KINETICS OF HEAT/ENZYMIC DEGRADATION OF ASCORBIC ACID IN FLUTED PUMPKIN (Telfairia occidentalis) LEAVES

Thermal/enzymic degradations of ascorbic acid in whole, chopped and pureed fluted pumpkin leaves were studied from 60 to 100C (5–60 min). Degradation of ascorbic acid followed first order kinetics with the rate constants having maximum values at 80–90C. Ascorbic acid degradation exhibited strong deviation from linearity in thermal resistance, Arrhenius and absolute reaction rate plots at 100C indicating inactivation of the oxidative enzymes around 90C. At lower temperatures (60–90C) ascorbic acid was more stable in the whole and chopped leaves than in the pureed system. Activation energies ranged from 49 to 50.8 KJ mol⁻¹. At 100C, the puree matrix offered more protection to ascorbic acid.     

ANALYSIS OF NATURALLY OCCURRING PHENOLIC COMPOUNDS IN AROMATIC PLANTS BY RP-HPLC AND GC-MS AFTER SILYLATION

Aromatic plants of Greek origin, Origanum dictamnus (dictamus), Eucalyptus globulus (eucalyptus), Origanum vulgare L. (oregano), Mellisa officinalis L. (balm mint) and Sideritis cretica (mountain tea) were examined for the content of phenolic substances. Reversed phase high performance liquid chromatography was used for the analysis of the plant extracts. Gas chromatography–mass spectrometry method was also used for identification of phenolic compounds after silylation. The most abundant phenolic acids were gallic acid (1.5–2.6 mg 100 g ^{− 1} dry sample), ferulic acid (0.34–6.9 mg 100 g ^{− 1} dry sample) and caffeic acid (1.0–13.8 mg 100 g ^{− 1} dry sample). ( + )-Catechin and ( − )-epicatechin were the main flavonoids identified in oregano and mountain tea. Quercetin was detected only in eucalyptus and mountain tea.

PRACTICAL APPLICATIONS

Plant-derived polyphenols receive considerable interest because of their potential antioxidant and antimicrobial properties. Undoubtedly, it is very important not only to determine those properties but also to determine each and every phenol in aromatic plants both qualitatively and quantitatively. A number of analytical methods have been proposed for the separation and determination of these compounds. Most of these protocols are based on a high performance liquid chromatography technique with ultraviolet spectrophotometry. Gas chromatography–mass spectrometry after silylation of the phenolic compounds is used in this research together with the aforementioned technique as an alternative and more sensitive method to detect and understand the compositional profile of the extracts as well as the structure and functional relationship of the components in the extracts, based on MS spectra.     

ASCORBIC ACID AND RIBOFLAVIN CONTENT OF ASPARAGUS DURING MARKETING

California-grown asparagus purchased from wholesale markets and retail stores in the greater New York area 6 to 9 days after harvest, and California asparagus purchased at retail stores in the greater New York area then stored 3 days at 5.5 °C and 90–95% relative humidity to simulate consumer holding were analyzed for total ascorbic acid (AA), L-ascorbic acid, dehydroascorbic acid (DHAA) and riboflavin content. Asparagus from wholesale markets, retail stores and storage averaged 15, 10, and 9mg AA/100g freshweight, respectively. The average was 77% less than reported in freshly harvested California asparagus. Samples of asparagus from wholesale markets contained significantly more AA than were found in retail or stored samples. Riboflavin content in asparagus from wholesale, retail and storage levels were .030, .029, and .033 mg/100g freshweight, respectively. These values were not statistically different, and were on the average 79% less than those reported for fresh California asparagus. DHAA ranged from 1.5 mg/100g freshweight in asparagus purchased from wholesale markets to 3.0 mg/100g freshweight in stored asparagus. Sixteen percent of the total AA in samples of wholesale, retail and stored asparagus was oxidized to DHAA. Thus it is questionable whether or not L-ascorbic acid is a good indication of the total vitamin C in asparagus purchased at terminal markets.     

