Distribution of ascorbic acid in potato tubers and in home-processed and commercial potato foods

HPLC was used to analyze the content of ascorbic acid (AA) in tubers of four Korean potato cultivars (Chaju, Sumi, Deso, and Dejima), in a series of baked, boiled, braised, fried, microwaved, pressure-cooked, and sauteed potato slices from the Dejima cultivar and in 14 commercial Korean and 14 processed potato foods sold in the United States (chips, snacks, mashed potatoes, fries). The AA content for the four cultivars ranged from 16 to 46 mg/100 g of fresh weight. The distribution of AA in each of the eight potato slices (sticks, plugs) cut horizontally from the stem end of the Dejima potato ranged from 6.8 to 19.3% of the total. The corresponding distribution in seven sticks cut vertically was much narrower, ranging from 11.7 to 17.5% of the total. Losses of AA in water (pH 5.2) were significantly greater than in 5% metaphosphoric acid (pH 1.0). Less degradation occurred in water solutions of the vitamin stored at 1 degree C than at 25 degrees C. Losses of AA observed during home-processing of three varieties with low (Dejima, 16 mg/100 g), intermediate (Sumi, 32 mg/100 g), and high (Chaju, 42 mg/100 g) AA contents were as follows: boiling in water, 77-88%; boiling in water containing 1-3% NaCl, 61-79%; frying in oil, 55-79%; sauteing, 61-67%; pressure-cooking in water, 56-60%; braising, 50-63%; baking, 33-51%; and microwaving, 21-33%. The content of the Korean foods ranged from trace amounts to 25 mg/100 g and that of the U.S. foods from 0.4 to 46 mg/100 g. These results permit optimization of the vitamin C content of the diet by (a) using high-vitamin C potato varieties such as Chaju, (b) selecting sticks cut horizontally for frying, (c) baking or microwaving rather than boiling or frying, and (d) selecting commercial potato foods with a high vitamin C content.     

不同马铃薯品种对Cd、Pb吸收累积的差异

采用田间试验法,以中南地区主要种植的11个马铃薯品种为研究对象,测定马铃薯植株各部位重金属Cd、Pb含量,探讨不同品种的马铃薯对Cd、Pb的吸收累积差异,为马铃薯的安全种植提供实践参考。结果表明:Cd—Pb复合污染下,马铃薯块茎鲜重、茎叶鲜重以及根、茎叶、块茎中Cd、Pb含量在品种间均表现出显著差异。11个马铃薯品种块茎Cd含量范围为0.39～0.67 mg/kg,超标率100%,块茎Pb含量为0.16～0.43 mg/kg,超标率81.8%。马铃薯各部位Cd、Pb含量均呈现根茎叶块茎的分布特点;马铃薯对Cd的富集系数为2.35～5.56,对Pb富集系数为0.11～0.22,马铃薯富集转运Cd的能力大于Pb。尽管复合重金属靶标危险系数(TTHQ)法评价显示,金湘等5种马铃薯的TTHQ值1,对人体健康风险较小,但结合块茎Cd、Pb含量,建议污染区种植的马铃薯作为工业原料使用更安全。     

Selection criteria for potato tubers to minimize acrylamide formation during frying

A number of parameters linked to the selection of potato tubers were evaluated with regard to their potential to influence acrylamide formation in French fries. The formation of acrylamide, which is a potential human carcinogen, can be minimized for a big extent by the selection of an appropriate tuber. This study focused on the following selection criteria: variety as influenced by storage time and soil type, underwater weight, and tuber size. A total of 16 varieties were compared, concerning their potential for acrylamide formation. From that survey, certain varieties, such as Tebina and Quincy, could be appointed as unsuitable for frying. The differences in the potential of acrylamide formation between the varieties could mainly be explained by the reducing sugar content of the potato (R2 = 0.82, n = 96). The investigated type of soil and storage time at 8 degrees C appeared to have a minor influence on the acrylamide formation during frying. On the other hand, the tuber size of the potato did contribute in a significant manner to the acrylamide formation. Smaller tubers were more susceptible to acrylamide formation and should be avoided in the frying process. The last selection parameter, the underwater weight, appeared to be of minor importance in the acrylamide formation. On the basis of these simple selection criteria, it is possible to make a first screening of potatoes to reduce the acrylamide formation during frying.     

