Effects of Blend and Processing Method on the Nutritional Quality of Weaning Foods Made from Select Cereals and Legumes

Weaning blends, formulated in a 60% cereal to 40% legume combination using teff, pearl millet, cowpea, and peanut, were evaluated for changes in nutritional quality due to the effects of blend and processing method. Four blends were prepared by each of four traditional processing methods: control (unprocessed), roasting, germination, and natural fermentation. The main effect of blend formulation proved to be the stronger determinant of nutrient density, while processing method produced the strongest effect on weaning food viscosity. Germinated blends yielded viscosity measurements significantly below those resulting from other processing methods. Germination of ingredients increased nutrient density and in vitro protein digestibility, while roasting and fermentation produced little change from the control product. Complementation of cereal flours with peanut yielded weaning foods with a significantly (P < 0.01) higher nutrient density, increased in vitro protein digestibility and lower viscosity when compared to cowpea-based blends. The use of 20% whole grain teff in weaning blends increased protein content but did not significantly increase nonstarch polysaccharide content as compared to weaning blends without teff.     

Qualitative Zymographic Studies of Major Proteinases from Malted Sorghum (Sorghum bicolor L.) and Effects of Cultivar

Proteolysis during cereal germination is vital both to seedling growth and the success of commercial malting and brewing. In this study, proteinases in proteolytic extracts from seeds and germinated grains of 11 Botswana sorghum cultivars were analyzed and partially characterized by one‐dimensional electrophoresis on SDS‐PAGE gels containing incorporated gelatin. Proteinase polymorphism was detected in both germinated and ungerminated sorghum grains. Fifteen distinct proteinase bands, with M_r values of 27,000–100,000 were detected in sorghum malt extract, while ungerminated sorghum displayed a maximum of four bands (M_r ≈ 78,000–100,000). Band numbers and identity varied markedly according to cultivar. More proteinase bands were detected at pH 4.6, than at pH 6.2 and 7.0, suggesting pH optima considerably below neutrality. Cysteine‐proteinases constituted a higher proportion (9 of 15) of the detected sorghum malt proteinases and were most detectable at pH 4.6. Multiple representatives were also detected for both serine‐ and metallo‐proteinases, although these were more active at pH 6.2 and 7.0. 1‐10 Phenanthroline inhibited malt metallo‐proteinase more strongly than EDTA, suggesting that these enzymes were most probably zinc‐dependent. Aspartyl‐proteinases were not detected, probably because of the substrate employed. Results indicate that the sorghum proteinase system is complex.     

Technological and Nutritional Properties of Flours and Tortillas from Nixtamalized and Extruded Quality Protein Maize (Zea mays L.)

Nixtamalized and extruded flours from quality protein maize (QPM, V‐537C) and tortillas made from them were evaluated for some technological and nutritional properties and compared with the commercial brand MASECA. Both QPM flours showed higher (P < 0.05) protein content, total color difference, pH, available lysine, and lower (P < 0.05) total starch content, Hunter L value, water absorption index, gelatinization enthalpy, resistant starch, and retrograded resistant starch than nixtamalized MASECA flour. Tortillas from nixtamalized and extruded QPM flours had higher contents of essential amino acids than tortillas from MASECA flour, except for leucine. Tortillas from processed QPM flours also showed higher (P < 0.05) values of the nutritional indicators calculated protein efficiency ratio (C‐PER 1.80–1.85 vs. 1.04), apparent and true in vivo protein digestibility (78.4‐79.1 vs. 75.6% and 76.4–77.4 vs. 74.2%, respectively), PER (2.30–2.43 vs. 1.31), net protein retention (NPR; 2.88–2.89 vs. 2.11), and protein digestibility corrected amino acid score (PDCAAS; 54–55 vs. 29% based on preschool children and 100 vs. 85% based on adults) than MASECA flour. The use of QPM for flour and tortilla preparation may have a positive effect on the nutritional status of people from countries where these products are widely consumed.     

Influence of Cooking Conditions on the Protein Matrix of Sorghum and Maize Endosperm Flours

To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three‐dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2‐mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β‐sheet structure relative to α‐helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disulfide bonding and an increase in β‐sheet structure occurred with cooking, with the increase in disulfide bonding being greatest in sorghum vitreous endosperm. The tendency for the sorghum protein matrix to collapse and mat more with cooking than the maize matrix appears to be due to greater disulfide bonding. This is responsible for the observed low starch digestibility of cooked sorghum flour as a result of the more disulfide‐bonded protein matrix limiting the expansion of the starch granules and hence amylase access.     

