Sweet Corn Kernels Research Articles

STUDIES ON SHELLING OF FROZEN SWEET CORN

ABSTRACT Commercially, the most common method of separating kernels from the sweet corn cob is by cutting the kernels with a sharp blade. This method does not allow the total removal of kernels from the cob. Approximately 20% of kernels remain on the cob. The objective of this study was to evaluate the shelling method for removal of kernels from frozen sweet corn cobs, on the base of hardness, separation rate, and share of damaged and total loss of kernels. The corn cobs prior to shelling were subjected to blanching in water and freezing by spraying liquid nitrogen. The freezing times of 2, 4 and 6 min significantly increased hardness and separation rate and decreased damage and kernels losses. Starting at 6 min there were no significant effects of increase in freezing time on average values of analyzed parameters. PRACTICAL APPLICATIONSCommercially, the most common method of separating sweet corn kernels from the cob is by cutting the kernels. The cutting operation severs the upper part of the kernel from the lower part, which remains on the cob. Thus, the hull of the kernel is broken open and part of each kernel is wasted. Furthermore, during subsequent wet‐processing, including washing and blanching of the severed kernels, part of the corn meat is leached from its pouch and lost. This work shows the new method for separation of kernels from the cob by freezing the kernels on the cob in nitrogen. The frozen cob is then subjected to impact in a threshing device. The advantage of this method is the reduction of waste and increased yield of corn. The results from this study can be used as reference for separating sweet corn in similar applications.

Nitrate and nitrite contents of sweet corn kernels as influenced by genotype and levels of nitrogen fertilization.

In sweet corn it is quite expectable that, in poor postharvest condition of ear storage, a smaller or a larger part of the kernel nitrates be converted to nitrites. The consumption of 3-4 freshly boiled ears/day adds up to an ADI of NO2¯-N which should be seriously taken into consideration. Five sweet corn hybrids were tested in field trials on four levels of mineral N fertilization (0 kg N/ha; 50 kg N/ha; 100 kg N/ha; 150 kg N/ha) applied to soil as NH4NO3 on a general organic fertilization of 30 t/ha manure applied once in three years. The trials were organized in three locations with obvious different soil and climatic conditions and in two years. At technical maturity, ten ears were harvested at random from each experimental plot and kernel samples of 20 g of each variant were taken on the same day of harvest and analyzed for nitrates and nitrites. Both the cultivar and the level of mineral N fertilization have significantly influenced the nitrate content of kernels. The average value of nitrate (34.41 mg/kg product) and nitrite (1.18 mg/kg product) contents are not very high and are far from being alarming as compared to AID values recommended by the UE Scientific Committee for Food in 2007 (0 – 3.7 mg/kg b.w. of NO3¯-N and 0 – 0.1 mg/kg b.w. of NO2¯-N). These limits of nitrite content in sweet corn kernels are, nevertheless, alarming since they were found following a rather proper handling and storage of harvested ears and kernel samples.

Increase in Nutritionally Important Sweet Corn Kernel Carotenoids following Mesotrione and Atrazine Applications

The herbicide mesotrione inhibits a critical enzyme, phytoene desaturase, in plant carotenoid biosynthesis. Mesotrione is currently labeled for selective weed control in sweet corn ( Zea mays var. rugosa). Mesotrione applied alone, or in mixtures with the photosystem II inhibitor atrazine, acted to increase concentrations of kernel antheraxanthin, lutein, and zeaxanthin carotenoids in several sweet corn genotypes. Kernel lutein and zeaxanthin levels significantly increased 15.6% after mesotrione + atrazine early postemergence applications, as compared to the control treatment. It appears that mesotrione applications resulted in greater pools of kernel carotenoids once the sweet corn genotypes expressing moderate injury overcame the initial herbicidal photo-oxidative stress. This is the first report of herbicides directly up-regulating the carotenoid biosynthetic pathway in corn kernels, which is associated with the nutritional quality of sweet corn. Enhanced accumulation of lutein and zeaxanthin is important because dietary carotenoids function in suppressing aging eye diseases such as macular degeneration, now affecting 1.75 million older Americans.

