广式腊肠干燥及贮藏过程中主要理化特性的变化

为了准确把握和控制广式腊肠加工贮藏过程中脂肪氧化和水解反应引起的理化指标和风味等变化,本文系统研究了烘烤和传统日晒两种加工方式生产出的广式腊肠的酸价、过氧化值、含水率等理化指标的变化。结果表明:加工过程中烘烤肠含水量、酸价及过氧化值的变化速度较日晒肠大,而贮藏过程中,日晒腊肠的酸价及过氧化值的变化速度高于烘烤腊肠。真空包装对酸价无明显抑制,但对过氧化值有明显的抑制作用。贮藏温度与酸价和过氧化值呈正相关,但在100d的贮藏期内广式腊肠的过氧化值均未超过国家标准,而无论是日晒肠还是烘干肠的酸价,即使在10℃抽真空包装的理想贮藏条件下,在60d和80d时分别超过了国家标准。烘烤腊肠在30℃散装贮藏条件下保质期为20d,添加0.15%瓜尔豆胶及0.15%硬脂酰乳酸钠可使腊肠保质期延长到60d左右。     

Profiles of carotenoids, anthocyanins, phenolics, and antioxidant activity of selected color waxy corn grains during maturation

Waxy corns are becoming increasingly consumed as fresh foods or as raw materials for whole grain foods facilitating human consumption in China, so they are usually harvested before complete maturity. Unfortunately, information on functional properties of immature waxy corns is very limited. Therefore, we investigated the profiles of carotenoids, anthocyanins, phenolics, and the antioxidant activity in three types of waxy corn with different colors (white, yellow, and black) during maturation, as well as a normal corn (yellow) used as control. The results showed that black waxy corn had the highest quantity of anthocyanins, phenolics and the best antioxidant activity, yellow corn contained a relatively large amount of carotenoids, while white corn had the lowest amounts of carotenoids, anthocyanins, phenolics, and antioxidant capacity. For each type of waxy corn, the higher carotenoids were found at the M2 stage (no major difference between the M1 and M2 stages for yellow corn). The levels of anthocyanin and phenolics decreased for white and yellow corns, contrary to those for black corn during maturation. The antioxidant activity determined by scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH), the ferric reducing antioxidant power (FRAP), and the Trolox equivalent antioxidant capacity (TEAC) assays increased with ripening, but no difference was found between the M2 and maturity stages for yellow and black corns. For white corn, the DPPH radical scavenging activity first increased and then decreased, while the antioxidant activity determined by TEAC and FRAP assay decreased during maturation. Differences in these parameters indicate that types and harvesting time have significant influences on functional properties of waxy corns.     

猪肉油炒过程传质参数测定及其对烹饪过程控制的影响

为提升油炒数值模拟的可靠性及准确度,揭示可控操作对烹饪过程参数的影响及关键过程参数对烹饪的影响。通过无量纲水分含量分析解法,测定了中式油炒猪里脊肉过程中的表面传质系数（surface mass transfer coefficient, h_m）和有效水分扩散系数（effective moisture diffusion coefficient, D_eff）,分析了预热油温及样品比表面积Ω对h_m及D_eff的影响;基于已构建的油炒热质传递数学模型、成熟值理论,对比了h_m和流体-颗粒表面传热系数（fluid-to-particle surface heat transfer coefficient, h_fp）对烹饪成熟控制的影响。结果表明：与油炸过程类似研究的文献数据相比,该研究中h_m值偏大在5.927×10^?6～2.481×10^?5 m/s之间,D_eff在6.281×10^?9～4.148×10^?8 m²/s之间,D_eff活化能（E_a）在24.2～30.6 kJ/mol范围内;预热油温、比表面积Ω对h_m及D_eff有显著影响（P<0.05）,预热油温越高h_m和D_eff越大,比表面积Ω越大h_m越大,D_eff越小;h_m对烹饪成熟控制影响较小,而h_fp是烹饪成熟控制的关键过程参数。研究结果为油炒过程模拟提供了重要参数,为烹饪过程控制提供依据。     