Evolution of ascorbic acid and peroxidase during industrial processing of broccoli

The ascorbic acid content and peroxidase activity of raw, canned and frozen (after blanching times of 60, 90, 120 and 150 s) broccoli florets and stems were determined. The ascorbic acid content represented 1.12 and 0.78 g kg⁻¹ fresh weight in raw florets and stems respectively. After blanching (for different times) and freezing, the ascorbic acid content decreased to values of 0.55–0.56 g kg⁻¹ fresh weight in florets and 0.35–0.36 g kg⁻¹ fresh weight in stems. The industrial processing involved in canning decreased the ascorbic acid content to 0.18 g kg⁻¹ fresh weight in florets. The peroxidase activity observed in the florets and stems of raw broccoli was 308.8 and 278.6 µmol min⁻¹ per 100 g fresh weight respectively. The peroxidase activity remaining in frozen florets varied from 0.9 to 0.2%, while that in stems showed values of between 7.5 and 8.4%. These values for stems were within the range recommended for residual activity after blanching and freezing. The peroxidase activity of canned broccoli florets was practically undetectable. © 2000 Society of Chemical Industry     

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).     

Determination of Anthocyanins, Total Phenolic Content, and Antioxidant Activity in Andes Berry (Rubus glaucus Benth)

ABSTRACT:  Anthocyanins, total phenolic content, ascorbic acid content, and the antioxidant activity were determined in extracts of Andes berry fruit ( Rubus glaucus Benth). Anthocyanis (ACNs) were isolated and characterized by means of high-performance liquid chromatography (HPLC) with photodiode array detection and electro spray ionization/mass spectrometry (PDA-ESI/MS/MS) analysis. The anthocyanin (ACN) content was 45 mg/100 g FW. The isolated anthocyanins were characterized as cyanidin 3-sambubioside, cyanidin 3-glucoside, cyanidin 3-xylorutinoside, cyanidin 3-rutinoside, pelargonidin 3-glucoside, and pelargonidin 3-rutinoside. The ascorbic acid content was 10.1 mg/100 g FW. The total phenolic content as determined by the Folin–Ciocalteau method was 294 mg GAE/100 g FW while the antioxidant activity as measured by ABTS ^{· +} radical scavenging capacity and ferric reducing antioxidant power (FRAP) was 2.01 and 4.50 mmol TE/100 g FW or 8.22 mmoles ferric iron reduced/100 g FW, respectively. The high phenolic content and antioxidant capacity of Andes berry suggest that this fruit could be a rich source of natural pigments, nutraceuticals, and natural antioxidants.     

EFFECT OF ALKALI AND ALKALI-EARTH HALIDES ON TEXTURE AND COOKING YIELD OF COOKED COMMINUTED LEAN PORK

The effects of alkali-and alkali-earth halides and sulfates on the texture and cooking yield of cooked lean comminuted pork were examined. Divalent cations (Ca²⁺ and Mg²⁺) associated with Br⁻, I⁻ and SO^2-₄ imparted a firm texture to meat (peak force values of 17.1–21.1 kg as compared to 8.4 kg for the control sample devoid of any added salt). Peak force values of samples containing monovalent cations were generally low, but for most cases, were higher (P < 0.05) than that of the control. The cooking yields of samples containing divalent cations (regardless of their anion counterparts) were not different (P>0.05) from that of the control. At 200 meq/kg sample, iodides of monovalent cations as well as sodium chloride increased the cooking yield by approximately 5–20% compared to the control.     