Cooking Characteristics and Quality of Noodles from Food Sorghum

Three white food sorghums, ATx631*RTx436, ATxARG*RTx436, and SC283‐14, were decorticated, milled into flour and processed into 100% sorghum noodles. Flour, water, and salt (1%) were preheated using a hotplate or a microwave oven. The mixtures were put through a forming extruder to produce noodles. Extruded noodles were dried by three methods: air‐dry method (23°C, 48 hr); one‐stage (60°C, 30% rh, 3 hr), or two‐stage (60°C, 100% rh for 2 hr followed by 60°C, 30% rh for 2 hr). Noodles were evaluated dry and after cooking. Sorghum flours with smaller particle sizes yielded better noodles. The microwave preheating method yielded better noodles than the hot‐plate method. Stronger and firmer noodles, dry or cooked, were prepared using two‐stage drying compared with the other drying methods. Fine flour that was preheated using a microwave oven and dried using the two‐stage method gave the best noodles with moderate (10%) dry matter loss. Optimized processing conditions yielded sorghum noodles with good qualities when properly cooked.     

Protein Quality and Physical Characteristics of Kisra (Fermented Sorghum Pancake‐like Flatbread) Made from Tannin and Non‐Tannin Sorghum Cultivars

Kisra is a naturally lactic acid bacteria‐ and yeast‐fermented sorghum thin pancake‐like flatbread produced in Sudan. Kisra has considerable potential as the basis for development of a gluten‐free sandwich wrap. To help direct cultivar selection for commercial production of these products, two white, tan plant non‐tannin Type I, one white Type II tannin, and one red Type III tannin sorghum cultivars were evaluated with respect to kisra protein quality and physical characteristics. Kisra from the non‐tannin sorghums were flexible and had an open‐textured structure with many regular gas cells, whereas those from the tannin sorghums were more brittle, denser in structure, and contained far fewer and smaller gas cells. Kisra from the tannin sorghums had the lowest reactive lysine content, in vitro protein digestibility, and Protein Digestibility Corrected Amino Score (PDCAAS), with values being lowest for the Type III sorghum. PDCAAS of kisra from the Type III sorghum was only 0.12, less than half of that from the Type I sorghums. As the tannins in tannin sorghums adversely affect kisra protein quality and physical characteristics, white tan plant, non‐tannin sorghum cultivars are most suitable for kisra production and for development of wrap‐type sorghum‐based baked goods.     

Grain and Nutritional Quality Traits of Southwestern U.S. Blue Maize Landraces

Anthocyanin‐rich Southwestern blue maize (Zea mays L.) landraces are receiving interest as functional foods, and commercial production is increasing. We determined variation in kernel color, anthocyanin content, texture, and selected compositional traits of representative varieties. In 2013, eight varieties were grown at four locations in New Mexico. Total kernel anthocyanin content (TAC) and component pigments were measured with spectrophotometry and HPLC, respectively. Oil, protein, starch, and kernel density were determined using NIR spectroscopy and amino acid concentrations using wet chemistry. An average of 49.6 mg/100 g of TAC with a range of 17.6–65.1 mg/100 g was observed. Cyanidin and pelargonidin were major components, and peonidin and succinyl 3‐glucoside were minor components. Low levels of disuccinyl glucoside were detected. Blue kernels were higher in anthocyanin than purple or red kernels. Floury kernels displayed the highest protein and oil contents and the lowest starch content and kernel density. The highest starch and kernel density levels were observed in small flint/dent and pop‐flint/dent kernels. Amino acid content was variable across genotypes and locations.     