Evaluation of Quantitative and Qualitative Losses of the Cutting Process for Sweet Corn Kernels

Sweet corn kernels for the food processing industry are mechanically removed from the cob. This mechanical process causes large quantitative and qualitative losses. The goal of this research was to determine the effect of cutter head speed on kernel losses, kernels of inferior quality, and sugars losses during the process of the cutting the kernel off the cob. The quantitative and qualitative sweet corn kernel losses were determined at three angular speeds of the corn cutter head: 167.5, 230.4, 293.2 rad/s with three standard sweet corn varieties (su-1): Boston, Jubilee, and Spirit. The kernel losses were determined as the percentage of the mass of kernels left on the cob core after removal. The condition of the cut kernel section was used as the index of the quality of kernel cut-off. The quality of cutting was estimated to be good if the cutting surface was smooth and no mass losses were observed. When the cutting surface was ragged or if mass loses were observed this indicated kernels of inferior quality. The data obtained confirmed statistically the effect of increasing cutter head speeds from 167.5 to 293.2 rad/s on the quantity and quality of cut kernels. The studies showed that kernel losses decreased from 51% to 27%, the number of kernels of inferior quality decreased from 64% to 44% and sugar losses from 48% to 33%. The cut kernel yield increased from 29% to 52%.

収穫後包皮付スイートコーンの弱光ＬＥＤ低温照射による品質保持および旨み成分増強効果

The present study was undertaken to develop an effective preservation system for sweet corn kernels by taking advantage of the properties of dim LED light and cool temperature. Dehusked sweet corns (Zea mays L. var. saccharata f. Peter corn) were stored at 5°C for 4 d under a photosynthetic photon flux density (PPFD) of 1μmol m-2 s-1 using red and blue LEDs. During storage, the Brix scale was measured daily, and an amino acid analysis was carried out after 4 d storage. The Brix scales were kept high under the blue LED irradiation and cool conditions (5°C) compared to those under dark-cool conditions.Similarly, sweet corn umami was enhanced by storage under the blue LED-cool conditions, which was in good agreement with the observed increase of aspartic acid and glutamic acid, a predominant amino acid, under the same conditions. Red LED-cool conditions had also a preserving effect on sweet corn kernels but not as pronounced as the blue LED-cool conditions. However it was much better than that of dark-room temperature conditions. These results suggest that light quality during storage determines the quality of sweet corn kernel and its umami constituents. The authors propose the blue LED-cool preservation as a practical and useful technique.

Moisture Dependent Physical Properties of Dry Sweet Corn Kernels

Physical properties of sweet corn kernels have been evaluated as a function of kernel moisture content, varying from 9.12 to 17.06% (db). In the moisture range, kernel length, width, thickness, and geometric mean diameter increased linearly from 9.87 to11.09 mm, 7.41 to 9.25 mm, 3.25 to 4.37 mm, and 6.18 to 7.62 mm, respectively, with increase in moisture content from 9.12–17.06%. The sphericity index, kernel volume, kernel surface area, and thousand seed weight increased linearly from 62.6 to 68.8, 93.8 to 194.3 mm3, 120.1 to 182.9 mm2, and 220 to 268 gr, respectively. Apparent density and bulk density decreased linearly from 1.315 to 1.232 g/cm3 and 0.765 to 0.698 g/cm3, respectively, while bulk porosity increased from 41.8 to 43.3%. The highest static coefficient of friction was found on the plywood surface. The static coefficient of friction increased from 0.680 to 0.891, 0.605 to 0.741, and 0.530 to 0.644 for plywood, galvanized iron, and aluminum surfaces, respectively. The angle of repose increased linearly from 30.2 to 35.2° with the increase of moisture content.

Fusarium verticillioides Migration in Attached and Detached Sweet Corn Ears

Mycotoxins harmful to humans and other animals are produced in kernels of sweet corn (Zea mays L.) during colonization by the fungus Fusarium verticillioides (Sacc.) Nirenberg. Experimentation is limited under field conditions, due to the seasonality of the organisms, to once each year in temperate climates and under greenhouse conditions by the number of plants that can be grown. The objective of this study was to examine grocer ears (pistillate inflorescence) from retail stores as an alternative source for experimental material to use in bioassays to study this important food safety problem. Fusarium verticillioides migration was compared in sweet corn ears from a local grocery store and from greenhouse and field plants. Ears were inoculated with a F. verticillioides transformant tagged with a selection gene encoding resistance to hygromycin, a fungicidal antibiotic, and with a reporter gene encoding for ß-glucuronidase, an enzyme detectable by histochemical staining. Screening kernels for both genes ensures unequivocal identification of the source of subsequent mycelia. Fusarium verticillioides colonized sweet corn ears towards the ear apex and base from the inoculation site regardless of ear source, incubation protocol, or attachment of the ear to the plant or to the shuck (spathe) and silks (styles) to the ear. Thus, ears from retail grocers can serve as experimental material for analyzing sweet corn and F. verticillioides interactions throughout the year.

