Retention of mineral constituents in frozen brassicas depending on the method of preliminary processing of the raw material and preparation of frozen products for consumption

The content of ash, P, K, Ca, Mg, Na, Fe, Zn, Mn, Cu, Cr and Ni was determined in four species of brassicas: Brussels sprouts, broccoli, and green and white cauliflowers. The investigation covered the raw material, the material blanched or cooked before freezing and frozen products after 12 months of refrigerated storage and prepared for consumption. Frozen products were obtained by the traditional method of freezing the blanched material or by the modified method of freezing the cooked material. The processing of vegetables before freezing (washing, grinding, blanching or cooking) caused statistically significant decreases in most constituents analysed. Blanching did not basically change the content of sodium and calcium; or that of chromium in both types of cauliflower; copper and nickel in white cauliflower; and nickel and phosphorus in Brussels sprouts. Cooking in brine, however, caused increases in the content of ash, sodium and calcium in white cauliflower, decreases in the content of potassium and iron and, in some species, of the remaining constituents. In comparison with the traditional method, a greater content of most analysed elements was found in frozen products obtained by the modified technology and prepared for consumption. However, no significant differences were noted in the level of chromium in all the samples; in the level of calcium in broccoli and green cauliflower; of nickel in broccoli; of nickel, copper and zinc in white cauliflower; and of copper in green cauliflower.     

Recent advances in the improvement of freezing time and physicochemical quality of frozen fruits and vegetables by ultrasound application

Freezing is widely used for the preservation of fruits and vegetables (FVs). Whereas, the conventional freezing method presents low process efficiency in frozen FVs. Ultrasound application is used as a supplementary technology to improve the freezing process of FVs. This reviewed paper shows the cavitation effect of ultrasound and the effect of ultrasound application on freezing time and the physicochemical quality of frozen FVs. The cavitation effect of ultrasound in the freezing process was described in detail. Compared with conventional freezing, ultrasound application in freezing of FVs can shorten the freezing time, and improve physicochemical quality including drip loss, colour, firmness, chemical compositions (ascorbic acid, total phenolic and anthocyanin), as well as microstructure. Therefore, the results of these studies illustrated that ultrasound is a potential technology to enhance freezing efficiency and retain the quality of FVs during freezing.     

Effects of cooking methods on chlorophylls, pheophytins and colour of selected green vegetables

The effect of microwave and conventional cooking methods on chlorophyll pigments and colour properties of squash, green beans, peas, leek, broccoli and spinach were studied, by HPLC and colorimetry, respectively. In five of six vegetables, chlorophyll a was found more heat resistant compared with chlorophyll b, except in peas. Chlorophylls in peas were retained to the 80–90%, the highest in all vegetables evaluated. Chlorophylls were retained to 19–100%, depending on the vegetable type and cooking method. Pheophytins increased in all vegetables after cooking. Highest chlorophyll a and chlorophyll b losses were observed in boiled leek while microwaved peas and boiled peas retained the most chlorophyll a and chlorophyll b, respectively. Pheophytin a and pheophytin b formation was highest at boiled squash and boiled green beans, which were fifty‐ninefold and twenty‐onefold compared with fresh ones, respectively. Most of the pheophytin formations occurred in boiled and the least in microwaved vegetables. Surface colour changed depending on the type of vegetable and cooking method.     

Influence of commercial freezing and storage on vitamin C content of some vegetables

Vitamin C levels of commercially frozen okra, potatoes, green beans, broccoli, spinach and peas, including the impact of processing and storage, were studied. Depending on the vegetable type, prefreezing operations caused a 19.1–51.5% decrease in the initial vitamin C levels. The freezing process alone did not influence the vitamin levels except in the cases of green beans and spinach. Total losses (%) were between 27.6 and 57.9 for the vegetables at the end of commercial frozen storage (6 months). All the data obtained from this study confirmed that, depending on the vegetable type, prefreezing operations have a major impact on the vitamin C contents and this influence persists in the frozen storage.     