Sulfur,Boron, and Zinc Fertilization Effects on Grain and Straw Quality of Maize and Sorghum Grown in Semi-Arid Tropical Region of India

Experiments were conducted on-farm during two seasons (2003–2004) to determine the effects of sulfur (S), boron (B), and zinc (Zn) fertilization on the grain and straw quality of sorghum and maize grown under rainfed conditions in the semi-arid zone of India. The farmers' fields were deficient in S, B, and Zn; in addition the soils were low in organic matter and extractable phosphorus (P), but adequate in extractable potassium (K). Results showed that the applications of S, B, and Zn (SBZn) with nitrogen (N) and P (SBZn + NP) significantly increased the grain N, S, and Zn concentrations in maize and sorghum compared to farmer inputs (FI) and SBZn treatments; the results relative to P and B composition of the grain of the crops were not consistent and did not show any definite trend. The application of SBZn + NP over FI generally increased N, S, and Zn concentration in sorghum and maize straw compared to FI and SBZn treatments. The straw composition of the crops relative to P and B did not show a consistent trend. The results of this study along with the results of our earlier research demonstrate that balanced nutrition of rainfed crops not only increases yields but also enhances N, S, and Zn contents in grain and straw of these crops.     

Comparison of Nutritional and Physicochemical Quality of Rice Under Organic and Standard Production Systems

Growing interest in sustainable agriculture has prompted this study aiming to evaluate nutritional content of rice grain produced from an organic production system. Here, we grew nine quality rice cultivars under organic methods in the wet and dry seasons, and the nutritional values, grain quality, and physiological parameters were compared with respective cultivars grown under the standard cultivation method (SCM). Obtained results revealed that the yield and plant height were lower, but tillering capacity was higher, in the organic field compared with the standard one. The organic crop showed significantly lower contents of protein and phytate compared with reference values under the SCM. Antioxidative capacity and its responsible phytochemicals such as phenolics, flavonoids, and γ‐oryzanol were also significantly higher under organic cultivation than under the SCM. Among physicochemical characteristics, apparent amylose content, gel consistency, and area and perimeter of grain were also higher in the organic crops, but hulling quality, milling quality, head rice recovery, and all other cooking qualities were at par. Higher crude oil and lower total protein content of rice bran were observed in the organic crop, but ash, fiber, and moisture contents did not vary significantly in these two cultivation systems.     

Relationships Between Simple Grain Quality Parameters for the Estimation of Sorghum and Maize Hardness in Commercial Hybrid Cultivars

Grain hardness affects sorghum and maize processing properties especially for dry milling. A variety of simple grain quality parameters were assessed on 17 sorghum and 35 white maize hybrid cultivars grown in six and four locations, respectively, in South Africa. The purpose was to determine tests that can be used to distinguish hardness in commercial sorghum and maize. The grains were characterized by test weight (TW), thousand kernel weight (TKW), decortication with the tangential abrasive dehulling device (TADD), and kernel size. Maize was also characterized for susceptibility to breakage, stress cracking, and near‐infrared transmittance (NIT) milling index. Principal component analysis showed that, in nontannin and tannin sorghums, TADD hardness and TW were closely correlated (P < 0.001). In maize, TADD hardness was closely correlated (P < 0.001) with NIT milling index and TW. Hence, TADD hardness and NIT milling index or TADD hardness and TW would be suitable for maize hardness evaluation. A combination of TADD hardness, TW, TKW, and kernel size >3.35 mm can be used together to select sorghum grain for hardness. It thus appears that TADD hardness is an excellent method of estimating both sorghum and maize hardness that can be applied for routine batch analysis and cultivar evaluation.     

Interaction Between Sorghum Protein Extraction and Precipitation Conditions on Yield,Purity, and Composition of Purified Protein Fractions

Sorghum proteins have the potential to be used as a bio‐industrial renewable resource for applications such as biodegradable films and packaging. This project was designed to evaluate the effect of interactions between sorghum protein extraction and precipitation conditions on the yield, purity, and composition of sorghum protein fractions. Proteins were extracted with 70% ethanol under nonreducing conditions, with ultrasound, or under reducing conditions using either sodium metabisulfite or glutathione as the reducing agent. Several conditions were used to isolate the extracted proteins through precipitation, including lowering ethanol concentrations alone or in combination with lowering to pH 2.5, or by adding 1M NaCl to the extract. Combinations of these conditions were also tested. All precipitation conditions effectively precipitated proteins and lowering the pH and adding 1M NaCl to the extracts enhanced precipitation in some cases. However, the conditions that precipitated the maxium amount of protein or highest purity of protein varied according to how the proteins were initially extracted. Precipitated proteins were characterized by RP‐HPLC, SEC, HPCE, and SDS‐PAGE to compare the protein fractions composition. Nonreduced and sonicated samples had a much wider M_w distribution than reduced extracts. Thus, extraction and precipitation conditions influenced the isolated proteins yield, purity, and composition. Because the extraction and purification processes influenced the composition, purity, and biochemical properties, it may be possible to prepare protein fractions with unique functionalities for specific end‐uses.     

