芦笋MA保鲜技术研究

对芦笋一次性充气MA贮藏保鲜进行了研究,结果表明,初始气体浓度比例对失重影响不明显,而对感官评价值、Vc含量、纤维素含量、叶绿素含量等影响较大。在各种初始气体浓度比例中以5％O_2 5％CO_2和10％O_2 10％CO_2的MA贮藏保鲜效果最好,4℃～5℃下贮藏18d后仍有较好的品质。     

Content of amino acids and the quality of protein in as‐eaten green asparagus (Asparagus officinalis L.) products

The content of amino acids in fresh green spears and in three as‐eaten products was considered, i.e., in fresh asparagus after cooking and in two products obtained from frozen asparagus stored for 12 months at ?20 °C. One of the frozen products was obtained using the traditional method (blanching–freezing–frozen storage) and then cooked. The other was obtained using the modified technology (cooking–freezing–frozen storage); after the storage period the product was defrosted and heated to consumption temperature in a microwave oven. The limiting amino acid of the first order was methionine with cystine, and of the second order leucine. Essential amino acids constituted 40–43% of the total amino acid content. The dominant amino acids were aspartic acid and glutamic acid. The culinary and technological procedures applied brought about a drastic decrease (50–56% in 16 g N) in tyrosine content.     

Effects of post-harvest stigmasterol treatment on quality-related parameters and antioxidant enzymes of green asparagus (Asparagus officinalis L.)

The effects of immersion of green asparagus spears in stigmasterol solution (0, 0.5 and 1.0 g l^?1, 15 min, 25°C) on weight loss, surface colour, enzyme activities and content of malondialdehyde, total phenol, lignin and chlorophyll were investigated during 40 days of storage at 4 ± 0.5°C. Of the concentrations tested, 0.5 g l^?1 treatment was most effective. Stigmasterol (0.5 g l^?1) treatment significantly reduced colour changes and losses of fresh weight and chlorophyll content. Superoxide dismutase (SOD) and catalase (CAT) activities were maintained higher in stigmasterol-treated (0.5 g l^?1) asparagus, whereas the activity of peroxidase (POD) was significantly reduced. Stigmasterol treatment (0.5 g l^?1) also significantly decreased the content of malondialdehyde (MDA) and increased total phenol content. Accumulation of lignin was positively correlated to activity of guaiacol-POD (r = 0.960, p < 0.01) in stigmasterol-treated (0.5 g l^?1) asparagus. The polyphenol oxidase (PPO) activity decreased and showed a significant negative correlation with the chroma L* value (r = –0.899, p < 0.01) in stigmasterol-treated (0.5 g l^?1) asparagus. It was concluded that stigmasterol treatment (0.5 g l^?1) could inhibit the senescence of green asparagus, and therefore prolong its shelf-life, maintaining the quality of post-harvest green asparagus.     

Possible regulatory role of phenylalanine ammonia‐lyase in the production of anthocyanins in asparagus (Asparagus officinalis L)

The regulatory role of phenylalanine ammonia‐lyase (PAL) in the light‐induced accumulation of anthocyanins in the epidermis of asparagus spears has been analysed. A correlation between the stimulation of PAL activity and the rise in total anthocyanin content has been observed. Light radiation induced PAL activity, which in turn stimulated anthocyanin accumulation, a hypothesis which has been confirmed by treating asparagus spears with S‐carvone, an inhibitor of PAL activity. A marked delay was observed in the rise in PAL activity and total anthocyanin content in asparagus spears treated with this compound during light irradiation. PAL activity and anthocyanin synthesis continued when the spears were stored in darkness for 5 days after being subjected to light, but the inhibitory effect of S‐carvone remained during this storage. When the asparagus spears were immersed in water for 20 h, no PAL activity could be detected and scarcely any total anthocyanin content was measured. However, after 5 days of storage in darkness a sharp upsurge in PAL activity was found, which was not translated into a parallel increase in total anthocyanin content. Copyright © 2005 Society of Chemical Industry     

