Polyamines Affect Activity of Aminopeptidases from Lactobacillus sake

The effects of polyamines (agmatine, cadaverine, putrescine, spermidine and spermine) on the activity of the main aminopeptidases (AP I and AP II) from Lactobacillus sake were determined. Concentrations in the range of 1 mM caused 6–25% inhibition of AP I except for spermine (45% inhibition). Higher polyamine levels (5–10 mM), except for putrescine, exerted a stronger inhibition (20–60%) on AP I. Agmatine and putrescine also reduced AP II activity (6–25%) at concentrations of 0.1–10 mM while cadaverine did not have a notable effect. Spermidine and spermine stimulated (15–70%) the activity of AP II at concentrations >1 mM. Thus, control of polyamine levels is important because they are a potential hazard for human health and also because of their effects on aminopeptidase activity.     

Effects of post-harvest putrescine and calcium treatments on reducing mechanical damage and polyamines and abscisic acid levels during lemon storage

The role of post-harvest putrescine and calcium (at 1 mM ), exogenously applied during storage of lemon at 15 °C, in relation to fruit firmness (fruit deformation force) and peel resistance (puncture force) was investigated. Also, the levels of endogenous polyamines (putrescine, spermidine and spermine) and abscisic acid (ABA) and the colour development in mechanically damaged fruits (50 N) were studied. Fruits under putrescine and calcium treatments maintained higher firmness values and more resistance to peel rupture than control ones during storage. Treated lemons showed also less deformation when the compression force (50 N) to induce mechanical damage was applied. Treated and damaged fruits showed a decline in polyamine content while ABA and colour changed in parallel with maturation during storage. In damaged control fruits, an increase of spermine and ABA levels as a consequence of mechanical damage was observed. From the results reported, spermine and ABA could be considered physiological markers of mechanical stress. © 1999 Society of Chemical Industry     

PREVENTION OF BROWNING OF POTATO SLICES USING POLYPHENOLOXIDASE INHIBITORS AND ORGANIC ACIDS

Browning of minimally processed potato slices stored at low temperatures without active modification of the atmosphere in the storage container was inhibited by use of combinations of polyphenoloxidase inhibitors with organic acids. Slices of two cultivars‘Atlantic’and‘Russet Burbank’were dipped in solutions of various combinations of 4‐hexyl resorcinol, N‐acetyl‐cysteine and citric acid. Treated potato slices were kept in storage at 5C without browning or decrease in firmness for up to 21 days. The limiting factor in storage became visible microbial decay. Browning of slices from potatoes stored 1 month longer at 10C was also inhibited, but storage was limited to 14 days because of increased susceptibility to decay and decreased firmness with most treatments. However, no differences were found in inhibition of browning or retention of firmness of slices of the two cultivars after treatment with the combination of 0.25 M citric acid, 0.25 M N‐acetylcysteine and 0.01 M 4‐hexylresorcinol.     

Volatile and Nonvolatile Amines in Mediterranean Hake as Function of their Storage Temperature

ABSTRACT: The main amines in frozen and fresh hake (Merluccius merluccius) are the natural polyamines, spermidine. The levels of volatile and nonvolatile amines during storage of hake were strogly dependent on temperature. In samples stored at -20° only changes in dimethylamine and agmatine were found, whereas major changes were observed in samples stored at higher temperatures. Cadaverine was the major amine formed followed by histamine, putrescine and tyramine. The maximum levels of biogenic amines were lower than those reported for other fish species. Trimethylamine and biogenic amines related to hake spollage showed levels higher in fresh than in frozen samples, whereas levels of natural polyamines were not statistically different.     