The effect of fertiliser P on crop biomass production, partitioning, and quality in 'Challenger' sweet corn

Sweet corn kernel yield responds to phosphorous (P) supply, but whether the response is mediated through a general increase in crop biomass or increased partitioning to kernels is unclear. Furthermore, changes in ear quality (ear length, diameter, and unfilled tip length) may also result from changes in crop biomass or partitioning. This research quantifies the partitioning between vegetative and reproductive (including ear quality) components for field-grown sweet corn crops, with a range of total biomass yield resulting from different rates of P fertiliser. To do this, ‘Challenger’ sweet corn was sown in 2 consecutive seasons (2001–02 and 2002–03) on a low-P site (Olsen P = 6.5 μg/g) at Lincoln, Canterbury, New Zealand. Five rates of P fertiliser were applied in each season. In 2001–02, 0, 50, 100, 150, or 200 kg P/ha was applied. These were followed by an additional 0, 0, 10, 20, and 40 kg P/ha in 2002–03. This gave a fertiliser range of 0–240 kg P/ha over 2 years. The resulting range in crop biomass (9.7–16.7 t DM/ha) was conservatively partitioned to vegetative (45%), rachis and husk leaf (32%), and kernel (23%) fractions, indicating that kernel yield responses were solely related to changes in crop biomass. The number of harvestable ears increased by 0.39 ears/m2 for every 1 t DM/ha increase in crop biomass. Similarly, ear quality was related to the kernel yield per primary ear. Specifically, the unfilled tip length decreased by 3.1 mm and individual kernel dry mass increased by 16 mg for every 10 g increase in kernel DM per ear. These results show that P fertiliser should be applied at optimum rates (in these experiments ≥100 kg P/ha) to maximise sweet corn crop biomass, which in turn will lead to maximum kernel yield and ear quality. The conservative partitioning of crop biomass suggests that other agronomic factors that increase total biomass production are likely to have a similar effect on crop yields.

Binomial sequential sampling plans for late instars of European corn borer (Lepidoptera: Crambidae), corn earworm (Lepidoptera: Noctuidae), and damaged kernels in sweet corn ears.

Late-season infestations of European corn borer, Ostrinia nubilalis (Hübner), and corn earworm, Helicoverpa zea (Boddie), were sampled to develop binomial sequential sampling plans for larval infestations and damaged kernels in sweet corn, Zea mays L., ears, near harvest. Fields were sampled to obtain a range of larval densities likely to be encountered over a range of infestation levels and field conditions. Binomial sampling plans were developed for O. nubilalis larvae, H. zea larvae, O. nubilalis, and H. zea larvae combined, and for damaged sweet corn kernels. Observed densities ranged from 0.01 to 4.40 larvae per ear for O. nubilalis, 0.005-1.62 larvae per ear for H. zea, and 0.004-36.12 damaged kernels per ear. Results of resampling analyses, based on the proportion of ears infested with one or more larvae, or damaged kernels, indicated an average sample size of 34-37 ears was necessary to classify whether larval infestations, or the incidence of damaged kernels, exceeded 5%. Two operating characteristic curves are presented for each of the four sampling plans. Initial results, with upper bounds of 0.10, and alpha (type I) and beta (type II) error rates at 0.10 and 0.05, respectively, resulted in a 90% probability of making the correct management decision at infestation levels >10%. To improve performance of the sampling plans, we modified the binomial plans by reducing the upper bound to 0.075, while maintaining the same error rates. This plan resulted in a higher probability (>95%) of making the correct management decision to reject a sweet corn load when infestation levels are >10%.

