养心菜漂烫工艺的研究

对不同漂烫条件下养心菜过氧化物酶活性、色泽、质构、齐墩果酸含量的变化情况进行了分析,并通过单因素实验考察漂烫温度、时间以及养心菜切分长度3个因素对VC含量的影响,再结合上述各项指标的变化情况选取因素水平。最后,通过Box-Benhnken的中心组合实验设计和响应面分析优化养心菜漂烫工艺,以VC保留率为响应值进行分析。实验结果表明:漂烫工艺的最优参数组合为:漂烫温度90℃、漂烫时间60s、切分长度8cm,在该工艺条件下进行实验,得到的养心菜VC保留率为80.01%。     

芦荟凝胶发酵乳工艺研究

研究芦荟凝胶发酵乳加工工艺。通过热烫灭酶、护色和酶解试验,确定了芦荟凝胶汁提取的最佳工艺条件;通过正交试验,确定了芦荟凝胶发酵乳的最佳工艺条件。结果表明,芦荟凝胶汁的最佳提取工艺为:90℃/5min热烫灭酶,0.05%IVc-Na 0.1?护色,0.05%Pe酶/45℃/1h酶解;芦荟凝胶发酵乳的最佳工艺条件为:发酵温度42℃、发酵时间4.5h、菌种接种量4.0%、蔗糖含量7.0%、芦荟凝胶汁含量10%。     

Sensory Evaluations and Changes in Peroxidase Activity During Storage of Frozen Green Beans

Total, soluble and bound peroxidase activities were studied on frozen green beans stored under proper conditions (–18°C, -22°C, and in display freezer) and under adverse conditions (with temperature fluctuations). Blanching inactivated the enzyme; there was no regeneration for 12 mo at -22°C, but a slight regeneration at - 18°C. Sensory quality of the properly stored product was acceptable 1 yr or longer. Storage in a display freezer over 60 days did not affect peroxidase activity. Temperature fluctuations were deleterious for sensory quality and total peroxidase activity was only slightly regenerated.     

Image analysis of microstructural changes in almond cotyledon as a result of processing

Release of oil from nuts due to damaged cellular structures can degrade the quality of products incorporating nuts. The aim of this study was to investigate the effects of different processing conditions on microstructure of almond tissue and to quantify these changes using image processing. Spinning disk confocal fluorescence microscopy was used for imaging changes in microstructure of almonds as a function of different thermal processing of almonds. Multiple staining of Nile Red and Calcofluor White was applied to differentiate cell wall structures and oil bodies within individual almond cells without chemical fixation. An algorithm for image processing, included image preprocessing, segmentation, and determination of morphological features of segmented objects, was developed. Oil-roasting processes (140 °C and 150 °C) were found to have a significant impact on microstructure of almonds when compared to the hot air-roasting and blanching processes. Oil-roasted almond at 150 °C had a greater cellular damage due to cell wall and membrane rupture. These changes in microstructure of almonds would make them slightly more susceptible to release oil during storage. The image analysis presented allows quantitative evaluation for the effect of different processing on almond microstructure.     

Towards a better understanding of the pectin structure-function relationship in broccoli during processing: Part I—macroscopic and molecular analyses

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. The macroscopic attributes of broccoli were linked to the chemical structure of broccoli pectin. By enhancing the cross-linking of pectic polymers, both LTB and HP reduced the texture loss that occurred during thermal processing of broccoli. During these pretreatments, homogalacturonan was de-esterified by pectin methylesterase, which led to changes in pectin solubility. When LTB or HP was combined with Ca²⁺ infusion, changes in the structure of pectin occurred, however not always reflected at the macroscopic level. The degree of esterification of pectin in Ca²⁺-soaked broccoli samples was lower compared to non-Ca²⁺-soaked samples and, in addition, a higher amount of ionically cross-linked pectin was retrieved.     