Root cation exchange capacity of sugarcane: An evaluation of methods

An investigation was undertaken to select the appropriate methods and sampling times for measuring root cation exchange capacity (CEC) for four sugarcane cultivars (H50–7209, H57–5174, NCo 310 and H56–5840) grown in solution and soil culture. The three methods selected for measuring root CEC in decreasing order of differentiation between cultivars, were isotope (Ca⁴⁵) dilution method using chilled fresh roots, calcium adsorption method using chilled fresh roots and a titration method using ground dry roots. The root CEC results were expressed as CEC/weight (mEq/l00 g dry roots) and CEC/area (mEq/100 g saturated calcium nitrate solution; this measures the surface area index of the root). The range of CEC values for roots was narrow between the cultivars examined. In these experiments CEC/area were different for the four cultivars in the same order of ranking. The values of CEC/weight were large when measured at 60 days in solution culture and at 120 days in soil culture. The CEC/area for the roots of sugarcane cultivars H50–7209, H57–5174, NCo 310 and H56–584O at 60 days in solution culture as measured by isotope dilution method were 0.40, 0.45, 0.50 and 0.51 mEq/100 g saturated calcium nitrate solution, respectively.     

Quality Measurement of Intact and Fresh-cut Slices of Fuji, Granny Smith, Pink Lady, and GoldRush Apples

ABSTRACT: Development of fresh-cut apple products requires consideration of cultivars that store well as both intact and fresh-cut fruit. We compared the instrumental and sensory quality of 2 apple cultivars, Granny Smith and Fuji, that are used for fresh cutting with 2 new cultivars, Pink Lady and GoldRush, which were considered to have quality characteristics suitable for fresh cutting. Firmness, titratable acidity (TA), soluble solids content (SSC), and aromatic volatile concentration were measured in intact fruit of the 4 cultivars during 12 mo storage in air at 0 °C and during 3 wk storage at 5 °C as fresh-cut slices. After 1 wk storage as fresh-cut slices, sensory evaluations for acceptability of flesh and peel appearance, flavor, texture, and overall eating quality were performed. During storage, GoldRush apples maintained > 80 N firmness, approximately 17% SSC, > 0.5% TA, and had high aromatic volatile production, that is, maintained quality better than the other cultivars. The quality and shelf stability of GoldRush slices were also as good as or better than slices from the other cultivars, whereas Granny Smith slices generally rated lower than the other cultivars. The acceptability of flavor, texture, and overall eating quality of GoldRush slices was as good as that for Pink Lady and Fuji. The quality of GoldRush apples can be maintained throughout the year in refrigerated air storage and still remain suitable for fresh-cut processing. The results indicate that GoldRush and Pink Lady are 2 promising new, high-quality apple cultivars for fresh cutting. Keywords: fresh-cut fruit, Malus × domestica , postharvest quality, respiration rate, shelf life     

Cutting Shape and Storage Temperature Affect Overall Quality of Fresh-cut Papaya cv. 'Maradol'

: The effect of cutting shape (cubes or slices) and storage temperature (5 °C, 10 °C, and 20 °C) on overall quality of fresh‐cut papaya were investigated. CO₂ production, color, firmness, total soluble solids (TSS), weight loss, overall quality, ascorbic acid, β‐carotene, and antioxidant capacity were evaluated as a function of shelf life. CO₂ production was high on day 0 for cubes and slices with an average of 150 and 100 mL/ kg/h, respectively. Storage temperature did not affect color changes; however, lower temperatures prevented loss of firmness. Fresh‐cut papaya stored at 20 °C showed the lowest TSS value and the highest weight losses. Shelf life based on visual quality ended before significant losses of total ascorbic acid, b‐carotene, and antioxidant capacity occurred. In general, quality parameters were not affected by shape. However, slices stored at 10 °C and 5 °C had a shelf life of 1 d and 2 d longer than cubes, respectively.     

Plum Storability Improved after Calcium and Heat Postharvest Treatments: Role of Polyamines

ABSTRACT: Plums were treated with calcium or heat (45°C) and then stored at 2°C for 28 d. Fruit firmness, ethylene, and CO₂ production rates were investigated. The concentrations of endogenous polyamines (free, conjugated-soluble, and cell wall-bound) were also studied. Both treatments improved fruit firmness by increases in Magness-Taylor force and force-deformation ratio, and decreases in flesh deformation. No differences were found in either ethylene or respiration rate production among fruits due to the low storage temperature. Calcium-treating plums increased the conjugated forms of putrescine (conjugated-soluble and cell wall-bound), which are related to higher firmness. Heat-treated plums mainly increased cell wall-bound spermidine, inducing a greater cell wall stability and plum firmness.     