Peroxidase activity, chlorophylls and antioxidant profile of two leaf vegetables (Solanum nigrum L. and Amaranthus cruentus L.) under six pretreatment methods before cooking

The study evaluated the effects of six pretreatment methods before cooking on the peroxidase activity, chlorophyll and antioxidant profile of Amaranthus cruentus L. and Solanum nigrum L. The six pretreatments methods used were chopped only (raw sample) (coded M1); chopped and dried at 50 °C for 5 h (coded M2); chopped and squeezed in water (at room temperature) (coded M3); chopped and soaked in warm water (approximately 60 °C), then cooled and squeezed (coded M4); chopped and soaked in salt‐treated water (approximately 20 g NaCl per litre of water) for 15 min, then squeezed (coded M5) and chopped and soaked in boiling water (100 °C), then cooled and squeezed (coded M6). The main effect of vegetable type and the main effect of pretreatment methods have significant effects (P 0.05) on the parameters measured, while the interaction of vegetable type and pretreatment methods have no significant effect on the parameters measured. Statistical analyses (P 0.05) showed that chlorophyll a and b occur in ratio 3:1 in the two vegetables, irrespective of the pretreatment imposed. Peroxidase activity test showed that A. cruentus, irrespective of the pretreatment imposed showed, no peroxidase activity, while S. nigrum showed high peroxidase activity for all the pretreatments except for M6. Results showed that there was a significantly (P 0.05) higher content of carotenoids in A. cruentus when compared with S. nigrum, while the total phenolics, total flavonoids and total tannins contents were higher in S. nigrum when compared with A. cruentus, irrespective of the pretreatment method used. For the two vegetables, the percentage losses in total carotenoids, phenolics, flavonoids and total tannins at M6 when compared with M1 were 53.3–60.5%, 55.6–57.1%, 62.4–63.6% and 66.1–73.5%, respectively. There was a sharp drop in the carotenoids, phenolics, flavonoids and tannins contents of the two vegetables at M4 and M6, with both treatments having closely similar values for each parameter.     

Effects of some technological processes on glucosinolate contents in cruciferous vegetables

Effects of blanching, boiling and freezing of selected cruciferous vegetables (Brussels sprouts, white and green cauliflower, broccoli, and curly cale) on their glucosinolate (GLS) contents were determined. It was found that blanching and cooking of the vegetables led to considerable (P < 0.05) losses of total GLS, from 2.7 to 30.0% and from 35.3 to 72.4%, respectively. No systematic changes in total GLS were found in the vegetables that were blanched and frozen for 48 h. In addition, the highest concentration of cancer-protective compounds, such as aliphatic and indole GLS, were found in Brussels sprouts (sinigrin and glucobrassicin) and in broccoli (glucoraphanin).     

Experimental study on the freezing characteristics of four kinds of vegetables

Mushroom, green cauliflower, navy bean and pea pod are four kinds of favored vegetables. Their freezing characteristics are studied in this paper. For fresh samples, the moisture contents of mushroom, navy bean, pea pod and green cauliflower were 88.7±4.9, 92.9±0.4, 87.7±1.0 and 89.7±0.9 g/100 g, respectively. After pre-treating, cooling curve method and differential scanning calorimetry (DSC) were employed to measure the end-points of freezing and glass transition temperatures. The initial freezing points varied from −0.1 to −2.7 °C. The end-points of freezing were all below −20.0 °C. The partial glass transition temperatures varied from −50.3 to −76.1 °C. With a cryomicroscope, the sizes of ice crystals in frozen vegetable saps were found to decrease from 26 to 3 μm when the freezing rates increased from 1.0 to 10.0 °C/min.     