Shelf‐life extension of refrigerated seabass slices under modified atmosphere packaging

The effect of CO₂‐enriched atmosphere in combination with either oxygen or nitrogen on the keeping quality of seabass slices stored at 4 °C was investigated. The inhibitory effect on bacterial growth increased proportionally to the CO₂ concentration in the packaging, maximum inhibition being achieved with 100% CO₂ (P < 0.05). Seabass slices stored in CO₂‐enriched atmosphere had lower total volatile base, trimethylamine, ammonia and formaldehyde contents than those stored in air (P < 0.05). However, increases in lightness and exudate loss were observed for samples packaged in high‐CO₂ atmosphere, suggesting the denaturation of both muscle and pigment proteins by carbonic acid formed. Thiobarbituric acid‐reactive substances (TBARS) increased as the CO₂ concentration increased (P < 0.05). However, odour, flavour and overall acceptability of CO₂‐enriched packaged samples, particularly with 80 and 100% CO₂, were acceptable throughout storage for 21 days. Chemical and microbial changes in all samples were generally in agreement with sensory panel evaluations. The shelf‐life of seabass slices packaged in 80–100% CO₂ atmosphere could be extended to more than 20 days at 4 °C, compared with 9 days for those packaged in air. © 2002 Society of Chemical Industry     

Thymol and modified atmosphere packaging to control microbiological spoilage in packed fresh cod hamburgers

A study on the use of mild technologies to produce packaged fish hamburgers was presented. In particular, the antimicrobial effect of some natural compounds (carvacrol, eugenol, thymol, green tea extract, rosemary extract, grapefruit seed extract and lemon extract), at various concentrations (500–10 000 ppm), was screened in vitro against the main fish spoilage micro‐organisms (Shewanella putrefaciens and Photobacterium phosphoreum). Lemon extract and thymol, in combination with modified atmosphere packaging, showed the greatest inhibition activity, therefore, thymol was subsequently used as an ingredient for producing fish hamburgers. Results pointed out that this combination is effective in controlling the growth of microbial species mainly involved in fresh fish spoilage; in particular, it significantly (P < 0.05) reduced the growth rate of bacterial population, performing about 4.8 log CFU g^?1 and 6.5 log CFU g^?1 reduction of the hydrogen sulphide producing bacteria and psychrotrophic aerobic specific spoilage organisms cell load, respectively, if compared with the control.     

Cell wall phenolics of white and green asparagus

Cinnamic acids influence physical and textural attributes of plant foods as they play an important role in lignification and cross‐linking of cell‐wall polymers. Several trans‐cinnamic acids have been detected in asparagus cell wall (CW), and, of these, amounts of ferulic acid (FA) and its dehydrodimers have been found to increase significantly during post‐harvest storage. The distribution of these compounds along the different sections of white and green spears, as well as their modifications during postharvest storage, has been investigated. It has been observed that the cell walls from the apical, middle and lower sections of the green spears contain equivalent amounts of FA derivatives (about 400 µg g^?1 CW), while these compounds are mainly located in the middle (681 µg g^?1 CW) and lower section (975 µg g^?1 CW) of the white ones. During asparagus post‐harvest storage a general increase of FA monomers and dimers took place that affected every section of both green and white spears. Major changes occurred in the middle and lower sections of the white asparagus, where the amounts of ferulic derivatives increased to 1700 and 1678 µg g^?1 CW after storage. A similar but less pronounced trend was observed for the green spears. Copyright © 2005 Society of Chemical Industry     

芦笋多糖提取纯化工艺及其体外抗氧化研究

目的：探讨芦笋多糖的提取纯化方法及其体外抗氧化活性。方法：采用L9(34)正交试验设计,考察提取温度、提取时间、料液比、提取次数等因素对芦笋粗多糖浸提效果的影响。进一步以酶法除蛋白纯化粗多糖,探索3种蛋白酶作用的最佳工艺条件及其除蛋白效果,用硫酸-苯酚法和DNS法定量分析粗多糖;并研究芦笋多糖对自由基的清除作用以及对红细胞溶血、肝线粒体肿大的抑制作用。结果：在提取温度100℃、提取时间3h、料液比1:20(g/mL),提取1次条件下,芦笋粗多糖的得率最高,为(8.50±1.07)%,经碱性蛋白酶纯化后,纯度可达(52.40±0.47)%。芦笋多糖在体外体系中可显著清除DPPH自由基、 ·OH、O2－ ·,并具有抑制红细胞溶血,抑制肝线粒体肿大的作用。结论：芦笋多糖具有较好的抗氧化活性。     