Changes in phenolic composition and antioxidant activity of virgin olive oil during frying

The concentration of hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA) in virgin olive oil decreased rapidly when the oil was repeatedly used for preparing french fries in deep-fat frying operations. At the end of the first frying process (10 min at 180 degrees C), the concentration of the dihydroxyphenol components was reduced to 50-60% of the original value, and after six frying operations only about 10% of the initial components remained. However, tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA) in the oil were much more stable during 12 frying operations. The reduction in their original concentration was much smaller than that for hydroxytyrosol and its derivatives and showed a roughly linear relationship with the number of frying operations. The antioxidant activity of the phenolic extract measured using the DPPH test rapidly diminished during the first six frying processes, from a total antioxidant activity higher than 740 micromol of Trolox/kg down to less than 250 micromol/kg. On the other hand, the concentration of polar compounds, oxidized triacylglycerol monomers (oxTGs), dimeric TGs, and polymerized TGs rapidly increased from the sixth frying operation onward, when the antioxidant activity of the phenolic extract was very low, and as a consequence the oil was much more susceptible to oxidation. The loss of antioxidant activity in the phenolic fraction due to deep-fat frying was confirmed by the storage oil and oil-in-water emulsions containing added extracts from olive oil used for 12 frying operations.     

Anion-exchange method for determination of phytate in foods: collaborative study

Phytate, a naturally occurring organic compound found in plant seeds, roots, and tubers, was determined in a collaborative study using a modified anion-exchange method. Seven samples (peanut flour, oats, rice, isolated soybean protein, a vegetarian diet composite, wheat bran, and whole wheat bread), supplied as blind duplicate samples, were analyzed in triplicate by 7 collaborators. Phytate concentrations in the samples ranged from 2.38 to 46.70 mg/g. Relative standard deviations (RSD = CV) for repeatability ranged from 2.5 to 10.1%, and for reproducibility, from 4.5 to 11.0%. The method has been adopted official first action.     

Induction of antioxidant flavonol biosynthesis in fresh-cut potatoes. Effect of domestic cooking

The effect of fresh-cutting and subsequent cold storage on phenolic compounds from five long-term-stored potato cultivars (Agria, Cara, Liseta, Monalisa, and Spunta) was studied. Fresh-cutting induced the biosynthesis of three flavonols, which were identified by HPLC-DAD-ESIMS as quercetin 3-rutinoside, quercetin 3-diglucoside, and quercetin 3-glucosylrutinoside. The flavonols were detected after a lag period of 3 days of cold storage. The content ranged from 6 to 14 mg/100 g of fresh weight depending on the cultivar after 6 days of storage. Chlorogenic acid as the main caffeic acid derivative and the amino acids tyrosine and tryptophan were also quantified. The effect of cold storage under light or in dark was studied with new-season-harvested Monalisa potatoes. The flavonol induction was higher in fresh-cut potatoes stored under light than in the dark. However, caffeic acid derivatives were not affected. Domestic cooking such as boiling, microwaving, and frying provoked a partial loss of the flavonols, which were retained in the range of 4-16 mg per serving (213 g). Steam-cooking resulted in the highest retention of caffeic acid derivatives and aromatic amino acids compared with the other cooking methods studied. This means that due to the large amount of potatoes consumed in the Western diet, fresh-cut potatoes can be a significant source of health-promoting phenolics.     

Cultivation of transgenic cyanophycin-producing potatoes does not negatively affect growth,reproduction and activity of the earthworm Lumbricus terrestris (L.)