Characterization of Seashore Paspalum (Paspalum vaginatum Swartz) Germplasm by Transferred SSRs from Wheat, Maize and Sorghum

One hundred and thirty SSR markers from wheat, maize and sorghum were screened for the transferability to Paspalum. The transfer rate was 67.5, 49.0 and 66.8% respectively. This would be a very efficient approach for DNA marker development for species which are not well studied molecularly. The polymorphism level for transferred SSR markers was 51.5% within species (Paspalum vaginatum) and 87.1% among Paspalum species. The high level of polymorphism is directly related to the high degree of heterozygosity maintained by its way of reproduction, i.e. self-incompatibility. Forty transferred polymorphic SSR markers were selected and used for characterization and evaluation of seventy-three Paspalum accessions. In total, 209 polymorphic bands were detected from these 40 SSR markers, with an average of five polymorphic bands per marker. The Paspalum accessions clustered into three major groups. Two very similar dendrograms can be generated from either 109 or 209 polymorphic bands. This led us to determine that 18 of the transferred SSR markers were sufficient for genetically differentiating the investigated germplasm accessions. The number of SSR markers required for germplasm characterization and evaluation is discussed. This is the first report of the transfer of SSR markers from major field crops to newly emerged environmental turfgrasses.     

青海黑青稞营养及活性成分分析与评价

为明确青海不同品种黑青稞的营养及化学成分含量,筛选优异种质资源,本研究开展了12种黑青稞营养及化学成分分析与评价.结果 表明,参试黑青稞蛋白、总淀粉、直链淀粉、粗脂肪、粗纤维、灰分、β-葡聚糖含量在部分品种间存在显著差异(P＜0.05),黑青稞具有较高含量的蛋白质(12.19％ ～14.07％)、纤维(2.13％～3....     

Study of Structural and Thermal Changes in Endosperm of Quality Protein Maize During Traditional Nixtamalization Process

This work presents the study of the structural changes of the endosperm of Quality Protein Maize (QPM H-368C), modified by alkaline cooking at two different temperatures (72 and 92°C) and steeping time of 0–7 hr. Structural changes in the outermost 10% layers, the subsequent 10%, and the remaining 80% of the endosperm as a function of the steeping time were studied using scanning electron microscopy (SEM), X-ray diffraction, and differential scanning calorimetry (DSC) techniques. SEM images revealed that soft and hard endosperm have different shapes and packing factors. The X-ray diffraction patterns of the hard and soft endosperm from raw corn suggest that the hard endosperm consists mainly of amylopectin and has a bigger relative crystallinity quality than the soft endosperm. Samples cooked at 72 and 92°C with and without the (Ca(OH)₂ and steeped for 0, 3, and 7 hr, showed structural changes, X-ray diffraction patterns from the outermost 10% layers and subsequent 10% of the endosperm were completely amorphous. This fact is related to the total or partial gelatinization of the starch. The crystallinity in the internal layers of endosperm (remaining 80%) did not have significant changes after the treatments and exhibited the characteristic patterns of crystalline amylose and amylopectin. DSC measurements in the outermost layers of the endosperm did not exhibit the characteristic endothermic peak of starch (from 64 to 81°C) compared with the raw sample, while the endotherm peak for 80% of the endosperm internal layers appears in all cases (72 and 92°C). According to these results, a new definition of the nixtamalization process can be developed as follows. During the nixtamalization process there is a total gelatinization of the starch granules from the most external layers, and a partial gelatinization of the innermost internal layers of the endosperm.     

