PHYSIOLOGICAL AND CHEMICAL STUDIES OF CHILLING INJURY IN PEPPER FRUITS

Physiological effects of low temperature (1-6°C) on pepper fruits were studied during and after exposure for various periods. The CO₂ production of the fruits stored at low temperature increased abnormally after transfer to 18°C. There was an accumulation of α-keto acids in chilled fruits: fumaric, succinic, citric and malic acids were detected and malic increased remarkably during low temperature storage. Using paper chromatography, chlorogenic acid was found to be a main phenolic substance in the pepper seeds: its content increased immediately after exposure of the peppers to low temperature and decreased rapidly during subsequent cold storage. The content of shikimic acid in chilled seeds showed a similar tendency to that of chlorogenic acid; phenylala-nine ammonia-lyase (PAL) activity increased rapidly after 2 days' cold storage, then decreased sharply; tyrosine ammonia-lyase (TAL) activity was fairly low compared with PAL activity.     

Determination of organic acids in fruits and vegetables by liquid chromatography with tandem-mass spectrometry

A method using liquid chromatography coupled to tandem-mass spectrometry (LC-MS/MS) with triple quadrupole in selective reaction monitoring mode was developed to determine organic acids (glutamic, tartaric, quinic, malonic, malic, shikimic, α-ketoglutaric, pyruvic, citric, succinic and fumaric acids) in fruits (melon, grape, peach, orange, lemon) and vegetables (green and red pepper, tomato, lettuce and lamb’s lettuce). The negative ion mode of ESI was used. All the validation parameters were found to be within the range of acceptance for all the compounds. Different matrix effects were observed in the studied vegetables and samples were quantified by the standard additions approach. The main advantages of this method are its selectivity, which is one of the main weaknesses of most methods when analysing organic acid in complex matrices, and its simplicity since little sample preparation is needed.     

Effects of freezing on the organic acid content of frozen green beans and Padrón peppers

HPLC (using a C₁₈ column and water at pH 2.2 as the mobile phase) was used to monitor the quantities of oxalic acid (UV detection at 245?nm) and quinic, malic, citric and fumaric acids (UV detection at 215?nm) of deep-frozen (?22?°C) green beans and Padrón peppers over 12 months. Malic, oxalic and citric acid contents decreased considerably in the first month of frozen storage, then oscillated before returning to those one-month levels after 12 months. The amount of fumaric acid increased, most notably in the peppers. Quinic acid was only detected in the peppers; its content also increased. Freezing the vegetables in vacuum-sealed bags did not moderate these changes. Blanching the beans decreased the quantities of all the acids in the vegetable; then, in most cases, values varied similarly to those of the unblanched beans (notably, the citric acid content of the blanched beans doubled during the first 6–8 months of frozen storage, then fell sharply to roughly its initial, post-blanching level). Overall, blanching and then freezing green beans led to greater losses of their organic acids compared to freezing alone.     

THE NONVOLATILE ACID AND SUGAR COMPOSITION OF MAYHAW FRUITS (CRATAEGUS AESTIVALIS, C. OPACA, C. RUFULA)

Nonvolatile acid and sugar compositions were determined in ten cultivars from three species of mayhaw fruits (Crataegus aestivalis, Walter, Torrey & Gray; C. opaca, Hook. & Arn.; C. rufula, Sarg.). Fructose and glucose were the major sugars and malic acid was the principle nonvolatile acid found in these fruits. Citric acid, quinic acid, sorbitol, sucrose, xylose, and inositol were quantitated but were found in lesser amounts and succinic acid, arabinose, and galactose were trace components in all fruits. Pyruvic acid and tartaric acid were tentatively identified in most cultivars based on GC retention times. The nonvolatile acid and sugar composition among all mayhaw fruit species were very similar although one unnamed cultivar of C. aestivalis had much higher levels of fructose and glucose, and the cv. T. O. Superberry had higher levels of malic acid. Malic acid levels were found to be much higher in mayhaw fruits than the levels reported in other stone and pome fruits. Three cultivars of C. rufula grown under cultivation yielded mature fruit with almost identical nonvolatile acid and sugar composition.     