Effect of production process on the amino acid content of frozen and canned Pleurotus ostreatus mushrooms

The aim of the work was to determine the effects of the freezing and canning processes, followed by a 12-month storage, on the amino acid content of Pleurotus ostreatus mushrooms. The pre-treatment involved blanching, or soaking and blanching, in mushrooms in water or in solutions containing sodium metabisulphite, citric acid, l-ascorbic acid and/or low-methylated pectin. Freezing and canning resulted in significant decreases in the levels of alanine, glutamine, cysteine and tyrosine (6–39%), and, in the case of canned mushrooms arginine, glycine, serine, histidine, methionine and threonine (1–31%). Frozen products obtained from blanched mushrooms had significantly higher levels of 12 out of the 17 amino acids examined (4–28%) whereas, in canned mushrooms, only 5 amino acids showed higher levels (3–20%), than those obtained from soaked and blanched mushrooms. With the exception of samples blanched in water, frozen mushrooms had higher levels than canned mushrooms of all the investigated amino acids. Limiting amino acids were not found in mushrooms.     

Effects of freezing and frozen storage on the microstructure and texture of ewe's milk cheese

Semi-hard ewe's milk cheeses, frozen immediately after manufacture either slowly at –35 °C or rapidly at –80 °C and stored at –20 °C for 4 months were studied for microstructural and textural characteristics during subsequent ripening. Two control groups were used to establish the effect of freezing: the fresh unfrozen cheese and cheese thawed immediately after freezing. Freezing proper did not result in any marked changes in the textural parameters of the cheeses, but considerable changes were found in slowly frozen cheeses after 4 months of frozen storage. Shear strength values were lower in all frozen and stored cheeses, particularly in cheese samples frozen slowly compared to those in the unfrozen control batch. This parameter and firmness values were significantly lower in both slowly and rapidly frozen cheeses at the completion of ripening. Ripening tended to offset differences in elasticity, noticeable in the cheeses during the first 30 days of ripening. Light microscopy and electron microscopy revealed small cracks and ruptures in the cheeses which could not be observed by the naked eye. More extensive damage to the cheese microstructure was found in slowly frozen cheese samples stored frozen for 4 months.     

Nitrate-N determination in leafy vegetables: Study of the effects of cooking and freezing

Nitrate upon reduction to nitrite can cause methaemoglobinaemia or act as precursor in the endogenous formation of carcinogenic nitrosamines. The leafy vegetables are the major vehicle for the entry of nitrate into the human system. The present study was conducted to establish a flow injection analysis (FIA) technique to investigate the nitrate-N contents of four commonly consumed fresh leafy vegetables (Chinese cabbage, celery, lettuce and English cabbage) from market in Fiji. Two extraction techniques (activated carbon and alkaline extraction) were assessed to extract nitrate-N and the activated carbon extraction was preferred over alkaline extraction and applied. The recoveries of spiked nitrate-N in vegetable matrices ranged from 90.40% to 112.80% in activated carbon extraction with an average of 100.62%. The effects of cooking (boiling, baking and frying) and deep-freezing on the nitrate-N contents were also studied. Nitrate contents in selected leafy vegetables were determined by FIA coupled with Greiss protocol involving sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride as color reagents. Nitrate was determined in the linear range from 1.0 to 20.0 mg L⁻¹ with the method detection limit of 0.042 mg L⁻¹ (0.34 mg kg⁻¹). The results of the study show that nitrate contents in fresh leafy vegetables ranged from 1297 to 5658 mg kg⁻¹. Boiling reduces nitrate content by 47–56% whereas frying in Soya bean oil elevates nitrate content by as much as 159–307%. No significant change was observed in nitrate content after baking. The deep-freezing of the selected leafy vegetables shows that nitrate-N content fluctuates slightly from the original nitrate-N values over the seven day period. The FIA throughput was 38 samples h⁻¹.     

4种叶菜有机磷和氨基甲酸酯类农药残留变化研究

研究了喷施氧化乐果、抗蚜威、敌百虫、敌敌畏对油麦菜、茼蒿、木耳菜、上海青4种叶菜中有机磷和氨基甲酸酯类农药残留的影响及降解变化.结果表明:分别用质量分数90%的晶体敌百虫135 mg/m2,体积分数40%的氧化乐果700倍液喷施4种叶类蔬菜后,其安全间隔期为3 d;用质量分数20%的粉剂抗蚜威135 mg/m2喷施4种蔬菜后,油麦菜、木耳菜、上海青的安全间隔期为3 d,茼蒿的安全间隔期为4 d;用体积分数80%的敌敌畏500倍液喷施,4种叶菜安全间隔期为4 d.     