LED光质对豌豆苗生长、光合色素和营养品质的影响

以豌豆苗为材料,采用基质穴盘培养的方法,研究不同LED光质处理(白光、红光、蓝光和红蓝光)对豌豆苗生长、光合色素(叶绿素a、b和类胡萝卜素)含量与营养品质(硝酸盐、维生素C、类黄酮和花青素含量)的影响.结果表明,与白光相比,蓝光与红蓝光处理显著提高了豌豆苗地上部生物量(P＜0.05),而红光对豌豆苗地上部生物量无影响.不同光质处理在豌豆苗根系生物量和总生物量指标上无显著差异.与白光处理相比,红蓝光处理显著提高了豌豆苗叶片中叶绿素a、b的含量(P＜0.05),但对类胡萝卜素含量无影响.在4种处理中,红光处理的叶绿素a含量最低,而蓝光处理的叶绿素b最低.红光和蓝光处理茎叶中类胡萝卜素含量间无差异,均显著低于白光和红蓝光处理(P＜0.05).红蓝光处理显著提高了豌豆苗叶片中维生素C的含量(P＜0.05),而红光和蓝光均无影响.不同光质处理的豌豆苗茎叶中硝酸盐含量和类黄酮含量无差异.白光处理的豌豆苗茎叶中花青素含量最高,蓝光处理最低.总之,蓝光和红蓝光可促进豌豆苗地上部生长,增加叶片叶绿素a、b含量,红蓝光处理可提高豌豆苗叶片维生素C含量;白光和红蓝光处理下豌豆茎叶中类胡萝卜素含量较高,白光处理的豌豆苗茎叶中花青素含量最高.说明蓝光和红蓝光有利于增加豌豆苗菜产量,而白光和红蓝光有利于提高豌豆苗的营养品质.     

Impact of Nutrient Seed Priming on Germination,Seedling Development,Nutritional Status and Grain Yield of Maize

Effects of seed priming with zinc (Zn) plus manganese (Mn), boron (B), and phosphate (P) on growth and nutritional status of maize were studied. Nutrient seed priming significantly increased seed contents of primed nutrients. In nutrient solution (NS) lacking Zn and Mn, growth of maize plants primed with Zn?+?Mn increased by more than 50% and 100%, respectively, as compared to control treatment. The primed nutrients were efficiently translocated to the growing shoot and could maintain Zn and Mn supply for at least three weeks of the culture period. In soil culture, plants suffered from P and Zn deficiency, which was mitigated to some extent by P and Zn?+?Mn priming. Particularly, translocation of Zn seed reserves to the shoot tissue was negatively affected by the highly calcareous soil. In the field experiment, Zn?+?Mn seed priming increased grain yield by 15%, demonstrating the potential for long-lasting effects of nutrient seed priming.     

Chemical,Physicochemical, and Nutritional Evaluation of Plantago (Plantago ovata Forsk)

Plantago ovata F. are small tan‐colored seeds with ≈30% weight husk. Plantago's husk high content of soluble fiber makes it a good lubricant of the intestinal track with demonstrated effects in lowering plasma cholesterol levels in humans and experimental animals. Plantago seeds grown in Northern Mexico were analyzed for proximate composition, combustion heat, soluble and insoluble dietary fiber, fatty acids, amino acids, and protein fractionation. In vitro digestibility and digestibility of dry matter, apparent and true digestibility, and net protein ratio (in vivo) were also analyzed. Plantago seeds had 17.4% protein, 6.7% fat, 24.6% total dietary fiber, 19.6% insoluble fiber, 5.0% soluble fiber, and a combustion heat of 4.75 kcal/g. Osborne fractionation (based on solubility) yielded albumin 35.8%, globulin 23.9%, and prolamin 11.7%. The oil from plantago seeds had a high percentage of linoleic acid (40.6%) and oleic acid (39.1%) and a minor proportion of linolenic acid (6.9%). In vitro protein digestibility of the plantago seed was 77.5%, suggesting a highly digestible protein. Lysine content was 6.82 g/100 g of protein, higher than wheat and oats (2.46 and 4.20 g/100 g of protein, respectively). Rat bioassays showed values of 89.6% digestibility of dry matter, 86.0% apparent digestibility, 88.1% true digestibility, and 4.40 net protein ratio corrected (NPRc). The importance of these findings is that plantago whole grain shows favorable nutritional quality when compared with cereals and legumes.     