桑葚果实不同发育期品质测定及其相关性分析

本研究对湛江地区7个桑葚品种青果期、转色期、成熟期三个时期桑葚果的单果重、可溶性固形物、可滴定酸含量及糖和有机酸组成和含量进行了测定,并进行了相关性分析。结果表明,在成熟过程中桑葚果实的可溶性固形物和糖含量呈增加的趋势,而酸则呈降低的趋势;在桑葚果实品种中检测出柠檬酸、苹果酸、奎宁酸、琥珀酸、酒石酸、酮戊二酸、抗坏血酸、草酸共8种有机酸,其中柠檬酸的含量最高,其在不同品种不同发育期含量为44.84%~80.86%,其次为奎宁酸和苹果酸;果糖和葡萄糖是桑葚重要的糖组成,其含量在成熟期的台湾长果桑的含量分别达到57.79 mg/g和66.72 mg/g,并且只有在台湾长果桑中检测到蔗糖;通过相关性分析,可滴定酸与可溶性固形物、果糖、葡萄糖、果重呈负相关,且可溶性固形物、果糖含量、葡萄糖含量三者之间呈极正相关。     

Internal quality and antioxidants content of cold-stored red sweet peppers as affected by polyethylene bag packaging and hot water treatment

Physical (weight, firmness) and compositional (sugars, organic acids, ascorbic acid, phenolic compounds and carotenoids) changes of red sweet peppers (Capsicum annuum L.) were monitored during 21 days of cold storage (at 7.5 °C); fruits were stored without packaging, packaged in low density polyethylene bags, or after hot water dipping (53 °C for 4 min) and packaging. Packaging prevented water loss, and preserved the firmness of the fresh product. Sugars (fructose and glucose) content was practically constant throughout the whole storage time, for all treatments. A moderate accumulation of citric acid was observed during storage, but no marked effects of packaging and hot water dipping on citric and malic acid content. Ascorbic acid content slightly increased in unpackaged and packaged fruits, but not in treated+packaged peppers. Hydroxycinnamics total content seemed not to be affected by cold storage, packaging or hot water treatment, whereas glycosylated flavonoids showed somewhat lowered levels during storage, particularly in the case of unpackaged and packaged+treated fruits. Regarding carotenoids content, the effect of the considered storage conditions seemed to be much smaller than that due to ripening stage. Provitamin A content showed an increasing trend in unpackaged and packaged fruits; packaged+treated peppers were characterised by a lower retention of provitamin A and a higher level of capsanthin and cucurbitaxanthin A with respect to not treated fruits. On the whole, packaging and hot water treatment did not produce noticeable adverse effects on the majority of the examined compositional quality parameters.     

Factors influencing quantities of sugars and organic acids in blackcurrant concentrates

 Use of endogenous non-volatile flavour components, i. e. sugars and organic acids, in fruit juice products is desirable. A study of 133 blackcurrant concentrates from three seasons examined variation in sugars and acids arising from storage of fruit at freezing or sub-ambient temperature, seasonal differences, geographical origin and choice of conventional thermal-evaporative or freeze concentration technology. Compared with freeze concentrates, conventional concentrates had significantly higher contents of total sugars and acids, notably malic acid, and higher fructose/glucose, lower malic/citric acid and similar sugar/acid ratios. Concentrates from frozen fruit generally had smaller amounts of fructose, total sugars and fructose/glucose ratios than those from fresh fruit, as well as less citric, ascorbic and total acids and lower sugar/acid ratios. Principal component analysis of 40 randomly chosen concentrates showed that variance is dominated by differences in fructose, total sugars and ascorbic acid contents and sugar/acid ratios. Geographical origin and concentration technology were major sources of variance but changes in post-production sub-ambient storage could not be excluded. Received: 4 July 1997 /  Revised version: 14 October 1997     

发酵前后甜石榴汁中有机酸的变化研究

本试验利用反相液相色谱（RP-HPLC）法分离测定发酵前后甜石榴汁中有机酸种类和含量。在甜石榴汁中检测到的有机酸包括草酸、苹果酸、α-酮戊二酸、乳酸、乙酸、柠檬酸与富马酸,其中主要有机酸为乳酸（占总有机酸的51.2%）、草酸（占总有机酸的26.8%）和柠檬酸（占总有机酸的16.8%）。发酵后甜石榴汁中的草酸与乳酸含量下降,乙酸含量增加,新生成酒石酸、丙酮酸与琥珀酸;苹果酸与柠檬酸含量增加。发酵后甜石榴汁的有机酸总量下降了7.8%.     