温湿度对斜纹夜蛾幼虫发育历期、取食量与生存率的影响

本文研究了温湿度对烟草最主要害虫之一斜纹夜蛾幼虫发育历期、取食量、日平均取食速率和存活率的影响.结果表明在试验温度范围内,除27C外,随温度的升高,斜纹夜蛾幼虫的发育历期缩短,取食量下降,日平均食叶速率增大,存活率提高;相对湿度对斜纹夜蛾幼虫发育历期呈显著负相关,对其取食量、日平均食叶速率和存活率呈显著正相关.温湿度对斜夜蛾幼虫发育历期、取食量、日平均取食速率以及存活率的关系表达式分别为D=66.6644-1.5411T-11.856H,S=49.5205-0.4595T+22.64H,V=-3.0317+0.1617T+3.002H,L=-0.526+0.0225T+0.5142H.     

Effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken meat

This study examined the effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken leg and breast meat. The meat was frozen at three different temperatures (−7, −12 and −18 °C) and then stored at −18 °C for up to 6 months. A significant effect of frozen storage duration on lipid oxidation was detected in leg and breast meat, whereas freezing temperature had no significant effect. In leg meat, freezing at −7 °C had a significant impact on protein oxidation, measured as the increase in carbonyl groups and the decrease in total sulphydryl groups, after 3 months of frozen storage. Lipid and protein oxidation appeared to occur simultaneously in chicken meat during frozen storage and was more intense in leg meat than in breast meat.     

The impact of home freezing on the sensory characteristics of ready-to-use leafy vegetables

BACKGROUND: Owing to the increasing trend of consumption of ready‐to‐use leafy vegetables, the necessity of determining the best conditions for their frozen storage and the considerable impact of freezing on their sensory attributes, research was carried out to determine the best freezing temperature and storage time for a mixture of Allium ampeloprasum, Lepidium sativum and Stureia hortensis. RESULTS: The results for freezing temperature at three different storage times showed that colour and overall acceptability at ? 18 °C were always ranked first (P < 0.05), while taste at ? 18 °C was ranked first on days 120 and 150. The results for frozen storage time at three different temperatures indicated that colour, taste and acceptability were not significantly different. CONCLUSION: Overall, the results of this research indicated that the sensory attributes of leafy vegetables during 180 days of frozen storage were affected mainly by freezing temperature rather than frozen storage time. Copyright © 2010 Society of Chemical Industry     

鲜切果蔬微冻技术的研究进展

鲜切果蔬具有天然、便利、营养、保健以及口感清脆爽口等优点,深受国内外快餐业、旅游业、零售业等行业青睐。但鲜切果蔬贮藏品质损耗严重,保鲜期限短,一直是困扰其工业化发展的瓶颈因素之一。目前,国内外研究者试图采用各种物理、化学方法改善果蔬的贮藏品质问题。虽然这些方法在杀菌或在改善质量方面取得一定成效,但在满足人们对果蔬天然、高营养、安全、较长的保鲜期限等综合品质的需求方面存在局限。微冻技术以其突出的保鲜效果,成为低温保鲜领域的研究热点。而关于微冻技术在果蔬保鲜上应用效果的报道还很少。基于此现状,本文从果蔬保鲜技术的研究现状、微冻保鲜作用效果及组织损伤机制3方面,探究了微冻技术在鲜切果蔬上的应用前景。     

鲜切对果蔬生理生化的影响及其调控方法

鲜切果蔬发展前景十分广阔。本文从伤呼吸和伤乙烯的产生、酶促褐变、细胞壁及膜组分降解等方面介绍了由鲜切引起果蔬的一系列生理生化反应,并总结了低温加工贮运、防腐保鲜剂、气调处理以及可食性涂膜等控制鲜切果蔬不良变化的方法,旨在为后续研究鲜切果蔬理论提供参考。     