加工过程中冷打浆沙棘浓缩浊汁理化特性的变化

为了研究沙棘浓缩浊汁加工及其品质的变化,该文以沙棘果为原料,研究了冷打浆法生产沙棘浊汁及浓缩浊汁加工和贮藏过程中的理化变化。结果表明:冷打浆工艺制得到的沙棘浊汁品质优良,其可溶性固形物质量分数高达18.0%,总酸度达4.24%,含维生素C 729.69 mg/100 mL,总黄酮445.17 mg/100 mL,总多酚924.67 mg/100 mL,多糖25.22 mg/100 mL。在45℃,真空度为0.095~0.1 MPa的条件下对沙棘浊汁减压浓缩,随着浓缩倍数的增加,加热时间延长,沙棘浊汁营养和保健成分减少,总酸度增加,pH值减小,褐变指数增大,5-HMF含量增加;与3倍和4倍沙棘浓缩浊汁相比,2倍沙棘浓缩浊汁营养和保健成分保存率最高,褐变指数较小、5-HMF含量较低。不同浓缩倍数的沙棘浊汁在自然室温(10~25℃)和冷藏条件(5~8℃)下放置60 d,维生素C、总黄酮、总多酚和多糖含量呈下降趋势,pH值和总酸度变化不明显,褐变指数增加,5-HMF含量增加;相同浓缩倍数的沙棘浊汁在冷藏条件下放置比在自然室温条件下放置时营养和保健成分的保存率高,冷藏条件下2倍沙棘浓缩浊汁的营养和保健成分的保存率最高,其维生素C、总黄酮、总多酚、多糖的保存率比室温条件下2倍沙棘浓缩浊汁分别高11.46%、20.44%、18.37%、9.83%,且冷藏条件下放置的沙棘浓缩浊汁褐变指数小,5-HMF含量低,冷藏条件有利于沙棘浓缩浊汁的保存;2倍沙棘浓缩浊汁在室温条件下贮藏不稳定,在冷藏条件下其贮藏稳定性优于3倍和4倍沙棘浓缩浊汁。     

Effect of cooking temperatures on chemical changes in species of organic arsenic in seafood

The concentrations of arsenobetaine (AB), tetramethylarsonium ion (TMA(+)), and trimethylarsine oxide (TMAO) were determined in samples of sole, dory, hake, and sardine, raw and after being subjected to cooking processes--baking, frying, and grilling--at various temperatures. In all cases, the temperature attained inside the product during the cooking process was measured. The arsenic species extracted from the samples with methanol/water were separated by means of a column switching technique between a PRP-X100 column and a PRP-X200 column. AB was detected by hydride generation atomic absorption spectrometry, whereas TMA(+) and TMAO were detected by hydride generation atomic fluorescence spectrometry. The results obtained showed that, in all of the types of seafood studied, TMA(+) appeared after cooking, possibly because heating facilitates decarboxylation of AB to TMA(+).     

Effect of nixtamalization (Alkaline cooking) on fumonisin-contaminated corn for production of masa and tortillas

Studies were undertaken to determine the fate of the mycotoxins, fumonisins, during the process of alkaline cooking (nixtamalization), using normal-appearing corn that was naturally contaminated with fumonisin B(1) (FB(1)) at 8.79 ppm. Corn was processed into tortillas, starting with raw corn that was cooked with lime and allowed to steep overnight; the steeped corn (nixtamal) was washed and ground into masa, which was used to make tortillas. Calculations to determine how much of the original fumonisin remained in the finished products took into consideration that FB(1) will be converted to hydrolyzed fumonisin B(1) (HFB(1)) by the process of alkaline cooking. All fractions, including steeping and washing water, were weighed, and percent moisture and fumonisin content were determined. Tortillas contained approximately 0.50 ppm of FB(1), plus 0.36 ppm of HFB(1), which represented 18.5% of the initial FB(1) concentration. Three-fourths of the original amount of fumonisin was present in the liquid fractions, primarily as HFB(1). Nixtamalization significantly reduced the amount of fumonisin in maize.     