Identification and quantitative analysis of sugars and non-volatile organic acids in Chinese gooseberry fruit (Actinidia chinensis Planch.).

The free sugars and non-volatile organic acids in Chinese gooseberry fruit were extracted and separated by lead salt and ion-exchange procedures. Sugars and acids were identified and quantitatively determined by gas-liquid chromatography (g.l.c.) of their trimethylsilyl (TMS) derivatives. Glucose, fructose, sucrose and trace amounts of sorbitol accounted for the total sugars. Citric, quinic and malic are the major acids, the outstanding feature being the high content of quinic acid in mature fruit. Small amounts of phosphoric, ascorbic, glucuronic, galacturonic, oxalic, succinic, fumaric, oxalacetic and p-coumaric acids are also present. Qualitative and quantitative analysis of acids prepared as lead salts agreed closely with the determination of acids isolated by the ion-exchange procedure. Identifications of sugars and acids were confirmed by paper and thin-layer chromatography. Reducing sugars, total sugars and titratable acidity were determined by AOAC methods and the results compared with those from g.l.c.     

利用反相高效液相色谱法测定梨汁中有机酸的种类和含量

研究了利用HPLC法分离测定梨汁中有机酸的条件 ,同时对来源于不同产地和品种梨汁中的有机酸的种类和含量进行了测定 ,并应用SAS统计软件对各有机酸含量之间的相关性进行了分析。结果表明 ,选择 0 0 1mol/LK2 HPO4 磷酸盐缓冲液 (pH 2 5 5 )和体积分数 3 %甲醇做流动相 ,流动相流速为 0 5mL/min ,柱温为 3 0℃ ,紫外检测波长为 2 1 0nm时 ,可以较好地分离和测定果汁中常见的 1 1种有机酸 ,该方法相对标准偏差 0 72 %～ 2 99% ,回收率 91 1 %～ 1 0 6 5 % ,各种酸的线性相关系数r>0 9996,具有较高的准确度和精确度 ;梨汁中的主要有机酸有苹果酸、柠檬酸、琥珀酸、莽草酸、酒石酸、奎宁酸、乳酸和富马酸 ,其中苹果酸含量最高 (为 1 1 4× 1 0 3～ 3 0 9× 1 0 3mg/L) ;不同品种梨汁中各有机酸含量差别较大 ,其中琥珀酸与乳酸和富马酸 ,莽草酸与柠檬酸和奎宁酸的含量之间表现出极显著相关性。     

ORGANIC ACID AND SUGAR CONTENTS OF SCUPPERNONG GRAPES DURING RIPENING

Changes in the principal organic acids and sugars of Scuppernong grapes ( V. rotundifolia ) were followed during the ripening season. The vines were sampled bi-weekly during the initial stages of berry development and then weekly as harvest approached until the "overripe" stage was reached. At the ripe stage, malate and tartrate constituted approximately 90% of organic acids with trace quantities of pyruvic, fumaric, succinic, citric and quinic acids. Glucose, fructose and sucrose constituted approximately 90% of the sugars with trace quantities of galactose and maltose. Malate concentration increased during the early stages of ripening, peaked and decreased to a plateau at the ripe stage. Tartrate decreased steadily until it leveled at the ripe stage. Sugars began to accumulate at veraison, increased rapidly thereafter, and leveled at the ripe stage. At harvest, Scuppernong grapes contained 1.60% total acid and 9.45% total sugars on a whole berry basis. Individual constituents were 0.67% malate, 0.92% tartrate, 3.86% fructose, 3.98% glucose, and 1.61% sucrose.     