Enzymatically hydrolysed asparagus (Asparagus officinalis L.) hard-stem exhibits the ability to inhibit angiotensin-converting enzyme (ACE)

Asparagus (Asparagus officinalis L.) hard-stem, woody bottom of the asparagus stalk, is a rich source of bioactive compounds and is discarded as an eco-friendly agricultural waste. Therefore, we intended to explore the antioxidant, amino acid composition, and antihypertensive potentials of enzymatically hydrolysed asparagus hard-stem. The treated samples exhibited higher total free amino acids (11437 mg 100 g⁻¹), total phenolics (1749 mg 100 g⁻¹), and ability to inhibit (78.38%) angiotensin-converting enzyme (ACE) compared to control (ACE inhibition of 46.88%). Hydrophobic amino acids (39%) and gallic acid (48%) were the highly eluted bioactive compounds. The ability to inhibit ACE had been positively correlated with hydrophobic amino acids (r = 0.959–0.987) and gallic acid (r = 0.966), indicating the role of amino acids and phenolics in controlling ACE reactions. Thus, asparagus hard-stem can be a potential source to develop natural health supplements for the management of hypertension and related health risks.     

Modified atmosphere packaging of filleted rainbow trout

Shelf‐lives of filleted rainbow trout (Oncorhynchus mykiss) packaged in over‐wrap, vacuum and gas mixture conditions and stored at 1 ± 1 °C were compared by measurement of pH, total volatile bases (TVB), hypoxanthine content, lipid oxidation (TBARS value), superficial counts of aerobic psychrotrophic flora and sensory analysis (colour, odour and flavour). The gas mixtures evaluated were 10% O₂ + 50% CO₂ + 40% N₂, 10% O₂ + 50% CO₂ + 40% Ar, 20% O₂ + 50% CO₂ + 30% N₂, 20% O₂ + 50% CO₂ + 30% Ar, 30% O₂ + 50% CO₂ + 20% N₂ and 30% O₂ + 50% CO₂ + 20% Ar. Sensory quality deterioration was delayed and bacterial growth as well as increases in pH, TVB and hypoxanthine levels were reduced by modified atmosphere packaging (MAP). Lipid oxidation was higher in gas packages with 20 and 30% O₂ than in those with 10% O₂. Vacuum‐packed fillets presented the lowest TBARS values. In summary, MAP gave rise to a significant extension of shelf‐life when compared with vacuum and over‐wrap packaging. No significant differences were found between the packages containing either N₂ or Ar. The best evaluated atmosphere consisted of 10% O₂ + 50%CO₂ + 40% N₂/Ar. © 2002 Society of Chemical Industry     

Degradation of malathion in aqueous extracts obtained from different developmental stages of asparagus (Asparagus officinalis)

When malathion was incubated in aqueous extracts obtained from 17 vegetables and fruits at pH 7.4 and 37 °C for 4 h, asparagus extract exhibited the highest malathion degradation. The degradation effects of the extracts ranged from 100% (asparagus) to 0.5% (papaya). The highest malathion‐degradation effects obtained from extracts of asparagus at different growing stages incubated at pH 7.4 and 37 °C for 1 h was 94.4 ± 0.45% (stem length, 5–10 cm), followed by 88.0 ± 0.31% (10–15 cm), 85.1 ± 0.94 (15–20 cm), 82.2 ± 0.52 (20–25 cm), 81.2 ± 1.4% (pre‐emergent), 67.3 ± 0.67% (>25 cm), and 42.7 ± 2.1% (fern). The protein content in an asparagus extract from different growing stages was not consistent with the degradation activity of malathion. Results of time course studies on malathion degradation in asparagus extracts from different growing stages yielded half‐life times of malathion degradation ranging from 51.7 min (fern stage) to 17.3 min (stem length, 5–10 cm). Formation of α‐ and β‐malathion mono acids from malathion was detected in an incubated sample by gas chromatography/mass spectrometry. The results support the presence of carboxylesterases in asparagus extracts. Copyright © 2006 Society of Chemical Industry     

