Pietro Santamaria

A survey of nitrate and oxalate content in fresh vegetables

A survey of nitrateONO ˇU and oxalate ((COO ˇ )2) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995). A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, inflorescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard. # 1999 Society of Chemical Industry The presence of nitrate in vegetables, as in water and generally in other food products, is a serious threat to mans health, although recent research has shown that nitrate also has beneficial effects on health related to its role in the bodys mechanism against pathogenic micro-organisms. 3 The harmful effects of nitrate are related not so much to its toxicity, which is low, but to the dangerous compounds that are synthesised in the organism. Indeed, the most serious danger comes from nitrite which is produced by nitrate reduction and which can lead to methaemoglobinemia or form nitrosamines and nitrosamides by reacting with amines and amides, whose carcinogenic action is well known. 4,5

Nitrogen nutrition, yield and quality of spinach

When grown in solution culture spinach plants confirmed the preference toward NO 3 - nutrition and showed heavy toxicity to NH 4 + . In open field condition the highest yield was achieved with the ammonium sulphate in Bari (autumn-winter cycle-110 days) and with calcium nitrate in Policoro (winter-spring cycle-64 days). By increasing N level, yield, nitrates and oxalates leaf content increased. Oxalate content was not affected by nitrogen form. Remarkable differences were observed between leaf petiole and blade in nitrate (4062 vs 925 mg kg -1 of fresh mass) and oxalate (1051 vs 6999 mg kg -1 of fresh mass).

EFFECT OF SOLUTION NITROGEN CONCENTRATION ON YIELD, LEAF ELEMENT CONTENT, AND WATER AND NITROGEN USE EFFICIENCY OF THREE HYDROPONICALLY-GROWN ROCKET SALAD GENOTYPES

Two species of rocket salad, Eruca vesicaria L. subsp. sativa Miller and Diplotaxis tenuifolia L. DC, were grown hydroponically in a growth chamber with two nitrogen levels (1 or 8 mM N) to evaluate nitrate accumulation and nitrogen use efficiency. One ecotype of Eruca and two of Diplotaxis were used. Nitrogen (N) increased leaf production and the contribution of leaves to the total dry mass production in E. vesicaria but not in D. tenuifolia, and emphasized leaf area differences between the two species. The two species also showed differences in the inorganic anions and N content. D. tenuifolia ecotypes accumulated more NO3 than E. vesicaria (7.7 vs. 4.7 g kg−1 fresh mass). By increasing N concentration in the nutrient solution, NO3 content in leaves expressed on fresh mass basis increased in both species by 52%. Nitrogen use efficiency was greater in E. vesicaria than in D. tenuifolia (19.0 vs. 18.0), and decreased with increasing nitrogen in the nutrient solution (19.0 vs. 17.6).

Fertilization strategies for lowering nitrate content in leafy vegetables: chicory and rocket salad cases

Abstract Studies have been carried out to evaluate whether chicory (Cichorium intybus L.) and rocket salad [Eruca vesicaria (L.) Cav. subsp. sativa (Mill)] nitrate (NO3) content can be reduced by decreasing nitrate‐nitrogen (NO3‐N) in the nutrient solution or by partially replacing it with ammonium‐nitrogen (NH4‐N) (chicory only) few days before harvest. Soilless culture method was used applying two levels of NO3 for chicory (2 and 4 mM NO3) and only one for rocket (2 mM NO3). Five (rocket) and six (chicory) days before harvesting, half of the plants were grown always in the same solutions, while the others were grown in a solution with 0.25 mM N (rocket and chicory transferred from 2 mM N) or in a solution where 3/4 of NO3‐N were replaced with NH4‐N (chicory transferred from 4 mM N). Two cultivars of chicory were used. ‘Clio’ hybrid had larger leaf area, but lower dry mass and NO3 concentration than ‘Frastagliata’ chicory. For rocket and chicory alike, the change of nutrient solution five or six days bef...

Subirrigation vs drip-irrigation: Effects on yield and quality of soilless grown cherry tomato

Summary This research was carried out with the aim of comparing drip-irrigation with the trough bench technique of growing a cherry tomato crop, in terms of i) pH and EC of the substrate, ii) production and quality of the fruits and iii) efficiency in the use of the water. In the latter system, pots of opaque plastic with different characteristics were also used: i) with six bottom holes for subirrigation and without risers on the bottom; ii) with four bottom holes and with 3 mm risers on the bottom; iii) with a furrow cross on the bottom and with eight holes and 3 mm risers. This last pot was also used for the drip-irrigation. With both the fertigation methods the EC of the substrate showed a similar pattern over time in the lower and middle layers (always below 3 dS m–1), whereas in the upper layer of the substrate it increased during the growing cycle with higher values with subirrigation compared with drip-irrigation, reaching 7.7 and 3.4 dS m–1, respectively. The pots without risers used for the subirrigation showed the highest variations and values of EC of the recirculating nutrient solution, and the pots with risers and four holes the lowest. Tomato yield was lower with subirrigation than with the traditional free drainage drip-irrigation technique, but the quality was higher (dry matter, total soluble solids, and titratable acidity). Furthermore, with subirrigation the most frequent size class of the fruits was that with a diameter between 25 and 35 mm (considered optimal for cherry tomato), while with the open cycle it was that greater than 35.mm. No significant differences emerged between the three pot types. The water efficiency of the system was greater with subirrigation than with drip-irrigation. To produce 1 kg of fruits, 41 l of nutrient solution were necessary with the subirrigation (closed system) and 59 l with the drip-irrigation (open system).

