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.     

Structural and physical properties of dried Anaheim chilli peppers modified by low‐temperature blanching

The effect of low‐temperature blanching and drying processes on the ultrastructural and physical properties of Anaheim chilli pepper was studied and optimum conditions to provide a final product with maximum firmness were determined. Lots of Anaheim pepper were blanched in water for 4 min at 48, 55, 65, 75 and 82 °C and maintained for hold times of 35, 45, 60, 75 and 85 min, blanched again for 4 min at 96 °C and dehydrated at 53, 60, 70, 80 and 87 °C. After treatment the samples were rehydrated in water at 30 °C. Rehydration ratio, texture and structural changes were evaluated. Optimisation used a second‐order rotatable central composite design. Texture and rehydration ratio were affected by blanching temperature and the interaction of blanching temperature with hold time (p ≤ 0.05); drying temperature did not show a significant effect. The best results, ie those which gave greatest firmness, were obtained by blanching at 64 °C for 4 min, holding for 55 min after blanching, followed by a second blanching at 96 °C for 4 min and then drying at 70 °C. Evaluation of the rehydrated dried pepper by microscopy showed that low‐temperature blanching close to the optimum conditions provided a protective effect in maintaining cell wall integrity. The results of processing increased firmness in the rehydrated product by a factor of 1.97. Copyright © 2003 Society of Chemical Industry     

即食栗蘑加工工艺研究

以新鲜栗蘑为原料,利用单因素和正交试验设计方法,研究硬化、漂烫的最佳工艺及拌料的最佳配方。结果表明:最适的硬化条件是在浓度为0.5%氯化钙和0.5%氯化钠的混合溶液中浸泡40 min。最佳漂烫条件是在浓度为0.3%的柠檬酸和0.06%的抗坏血酸混合溶液中漂烫4 min。最佳拌料配方为每100克栗蘑中加入3 g盐,0.7 g糖,3 g辣椒粉。可制得具有栗蘑特有风味,口感脆嫩,营养丰富,方便安全的新型即食栗蘑食品。     

大豆破碎耦合蒸汽灭酶工艺优化

为最大程度减少豆浆制浆过程中产生的豆腥味,通过破碎耦合蒸汽热烫对浸泡大豆的脂肪氧化酶(lox)进行灭活。以单因素试验为基础,研究蒸汽结束时豆浆的温度、豆浆升温速率和大豆浸泡时间对lox活性和豆浆气味感官品质的影响。然后依据Box-Behnken试验设计原理进行了三因素三水平响应面法优化试验,优化后得到的最佳工艺条件为:温度95.34℃、升温速率0.37℃/s、浸泡时间10.53h。该条件下,lox已完全灭活,同时豆浆气味感官评价好。     

一种具有清凉解渴作用的莲藕饮料的工艺研究

目的以莲藕为主要原料,贡菊汁、蜂蜜及木糖醇为辅料,研制一种具有清凉解渴作用的莲藕饮料,探究影响莲藕饮料品质的各种因素并探索出最佳的饮料配方。方法设计单因素试验,探究其最适护色条件(柠檬酸添加量、漂烫时间和漂烫温度)、酶解条件(纤维素酶及淀粉酶的添加量、酶解温度、时间及pH)、莲藕汁、贡菊汁、蜂蜜及木糖醇的添加量。在此基础上,通过L9(3~4)正交试验确定莲藕饮料的最佳配方。结果当柠檬酸添加量为0.3%,漂烫时间为3 min,漂烫温度为85℃时护色效果最好;最适的酶解条件为纤维素酶和淀粉酶添加量均为0.3%,酶解温度为65℃,酶解时间为2.5 h,酶解p H为5.5;莲藕饮料的最佳配方是藕汁50%,贡菊汁25%,蜂蜜4%以及木糖醇12%。结论该莲藕饮料清凉解渴、风味浓郁、口感极佳,是一款适合广大消费者饮用的风味饮料。     

Low Temperature Blanching Effects on Chemistry, Firmness and Structure of Canned Green Beans and Carrots

Green beans and carrots were canned using extended blanching at 64–65°C and added calcium and/or acid. Firmer products resulted from all treatments but lowered pH was most effective. Blanched green beans were firmer with lower pectin esterification, indicating pectin methyl esterase activity. Green beans and carrots treated with calcium and/or acid and then cooked were firmer than controls. Acid exhibited a firming effect, perhaps by loosening tissue, while calcium reduced the influence of heat. Instrumental bioyield values correlated with sensory results of canned green beans; bioyield may result from a scleriformic layer. Microscopy showed firmer beans had intact middle lamellae while softer samples contained separated cells. These data suggest that the treatments rendered pectates in the middle lamella less heat labile.     