Impacts of Kafirin Allelic Diversity,Starch Content,and Protein Digestibility on Ethanol Conversion Efficiency in Grain Sorghum

Seed protein and starch composition determine the efficiency of the fermentation process in the production of grain‐based ethanol. Sorghum, a highly water‐ and nutrient‐efficient plant, provides an alternative to fuel crops with greater irrigation and fertilizer requirements, such as maize. However, sorghum grain is generally less digestible because of extensive disulfide cross‐linking among sulfur‐rich storage proteins in the protein– starch matrix. Thus, the fine structure and composition of the seed endosperm directly impact grain end use, including fermentation performance. To test the hypothesis that kafirin (prolamin) seed storage proteins specifically influence the efficiency of ethanol production from sorghum, 10 diverse genetic lines with allelic variation in the β‐, γ‐, and (δ‐kafirins, including three β‐kafirin null mutants, were tested for ethanol yield and fermentation efficiency. Our selected lines showed wide variation in grain biochemical features, including total protein (9.96–16.47%), starch (65.52–74.29%), and free amino nitrogen (FAN) (32.84–73.51 mg/L). Total ethanol yield (ranging from 384 to 426 L/metric ton), was positively correlated to starch content (R² = 0.74), and there was a slight positive correlation between protein digestibility and ethanol yield (R² = 0.52). Increases in FAN content enhanced fermentation efficiency (R² = 0.65). The highest ethanol producer was elite staygreen breeding line B923296, and the line with the highest fermentation efficiency at the 72 h time point was inbred BT×623. A large‐seeded genotype, KS115, carrying a novel γ‐kafirin allele, was rich in FAN and exhibited excellent short‐term fermentation efficiency at 85.68% at the 20 h time point. However, the overall ethanol yield from this line was comparatively low at 384 L/metric ton, because of insufficient starch, low digestibility, and high crude protein. Multivariate analysis indicated an association between the β‐kafirin allele and variation in grain digestibility (P = 0.042) and FAN (P = 0.036), with subsequent effects on ethanol yield. Reversed‐phase HPLC profiling of the alcohol‐soluble kafirin protein fraction revealed diversity in protein content and composition across the lines, with similarities in peak distribution profiles among β‐kafirin null mutants compared with normal lines.     

浙江省不同地区香榧生籽营养品质差异性分析与评价

为综合评价香榧营养品质,本试验以浙江省8个不同地区共32份香榧生籽样品为研究对象,对包括宏量营养素、矿质元素及维生素E在内的38项营养品质指标含量进行差异性分析及相关性分析,建立模糊数学综合评价模型以评价其营养品质。结果表明,不同地区香榧营养品质指标含量存在一定差异,宏量营养素中可溶性糖与淀粉的变异系数相对较大,微量营养素中钠的变异系数最大。相关性分析结果表明,脂肪与蛋白质、淀粉间存在较强的负相关,多数氨基酸间表现为极强的正相关,亚油酸与金松酸、硬脂酸与油酸两组脂肪酸在组内具有较强的正相关,组间表现为较强负相关。模糊数学综合评价结果显示磐安县、东阳市与诸暨市3个地区宏量营养素指标评分较高;微量营养素评分较高的为柯桥区、嵊州市与松阳县,整体综合评分在0.403~0.528之间。本研究结果为香榧营养品质评价及产品分级利用提供了研究基础与参考依据。     

台湾农村生活废水之水质特性及其影响研究

本研究之目的乃以桃园灌区农村生活废水为对象,调查其水质特性受季节变化之影响等,并与桃园大圳第二支线上游之灌溉水质进行比较。结果显示,农村生活废水的各项水质浓度与社区户数间并没有一致性存在,而是与社区规划、社区生活形态有关。其中,若因洗车、花园浇灌水等的稀释作用较小时,社区生活废水的化学需氧量约为 159～563mg/L、总氮 15～68mg/L,总磷 0.6～5.7mg/L。在季节变化的影响方面,发现生活废水中的 pH值乃随雨季初期→中期→末期而逐渐降低;电导度、生化需氧量、有机氮、凯氏氮及总氮的平均污染浓度则随雨季初期→中期→末期的顺序而升高;至于化学需氧量、氨氮、硝酸盐氮、亚硝酸盐氮及总磷,是以雨季中期之污染值最高。最后,研究指出,农村生活废水的污染浓度非常高,其中,电导度是桃园大圳第二支线上游灌溉水质的 2.2倍,化学需氧量为 22.5倍,生化需氧量 45.6倍,氨氮 2.2倍,有机氮 122.4倍,凯氏氮 44.0倍,亚硝酸盐氮 2.4倍,总氮 14.3倍及总磷 128.3倍。因此,若不慎将生活废水排入灌溉水道,将严重影响灌溉水的品质。