Organic Acid Changes During Ripening of Processing Peaches

Organic acids and their changes during peach (Prunus persica L. Batsch) fruit ripening were quantified by HPLC for clingstone culti-vars,‘Babygold 5’and‘Babygold 7′, and a freestone cultivar,‘Cresthaven’. At full maturity,‘Babygold 5’and‘Babygold 7’had about 60% malic, 20% citric and 19% quinic acid; whereas‘Cresthaven’had similar amounts of all three organic acids (37, 3.5 and 28%, respectively). During fruit ripening,‘Babygold 5’and‘Babygold 7’increased in malic acid and decreased in citric and quinic acids, whereas,‘Cresthaven’showed little change in these organic acids.     

连平鹰嘴桃矿物元素及糖酸组分与糖酸比的灰色关联分析

目的 研究连平鹰嘴桃种质资源的品质,积累相关数据。方法 采集鹰嘴桃主产区58个样品,运用电感耦合等离子体发散光谱法（inductively coupled plasma spectrometer, ICP）检测14种矿物元素,液相色谱法测定4种可溶性糖组分和4种有机酸组分。运用灰色关联度分析矿物元素、糖酸组分、总糖和总酸含量等营养成分含量与糖酸比的关联度。结果 鹰嘴桃样品的14种矿物元素(K、P、Mg、Ca、Na、Al、Fe、Cu、Mn、B、Zn、Co、Ni、Li), 含量分别为1682～2781、101.7～225.6、51.05～95.90、32.05～105.30、31.24～57.01、0.15～5.85、0.71～9.28、0.15～1.39、0.34～3.53、0.81～2.14、2.01～6.00、0.010～0.066、0.011～0.130、0.022～0.056 mg/(kg FW);4种糖组分(蔗糖、山梨糖醇、葡萄糖、果糖)的含量分别为165.12～367.58、28.90～85.93、20.68～34.39、11.24～29.21 mg/(g FW);4种有机酸组分（苹果酸、奎尼酸、柠檬酸、琥珀酸）的含量分别为1.61～4.19、1.08～3.00、0.14～0.76、0.022～0.100 mg/(g FW)。矿物元素、可溶性糖组分和有机酸组分跟鹰嘴桃糖酸比都有较高的关联度。P、K、Na、Mg含量与糖酸比关联度相对较高;蔗糖含量与糖酸比关联度最大,果糖含量关联度相对最小;有机酸组分与糖酸比关联度依次为苹果酸＞奎尼酸＞琥珀酸＞柠檬酸。结论 糖酸比可以较好的反映鹰嘴桃的品质。P、K、Na、Mg、蔗糖含量、苹果酸含量与鹰嘴桃品质关联度相对较大。     

HRMAS-nuclear magnetic resonance spectroscopy characterization of tomato “flavor varieties” from Almería (Spain)

¹H HRMAS NMR spectroscopy has been applied to investigate differences at a metabolic level between “flavor varieties” of high quality tomatoes marketed as Protected Geographical Indication from Almería (Spain). The varieties studied include the non-hybrid Raf tomato, one of the most tasteful commercial tomatoes that is traditionally grown in this Spanish region, together with other two hybrid varieties of commercial names Rambo and Zayno. Standard quality parameters were poorly reliable for establishing specific correlations with a given variety. In contrast, ¹H HRMAS NMR spectroscopy, in combination with principal component analysis (PCA) and assigned signal analysis (ASA) provided a clear differentiation between varieties as a function of the ripening process and revealed the existence of variety-dependent relationships between external appearance and metabolic content. ??-Aminobutyric acid (GABA) is envisioned as a good marker for monitoring the ripening process. The content in other taste-relevant metabolites (fructose and organic acids) proved to be variety-dependent. The results show a preferential accumulation of citric acid and fructose in Rambo and Raf varieties, respectively. Raf fruits are characterized by high fructose to glucose and fructose to citric acid ratios. The content of malic acid during ripening also remains high for Raf tomato. These combined features are responsible of the unique characteristic and exceptional taste of this traditional line of tomato.     