EFFECT OF APPLE DECAY PROPORTION ON THE PATULIN, FUMARIC ACID, HMF AND OTHER APPLE JUICE PROPERTIES

Starking apples, classified by the decay proportion on the fruit surface as sound, 30, 60 or 100% decayed were used in the production of apple juice. Then patulin, fumaric acid, HMF, pH, brix and Hunter L, a and b values of apple juice samples were determined. Patulin and fumaric acid analysis were done with HPLC. The patulin concentration in juice samples produced with Starking apples that are sound, 30, 60 and 100% decayed ranged between 0.0–15.9 μg/kg, 47.1–500.3 μg/kg, 156.4–2257.5 μg/kg, 54.9–2508.6 μg/kg, respectively. The fumaric acid concentration in the same juice samples ranged between 0.00–0.20 mg/kg, 0.23–0.69 mg/kg, 0.41–2.08 mg/kg and 1.40–4.14 mg/kg. In general, the color values (L, a, b) of the samples produced from 100% decayed apples measured by reflectance with a Hunter colorimeter were low when compared with the others.     

ANTIOXIDANT ACTIVITY AND QUALITY OF SOY ENRICHED APPLE BAR

Antioxidant activity of a soy enriched apple bar (SEAB) prepared from the pulp of culled apples and soy protein isolate (3%) was determined using a ferric reducing antioxidant power (FRAP) assay. The antioxidant activity was 8500 μM g⁻¹ FRAP and phenol content was 175 mg 100 g⁻¹. The soy enriched apple bar had 20 fold protein and 1.6 fold higher antioxidant activity than the plain apple bar. No significant change in antioxidant activity and total phenols was recorded during storage at ambient (22–31C) or low (4±1C) temperatures. The pectin, protein and ascorbic acid contents decreased while nonenzymatic browning and total sugars increased significantly with increase in storage periods. The product was organoleptically acceptable and microbiologically safe after 180 days of storage. A shelf stable soy enriched apple bar with high antioxidant activity, phenol content and sensorial quality can be an ideal source of dietary antioxidants.     

ANTIOXIDANT POTENTIAL OF DESI CHICKPEA VARIETIES COMMONLY CONSUMED IN PAKISTAN

Antioxidant potential of four Desi chickpeas ( Cicer arietinum L.) varieties indigenous to Pakistan, namely Balksar 2000, CM98, Dasht and Winhar 2000, was evaluated. All studied varieties exhibited appreciable total phenolic content (0.92–1.12 mg gallic acid equivalents/g), total flavonoid content (0.79–0.99 mg catechin equivalent [CAE]/g) and condensed tannin content (0.58–0.69 mg CAE/g). In addition, antioxidant activities were tested using 2,2-diphenyl-1-picrylhydrazyl radical (1.05–1.24 µmol trolox/g), 2,2 ' -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (37.24–45.32 µmol trolox/g), ferric-reducing antioxidant power (0.73–0.90 mmol Fe^{2 +} equivalents/100 g) and oxygen radical-absorbing capacity (8.58–11.4 µmol trolox/g). All varieties exhibited appreciable antioxidant potential and significant differences ( P <  0.05) were observed among the varieties in different systems of antioxidant activity evaluation. The results of the present analytical study showed Desi chickpea ( C. arietinum L.) indigenous to Pakistan to be a potentially valuable legume crop with high antioxidant potential.

PRACTICAL APPLICATIONS

The analytical findings of this study provide a regional database for this valuable legume crop, which has not been explored so far. The data obtained will be useful to both producers and consumers. Chickpeas may be used as functional ingredients for processing into health foods in the food industry.     

Some effects of modified-atmosphere packaging and vacuum packaging in combination with antioxidants on quality and storage life of chilled potato strips

A modified-atmosphere packaging system for chilled fresh potato strips, which rapidly produced oxygen levels < 3%, was identified. This system enclosed the strips within 25 μ low density polyethylene film heat sealed to a fibre tray lined with Surlyn-PVdC-Surlyn, and the package flushed with an initial atmosphere of 5% O₂, 10% CO₂. An equilibrium-modified atmosphere of 3–4% CO₂, 1–2% O₂ was established after 3 days' storage at 5°C. This modified-atmosphere package, used in combination with dipping of potato strips in a 10% ascorbic acid solution, inhibited enzymatic discoloration for 1 week at 5°C. Vacuum packaging within a Surlyn/PVdC-coated polyester film, with or without dipping in ascorbic acid solution, inhibited discoloration of chilled potato strips stored at 5°C for at least 2 weeks.     