Colorimetric determination of alkaline phosphatase as indicator of mammalian feces in corn meal: collaborative study

In the official method for rodent filth in corn meal, filth and corn meal are separated in organic solvents, and particles are identified by the presence of hair and a mucous coating. The solvents are toxic, poor separation yields low recoveries, and fecal characteristics are rarely present on all fragments, especially on small particles. The official AOAC alkaline phosphatase test for mammalian feces, 44.181-44.184, has therefore been adapted to determine the presence of mammalian feces in corn meal. The enzyme cleaves phosphate radicals from a test indicator/substrate, phenolphthalein diphosphate. As free phenolphthalein accumulates, a pink-to-red color develops in the gelled test agar medium. In a collaborative study conducted to compare the proposed method with the official method for corn meal, 44.049, the proposed method yielded 45.5% higher recoveries than the official method. Repeatability and reproducibility for the official method were roughly 1.8 times more variable than for the proposed method. The method has been adopted official first action.     

Synthesis and characterization of highly flexible thermoplastic films from cyanoethylated corn distillers dried grains with solubles

Corn distillers dried grains with solubles (DDGS) can be made into highly flexible thermoplastic films without the need for plasticizers. DDGS is an abundantly available coproduct of ethanol production that is inexpensive ($80-130/ton) compared to most of the polymers used for thermoplastic applications. In this research, oil-and-zein-free DDGS was cyanoethylated using acrylonitrile, and cyanoethylation conditions were optimized to obtain high percent weight gain of up to 42%. Cyanoethylated DDGS was characterized using (1)H NMR, FTIR, DSC, and TGA. Cyanoethylated DDGS was compression molded into thermoplastic films, and the tensile properties of the films were studied. It was found that DDGS films with elongation as high as 38% and strength of 14 MPa could be obtained without the use of any plasticizers. Alternatively, films with strength as high as 651 MPa but with relatively low elongation (2.5%) were obtained by varying the extent of cyanoethylation. This research showed that cyanoethylation could be a viable approach to develop biothermoplastics from biopolymers for applications such as packing films, extrudates, and resins for composites.     

Lipids from flax fibers and their fate in alkaline pulping

The chemical composition of lipids from bast fibers of flax (Linum usitatissimum), which are commonly used for high-quality paper pulp production, was thoroughly studied by gas chromatography-mass spectrometry. The main compounds identified were waxes, series of long chain n-fatty alcohols, n-aldehydes, n-fatty acids, and n-alkanes. Free and esterified sterols and triterpenols, steroid hydrocarbons, steroid and triterpenoid ketones, as well as sterol glycosides were also found in the flax bast fibers. On the other hand, the fate of these lipophilic compounds in alkaline pulping of flax fibers was investigated by analyzing two pulps obtained under distinct industrial cooking conditions. The results revealed that while waxes could be efficiently hydrolyzed during pulping depending on the alkali charge, most of the other lipophilic compounds present in flax fibers survived cooking and were present in the unbleached pulps.     

Physicochemical changes and mechanism of heat-induced gelation of arrowtooth flounder myosin

Physicochemical changes of myosin during heating were investigated to elucidate the mechanism of heat-induced gelation of arrowtooth flounder (ATF) myosin at high ionic strength. Changes in dynamic properties indicated ATF myosin formed a gel in three different stages as shown by the first increase in G' (storage modulus) at 28 degrees C, followed by the decrease at 35 degrees C and the second increase at 42 degrees C. DSC thermogram showed the onset of myosin denaturation at 25 degrees C with two maximum transition temperatures at 30 and 36 degrees C. The decrease in alpha-helical content indicated ATF myosin began to unfold at 15 degrees C and the unfolding continued until it reached 65 degrees C. Turbidity measurement showed myosin began to aggregate at 23 degrees C and the aggregation was complete at 40 degrees C. Surface hydrophobicity increased consistently in the temperature range studied, 20-65 degrees C. Sulfhydryl contents decreased significantly at 20-30 degrees C due to the formation of disulfide linkages but remained constant at temperatures >30 degrees C. ATF myosin was shown to be extremely sensitive to heat, resulting in denaturation at lower temperature than other fish myosin. Denaturation was initiated by unfolding of the alpha-helical region in myosin followed by exposure of hydrophobic and sulfhydryl residues, which are subsequently involved in aggregation and gelation processes.     