BROWNING OF FRESH-CUT SWEET CORN KERNELS AFTER COOKING IS PREVENTED BY CONTROLLED ATMOSPHERE STORAGE

Reduced O2 plus elevated CO2 (2% O2 + 10% CO2) was very beneficial in maintaining the visual quality of fresh-cut sweet corn kernels and reduced sugar and flavor losses during 10 days storage at 5 °C compared with storage in air. The main benefit of this controlled atmosphere (CA) was to prevent after cooking browning. Preliminary results indicate that after cooking browning is not associated with a Maillard reaction since 5-hydroxymethylfurfural (HMF), the characteristic intermediate compound produced during the Maillard reaction, is not present in cooked sweet corn kernels exhibiting browning. There were no significant changes in the total soluble phenolics content during storage in air or CA, but the soluble phenolic levels decreased with cooking, which suggests that the after cooking brown color may be due to as yet unidentified insoluble phenolic-protein complexes in the cooked sweet corn tissue The total aerobic microbe count increased with storage and the increase was significantly greater in air. This suggests that the browning could be a response of the sweet corn tissue to the microorganisms, or it may be associated with some product of microbial enzyme activity. INTRODUCTION Fresh-cut sweet corn is a very perishable product since the kernels have a very high respiration rate that increases the rate of deterioration compared to intact sweet corn. Previous work with fresh-cut sweet corn showed that this product can be stored for 10 days in low temperature (0-1 °C). Using atmosphere modification (2% O2 plus 10% CO2) allows storage even at higher temperature (5 °C) without much loss in visual or chemical quality (Brecht, 1999; Riad and Brecht, 2001). There are two main problems associated with this product: loss of sugar and flavor (dimethyl sulfide, the main component of sweet corn aroma), and browning that can occur after cooking when the cut kernels are stored in air at higher than optimum temperatures (Riad and Brecht, 2001). Blanchard et al. (1996) described a similar after cooking browning problem in air-stored diced onion, which was eliminated by storage in 10% CO2. After-cooking browning as a result of the Maillard reaction (a nonenzymatic reaction between sugars and free amino acids usually associated with thermal processing) is common in the food processing industry. This reaction produces 5-hydroxymethylfurfural (HMF) (Bayindirli et al., 1995; Gogus et al., 1998). In the case of sweet corn, the possibility of Maillard reaction would seem to be very high since sweet corn has high levels of free amino acids and sugars (Courter et al., 1988; Grunau and Swiader, 1991), and because the brown color does not develop until the kernels are cooked. Another possibility for this browning is the autooxidation of phenolic compounds that cause polymerization of polyphenolic compounds (Talcott and Howard, 1999). It is well known that phenolic acids increase after wounding (Babic et al., 1993a,b; Howard and Griffin, 1993; Ramamurthy et al., 1992). Brecht (1999) noticed that the browning is severe in cut kernels but there is no browning in intact kernels, which also suggests that the cutting or injured tissues in the kernels might result in elevated levels of phenolics that may play a role in the after cooking browning. Fresh-cut products may have high microbial loads (circa 10 to 10 CFU/g) and these populations may increase during storage and reach high levels (e.g., 10 CFU/g) in Proc. XXVI IHC – Issues and Advances in Postharvest Hort.

Effect of processing conditions on phospholipase D activity of corn kernel subcellular fractions.

The influence of physicochemical conditions on the phospholipase D (PLD) activity of subcellular preparations of sweet corn (Zea mays L. cv. Peaches and Cream) kernels has been studied. The microsomal, mitochondrial, and cytosolic preparations of corn kernels possessed PLD activity albeit at varying proportions. The microsomal and cytosolic PLD activities were stimulated 2-fold between 5 and 15 degrees C. Ethanol had varying modulatory effects on PLD activity. By contrast, acetaldehyde was a potent inhibitor of PLD. As well, a naturally occurring C(6) aldehyde such as hexanal and an alcohol such as hexanol inhibited PLD activity efficiently. Divalent cations such as calcium chloride and magnesium chloride stimulated PLD activity at micromolar levels. Monovalent cations such as KCl and NaCl did not appear to affect PLD activity. Partial purification of PLD from the microsomal, mitochondrial, and cytosolic fractions separately revealed four major isoforms with relative molecular masses of 200, 140-150, 102-108, and 60-66 kDa. The importance of PLD in the maintenance of processed food quality is discussed.