Effect of different blanching times on antioxidant properties in selected cruciferous vegetables

This study aimed to evaluate the effect of different blanching times on the antioxidant properties (antioxidant and free radical scavenging activities) and phenolic content of selected cruciferous vegetables. The study revealed that a 10‐min blanching time had a significant effect (p < 0.05) on the antioxidant properties and phenolic content of all the vegetables except for cabbage and mustard cabbage. The loss of antioxidant activity was highest in Chinese cabbage (40%) after 15 min of blanching, followed by cabbage (27%), Chinese white cabbage (19%), mustard cabbage (9%) and red cabbage (4%). Red cabbage had lost a total of 40% scavenging activity after 15 min of blanching followed by Chinese cabbage (38%), cabbage (36%), mustard cabbage (23%) and Chinese white cabbage (11%). Only Chinese cabbage showed an increase (p < 0.05) in total phenolic content after 15 min of blanching compared with other vegetables. Minimal heat treatment through blanching process is recommended to prevent the major loss of antioxidant properties and phenolic content in selected cruciferous vegetables. Copyright © 2005 Society of Chemical Industry     

Blanch Temperature/Time Effects on Rheological Properties of Applesauce

Peeled and cored ‘Idared’ and ‘Rome’ apples were blanched in water for 20, 40, and 60 min at 35°. 47°. 59°. 71°. and 83°C minor to making into applesauce by a conventional process each month from Nov. through March. USDA Consist meter values decreased as blanch temperature increased from 35° to 59°C and increased again from 71° to 83°C. There was little variation in flow behavior index (“n” values). Yield stress increased as blanch temperature increased from 35° to 59°C and decreased from 71° to 83°C. The consistency index (K) and serum viscosity were almost unchanged by blanching temperature but both decreased with increasing storage time of fresh fruit. Blanching apples at 59° to 71°C before making into applesauce gave substantially thicker sauces than unbalanced apples.     

Chemical and physical pretreatments of fruits and vegetables: Effects on drying characteristics and quality attributes – a comprehensive review

Pretreatment is widely used before drying of agro-products to inactivate enzymes, enhance drying process and improve quality of dried products. In current work, the influence of various pretreatments on drying characteristics and quality attributes of fruits and vegetables is summarized. They include chemical solution (hyperosmotic, alkali, sulfite and acid, etc.) and gas (sulfur dioxide, carbon dioxide and ozone) treatments, thermal blanching (hot water, steam, super heated steam impingement, ohmic and microwave heating, etc), and non-thermal process (ultrasound, freezing, pulsed electric field, and high hydrostatic pressure, etc). Chemical pretreatments effectively enhance drying kinetics, meanwhile, it causes soluble nutrients losing, trigger food safety issues by chemical residual. Conventional hot water blanching has significant effect on inactivating various undesirable enzymatic reactions, destroying microorganisms, and softening the texture, as well as facilitating drying rate. However, it induces undesirable quality of products, e.g., loss of texture, soluble nutrients, pigment and aroma. Novel blanching treatments, such as high-humidity hot air impingement blanching, microwave and ohmic heat blanching can reduce the nutrition loss and are more efficient. Non-thermal technologies can be a better alternative to thermal blanching to overcome these drawbacks, and more fundamental researches are needed for better design and scale up.     

Drying of Orthosiphon aristatus leaves: Mathematical modeling,drying characteristics,and quality aspects

The stage of maturity for Orthosiphon aritatus (OA) leaves revealed that stage I (young leaves) provided the highest bioactive compounds. Vacuum blanching (VB) for 75?s gave the highest sinensetin (28.4% increment) and eupatorin (21.0% increment) compared with heated water blanching (HWB). The modified Henderson model was the most suitable desorption isotherm model for the OA leaves. The VB and unblanched OA leaves were dried by different drying methods, including convection tray drying (CTD, 40–60°C), heat pump dehumidify drying (HPD, 40–60°C), mixed mode solar drying (64.6°C), and freeze-drying. Three-parameter model (TP) was the best model to explain all drying curves. The drying constant, K in the TP and activation energy were fitted to the Arrhenius model. Effective moisture diffusivities were increased with the VB, drying temperatures, and HPD. The highest specific moisture extraction rate was obtained from the VB and dried in the HPD at 60°C. The quality aspects of sinensetin (10.2% retention), eupatorin (10.7% retention), total phenolics, and antioxidant activity revealed the best quality for the OA leaves pretreated by the VB and dried in the HPD at 60°C and could reduce drying time by 44.8% compared with the CTD. The VB of the OA leaves and dried using the HPD at 60°C were recommended.