PURIFICATION AND CHARACTERIZATION OF POLYPHENOL OXIDASE FROM POTATO: II. INHIBITION AND CATALYTIC MECHANISM

KCN and ascorbic acid showed competitive inhibition patterns with K_is values of 0.032 and 0.27 mM, respectively. Uncompetitive inhibition patterns were obtained with sodium azide, L-cysteine and NaCl with K_ii values of 3.3 mM, 0.12 mM and 0.3 M, respectively. A noncompetitive inhibition pattern was obtained for thiourea with 0.067 mM for K_is and 0.59 mM for K_ii. Cu₂⁺ increased the activity about 2.5 fold at or above 40 μM and K⁺ decreased the enzyme activity about 33% at 0.4 M. Other metal ions did not have any effects on the activity. Two pK values of 5.8 and 8.0 were obtained from V_max profile and two pK values of 5.9 and 8.1 from V_max/K_m profile. The data suggest that cysteine is likely to be involved in catalysis and histidine in binding. Data from chemical modification show that cysteine was completely inactivated at 1.74 mM o-methylisourea, and histidine and tryptophan were modified at much higher concentrations of diethylpyrocarbonate and N-bromosuccinimide, respectively. It is suggested that the protonated cysteine works as a general base, tryptophan as a substrate binding residue and histidine as a oxygen binding residue.     

SIMULTANEOUS DIFFUSION of CITRIC ACID and ASCORBIC ACID IN PREPEELED POTATOES

The study of the simultaneous diffusion of chemical preservatives in vegetable tissues permits the determination of the time required to complete this process and the concentration distributions of the preservatives.
The individual or simultaneous diffusion of citric and ascorbic acids in pre-peeled potatoes was analyzed; the effect of pH decrease on the diffusive flux of ascorbic acid and the interaction between both acids was considered as the multicomponent diffusion problem.
Potato spheres of different radii were immersed in individual solutions or mixtures of citric and ascorbic acids in concentration ranging from 0.5% to 2% W/V for different immersion times and agitation conditions. the residual concentration of citric acid was determined by titrable acidity (22058 AOAC method) and that of ascorbic acid by 2–6 dichlorophenol-indophenol method.
Experimental data were fitted to the mathematical models and the effective diffusion coefficients were determined for citric (D_e= 4.3 ± 0.2 × 10⁻¹⁰ m²/s) and ascorbic acids (D_e= 5.45 ± 0.4 × 10⁻¹⁰ m²/s) diffusing individually. When mixtures of two acids were used, multicomponent analysis was adopted and interaction coefficients were evaluated (D₁₂= 6.67 ± 0.8 × 10⁻¹¹ m²/s and D₂₁= 8.33 ± 0.8 × 10⁻¹¹ m²/s); they were an order of magnitude lower than binary diffusion values.
The pH effect on the diffusive flux of ascorbic acid was decoupled from the interaction of both acids during simultaneous diffusion by studying the diffusion of the first acid in potatoes preacidified with the second acid.     

LOW TEMPERATURE BLANCHING OF FROZEN CARROTS WITH CALCIUM CHLORIDE SOLUTIONS AT DIFFERENT HOLDING TIMES ON TEXTURE OF FROZEN CARROTS

The objective of this study was to evaluate the effect of low temperature blanching in calcium chloride solutions to increase firmness retention of frozen carrot slices and to determine optimum conditions to provide a final product with maximum firmness. Low temperature (65 C) blanching in CaCl² solutions (0.05–0.6 molar) for holding times (5–90 min) was performed on carrots 'Apache' cultivar. Calcium absorption was affected (P≤0.05) by the CaCl² concentration. Behavior of this variable was adequately fitted by a second order model (R²=0.99). Firmness was affected (P≤0.05) by the CaCl² solutions and holding times. Optimum conditions gave extrusion forces of 1693–2095 N and calcium levels of 69–144 mg/100 g. These were verified experimentally and agreed closely with predicted calcium absorption and firmness values.     

