成分交联而成的褶皱和缝隙结构是其发挥风味吸附作用的重要基础,研究结果可为进一步开发利用甜橙果肉提供参考。     

Effect of calcium propionate on the microstructure and pectin methy‐ lesterase activity in the parenchyma of fresh‐cut Fuji apples

There is an increasing demand for fresh‐cut fruits. One of the main problems with these products is their short shelf life. The use of additives such as calcium propionate may increase their shelf life, because calcium preserves the structural integrity of the cells and propionate acts as food preservative. This work analyses the microstructure of Fuji apple parenchyma treated with calcium propionate immediately after treatment and after storage for 1 and 2 weeks at 4 °C by using light microscopy (LM) and low‐temperature scanning electron microscopy (cryo‐SEM). This work also studies the effects of treatment and storage time on the enzymatic activity of pectin methylesterase (PME) by measuring the amount of acid released per unit of time at pH 7 and at 63 °C. The results show that calcium propionate treatment has consolidating and structuring effects on the parenchyma and partially minimises the degrading effects of fresh‐cut apples. In addition, treatment with calcium propionate decreases the activity of the PME both in non‐stored apples and in those stored for 1 and 2 weeks probably due to the inhibiting effect of propionate. Copyright © 2006 Society of Chemical Industry     

The effect of slaughter method on the quality of rainbow trout (Salmo gairdneri) during storage on ice

Rainbow trout ( Salmo gairdneri ) were stunned by electrocution, exposure to elevated concentrations of carbon dioxide and by a blow to the head, and subsequently bled. The fish were stored ungutted in ice for up to 15 days, and the changes in the textural properties of the flesh of the fish were measured by a sensory panel and with a texturometer. Parallel changes in the concentrations of spoilage-related biochemical constituents, in water-holding capacity and in bacterial counts were also determined. Slaughter by electrocution and by carbon dioxide narcotization led to a greater initial production of lactic acid and a slightly reduced pH, compared with slaughter by a blow to the head. No significant differences were found in the values of the other indices of quality, either immediately after death or during post-mortem storage.     

The effect of preliminary processing and period of storage on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms

This paper investigates the effect on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms of blanching or soaking and blanching in aqueous solutions containing combinations of added substances safe for human consumption, or period of frozen storage. During 12 months of storage, sensory evaluations, instrumental colour measurements and chemical analyses of the frozen products were carried out every four months. Based on the results of the sensory evaluation, a maximum storage period of four months was set for the frozen product obtained from unblanched mushrooms. Frozen products having undergone preliminary processing retained good sensory quality for up to 12 months. Soaking, blanching and freezing resulted in the appearance of colours, such as yellow, honey and pink–violet. As a result of freezing, decreases in the contents of thiamine, riboflavin and vitamin C were noted. Blanching in water, as a method of pre-processing, was sufficient for maintaining acceptable sensory quality.     

Influence of free‐air CO2 enrichment (FACE) on the eating quality of rice

Rice plants (Oryza sativa L cv Akitakomachi) were grown under free‐air CO₂ enrichment (FACE) in farmers' fields in Shizukuishi, Iwate, Japan during 1999 and 2000. The grains were harvested and subsequently analyzed for protein and amylose contents as well as the traits related to cooked‐rice viscosity. The cooked rice was also subjected to sensory evaluation. The protein content of rice grains grown under elevated CO₂ was significantly lower than that of rice grown under ambient conditions. In addition, CO₂ enrichment increased the whiteness of the grains in both brown and milled rice and reduced their surface hardness. Although the amylose content of rice grains was unaffected, starch pasting properties demonstrated that rice grains in elevated CO₂ had higher maximum viscosity and breakdown than those grown in ambient conditions. Sensory evaluation of cooked rice with respect to umami (deliciousness), appearance, aroma, hardness, stickiness and overall palatability index indicated that the sensory properties were not significantly altered by the CO₂ enrichment treatment. Therefore, we conclude that the growth of the rice cultivar Akitakomachi under elevated CO₂ concentration decreased the protein content, but did not change the palatability to a level that may be detected by sensory taste panel evaluation. Copyright © 2005 Society of Chemical Industry     

The effect of the pre-treatments and the long and short-term frozen storage on the quality of raspberry (cv. Heritage)

Results are presented of the effect of pre-treatments before freezing followed by long and short-term frozen storage (12 months at –18 °C and 24 days suffering temperature fluctuations between –18 °C and –12 °C) on quality parameters of raspberry. Pre-treatments were carried out with calcium, low methoxyl pectin, a combined solution, and results compared with untreated control fruits. Kramer shear, back extrusion, compression, and multiple penetration tests were used to measure rheological behavior. One-hundred mM CaCl₂ reduced the long and short-term frozen storage induced loss of firmness. For long-term storage at –18 °C, a softening of the tissue became evident between 3 and 12 months and at each date test the stored fruits were firmer than those without storage. For short-term storage with fluctuations, the loss of firmness was evident between 0 and 24 days, and at all the testing dates the stored fruits were softer than those without storage. Results evidenced a higher cell damage in the short-term frozen storage. Coefficients of softening per day suffering fluctuation were determined, the highest values being given by Kramer shear energy and back extrusion maximum force (>1%). Short-term frozen storage affected physical and physico-chemical characteristics, increasing the saturation (r) and the anthocyanins and decreasing the ascorbic acid of the raspberries. In both storage conditions, pre-treatments reduced the drip loss, which correlated best with the Kramer shear energy. Panelists detected mainly time effect on the sensory firmness. For long-term, sensory firmness and juiciness gave the highest correlations with back extrusion maximum force, while for the short-term, sensory firmness and drip loss gave the highest correlations with the Kramer shear energy. SEM revealed different degrees of mechanical damage to structure, which accounted for rheological behavior of the fruits.     

The effect of thawing methods on the quality of eels (Anguilla anguilla)

Physical (colour), chemical (pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid values (TBA)) and microbiological (total aerobic mesophylic bacteria, salmonella, coliform, yeast and mould counts) analyses were carried out on thawed European eel (Anguilla anguilla). Different thawing treatments were used (in a refrigerator, in water, in air at ambient temperature and in a microwave oven). The results obtained were compared statistically with those of fresh fish. pH, TBA and a^∗ values of thawed samples usually decreased significantly (P < 0.05) when compared to the fresh control. Salmonella was not detected in any of the samples. Coliform and mould counts of fresh control and thawed samples were <1 CFU/g. Total aerobic mesophylic bacteria count of all thawed fish decreased. However, the yeast count of the refrigerator–thawed samples increased. The lowest total aerobic mesophylic bacteria and yeast counts were determined in water–thawed samples. Water thawing is therefore suitable for frozen eel.     

高能电子束辐照对奇亚籽发芽率及奇亚籽毛油品质的影响

奇亚籽繁殖力超强,引入我国易形成优势种群,破坏生态系统,因此考虑对奇亚籽进行灭活后引入。探究利用辐照技术使奇亚籽丧失活力,并研究辐照对奇亚籽毛油品质的影响。结果表明:辐照处理可延缓奇亚籽开始萌发的时间,并使其发芽率降低,随着辐照剂量的增大,10 k Gy处理时奇亚籽发芽率为0;10 k Gy辐照处理与不经辐照处理的奇亚籽毛油相比,酸值显著升高(P0.05)(但仍符合亚麻籽油的一级标准),过氧化值、脂肪酸组成差异不显著(P0.05);辐照处理后奇亚籽毛油的品质高,符合亚麻籽油的一级标准。