水果、蔬菜中乙烯利残留量的测定方法

乙烯利是一种人工合成的植物激素,广泛用于水果和蔬菜的催熟,同时,也易造成食品中的残留污染。为此,研究提出了一种用顶空气相色谱法测定蔬菜、水果中乙烯利残留量的较简便和快速的方法。样品置于顶空瓶中,添加碱液后立即密封加热,吸取样品顶空气体,用气相色谱仪和氢火焰离子化检测器测定,标准曲线法定量。本方法添加回收率在99.1%～105.0%之间;变异系数为8.64%～10.20%;最小检出限为0.01mg/kg。适于水果、蔬菜中乙烯利残留量的检测。     

自动顶空气相色谱法测定芒果浆中 乙烯利的残留量

目的建立芒果浆中乙烯利残留量的自动顶空气相色谱法检测方法。方法将芒果浆样品加入顶空样品瓶中,加入适量饱和氢氧化钾溶液,在80℃的条件下恒温加热,氢火焰检测器检测产生的乙烯含量,外标法定量。结果乙烯利在0.5~100.0μg/m L浓度范围内线性关系良好,相关系数均大于0.9999。添加水平为0.02、0.05、0.10 mg/kg时,乙烯利的平均回收率分别为79.9%、85.4%和86.8%,相对标准偏差为3.97%~5.26%。结论该方法简便、快速、经济实用,适用性强,结果准确可靠,可用于样品批量快速检测。     

HPLC法测定动物组织中氯氰碘柳胺的残留量

将样品经乙腈提取,色谱柱为COSMOSIL 5C18-AR-Ⅱ(250 ×4.6 mm,5μm);柱温为35℃;紫外检测波长设在260 nm:流动相为甲醇:0.1%甲酸水溶液(95:5,V:V);流速1.0 mL/min;进样量50μL.结果氯氰碘柳胺样品平均回收率为74.35%～95.92%,相对标准偏差(ItSD)为3.19%～7.69%;最低检测限(LOD)为50μg/kg.该方法简便,准确,灵敏度高,是快速检测和监测动物组织中氯氰碘柳胺的残留可借鉴的分析方法.     

顶空气相色谱法测定河蟹中三甲胺的含量

采用顶空气相色谱法,对河蟹腿肉中的三甲胺含量进行测定,并探索了NaOH加入量、样品平衡温度、超声波处理时间对三甲胺含量测定的影响.结果表明:NaOH加入量为2.00g、样品平衡温度为40℃、超声波处理时间为10min时,蟹腿肉中的三甲胺可得到充分释放且灵敏度较高.并且测得峰面积与三甲胺浓度在0～25mg/L范围内呈良好的线性关系(R2=0.9994,n=8),相对标准偏差为0.91%,平均回收率为97.02%,检测限为0.2mg/L.该方法操作简单快速、准确性好,为评价河蟹新鲜程度提供了一种灵敏高效的测定方法.     

液相色谱-质谱法测定果蔬中8种甲氧基丙烯酸酯类杀菌剂残留量

建立一种测定果蔬中8种甲氧基丙烯酸酯类杀菌剂农药残留量的液相色谱-质谱检测方法.样品经乙腈提取,固相萃取柱净化,液相色谱分离,选择离子监测-大气压化学电离质谱测定.8种被测物在0.05 mg/L～5 mgL范围内线性关系良好,相关系数大于0.995 3.方法的测定低限为0.01 mg/kg,平均回收率为76.5%～92.5%,重复试验7次,RSD值小于10.2%.     

MECHANICS OF FAILURE IN FRUITS AND VEGETABLES

An understanding of mechanical failure in fruits and vegetables is essential to the reduction of damage in processing, handling and transport operations and to the evaluation of textural characteristics of foods. This paper proposes a theory of failure for solid horticultural materials based on the classification of failure as cleavage, slip or bruising. For each of these three modes of failure, the role of intensity of loading or stress in initiating failure is described. It is shown that cleavage is a normal stress phenomenon and that slip and bruising are shear stress phenomena. The mechanical properties of horticultural produce are described in terms of cleavage strength, slip strength and bruising strength; properties which may vary with ripening and loading conditions.
A failure diagram is constructed by superimposing strength boundaries on the normal and shear stress axes of the Mohr's circles representation of the applied stress state. This novel diagram is shown to apply to selected fruits and vegetables. The model can be extended to include buckling. It is shown that horticultural materials do not fail according to one failure criterion alone, but fail, on a rising load, according to the current strength boundary first encountered by an expanding stress state. Potatoes, for example, may fail by cleavage, slip or bruising, depending on the loading conditions.     