A microcosm experiment was performed to investigate the effects of post-harvest potato tubers from transgenic cyanophycin-producing potatoes on Lumbricus terrestris (L.) activity and biomass, number of cocoons and their hatchability as well as the remaining cyanophycin content in soil and cast samples during a period of 80 days. Potato tubers from four transgenic potato events with different cyanophycin content in a range from 0.8 to 7.5% were compared to the near isogenic, non-transgenic control (Solanum tuberosum L. cv. Albatros) and a comparative potato cultivar (S. tuberosum L. cv. Désirée). One treatment with transgenic tuber residue but without earthworms was prepared as an additional control. Potato tuber loss from the surface of the microcosms was significantly higher in the treatments with transgenic potato tubers compared with non-transgenic treatments. It can be estimated that the earthworm contribution to potato tuber loss from the soil surface was approximately 61%. Mean number of cocoons in addition to the number of hatched cocoons varied from 2.6 to 6.2 and from 7 to 15 accounting for 45.2–83.35% hatchability, respectively, but no significant differences between the treatments were found. The same was true for the development of earthworm biomass in the various treatments. The cyanophycin content in soil samples was significantly higher when earthworms were present indicating that the cyanophycin content in the upper soil layer might have been enhanced through earthworm burrowing activity. Overall, it is concluded that tubers from transgenic cyanophycin potatoes are easily degradable and neither inhibit nor stimulate earthworm growth, reproduction, and activity.     

Genetic manipulation for enhancing calcium content in potato tuber

Increased calcium (Ca) in potatoes may increase the production rate by enhancing tuber quality and storability. Additionally, increased Ca levels in important agricultural crops may help ameliorate the incidence of osteoporosis. However, the capacity to alter Ca levels in potato tubers through genetic manipulations has not been previously addressed. Here we demonstrate that potato tubers expressing the Arabidopsis H+/Ca2+ transporter sCAX1 (N-terminal autoinhibitory domain truncated version of CAtion eXchanger 1) contain up to 3-fold more Ca than wild-type tubers. The increased Ca appears to be distributed throughout the tuber. The sCAX1-expressing potatoes have normally undergone the tuber/plant/tuber cycle for three generations; the trait appeared stable through successive generations. The expression of sCAX1 does not appear to alter potato growth and development. Furthermore, increased Ca levels in sCAX1-expressing tubers do not appear to alter tuber morphology or yield. Given the preponderance of potato consumption worldwide, these transgenic plants may be a means of marginally increasing Ca intake levels in the population. To our knowledge, this study represents the first attempts to use biotechnology to increase the Ca content of potatoes.     

Method for the detection of synthetic cry3A in transgenic potatoes

All transgenic cultivars of potatoes registered in Canada and the United States have been modified to express a synthetic cry3A gene as a means of conferring resistance against the Colorado potato beetle, an important economic pest of potatoes. A PCR method was developed to amplify a 499 bp region of the synthetic cry3A gene. Using this method, synthetic cry3A could be detected in six different transgenic cultivars. Positive results could be confirmed with PvuII restriction digestion of the PCR-generated amplicon, which resulted in two fragments that were 283 and 216 bp in size. Of the 52 tuber extracts tested with this method, no false positive or false negative results were obtained, suggesting the method could be used with a high degree of accuracy. The absolute limit of detection was the number of cry3A copies present in one or perhaps two haploid copies of the potato genome. The practical limit of detection in tubers on a fresh weight basis was 0.02% for the NL 10-SUP and 0.01% for the remaining cultivars. Synthetic cry3A could also be detected in processed food products such as potato chips, shoestring potatoes, and frozen French fries. The method was suitable for screening potato tuber lots and some processed foods for the presence of synthetic cry3A.     

Field trials to determine residues of chlozolinate in table grapes

Chlozolinate (Serinal) is a dicarboximide fungicide used in southern European countries principally on grapes. Maximum residue levels have not yet been set by FAO/WHO and are under evaluation in the EU. Field trials have been carried out in Greece on two varieties of table grapes (Cardinal and Victoria) during two consecutive years to assess residues remaining after application according to good agricultural practice. Analysis using a multiresidue method with gas chromatography (ECD) showed that the parent compound decays with a first-order rate constant of 0.057 +/- 0.011 day(-)(1) and that residues had fallen below the proposed MRL of 5 mg/kg in all samples by 21 days postapplication (the proposed PHI). The contribution of the main metabolite, S1, to the total residue is generally <20%. Washing removes a substantial amount (up to 80%) of chlozolinate, which appears to be nonsystemic on grapes, thus reducing real consumer exposure to this pesticide.     