Comparison of Silk Maysin, Antibiosis to Corn Earworm Larvae (Lepidoptera: Noctuidae), and Silk Browning in Crosses of Dent × Sweet Corn

J. Econ. Entomol. 92(3): 746-753 (1999) Sweet corn is one of the highest ranking vegetable crops in the United States in terms of both market value and total acreage: it also ranks among the top vegetable crops in terms of pesticide usage. Ear damage caused by insects is the most significant concern to producers. An estimated 25-40 insecticide applications may be made in a single season to control ear-feeding insects. Plant resistance is an alternative strategy to alleviate environmental concern when pesticides are used. In this study we investigated the feasibility of transferring antibiosis to corn earworm. Helicoverpa zea (Boddie), from dent corn with high silk maysin to sweet corn. Relationships among silk maysin concentration, antibiosis to corn earworm, and silk browning in their F 2 segregating populations were determined. Lyophilized high maysin silks bioassays produced low larval weights, thus providing evidence that damage to sweet corn by corn earworm could be reduced by increasing silk maysin concentration. Simple correlation coefficients indicated a highly significant negative association between silk maysin concentrations and 8-d corn earworm larval weights (r -0.80, P< 0.0001). Silk browning was also closely associated with silk maysin concentrations and antibiosis. Diets containing mid-dark silks reduced larval weights by 68% compared with larval weights (588 mg) on the bean diet control. Maysin analyses and dry-silk bioassays also revealed that if maysin is present in F 2 plants from sweet corn kernels, it is always in a higher concentration than in plants from dent kernels, These results suggest that sweet corn parents in these populations may have a recessive gene, which may be closely linked to sh2 locus enhancing/regulating maysin synthesis when crossed to a maysin producing dent parent.

464 Distribution of Sugars in Sweet Corn

Sweet corn (Zea mays L.) kernels are sinks, and sugars found in kernels must be translocated from a source. Stalk tissues can act as a source and a sink as sweet corn plants age. Quantity and types of sugars present in various sweet corn tissues during plant development are not well documented. Concentrations of fructose, glucose, sucrose, and their total were determined in the ninth stalk internodes (I9) from the 12-leaf stage (V12) to fresh-market maturity (R3) in sweet corn cultivars carrying either the su1se1, su1, or sh2 endosperm genotype. Developing ears were sampled at tassel emergence (VN) and silking (R1). Kernels and cob tissue were sampled separately at blister stage (R2) and R3. Correlation analysis was performed on concentrations of sugars at all developmental stages. In I9, from V12 to R3, levels of fructose and glucose declined and sucrose increased. In developing ears, concentrations of fructose and glucose increased from VN to R1. Concentrations of sugars in cobs in all cultivars were generally the same at R2 and R3. In kernels from R2 to R3 in the su1se1 cultivar, glucose decreased while the other sugars were unchanged; in the su1 cultivar, fructose decreased while levels of the other sugars stayed the same; and in the sh2 cultivar, fructose decreased, glucose was unchanged and sucrose increased. Correlation analysis suggested that the cultivars moved sugars to the kernels differently. The pattern of movement of sugars to kernels was most complex in the su1se1 cultivar than in the su1, which was more comlex than in the sh2 cultivar. Knowing how sugar content changes in the plant may be used to predict sugar content in kernels.

Uptake of natural and anthropogenic actinides in vegetable crops grown on a contaminated lake bed

Activity concentrations and plant/soil concentration ratios (CRs) of 239,240Pu, 241Am, 244Cm, 232Th, and 238U were determined for three vegetable crops grown on an exposed, contaminated lake bed of a former reactor cooling reservoir in South Carolina, USA. The crops included greens and tubers of turnips ( Brassica rapa var. white-globe), bush beans ( Phaseolus vulgaris), and husks and kernels of sweet corn ( Zea mays var. silver queen). Although all plots were fertilized, some received K 2SO 4, while others received no K 2SO 4. The K 2SO 4 fertilizer treatment generally lowered activity concentrations for 241Am, 244Cm, 232Th and 238U, but differences were statistically significant for 241Am and 244Cm only. Highly significant differences occurred in activity concentrations among actinides and among crops. In general, turnip greens exhibited the highest uptake for each of the actinides measured, while corn kernels had the least. For turnip greens, geometric mean CRs ranged from 2.3×10 -3 for 239,240Pu to 5.3×10 -2 for 241Am (no K 2SO 4 fertilizer). For corn kernels, geometric mean CRs ranged from 2.1×10 -5 for 239,240Pu and 232Th to 1.5×10 -3 for 244Cm (no K fertilizer). In general, CRs across all crops for the actinides were in the order: 244Cm> 241Am> 238U> 232Th > 239,240Pu. Lifetime health risks from consuming crops contaminated with anthropogenic actinides were similar to the risks from naturally occurring actinides in the same crops (total ∼2×10 -6); however, these risks were only ∼0.3% of the risk from consuming the same crops contaminated with 137Cs.