速冻果蔬生产加工关键工艺技术研究进展

速冻果蔬产品为目前市场前景非常好的一类初级加工农产品。从速冻果蔬生产加工关键工艺、包装材料和解冻方式对品质的影响、干耗、玻璃态保藏技术和面临的质量安全问题等方面对速冻果蔬的生产加工关键技术现状进行了梳理总结,并简要对其发展趋势进行了展望。     

Daily consumption of phenolics and total antioxidant capacity from fruit and vegetables in the American diet

The daily intake of total phenolics, total flavonoids and antioxidants in the American diet was estimated from the most common 34 fresh fruit and vegetables and their daily consumption data. Among 14 fruit and 20 vegetables, orange contributed the highest amount of total phenolics [117.1 mg gallic acid equivalent (GAE) person^?1 day^?1] and antioxidants [146.6 mg vitamin C equivalents (VCE) person^?1 day^?1]. Orange contributed about 26 and 25% of total phenolics and antioxidant, respectively, in the daily consumption of fruit and vegetables. Apples showed relatively high levels of total phenolics and antioxidant capacity comparable to those of oranges and their phenolics and antioxidants contribution is the second highest. Even though potatoes had lower levels of phenolics and antioxidant capacity, they were third due to the fact that their consumption is the highest (137.9 lb person^?1 year^?1) in the American diet. Although plums and strawberries were ranked as the group with the highest total phenolics and antioxidant capacity among 34 tested fruit and vegetables, their contributions were relatively low due to their lower daily consumption. Generally, the levels of total phenolics, total flavonoids and antioxidant capacity of fruits were higher than those of vegetables. American daily intake of phenolics, flavonoids and antioxidants from fruits and vegetables was estimated to be 450 mg GAE, 103 mg catechin equivalents and 591 mg VCE, respectively. Although we do not yet know the required minimum daily amounts of antioxidants, when we estimate the daily requirement of antioxidants, we must consider not only the antioxidant concentrations of the particular food, but also the daily intakes of the food. Copyright © 2005 Society of Chemical Industry     

常见蔬菜的黄酮含量及烹饪对其含量的影响

本实验目的在于了解我国辽宁省地区常见蔬菜的黄酮类物质含量及黄酮类物质在不同烹饪方式下的变化情况,为进一步估算膳食中黄酮类物质的摄入水平提供依据。结果表明,叶菜中黄酮类物质含量较高,花、果类和根、茎类次之。萝卜缨、韭菜、芹菜中黄酮类物质含量较高,分别达到39.18,36.26和32.20mg/100g。经过烹饪后,大部分蔬菜中黄酮类物质含量均有所增加,其中,中火炒制的烹饪方式使蔬菜中的黄酮含量增加得较为显著,增加幅度在12.11%～166.38%之间。增加绿叶蔬菜的摄入量,可获得充足的黄酮类物质,采用中火炒制的烹饪方式有利于黄酮类物质的释放。     

不同处理方式对蔬菜中拟除虫菊酯类农药残留的影响

目的探究不同处理方式对蔬菜中拟除虫菊酯类农药残留的影响。方法分别于2016年10月、2017年1月、2月在济南市农贸市场随机抽样采集根茎类,叶菜类,果菜类,薯芋类蔬菜样品共34份,将样品粉碎后提取拟除虫菊酯,采用酶联免疫吸附法(enzyme linked immunosorbent assay,简称ELISA)检测蔬菜中拟除虫菊酯残留量。随后,分别通过碱水溶液浸泡、洗涤剂清洗的方法处理样品,检测处理后蔬菜中拟除虫菊酯残留量,评价不同处理方法对蔬菜中拟除虫菊酯类残留的影响。结果 34份蔬菜中拟除虫菊酯检出率为100%;蔬菜中拟除虫菊酯类农药的残留量随着采样时间的不同而发生变化,秋季残留量较高,冬季残留量较低;碱处理和洗涤剂洗涤对蔬菜中拟除虫菊酯无明显去除效果。结论拟除虫菊酯类农药普遍存在与蔬菜中,且经碱处理和洗涤剂处理均无法有效去除蔬菜中此类农药残留。