Influence of storage practices on acrylamide formation during potato frying

A number of parameters linked to storage of potatoes were evaluated with regard to their potential to influence the acrylamide formation in French fries. Acrylamide, which is a potential human carcinogen, is reported to be formed during the frying of potatoes as a result of the reactions between asparagine and reducing sugars. This study was conducted using three potato varieties (Bintje, Ramos, and Saturna) typically used in Belgium, The Netherlands, and the northern part of France for French fry and crisp production. Saturna, mainly used in crisp production, appeared to be the least susceptible for acrylamide formation during frying. Especially storage at low temperatures (4 degrees C) compared to storage at 8 degrees C seemed to enhance acrylamide formation due to a strong increase in reducing sugars caused by low-temperature storage. Because of the reversible nature of this physiological reaction, it was possible to achieve a significant reduction of the reducing sugars after a reconditioning of the cold-stored potatoes for 3 weeks at 15 degrees C. All changes in acrylamide concentrations could mainly be explained by the reducing sugar content of the potato (R2 = 0.84, n = 160). This means that, by ensuring a low reducing sugar content of the potato tuber, the risk for acrylamide formation will largely be reduced. Finally the use of a sprout inhibitor did not influence the composition of the potato, and thus acrylamide formation was not susceptible to this treatment.     

Residues of azoxystrobin from grapes to raisins

Azoxystrobin, a fungicide of the strobilurin group, has an European Union maximum residue level (MRL) of 2 mg/kg for grapes. This work aimed to assess residues on fresh and washed grapes and on raisins following processing with (i) alkali treatment and sun drying and (ii) sun drying only. QUADRIS 25% SC was applied according to good agricultural practice for two consecutive years on a typical cv. Thomson seedless and a seed-producing clone. Samples were collected 0, 15, and 21 days postapplication and analyzed using gas chromatography/electron capture detection; recoveries were 86 +/- 12% for grapes and 99 +/- 15% for raisins. Residues on grapes were 0.49-1.84 mg/kg, and washing removed 75% of the residue. Residues in raisins produced from seedless grapes were 0.51-1.49 (treatment 1) and 1.42-2.08 mg/kg (treatment 2), with residue transfer factors sometimes >1, even following alkali treatment, which reduced residues considerably. To avoid trade problems, a higher MRL for raisins is necessary.     

马铃薯新品种天薯19号选育报告

为解决甘肃省乃至西北地区马铃薯专用品种缺乏的问题,天水市农业科学研究所以晋薯11号为母本、天薯9号为父本杂交,利用常规杂交育种技术选育出了晚熟鲜食菜用型马铃薯新品种天薯19号。该品种在2019 — 2020年进行的国家马铃薯西北晚熟组区域试验中,2 a 18点(次)平均折合产量为32 490.0 kg/hm2,较对照品种陇薯6号增产3.0%。该品种生育期119 d左右,薯块卵圆形、黄皮黄肉、芽眼少而浅。薯块品质优良,鲜薯块茎含干物质204 g/kg、淀粉166 g/kg、维生素C 547 mg/kg、粗蛋白22.1 g/kg、还原糖3.5 g/kg。适宜在甘肃中东部、宁夏中南部、青海东部及生态类似区种植。     

Accumulation of Lead and Arsenic by Potato Grown on Lead–Arsenate-Contaminated Orchard Soils

There are concerns of potential food chain transfer of metals in crops grown on lead–arsenate-contaminated soils. The objective of this study was to investigate lead and arsenic uptake by four potato (Solanum tuberosum L.) cultivars grown on lead–arsenate-contaminated soils with lead and arsenic concentrations ranging from 350 to 961 and 43 to 290 mg kg^?1, respectively. Yield was not reduced due to treatment. Potato tubers were washed thoroughly before peeling. Lead concentration in both peeled tubers and peel was below instrument detection limit. Arsenic concentration in peeled tubers grown on the lead–arsenate soils ranged from 0.24 to 1.44 mg kg^?1. Arsenic concentration was 60% higher in the peel than in the peeled tuber. The relatively high arsenic levels in the peel demonstrated that arsenic was taken up into the potato peel tissue. It is recommended that if potatoes are grown on these soils they should be peeled before consumption.