Yield, vitamin and mineral contents of organically and conventionally grown potatoes and sweet corn

An experiment was conducted for three years in a Pugwash sandy loam near Truro, NS. Five replicates of two treatments (organic and conventional) were established annually in different plot areas for potatoes ( Solanum tuberosum L. Superior) and sweet corn ( Zea mays L. var. saccharata `Sunnyvee' or `Pride and Joy'. The addition of pesticides, lime and NPK fertilizer to the conventional plots followed a soil test and provincial recommendations; lime, composted manure and insect control applications to the organic plots were according to the guidelines of the OCIA [Organic Crop Improvement Association, 1990. OCIA Certification Standards. OCIA, Bellefontaine, OH, 11 pp.] The compost was analysed for total N and applied to provide 260 kg N/ha for potatoes and 200 kg N/ha for sweet corn, which assumed 50% availability of the total N. Marketable yields were determined, and potato leaves and tubers, as well as sweet corn kernels and ear leaves were digested and analysed for 12 macro- and micronutrients. In addition, the vitamin C content of the tubers and the vitamin C and E contents of the kernels were analysed. Soil samples were also taken at harvest and analysed for essential nutrients and available N. Analysis of the three years of data showed that the yield and vitamin C content of the potatoes was not affected by treatments. However, the conventionally grown treatment outproduced the organically grown treatment for Pride and Joy (cv.) corn, but there was no difference between treatments in the yield of Sunnyvee (cv.) corn or the vitamin C or E contents of the kernels in any year. At p<0.11, four elements in potato tubers (P, Mg, Na, Mn) and four elements in potato leaves (N, Mg, Fe, B) were influenced by treatments, but only leaf Cu was affected in the sweet corn. Correspondingly, extractable P, Ca, Mg and Cu were higher in organically fertilized potato plots; only extractable Mg was affected by treatments in the sweet corn, with the Mg content higher in the organic plots. Only leaf P and K were significantly positively correlated with extractable P ( r=0.70) and K ( r=0.73) in the potato plots, while leaf Cu and kernel S were positively correlated with extractable Cu ( r=0.56) and S ( r=0.62) in the sweet corn plots.

Effects of Degree of Branching on Dispersion Stability of Phytoglycogen in Aqueous Solution

It was supposed that the solubility of (l→4)(l→6)-linked α-d-glucans, e.g., glycogen, phytoglycogen, and amylopectin, in water was related to the colloidal dispersion stability of such molecules and depended on the degree of branching. Since phytoglycogen has various degrees of branching according to the maturation of plant seeds, it was extracted from sweet corn kernels at several days after pollination (DAP), and we have investigated the effects of the degree of branching on the dispersion stability of phytoglycogen (DSP) by salting out, using ammonium sulfate ((NH4)2SO4).As the sweet corn kernels matured, the concentration of (NH4)2SO4 needed for salting out of phytoglycogen increased. According to the degree of branching measured by periodate oxidation analysis and β-amylolysis, the fraction of phytoglycogen precipitated at the high concentration with (NH4)2SO4 has a highly branched structure. The turbidity of phytoglycogen aqueous solution was also measured to discuss the relation between the dispers...

Sugar and Cyclitol Determination in Vegetables by HPLC Using Postcolumn Fluorescent Derivatization

ABSTRACTNonreducing sugars such as sucrose, raffinose, myo‐inositol, pinitol and galactinol were separated on a polyamine‐bonded polymer gel (NH2 type) column using acetonitrile‐water as mobile phase. Sugars in the eluate were detected by periodate oxidation and the subsequent derivation of guanidine to fluorescent compounds. Detection limits were: sucrose 2.5, D‐glucose 2.5 and pinitol 4 ng. This highly sensitive method was more accurate and rapid for determining sugar contents in immature soybean seeds, sweet corn kernels and chinese mustard leaves than the conventional method using refractive index detection. Also, this method reduced the injection volumes of extracts to the column and allowed to lengthen the column life.

