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。     

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。     

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。     

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     

Potato Cubes Response to Water Blanching and High Hydrostatic Pressure

High hydrostatic pressure treatment (400 MPa, 15 min, 5–50°C) of potato cubes (2 × 2 × 2 cm) was compared with hot water blanching (100°C, 30–180 set). Inactivation of microorganisms and polyphenoloxidase, texture and density change, leaching of potassium and loss of ascorbic acid were monitored. Reduction of microbial counts was comparable for both methods and polyphenoloxidase was completely inactivated at 20°C, when dilute citric acid solutions (0.5 or 1.0%) were used as “immersion” medium. Hot water blanching and high pressure treatment resulted in samples of similar softness. Leaching of potassium was reduced 20% after pressure treatment on vacuum-packaged samples. Retention of ascorbic acid in pressure-treated samples was temperature dependent ranging from = 90% at 5°C to = 35% at 50°C.     

Chlorophyll changes in some green leafy vegetables during cooking

Five green leafy vegetables commonly consumed in Nigeria (Talinum triangulare, Corchorus olitorius, Celosia argentea, Amaranthus hybridus and Vernonia amygdalina) were examined for their chlorophyll contents. These varied between 0.038% for Talinum triangulare and 0.137% for Vernonia amygdalina, with chlorophyll-a constituting between 68 and 75% of the total chlorophyll. By bringing the temperature of the leaves to 100°C, at least 56% of the total chlorophyll was lost, the rate of loss decreasing with the initial total chlorophyll content. When the leaves were blanched by immersion in boiling water, they showed a greater rate of chlorophyll loss. This was reduced when the pH was adjusted to 6.     

Effects of low‐temperature blanching on tissue firmness and cell wall strengthening during sweet potato flour processing

Free starch rate has been one of the most important criterions to evaluate the quality of sweet potato flour. Low‐temperature blanching (LTB) of sweet potatoes before steam cooking has shown significant increase in tissue firmness and cell wall strengthening. This research indicated that pectin methylesterase (PME) activity decreased by 87.8% after 30 min of blanching in water at 60 °C, while polygalacturonase (PG) and β‐amylase activity decreased 69.4% and 7.44%, respectively, under the same condition. Both PME and β‐amylase played important roles in tissue firmness. Further studies of tissue firmness and methyl esterification showed that the combination of LTB and Ca²⁺ could increase the activity of PME and significantly enhance the pectin gel hardness to strengthen the cell walls and decrease free starch rate from 12.83% to 7.28%.     

STRUCTURAL CHANGES AND MASS TRANSFER DURING GLUCOSE INFUSION OF APPLES AS AFFECTED BY BLANCHING AND PROCESS VARIABLES

ABSTRACT

The effect of process variables and blanching on the rate of dewatering of apple slices through immersion in glucose solutions was analyzed. The adequacy of the Hawkes and Flink's and Peleg's models for fitting the rate data was evaluated as well as the structural changes produced in the tissue subjected to osmotic process. High concentration values (33-42 % (w/w)) of the soaking solution favored significantly water loss (WL) but only slightly affected solid gain (SG). Increasing system temperature over the range 20-50 °C generally provided an increase in WL and in SG. The increase in thickness decreased significantly both mass transfer rates. The use of sucrose instead of glucose lead to a greater SG while blanched samples showed higher rates of WL and SG. Microscopic studies revealed that, when applying short treatments, cells appeared slightly shrinked and cells walls folded. After long treatments, although an extensive