Abbreviations Pb, lead; As, arsenic; DW, dry weight; FW, fresh weight     

Residue levels, decline curves, and plantation distribution of procymidone in green beans grown in greenhouse

Residue levels and degradation rates of procymidone residues were studied in green beans grown in a greenhouse. Experiments were planned to also assess the influence of planting density on the behavior of procymidone residues on this type of crop. The study was carried out in four random blocks considering three sub-blocks of different planting densities into each block. Plants were sprayed with Sumisclex 50 WP (1077.5 g of ai/ha) 52 days after the transplantation, and sampling was carried out daily during two different periods of 6 and 5 consecutive days, respectively, around the two harvest days (days 12 and 28 after the treatment). Residue levels of procymidone were determined by using the Luke extraction method and GC-NPD. The average residue levels of procymidone in the overall planting (mean of 12 determinations) were below 2 mg/kg (European maximum residue limit) for all the sampling days, obtaining values of 1.01 +/- 0.55 and 0.37 +/- 0.10 mg/kg, respectively, at the two harvest days. The decline behavior of procymidone residues in the overall plantation and in each block could be described as a pseudo-first-order reaction, obtaining half-life values (t(1/2)) of 10-11 days in all cases. The calculated residue level at the preharvest time (5 days) in the overall plantation was 1.7 mg/kg, but this value in the blocks depended on the block position along the greenhouse and ranged from 2.3 to 0.9 mg/kg. In this work, additional data on the residual behavior of the fungicide pyrazophos in green beans were also obtained.     

收获期马铃薯块茎碰撞恢复系数测定与影响因素分析

为了建立马铃薯块茎在土薯分离机构和振动筛上发生碰撞时的碰撞模型,该文基于质点对固定面的碰撞动力学理论在自制测定装置上对马铃薯块茎碰撞恢复系数进行了试验测定。对块茎碰撞恢复系数的主要影响因素碰撞材料、下落高度、块茎质量、含水率、跌落方向和马铃薯品种等进行了混合正交试验和单因素试验。混合正交试验结果表明,各因素对马铃薯块茎碰撞恢复系数的影响顺序为:碰撞材料、下落高度、块茎质量、含水率、跌落方向和马铃薯品种,其中碰撞材料、下落高度、块茎质量和含水率影响较为显著。单因素试验结果表明,马铃薯与65Mn钢、橡胶、马铃薯和土块间块茎碰撞恢复系数依次减小,其中新大坪的值分别为0.791 2、0.710 5、0.663 2、0.525 3,陇薯7号的值分别为0.762 7、0.695 2、0.690 4、0.563 1;马铃薯块茎碰撞恢复系数随着下落高度、块茎质量和含水率的增加而减小,回归方程决定系数均大于0.9。研究结果可为马铃薯收获机挖掘及土薯分离装置关键部件的优化设计提供参考。     

Potato uptake and recovery of nitrogen 15N-enriched ammonium nitrate

Tuber yield and nitrogen uptake in potatoes were recorded during 1996 and 1997 in Southern Bavaria. Recovery of applied fertilizer nitrogen was measured by using ¹⁵N (¹⁵NH₄¹⁵NO₃). Nitrogen fertilizer was brought out either broadcast or in the ridge; 150 kg N ha⁻¹ were applied either at planting or in split doses of 50 kg N ha⁻¹ (at planting, emergence and at 20-cm plant height). Due to unfavorable conditions, tuber yield and fertilizer N recovery were lower in 1996 as compared with 1997. Fertilizer N recovery in plant biomass (tuber and foliage) ranged from 35.9% to 68.5% at growth stage EC 79; the main fraction was allocated to tubers. Placement of fertilizer N in the ridge had a positive effect on N recovery, when the total N amount was applied at planting. In broadcast application, fertilizer N recovery was higher when the fertilizer doses were split, as compared with a single broadcast application at planting. When fertilizer N was applied in split doses, the effect of N placement became negligibly small. Fertilizer N recovery in soil ranged from 19.5% to 24.6%, and total recovery ranged from 60.1% to 88.0%. Rainfall between planting and plant emergence, and conditions restricting plant development in early developmental stages were related with unaccounted fertilizer N losses. Therefore, the positive effects of split N applications or fertilizer placement are most likely to occur under unfavorable growing conditions.     