A survey on free biogenic amine content of fresh and preserved vegetables

A survey on free biogenic amine contents in fresh and preserved vegetable products was carried out. A simple extraction method, involving an homogenisation step with 0.1 M HCl, was applied. Two different derivatization procedures (using o-phthaldialdehyde and dansyl chloride) were applied on different aliquots of the same acid extracts and HPLC analyses were carried out with the same reversed phase (C18) HPLC column. Results obtained with the two procedures were compared. With the exception of sauerkraut, putrescine (0.2–0.5 mg/100 g fresh weight) and spermidine (0.4–4.5 mg/100 g) were always the most represented amines, generally followed by spermine (maximum 1.1 mg/100 g). Tyramine level was 4.9 mg/100 g in canned sauerkraut while other samples presented levels not exceeding 1.2 mg/100 g. The spinach sample showed the highest histamine content (2.0 mg/100 g).     

Effects of variety, ripening condition and ripening stage on the quality of sulphite-free dried mango slices

The influence of cultivar and fruit ripeness on sensory properties and all-trans-β-carotene contents of dried mango slices was evaluated. Different ripeness stages, quantitatively defined by a ripening index (RPI), were generated from a single lot per cultivar by subjecting mature-green mangoes of the cultivars ‘Nam Dokmai’, ‘Kaew’, and ‘Chok Anan’ to different postharvest ripening regimes. Fruits were ripened for 2 and 3 days at 24±2 °C/45–60% relative humidity (RH) and 33±2 °C/50–70% RH, with application of calcium carbide (CaC₂) or 2-chloroethylphosphonic acid (CEPA, Ride^®) beside the control, terminating postharvest ripening when fruit firmness allowed proper peeling and slicing. After ripening, fruits were washed, peeled, sliced and subsequently dried in a conventional tray dryer at 70 °C for 8–10 h, until the water activity of the dried fruits was below 0.65. Mangoes cv. ‘Kaew’, followed by ‘Chok Anan’, were more suitable for drying than cv. ‘Nam Dokmai’ because of superior all-trans-β-carotene contents of the products. Maximum β-carotene contents of dried mango slices from cvs. ‘Chok Anan’ and ‘Kaew’ corresponded to retinol equivalents of 333–383 and 483–905 per 100 g of edible portion (dry weight), meeting daily mean requirements of vitamin A for adults according to FAO/WHO. Similar to the fresh fruit, exponential rise of all-trans-β-carotene contents with increasing fruit ripeness was also observed for the dried products of cvs. ‘Nam Dokmai’ and ‘Chok Anan’. Consistently, accelerated ripening at 33 °C, instead of 24 °C, resulted in higher all-trans-β-carotene contents of dried fruits. Both good sensory acceptance and cultivar-specific maximum all-trans-β-carotene contents of 13–16 and 20–23 mg kg^?1 usually characterised the products of ‘Nam Dokmai’ and ‘Chok Anan’ fruits with RPI levels between 3 and 4. Conversely, fruits cv. ‘Kaew’ of RPI levels above 6 generally yielded products inferior in sensory acceptance and β-carotene contents, while superior product quality was found at higher RPI levels than for the other two cultivars.     

COMPARISON OF QUALITY CHARACTERISTICS OF THREE NONMELTING CLINGSTONE PEACH SELECTIONS

The effect of maturity and ripening on the quality characteristics of three nonmelting clingstone peach cultivars was compared. In general, size, weight, Minolta “a” values and SS/TA increased significantly with increased degree of maturity of fruit as harvested; whereas, firmness, hue angle, acidity and total pectins decreased significantly. Ripening for 7 days at 20C resulted in softening of L9-A47–33 and Babygold 7 peaches but had no significant effect on the firmness of FLA 9–20C. Ripening appeared to have little effect on the chemical characteristics of all three cultivars except for water soluble pectin, which increased slightly. L9-A47–33 peach selection was significantly more fruity, peachy, sweet, juicy and had a higher overall acceptance score than Babygold 7 or FLA 9–20C, indicating it might have potential for fresh market use.     