Flavoring components of raw monsooned arabica coffee and their changes during radiation processing

Volatile aroma principles, nonvolatile taste constituents (caffeine and chlorogenic and caffeic acids), and glycosidically bound aroma compounds of monsooned and nonmonsooned raw arabica coffee were analyzed using gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). Among the most potent odor active constituents known to contribute to the aroma of the green beans, 3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine, 4-vinylguaiacol, beta-damascenone, (E)-2-nonenal, trans,trans-2,4-decadienal, phenylacetaldehyde, and 3-methylbutyric acid were detected by GC-MS in both samples. A decrease in content of methoxypyrazines and an increase in 4-vinylguaiacol and isoeugenol resulted in a dominant spicy note of monsooned coffee. These phenolic compounds exist partly as their glycosides, and their release from the bound precursors during monsooning accounted for their higher content in monsooned coffee. A considerable decrease in astringent chlorogenic acid as a consequence of hydrolysis to bitter caffeic acid was noted in monsooned coffee. Radiation processing of nonmonsooned beans at a dose of 5 kGy resulted in an increased rate of monsooning. At this dose a quantitative increase in most of the aroma active components could be observed in all samples studied. Hydrolysis of chlorogenic acid to caffeic acid was noted in radiation-processed monsooned coffee beans irrespective of whether the treatment was carried out before or after monsooning. These changes were, however, not observed in irradiated, nonmonsooned coffee beans, suggesting an enzymatic rather than a radiolytic cleavage of chlorogenic acid. A rationale behind the mechanism of monsooning and radiation-induced enhancement of the monsooning process is discussed.     

蒸汽爆破前后生物质秸秆的物理化学特性

为深入了解汽爆过程对生物质秸秆的影响,采用扫描电镜和太赫兹时域光谱系统,对汽爆前后的秸秆分别做了检测,分别得到了它们的形貌特征、微区成分分布和太赫兹图谱。其形貌特征显示,秸秆薄壁细胞和表皮被汽爆过程所粉碎,秸秆物质的比表面积大大增加,致使增加了物料的接触面积,在制备沼气或生物质燃料过程中,使得其发酵速度增加。太赫兹时域图谱表明,薄壁细胞和表皮物质的吸收系数,随着频率的增加而增加。同时,由于汽爆因素的影响,它们的吸收系数在汽爆前后明显不同,表明其结构发生了一些变化,微区成分分析也证明了这一点。更为重要的是,薄壁细胞在汽爆前后,其吸收光谱分别检测出2个明显的吸收峰,且前后频率位移较大,但其结构变化的机制、变化与振动峰的关系和对振动峰的归属和指认需要做进一步的研究。     

Kinetics of changes in glucosinolate concentrations during long-term cooking of white cabbage (Brassica oleracea L. ssp. capitata f. alba)

Brassica vegetables are the predominant dietary source of glucosinolates (GLS) that can be degraded in the intestinal tract into isothiocyanates, which have been shown to possess anticarcinogenic properties. The effects of pilot-scale long-term boiling on GLS in white cabbage (Brassica oleracea L. ssp. capitata f. alba cv. 'Bartolo') was experimentally determined and mathematically modeled. Cabbage was boiled, resulting in a dramatic decrease of 56% in the total GLS levels within the plant matrix during the first 2 min. After 8-12 min of boiling, the decrease progressed to over 70%. Progoitrin had an exceptionally higher decline rate in comparison to all other GLS. As boiling progressed the concentration of all GLS continued to decrease at a lower rate for the remaining cooking period. A mathematical model was used to describe the concentration profile of the GLS in the plant matrix, based on leaching of GLS to the water phase due to cell lysis and thermal degradation of the GLS both in the plant matrix and in the water phase. The model described the concentration profiles very well. Estimated lysis and degradation rate constants for white cabbage differed from those reported in the literature for red cabbage. The degradation rate constants found were significantly higher in the plant matrix when compared to those in the water phase for all GLS. Identification of the kinetics of decline of GLS during cooking can aid in designing processing and preparation methods and determining the conditions for the optimal effects of ingestion of Brassicaceae toward cancer prevention.     