未除气与除气淡爽型啤酒中9种有机酸的阈值

采用ASTM679标准方法测定了未除气与除气淡爽型啤酒中乙酸、乳酸、柠檬酸、苹果酸、琥珀酸、富马酸、丙酮酸、酒石酸和草酸的个人和小组阈值。结果发现,在未除气啤酒中,9种有机酸的小组阈值大小顺序为苹果酸、富马酸、乳酸、柠檬酸、丙酮酸、琥珀酸、乙酸、草酸、酒石酸。其中品评员对苹果酸、琥珀酸、富马酸、草酸和柠檬酸的口感差异相对较小,而对酒石酸、乙酸、丙酮酸和乳酸的口感差异较大。在除气啤酒中,9种有机酸的小组阈值大小顺序为丙酮酸、乳酸、乙酸、富马酸、琥珀酸、苹果酸、酒石酸、草酸、柠檬酸。品评员对柠檬酸、苹果酸和乳酸的口感差异相对较小,而对丙酮酸、草酸、酒石酸、富马酸、琥珀酸和乙酸的口感差异较大。此外还发现未除气和除气啤酒中有机酸阈值差异很大,其中差异最大的是三元酸柠檬酸,其次为二元酸,包括苹果酸、草酸、酒石酸、琥珀酸和富马酸,差异最小的是一元酸,包括乳酸、乙酸和丙酮酸。     

Growth of Campylobacter in media supplemented with organic acids

The growth of Campylobacter spp. in media supplemented with organic acids was examined. A Bioscreen C Microbiology Reader was used to measure growth of cultures incubated at 37 degrees C for 48 h in a tryptose-yeast extract basal broth medium and in basal broth supplemented with 10, 20, 30, 40, or 50 mM citric, fumaric, lactic, malic, or succinic acid. Growth of three of six isolates was significantly greater (P < or = 0.05) in media supplemented with 20 to 50 mM citric acid than in nonsupplemented media, growth of five of six isolates was significantly greater in media supplemented with 10 to 50 mM succinic acid than in nonsupplemented media, and growth of six of six isolates was significantly greater in media supplemented with 10 to 50 mM fumaric or malic acid or with 20 to 50 mM lactic acid than in nonsupplemented media. Isolates were also cultured in basal media supplemented with a mixture of 10, 20, 30, 40, or 50 mM fumaric, malic, lactic, and succinic acids. Results indicated that the growth of all Campylobacter isolates was significantly greater in media supplemented with mixtures containing each of these organic acids at 10 to 40 mM than in nonsupplemented media. These findings indicate that in vitro growth of Campylobacter spp. may be significantly enhancedin media supplemented with organic acids that support the growth of these bacteria.     

Organic acids in vegetables. I. Brassica, leaf and bulb vegetables as well as carrots and celery

18 German vegetable species were analyzed for their organic acid content. Organic acids were isolated by methanol extraction followed by ion exchange. After derivatisation with BSA the trimethylsilyl derivatives were analyzed by gas chromatography using SE-52 and OV-1701 glass capillaries. The predominate acids are malic and citric acid, and in most cases malic acid was the most abundant. Succinic, fumaric, and quinic acids are wide spread, tartaric acid was found in carrots, lettuce, endives, chicory, and celery. Other acids such as malonic, shikimic, and t-aconitic acids occurred sporadically. Lactic acid which was determined by two other methods was not detected in any vegetable species.     

Sugar and Nonvolatile Acid Composition of Persimmons During Maturation

Sugars and nonvolatile acids of Japanese persimmons were identified and quantitated by GLC as oxime-TMS derivatives. Sugars quantitated were arabinose, galactose, glucose, fructose and sucrose. Fructose, glucose and sucrose were predominant and present in all cultivars from mature green to fully ripe. Quantities of all sugars varied significantly by cultivar and maturity. Nonvolatile acids quantitated were succinic, malic, citric, and quinic. Malic was the predominant acid in all cultivars followed by citric. Quantities of malic increased with maturity; citric decreased. Sorbitol and inositol were present in minor quantities and varied significantly by cultivar and maturity stage.