绿芦笋木质化过程中细胞壁多糖与酚类物质变化研究

以绿芦笋栽培品种Mary Washington 500为试验材料，采用HPLC分析方法，研究了常温贮藏条件下，绿芦笋细胞壁多糖、酚类物质和木质素含量的变化。结果表明，随贮藏时间延长，绿芦笋细胞壁半纤维素的主要降解物木糖、岩藻糖残基增加了211．2％，纤维素的主要降解物葡萄糖残基增加了329．3％，木质素含量增加了280．3％。木质素合成前体物中，香豆酸含量最高，其次为咖啡酸和阿魏酸，三者的含量变化与木质素合成密切相关。     

Utilisation of modified atmosphere packaging to extend the shelf life of Khalas fresh dates

Completely matured tamr stage dates are widely available and consumed throughout the year. However, for some date varieties, the earlier khalal stage crunchy fruit is considered a premium product. This work examines the use of modified atmosphere packaging to extend the shelf life of khalal dates under refrigerated conditions. Modified atmosphere packaging with 10% or 20% CO₂ in air was successful in reducing the rate of the ripening processes while control‐packaged dates showed signs of ripening development such as significant weight loss and darkening in date colour (identified visually and as low lactic acid bacteria measurements at 18 and 27 days after packaging), similar to that observed in tamr stage fruit.     

Fumonisin detection and analysis of potential fumonisin‐producing Fusarium spp. in asparagus (Asparagus officinalis L.) in Zhejiang Province of China

BACKGROUND: Fumonisins are mycotoxins produced by a number of Fusarium species, including several pathogens of asparagus plants. China is one of the largest asparagus producers in the world. In this study, we analysed the contamination of fumonisins and fumonisin‐producing fungi in asparagus spear samples from Zhejiang Province, the major asparagus production province in China. RESULTS: The asparagus did not contain a detectable level of fumonisins. However, the recovery of Fusarium in asparagus was 72.7%, including F. proliferatum (40.9%), F. oxysporum (22.7%), F. acuminatum (4.55%) and F. equesti (4.55%). A multiplex PCR targeting the internal transcribed spacer sequence (ITS), translation elongation factor 1‐α (TEF), and key biosynthetic genes FUM1 and FUM8, was used to simultaneously determine the identity and the biosynthetic ability of the fungal isolates. Fungal isolates containing the FUM genes also produced fumonisins in cultures, ranging from 28 to 4204 µg g^?1. F. proliferatum was the only fumonisin‐producing Fusarium species in asparagus. CONCLUSION: Although no fumonisin contamination was detected in asparagus in the current survey, we found that the majority of samples contained Fusarium spp. Because F. proliferatum is a high fumonisin‐producing species, potential health risks for human consumption of asparagus exist, if the appropriate environmental conditions are present for this fungus. Copyright © 2010 Society of Chemical Industry     

Effect of irradiation, active and modified atmosphere packaging, container oxygen barrier and storage conditions on the physicochemical and sensory properties of raw unpeeled almond kernels (Prunus dulcis)