Sensory and instrumental analyses of volatiles generated during the extrusion cooking of oat flours

Three batches of oats were extruded under four combinations of process temperature (150 or 180 degrees C) and process moisture (14. 5 and 18%). Two of the extrudates were evaluated by a sensory panel, and three were analyzed by GC-MS. Maillard reaction products, such as pyrazines, pyrroles, furans, and sulfur-containing compounds, were found in the most severely processed extrudates (high-temperature, low-moisture). These extrudates were also described by the assessors as having toasted cereal attributes. Lipid degradation products, such as alkanals, 2-alkenals, and 2, 4-alkadienals, were found at much higher levels in the extrudates of the oat flour that had been debranned. It contained lower protein and fiber levels than the others and showed increased lipase activity. Extrudates from these samples also had significantly lower levels of Maillard reaction products that correlated, in the sensory analysis, with terms such as stale oil and oatmeal. Linoleic acid was added to a fourth oat flour to simulate the result of increased lipase activity, and GC-MS analysis showed both an increase in lipid degradation products and a decrease in Maillard reaction products.     

Impact of physicochemical parameters on the decomposition of deoxynivalenol during extrusion cooking of wheat grits

Deoxynivalenol (DON) is a toxic secondary metabolite produced by molds of the Fusarium genus and is known to cause a spectrum of diseases in animals such as vomiting and gastroenteritis. It is found in cereals and cereal products as most processing techniques lead only to a partial reduction of deoxynivalenol levels. One technique with a reported relatively high impact on deoxynivaleol decomposition is extrusion cooking. In the current work, systematic studies of a range of physicochemical parameters, such as temperature, moisture, compression, residence time in the extruder, pH value, and protein content, on their impact on deoxynivalenol decomposition during extrusion cooking were performed. The analysis of deoxynivalenol was made by high-performance liquid chromatography--tandem mass spectrometry using a quick, easy, cheap, effective, rugged, and safe-based cleanup with 15-d(1)-deoxynivalenol as an internal standard. It could be shown that the reduction of deoxynivalenol levels is dependent on a set of parameters partially interacting with each other. Especially the moisture content and compression are key factors for the reduction of deoxynivalenol levels. A correlation between residence time of the mycotoxin in the extruder and deoxynivalenol degradation was also observed when screws without a compression factor were used. Generally, the reduction of deoxynivalenol levels was increased by the use of screws with a high compression factor. As known from cooking, deoxynivalenol could also be easily degraded by extrusion under alkaline conditions. Furthermore, an increase of the protein content of the starting material resulted in higher reduction rates of deoxynivalenol.     

Antioxidant activity and total phenolics in selected cereal grains and their different morphological fractions

The purpose of this study was to examine the antioxidant properties of water and 80% methanolic extracts of cereal grains and their different morphological fractions. Wheat (Triticum aestivum L.) cv. Almari and cv. Henika, barley (Hordeum vulgare L.) cv. Gregor and cv. Mobek, rye (Secale cereale L.) cv. Dańkowskie Zlote, oat (Avena sativa L.) cv. Slawko and buckwheat (Fagopyrum esculentum Moench) cv. Kora were used. PC (L-alpha-phosphatidylcholine) liposome system and spectrophotometric assay of total antioxidant activity (TAA) were used to evaluate the antioxidative activity of extracts. Among the water extracts, only the one prepared from buckwheat exhibited antioxidant activity at the concentration analyzed. The following hierarchy of antioxidant activity was provided for 80% methanolic extracts originated from whole grain: buckwheat > barley > oat > wheat congruent with rye. The antioxidant activity was observed in extract prepared from separated parts of buckwheat and barley. In respect to hulls, the antioxidant hierarchy was as follows: buckwheat > oat > barley. The correlation coefficient between total phenolic compounds and total antioxidative activity of the extracts was -0.35 for water extracts and 0.96, 0.99, 0.80, and 0.99 for 80% methanolic extracts originated from whole grains, hulls, pericarb with testa fractions and endosperm with embryo fractions, respectively.