Mesophilic Aerobic Population of Fresh-cut Spinach as Affected by Chemical Treatment and Type of Packaging Film

ABSTRACT: Fresh-cut spinach was treated with citric acid and ascorbic acid solutions and packaged in mono-oriented polypropylene bags or low-density polyethylene bags. Response surface methodology was used to study the simultaneous effect of chemical treatment and refrigerated storage time on headspace gas composition, mesophilic aerobic population (AP), and pH of fresh-cut spinach. Type of film affected %CO₂, %O₂, and pH but did not influence AP. Chemical treatment reduced initial pH values and initial microbial counts. AP and pH increased during refrigerated storage. The model developed for AP enabled finding acid concentrations that lowered AP below any proposed microbiological criterion at production and consumption stages of fresh-cut spinach stored at 4 °C.     

The impact of both the season of collection and drying on the volatile constituents of Origanum vulgare L. ssp. hirtum grown wild in Croatia

Samples of Origanum vulgare ssp. hirtum were collected from the same geographic area in the south of Croatia at different seasons of growth. The maximum fluctuations found for the main components from fresh plant material were: thymol [149.2–1124.4 mg (100 g)^–1], carvacrol [51.6–564.3 mg (100 g)^–1], p-cymene [20.2–220.9 mg (100 g)^–1] and γ-terpinene [50.1–217.5 mg (100 g)^–1]. The oregano that was analysed belonged to a thymol/carvacrol chemotype. The season of collecting affected the qualitative and quantitative composition of the essential oil. The most impressive difference was the increase of p-cymene content in August. After the drying of the plant material, all samples showed a minor decrease in essential oil yields when compared with fresh plants. Drying, at room temperature, had no effect on the qualitative composition of oregano oil. Because of the variability of essential oil compositions from seasonally collected fresh and dried oregano, it would be important to check the quantity and quality of such components before usage.     

HYGIENIZATION OF INDIAN CHICKEN MEAT BY IONIZING RADIATION

Both fresh and frozen chicken meat were evaluated for microbiological status by screening for total bacterial counts and for the presence of pathogens like Enterobacteria , Bacillus cereus, coagulase positive Staphylococci and Salmonella spp. Most of the samples exhibited heavy bacterial contamination (1.2 × 10⁵ - 2.6 × 10⁶/g), mainly with Staphylococcus spp. (1.5 × 10⁴ - 2.8 × 10⁵/g). All the chicken samples also showed the presence of Salmonellae (3 × 10¹ - 2.1 × 10²/g). Among the different serotypes observed in chickens . S. typhimurium was common in fresh as well as frozen chicken. Radicidation at 2 kGy at cryogenic conditions (−40°C) was efficient in eliminating the natural pathogenic contamination of the poultry . Salmonella spp. viz. S. seftenberg and S. typhimurium differed in radiation sensitivity, the D₁₀ values in phosphate buffer (pH 7.2) being 0.25 kGy and 0.12 kGy, respectively. Chicken homogenate (10%) offered approximately 2-fold protection to these cells. Chicken samples artificially inoculated with a heavy inoculum (10⁸ cells/g) of these 2 serotypes required higher gamma radiation doses of 4–5 kGy. The findings suggested that a dose of 2 kGy is adequate for normally contaminated chicken samples, but for the heavily contaminated chicken a dose of 4–5 kGy, depending upon the predominating Salmonella serotype present, is required .     