Growth,Yield and Nutrition of Potato in Fumigated or Nonfumigated Soil Amended with Spent Mushroom Compost and Straw Mulch

Four cultural amendments; spent mushroom compost, straw mulch, both compost and straw mulch, or neither, were applied to soils that were either fumigated or not fumigated in a field of potatoes subject to early dying and Colorado potato beetle defoliation. Two plant samples were harvested at two week intervals to measure shoot and tuber growth and mineral nutrition, and two rows were harvested for yield at maturity. Amending the soil with compost increased vegetative growth and shoot weight more than final yield of tubers. Compost amendment delayed tuber filling by several days. Fumigation partly controlled the loss of leaf area due to early dying, but it did not increase tuber yields, and in 1994 fumigation reduced tuber yield in compost amended soils. The effects of compost and straw mulch on tuber yield were related to the concentrations of N and P in leaves. The potato crop did not benefit from compost amendment combined with fumigation, because in fumigated soil there was no improvement in plant nutrition due to compost.     

Effects of residues of lime and phosphorus fertilizer on cadmium uptake and yield of potatoes and carrots

Potatoes (Solarium tuberosum L.) and carrots (Daucus carota L.) were grown in the field on Tasmanian ferrosols (humic eutrudox) which had been limed either 2, 3, or 5 years earlier, and where tuber cadmium (Cd) concentrations in potatoes grown a few months after the liming had shown no lime response. In the current crops lime decreased potato tuber Cd by about 30% and carrot root Cd by about 50%. We attributed the decrease to more even and deeper mixing of the lime with the soil by the harvest of the first potatoes. Phosphorus (P) fertilizer residues from the earlier potato crops did not significantly affect tuber or root Cd, but there was a positive effect at 1 site where some high Cd P fertilizer had earlier been used. Neither lime nor P fertilizer residues affected potato or carrot yields. Analysis at one site of potato tubers from the upper part of the soil ridges showed that they had slightly higher Cd concentrations than did deeper tubers near the fertilizer band, whether P fertilizer was in the band or not. This suggests that either the Cd in the fertilizer band was relatively unimportant as a Cd source for the current crop, or that Cd was redistributed within the plant during the season, or both. Liming may be a suitable medium to long‐term strategy for decreasing Cd uptake by root crops, but site to site and seasonal variation can still be great, and knowledge of other major influences is needed for assurance of produce quality. Our observations need to be extended to sites which gives rise to higher Cd concentrations in agricultural produce, and to other soil types. Potato common scab was severe in the limed plots at one site. However, this site had grown 3 potato crops in 5 years, which probably exacerbated the disease. Potato processors in Tasmania demand a minimum of 5 years between successive crops which should slow any build up of scab due to liming, but more work on possible interactions between lime and rotation length on scab incidence is needed before liming can be recommended as a Cd control measure for potatoes.     

施氮对块茎形成期高温胁迫后马铃薯块茎产量、淀粉含量和相关酶代谢活性的影响

为了明确不同施氮量对高温胁迫后马铃薯块茎淀粉合成酶、淀粉含量及产量的影响,本研究于2019-2020年在宁南山区海原县进行田间试验.供试品种为青薯9号,通过搭建高温棚构建高温环境,设2个温度处理(T1:块茎形成初期高温胁迫,T2:自然温度),4个氮肥水平(不施氮N0:0 kg·hm-2,低氮水平N1:75 kg·hm-...