Comparison between nitrate and ammonium nutrition in fennel, celery, and Swiss chard

Abstract To evaluate the chance to reduce leaf NO3 content and to increase capability to use NH4‐N even in the absence of NO3‐N in the nutrient solution, plants of two Apiaceae species, fennel (Foeniculum vulgare Miller var. azoricum Mill. Thell.) and celery (Apium graveolens L. var. dulce Mill. Pers.), and of one species of Chenopodiaceae, Swiss chard (Beta vulgaris L. var. vulgaris), were hydroponically grown in a growth chamber with three different NH4‐N: NO3‐N (NH4: NO3) ratios (100: 0,50: 50, and 0: 100), but with the same total N level (4 mM) for 14 days. Swiss chard growth was inhibited by NH4 nutrition and reached the highest values with the NH4: NO3 ratio 0: 100. For all the morphological and yield features analyzed, fennel and celery resulted to be quite unresponsive to nitrogen (N) chemical form. Water use efficiency increased in Swiss chard and decreased in fennel and celery with the increase of NO3‐N percentage in the nutrient solution. The dependency of N uptake rate on shoot increment per u...

Quality evaluation of cook‐chilled chicory stems (Cichorium intybus L., Catalogna group) by conventional and sous vide cooking methods

BACKGROUND Chicory stems, appreciated both raw and cooked, represent a nutritious and refined food. In this study the effects on the quality of stems cooked by conventional (boiling, steaming and microwaving) and innovative (sous vide) methods were analysed. Several physical, chemical and sensory traits were compared using two local varieties (Galatina and Molfettese) of southern Italy (Puglia region). RESULTS Independently of the variety, the sous vide method did not significantly affect (redness, yellowness and hue angle) or had the least impact on (lightness and total colour difference) quality parameters among the four methods as compared with the raw product. Following sensory analysis, the sous vide product always showed the highest score among the cooking methods. Moreover, this innovative method did not affect total phenol (TP) content and antioxidant activity (AA) compared with uncooked stems of both varieties. Microwaving increased TP content and AA (though associated with higher weight loss), while different responses depending on the chicory variety were observed after boiling and steaming. CONCLUSION The results indicate the sous vide technique as optimal to preserve several traits, including organoleptic ones, for the quality of cook-chilled chicory stems. They also provide product-specific information usually required for cooking process strategies in the industrial sector of ready-to-eat vegetables.

Comparative management of offshore posidonia residues: Composting vs. energy recovery

Residues of the marine plant posidonia (Posidonia oceanica, PO) beached in tourist zones represent a great environmental, economical, social and hygienic problem in the Mediterranean Basin, in general, and in the Apulia Region in particular, because of the great disturb to the bathers and population, and the high costs that the administrations have to bear for their removal and disposal. In the present paper, Authors determined the heating values of leaves and fibres of PO, the main offshore residues found on beaches, and, meantime, composted those residues with mowing and olive pruning wood. The final composts were characterized for pH, electrical conductivity, elemental composition, dynamic respiration index, phytotoxicity, fluorescence and infrared spectroscopic fingerprints. The aim of the paper was to investigate the composting and energy recovery of PO leaves and fibres in order to suggest alternative solutions to the landfill when offshore residues have to be removed from recreational beaches. The fibrous portion of PO residues showed heating values close to those of other biofuels, thus suggesting a possible utilization as source of energy. At the same time, compost obtained from both PO wastes showed high quality features on condition that the electrical conductivity and Na content are lowered by a correct management of wetting during the composting.

Ammonium and nitrate influence on artichoke growth rate and uptake of inorganic ions.

Abstract Artichoke plants (Cynara scolymus L.) were grown in a growth chamber in a modified Hoagland solution for seven weeks to determine the influence of ammonium:nitrate (NH4:NO3) ratio (100:0, 70:30, 30:70 and 0:100) on growth, water use, and the uptake of nitrogen (N) and inorganic anions and cations. Typical pH changes were recorded: the nutrient solution became acidified with NH4 or NH4:NO3 nutrition; pH increased when NO3 was the only N source. Ammonium‐fed plants (100:0 ratio) were stunted, with signs of marginal leaf necrosis, progressive wilting of leaves and poor root growth. After 49 days, leaf area was 77, 998, 2,415, and 1,700 cm2 and dry weight was 1.0, 12.9, 38.0, and 26.0 g/plant, with NH4:NO3 100:0, 70:30, 30:70, and 0:100, respectively. Leaf area ratio (LAR) was lower in plants supplied solely with NO3 than in those with mixed NH4‐NO3. Increasing NO3‐N percentage in the nutrient solution increased water use efficiency (WUE): 623, 340, and 243 mL of water were necessary to produce 1 g o...

Potassium nutrition increases the lycopene content of tomato fruit

Summary To determine the influence of potassium levels in the nutrient solution on lycopene content, tomato plants were grown in a soil-less system using rockwool slabs as substrate. Two growing seasons were studied with the aim of comparing three potassium levels: low, medium and high (corresponding to 150, 300 and 450 mg K l–1 in the nutrient solution). In the first growing season (Spring–Summer), two high-pigment cultivars of tomato (Solanum lycopersicum L.,‘SVR’ and ‘Kabiria’) were compared. In the second growing season (Summer–Winter) ‘Esperanza’, a non high-pigment hybrid and the two previous cultivars were used. Total fruit yield was higher in the Summer–Winter growing season than in the Spring–Summer season, but was not influenced by potassium nutrition. Growing season, potassium level, and the genetic traits of the cultivars influenced the principal quality parameters of fruit, with higher dry matter and total soluble solids contents in the first growing season, correlating with lower lycopene and K+ contents in the fruit. The lycopene content increased linearly with increasing potassium level in the nutrient solution. The high-pigment genotypes showed a higher lycopene content than ‘Esperanza’. The higher lycopene content in ‘Kabiria’ fruit can also be related to the size of the fruit.