NUTRITIONAL AND SENSORY SURVEY OF CITRUS SINENSIS (L.) CULTIVARS GROWN AT THE MOST NORTHERN LIMIT OF THE MEDITERRANEAN LATITUDE

ABSTRACT

This report describes Citrus sinensis fruit grown in the Lake Maggiore area (Italy), the upmost Northern distribution range of the genus Citrus in Europe. Total ascorbic acid (TAA), bioflavonoids, total polyphenol content (TPC), antioxidant activity, total soluble solid, total acidity and sensory characteristics were evaluated on oranges harvested during the 2009–2010 season. The range of values detected was as follows: TAA from 36.89 to 67.34 mg/100 mL, hesperidin from 18.97 to 31.87 mg/100 mL, narirutin from 17.30 to 29.28 mg/100 mL and rutin from 4.39 to 5.36 mg/100 mL; antioxidant activity (ferric reducing antioxidant power assay) from 8.62 to 17.00 mmol Fe²⁺/kg, fresh fruit weight; TPC (Folin–Ciocalteu method) from 87.16 to 135.16 mg GAE/100 g. This first attempt to characterize cultivars grown in the Piedmont region showed that these oranges had acceptable nutritional components and sensory quality, if compared with bibliographic data about cultivars grown in the subtropical and Mediterranean area.

PRACTICAL APPLICATIONS

The identification, characterization and valorization of old cultivars are essential to avoid loss of potentially useful germplasm. The reduction of biodiversity of cultivars found in agriculture could lead to problems such as higher susceptibility to widespread outbreaks of plant diseases and pests, and at the same time, the loss of precious source of nutrients. This survey was carried out to characterize a germplasm that could also be used in breeding programs to obtain new cold‐tolerant varieties.     

DETERMINATION OF CARBOXYMETHYLCELLULOSE IN FOOD PRODUCTS

SUMMARY –A method was developed to determine sodium carboxymethylcellulose (CMC) in food products containing three or more hydrocolloids after prior removal of interfering substances. Papain was used to digest the proteins; calcium chloride was added to precipitate algin and pectic acid and sulfated hydrocolloids were then precipitated by cetylpyridinium chloride (CPC) in the presence of 0.5M NaCl. Celite 535 or Hyflo Super Cel was added, the mixture filtered over Reeve angel No. 202 paper and the residue washed with 0.01% CPC-0.01M NaCl. The filtrate and washings were collected and diluted with distilled water to attain a final concentration of 0.2M NaCl at which concentration the CMC was precipitated selectively by CPC. The mixture was filtered over a Celite 535 or Hyflo Super Cel column and the residue washed with 0.5M Na₂SO₄ and then with 0.01% CPC-0.01M NaCl until the washings were negative to the phenol-H₂SO₄ reagent. Finally, the residue on the column was washed with hot 30% H₂SO₄ and the hydrolyzed CMC in the eluate determined by the 2,7-naphthalenediol test. Based on the amount added to mixtures, recoveries of 75–86% were obtained from milk and other highly complex and proteinaceous products, with a standard deviation of ± 0.58 mg, when 10 mg of CMC were added. The determination is critically dependent upon the degree of substitution (DS) of the CMC. As a consequence, the method cannot be applied with absolute certainty to unknown samples.     

ANTIMICROBIAL PROPERTIES OF LAURICIDIN IN MECHANICALLY DEBONED CHICKEN, MINCED FISH AND CHICKEN SAUSAGE

Aerobic plate counts on Plate Count Agar at 25°C were used to determine the time required to reach a microbial spoilage level of 1.0 × 10⁷ C.F.U./g, for mechanically deboned chicken meat, minced fish and chicken sausage stored at 2°C. The storage times were 5, 8 and 9 days, respectively. Addition of citric acid (0.2%), ascorbic acid (0.2%) or lauricidin (250 ppm) alone extended the shelf-life by 0–2 days. The combination of lauricidin and citric acid or lauricidin and ascorbic acid extended the time required to reach a microbial spoilage level for mechanically deboned chicken meat by as much as 7 days, minced fish by as much 4 days and chicken sausage by 8 days.