Nitrate Analysis in Meats; Comparison of Two Methods

A high performance liquid chromatographic method (HPLC) was compared to cadmium reduction-Griess (Cd-Griess). Nitrate and nitrite were measured in fresh and cured meats. Nitrate levels by HPLC ranged from 6.2 to 26.7 nmol/g in fresh meats and from 124 to 3018 nmol/g in cured meats. Nitrate contents by HPLC were significantly higher (p<0.05) than those by Cd-Griess. Small amounts of nitrite (0–7.3 nmol/g) were detected in fresh meat samples by Cd-Griess. Results were similar to those used by the National Academy of Sciences to estimate human exposure to nitrate from fresh meats. Results from HPLC methods may provide more accurate estimates of human exposure to nitrate and nitrite.     

EFFECT of HEAT TREATMENT ON FIRMNESS of APPLES and APPLE SLICES

Effects of heat treatment on firmness of apples (Golden Delicious, McIntosh and Delicious) and apple slices were studied. Heat treatment (45C, for 1.75 h) of Golden Delicious and Delicious apples significantly increased their firmness, but no significant increase was observed for the McIntosh cultivar. After storage for 7 days at 2C, the treated apples were firmer than those stored at 10, 18, and 25C. Apple slices prepared from the heat treated apples were also firmer at 21 days storage than those prepared from nontreated apples: differences ranging from 12% for McIntosh to 48% for Delicious. This beneficial firming effect of heat treatment might have application in producing high quality minimally processed slices from Golden Delicious and Delicious apple cultivars.     

Effects of Postharvest Putrescine Treatment on Extending Shelf Life and Reducing Mechanical Damage in Apricot

ABSTRACT: Apricots ( Prunus armeniaca L. cv Mauricio) harvested at commercial ripening stage were treated with putrescine (1 mM), then mechanically damaged with a 25 N force and stored at 10 °C for 6 d. Putrescine treatment increased fruit firmness and reduced the bruising zones caused by the mechanical damage. Putrescine-treated fruits (both damaged and nondamaged) showed different physiological behavior than controls. Color change, weight loss, ethylene emission, and respiration rate were reduced in putrescine-treated fruits. The most remarkable effect of the mechanical damage was the significant increase in spermidine concentrations found after the compression in control apricots, which could be considered as a physiological marker of mechanical damage.     

Inorganic Cations and Polyamines Moderate Pectinesterase Activity

Inorganic and organic cations influenced pectinesterase (PE) activity and solubilization from Marsh grapefruit pulp. Activity increased to 281%, 183%, and 130% with lead acetate (6.8 mM), ferric chloride (0.2 mM), and calcium chloride (20 mM), respectively. The polyamines, putrescine, spermidine, and spermine had negligible stimulating effect. All cations tested inhibited PE activity at higher concentrations. Solubilization of total PE was decreased and thermostable PE (TS-PE) was not affected by polyamines. There was a progressive decline in total PE activity above 1.6 mM spermidine, 7.6 mM putrescine and 20.0 mM spermine. Loss of activity upon solubilization suggests that the TL-PE-pectate complex stabilized TL-PE. No change in TS-PE activity suggests that it may be bound with greater affinity, physically entrapped, or non-electrostatically bound.     

Identification,quantification and comparison of the principal bioactive compounds and external quality parameters of two broccoli cultivars

In this research work, we aim to identify, quantify and compare the phytochemical such as vitamin C, carotenoid and chlorophyll pigments, phenolic compounds and intact glucosinolates, as well as the in vitro antioxidant activity and physical quality parameters (colour, firmness, moisture contents, weight/broccoli head and soluble solid contents) of Monaco and Parthenon broccoli cultivars. We found that the bioactive compounds were more abundant in Parthenon compared with Monaco. In fact, higher amount of chlorophylls (12.62 mg/100 g fresh weight), total phenolic compounds (147.15 mg chlorogenic acid equivalent/100 g fresh weight), and total intact glucosinolates (203.85 μmol of sinigrin equivalent/100 g fresh weight) were found in Parthenon. On the other hand, no significant differences were observed in terms of external quality parameters among the studied cultivars except in the colour and moisture contents.     