THE CHEMISTRY OF TEXTURE IN FRUITS AND VEGETABLES

This review is concerned with the chemistry of the major primary cell wall components, pectins, hemicelluloses and cellulose, under conditions found during the normal handling of fruits and vegetables. These polymeric components are considered separately, then their combined changes during maturation, storage and processing are covered. The effects of tissue conditions, pH, enzymes and salt concentrations on the rate and degree of change are discussed. A large part of the review deals with the important texture-affecting reactions of pectic materials including glycosidic hydrolysis, β-elimination type depolymerization, demethoxylation, and complex formation.     

PESTICIDE RESIDUES IN BEEF TISSUES FROM CATTLE FED FRUITS, VEGETABLES AND THEIR BYPRODUCTS

Muscle, adipose, liver and kidney tissue samples were collected from cattle fed potato processing residue (n=20), apple pomace (n=20), pear pomace (n=10), cannery corn waste (n=20), cotton gin trash (n=20), tomato pomace plus almond hulls (n=16), dried grape solids (n=10) or dried citrus pulp (n=6) as well as from control cattle which were not fed fruits, vegetables or their byproducts (n=21). All adipose tissue samples (n=143), representative samples of the above feeds (n=24) and representative samples of muscle (n=35), liver (n=35) and kidney (n=35) tissues were assayed for acephate, benomyl, captafol, cypermethrin, folpet, azinphos-methyl, captan, chlorothalonil, ethyl parathion, and permethrin. In 2,720 tests for the aforementioned oncogenic pesticides, eight tests were positive, but no residue amount that would be considered violative was detected. The only pesticide detected was benomyl and it was detected at nonviolative levels in the adipose tissue of cattle that had been fed either apple pomace or pear pomace.     

TEXTURE OF FROZEN FRUITS AND VEGETABLES

This review discusses factors responsible for the texture of fruits and vegetables and the changes brought about by freezing. It describes some of the early work on frozen food texture, as well as the more recent studies of cryogenic and other rapid freezing methods. The effects of storage and cooking on texture are also considered.     

THE STORAGE LIFE OF FRUITS AND VEGETABLES

Exponential curves have been fitted to published temperature/time/quality data for both fresh and frozen fruits and vegetables. The two constants in the exponential equation are used as measures of the relative storage life of the product and of its sensitivity to temperature change. Of these 2 constants, 1 is analogous to the “Q₁₀” value often used to express temperature sensitivity, but it is independent of actual temperature. The two constants are used to provide an index of “storability” of different fruits and vegetables and a tentative classification of produce according to this “storability” is presented. Fitting curves to temperature/time/quality data also allows prediction of the effects on storage life of fluctuating product temperatures, such as are experienced during normal transport and storage.     

果蔬的褐变及其控制方法

果蔬贮藏和加工过程中的褐变是影响其品质的一个重要因素.褐变产生的因素较多,其中酶促褐变是果蔬褐变的最主要原因,也是果蔬贮藏和加工品质保证的主要障碍.概述褐变产生的原因及其控制的方法.     

QUALITY OF MINIMALLY PROCESSED FRUITS AND VEGETABLES

Consumer demand for fresh fruits and vegetables coupled with a demand for convenience is fueling an interest in minimally processed products. Advances in packaging technology provide a potential for improved quality and extended shelf-life of these products, but little is known about the physiological, microbiological and nutritional consequences of minimal processing. Mass marketing and brand-label identification of these products will require a new perspective on shelf-life and quality assurance. A systems approach has been proposed as a framework for quality management of fresh and minimally processed product based on the concept of providing the consumer with optimum quality at purchase and consumption.