Residual peroxidase activity as influenced by blanching,SO2 treatment and freezing of cauliflowers

The influence of blanching time and SO₂ treatment on the residual peroxidase activity and its implication for the sensory quality of frozen cauliflowers were assessed after storage for up to one year at ?18°C. The treated cauliflowers, sealed in polythene bags, were placed in waxed paperboard cartons and frozen in a contact plate freezer at ?35°C. The sensory quality of frozen stored cauliflowers related well to their residual peroxidase activity, which was sensitive to the SO₂ treatment. Blanched cauliflowers following a brief dip in a metabisulphite solution prior to freezing gave a significantly (P<0.05) superior product even when stored for one year. The residual peroxidase activity, which ranged from 1 to 5.5% in the blanched samples, was below 1 % in the SO ₂-treated samples, and the SO₂ content of50 ppm found in these stored samples disappeared after 3 min cooking in boiling water.     

Influence of different preservation treatments on the volatile fraction of desalted cod

In the present study, desalted cod underwent a water blanching treatment and the incorporation of additives (citric acid and potassium sorbate), combined with different types of packaging (air, vacuum and modified atmosphere), to achieve an improvement of the shelf life of ready-to-use desalted cod. The purpose of this work was to evaluate the effect of these combined methods of preservation on the volatile fraction of desalted cod during 42 days in cold storage. The volatile compounds identified in all samples were those mainly related to fresh odor in whitefish, although with some exceptions. Untreated desalted cod showed a high increase of 3-methyl-1-butanol (described as a microbial spoilage index) during the storage period; a higher increase in air packaging than in vacuum and modified atmosphere packaging. The slow increase of this compound, as well as the evolution of ketones and aldehydes observed for the rest of the samples submitted to treatment, demonstrated the effectiveness of the combined treatments applied. The most efficient treatment was the combination of additives together with modified atmosphere packaging.     

Towards a better understanding of the pectin structure–function relationship in broccoli during processing: Part II — Analyses with anti-pectin antibodies

To investigate the structure–function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. Anti-homogalacturonan antibodies were used to perform in situ (microscopy) and ex situ (immuno-dot assays) analyses on broccoli pectin which resulted in information concerning the localisation of defined pectic domains in broccoli cell walls and pectin's structure. Water-soluble pectin appears to contain unbranched, high-esterified pectin and some pectic polymers with abundant side chains that are less esterified. Ionically cross-linked pectin, on the other hand, contains low-esterified pectin with either highly branched or unbranched domains. The in situ visualisation of pectin in broccoli suggested that de-esterification of pectin by PME during LTB as well as during HP mainly takes place in the tricellular junctions of adjacent cells in broccoli tissue. Ca²⁺-cross-linked pectin could be found in cell walls lining intercellular spaces and was particularly abundant at the corners of intercellular spaces, indicating its important role in cell–cell adhesion. Both LTB and HP created pectin–Ca²⁺-cross-links in parts of the cell wall where these cross-links were originally absent. The influence of thermal processing and the effect of pressurisation on the pectic components in the cell wall could also be visualised using the antibodies.     

Osmotic dehydration process for low temperature blanched pumpkin

This study investigated the influence of stepwise blanching over the kinetics of osmotic dehydration process and over the physical characteristics of pumpkin (Cucurbita moschata). The 2³ factorial design and response surface methodology was used to optimize the blanching process. The independent variables for blanching were temperature, blanching time and holding time. These independent variables showed different effects on the two studied answers: texture and color. The kinetics of osmotic dehydration were investigated using 50% and 65% sucrose solutions, using samples previously blanched by both stepwise and conventional means. The diffusivity values for the water and sucrose were similar for the two components, showing greater gains of solute than loss of water in many samples. Blanching affected the color of the pumpkin, whereas osmotic dehydration did not change it significantly. The impregnation process maintained or even increased the tissue firmness when compared to the blanched samples.