Canning Quality Evaluation of Pinto and Navy Beans

Thermal processing of pinto and navy beans at 121.1°C for 16 or 14 min in a still retort gave similar sterilization value (F_o= 10) as the processing at 115.6°C for 45 min. The 121.1°C/16 or 14 min process produced beans with greater firmness than the 115.6°C/45 min process. The addition of CaCl₂ and EDTA improved firmness and color of canned beans. Calcium chloride also reduced clumping and splitting of the canned beans. Sensory evaluation showed that the acceptability of canned beans was reduced when CaCl₂ was increased up to 10 mM. High correlation between firmness and soluble pectin in various bean cultivars implied that soluble pectin content could be used as a parameter for screening bean cultivars with desirable firmness.     

Cultivar Effects on Quality of Fresh Cut Apple Slices from 1-Methylcyclopropene (1-MCP)-Treated Apple Fruit

ABSTRACT: The effects of 1 -methylcyclopropene (1 -MCP) treatment of whole fruit on the subsequent quality and shelf-life of fresh-cut apple slices have been investigated. 'Delicious,' Empire, 'Idared', Law Rome, and 'Mutsu' apples were treated at 0.5°C with 1 μL/L of 1 -MCP for 24 h and stored in air 1 and 4 mo before being used for preparation of slices. 1-MCP reduced internal ethylene concentrations and maintained firmness of the whole fruit in'Delicious,' Empire, and 'Idared', but not consistently for 'Law Rome' and 'Mutsu.' Slices prepared from fruit of cultivars that responded to 1 -MCP had lower ethylene production rates and were firmer than those from untreated fruits. However, 1-MCP treatment did not consistently affect the extent of browning or aroma volatile concentrations. In cultivars in which treatment of apples with 1-MCP at harvest maintained the original fresh quality of intact fruit by suppressing ethylene production, fruit were firmer, and thus a superior fresh- cut product with an extended shelf-life potential was obtained. However, in general, slices prepared from untreated and 1-MCP-treated fruit deteriorated at similar rates.     

采后多胺处理对杏果实黑斑病的控制及贮藏品质的影响

以兰州大接杏果实为原料,研究了采后外源多胺处理对杏果实黑斑病的控制效果及对贮藏品质的影响。结 果表明采后多胺处理能显著抑制果实黑斑病的扩展,有效提高果实的抗病性,且控制效果存在多胺种类和浓度效 应,其中1.5 mmol/L精胺、1.5 mmol/L亚精胺和10 mmol/L腐胺的效果最佳,其病斑直径分别较对照减少了38.0%、 26.6%和34.2%。同时采后多胺处理能降低杏果实质量损失率,延缓硬度下降,抑制果实的呼吸强度和乙烯释放量 的升高,并且能有效延缓果实可溶性固形物含量的下降和颜色的变化。可见,多胺在杏果实防腐保鲜上具有较好的 应用前景。     

Flavonoid constituents and antioxidant capacity in flowers of different Zhongyuan tree penoy cultivars

Flavonoid components in flowers of 48 Zhongyuan tree penoy cultivars were identified by means of a hyphenated technique of HPLC coupled with a photodiode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESIMS). The total phenolic content (TPC) was determined by Folin–Ciocalteu method and the antioxidant activity with both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. About 14 flavonoids including five anthocyanins, three flavonol glycosides and six flavone glycosides were described. Apigenin-pento-hexoside and Apigenin-hexo-glucuronide were reported for the first time. TPC, expressed as gallic acid content, varied between 3.97 and 21.73 mg/g fresh weight. Antioxidant activity varied among the cultivars (7.66–31.36 and 4.80–17.87 mg ascorbic acid equivalents/g fresh weight for DPPH and FRAP assays, respectively) and highly corresponded with TPC.