BACKGROUND: The present study investigated the effect of irradiation, active and modified atmosphere packaging, and storage conditions on quality retention of raw, whole, unpeeled almonds. Almond kernels were packaged in barrier and high‐barrier pouches, under N₂ or with an O₂ absorber and stored either under fluorescent lighting or in the dark at 20 °C for 12 months. Quality parameters monitored were peroxide value, hexanal content, colour, fatty acid composition and volatile compounds. Of the sensory attributes colour, texture, odour and taste were evaluated. RESULTS: Peroxide value and hexanal increased with dose of irradiation and storage time. Irradiation resulted in a decrease of polyunsaturated and monounsaturated fatty acids during storage with a parallel increase of saturated fatty acids. Volatile compounds were not affected by irradiation but increased with storage time indicating enhanced lipid oxidation. Colour parameters of samples remained unaffected immediately after irradiation. For samples packaged under a N₂, atmosphere L* and b* values decreased during storage with a parallel increase of value a* resulting to gradual product darkening especially in irradiated samples. CONCLUSION: Non‐irradiated almonds retained acceptable quality for ca. 12 months stored at 20 °C with the O₂ absorber irrespective of lighting conditions and packaging material oxygen barrier. The respective shelf life for samples irradiated at 1.0 kGy was 12 months packaged in PET‐SiOx//LDPE irrespective of lighting conditions and 12 months for samples irradiated at 3 kGy packaged in PET‐SiOx//LDPE stored in the dark. Copyright © 2010 Society of Chemical Industry     

Effect of modified atmosphere packaging on microbial growth,quality and enzymatic defence of sanitiser washed fresh coriander

Fresh coriander samples were washed in an aqueous chlorine dioxide solution and stored in modified atmosphere packaging (MAP) with air (T0), 4%O₂ + 3%CO₂ + 93%N₂ (T1); 10%O₂ + 3%CO₂ + 87%N₂ (T2); 15%O₂ + 3%CO₂ + 82%N₂ (T3); 20%O₂ + 3%CO₂ + 77%N₂ (T4) at 4 °C for 14 days. After 14 days, the ascorbic acid contents in samples were 24.8 (T3), 22.4 (T4), 19.6 (T0), 18.2 (T2) and 8.8 (T1) mg/100 g; the total phenol contents were 59.9 (T3), 53.8 (T0), 50.1 (T4), 44.8 (T2) and 39.3 (T1) mg gallic acid/100 g; and the total chlorophyll contents were 1.60 (T3), 1.52 (T4), 1.05 (T2), 0.91 (T0) and 0.63 (T1) mg g^?1 respectively. T3 treatment resulted in the best colour maintenance, the least bacterial growth, and the highest activities of superoxide dismutase and catalase throughout the storage period as compared to others. The data revealed that the T3 MAP condition in combination of aqueous chlorine dioxide washing significantly (P < 0.05) maintained the quality and extended the shelf life of fresh coriander.     

Nutritional evaluation of mineral content changes in fresh green asparagus as a function of the spear portions

Changes in the copper, iron, zinc, manganese, nickel, chromium, calcium, magnesium, sodium, potassium and phosphorus content of fresh green asparagus (Asparagus officinalis L) according to the portion of spear considered and differences existing between varieties (Mary‐Washington and UC‐150) and thicknesses (<11 and 14 mm) asparagus were investigated. Using a three‐factors (portions, varieties and thicknesses) ANOVA and the Scheffé multiple range test (P < 0.05), statistically significant differences (P < 0.001), between the 10 portions in which the spears was cut, were observed for the 11 mineral elements investigated and the more apical portions presented, except for sodium, a higher mineral content which showed a generalised decrease when the portions were furthest away from the asparagus tip. By multivariate study of cluster between portions, the 0 apical portion (asparagus tip) was grouped separately to the rest of portions of the spear. These changes between portions involved a greater nutritional value of the apical zone spear in basis to the nutritional profile established for the mineral content. The diminishing distribution of the mineral concentration throughout the spear was also observed in the varieties and thicknesses of fresh green asparagus investigated which showed significant differences in this mineral content without these changes involved any nutritional significance since the mineral RDAs supplied were similar. Nutrient density percentages of the total fresh green asparagus are much higher than 100% for all the elements studied, except for sodium, and therefore, if the fresh green asparagus is consumed in sufficient quantities, contributes substantially to the intake of these mineral elements. © 1999 Society of Chemical Industry