Variation in sweet corn kernel characteristics associated with stand establishment and eating quality

A better understanding of the relationships between kernel characteristics associated with eating quality and stand establishment could be helpful in selection of superior genotypes by the sweet corn industry. A set of sweet corn (Zea mays L.) inbred lines with different endosperm mutations (su1, su1 se1 and sh2) were evaluated for field emergence and seedling growth rate at two locations over two years. Kernel characteristics associated with eating quality (kernel moisture concentration, kernel tenderness, sugars, phytoglycogen and dimethyl sulfide (DMS) concentrations were determined for the same inbreds by laboratory analysis from ears harvested at 18 and 22 days after pollination (DAP). Amounts of sugars, phytoglycogen and starch were also measured in mature dry kernel samples of the same inbreds. Extensive genetic variability was found among endosperm mutations and among genetic backgrounds within the different endosperm groups for most of the characteristics under study. Most of the kernel attributes associated with eating quality were uncorrelated indicating that selection to improve specific eating quality characteristics can be conducted simultaneously. A negative correlation between field emergence and sugar concentrations in immature kernels suggests that in breeding programs designed to develop germplasm with improved germination and stand establishment, concurrent attention must be given to the fresh quality of the harvested product. This information is of value to breeders and commercial growers for selection of sh2 and su1 se1 lines with superior field emergence and eating quality.

RELATIONSHIP OF NITROGEN‐SULFUR FERTILIZATION AND HYBRID TO SENSORY CHARACTERISTICS OF shrunken2 SWEET CORN KERNELS

ABSTRACTSweet corn hybrids significantly affected the primary components of eating quality, i. e. sweetness (P &lt; 0.001), sweet corn aroma (P = 0.004), crisp pericarp (P = 0.002) and tender endosperm (P = 0.020). To some degree, N‐S fertilization had an influence on the sweetness of the kernerl (P = 0.067). Hybrids with high levels of kernel DMS and sucrose had more intense sweet corn aroma and sweetness, respectively, with a corresponding increase in sweet corn flavor. A positive relationship was also observed between sweet corn aroma and kernel DMS concentration. Although overall liking did not display significant differences between hybrids and was not correlated with any of the chemical components of flavor, it was positively related to aroma, sweetness and texture, and negatively related to grassiness and starchiness in the kernels. The results in this study demonstrated the importance of conducting sensory evaluation to understand the complex nature of the sensory quality in food crops.

A Comparison of α-Amylase Isozyme Profiles in Selected Su and High-Sugar Sweet Corn (sh-2, su-1, su-1 se) Lines (Zea mays L.)

α-Amylases were purified from germinating starchy (Su) maize kernels (Funks G4646) using glycogen precipitation and preparative SDS-PAGE. Antiserum to the purified α-amylases was produced in rabbits. Isozymes of α-amylase from the scutellum and aleurone tissues of kernels of five Su lines were compared with a sweet corn (su-1) and two high-sugar sweet corn (su-1 se and sh-2) inbred lines in the same genetic background, using isoelectric focusing gels, starch zymograms, and immunoblotting analyses. The most notable differences were found in the high-sugar sweet corn kernels. In the sh-2 aleurone, there were no α-amylase isozymes detected on the zymogram and immunoblot, indicating a lack of enzyme accumulation. In the su-1 se scutellum, there were fewer isozymes compared with most of the lines examined, but the significance of this is not clear. Comparison of the five Su lines revealed several isozymes common to all the kernels examined, but there were considerable tissue-specific differences in the number of isozymes between the aleurone and scutellum tissues. The Funks G4646 (Su) and RB-4 (Su) had similar scutellar and aleurone isozyme patterns, with the aleurone having one more isozyme than the scutellum. In OH43 (Su) kernels, the scutellum had one to two more isozymes with α-amylase activity than the aleurone, while the IL451b (Su) scutellum had fewer isozymes (seven to eight) than the aleurone (14-16). Both high- and low-pI isozymes of wheat and barley, and the low-pI isozymes of rice, were recognized by the antibodies to maize α-amylases developed in this study. These data indicate a complex relationship between the carbohydrate and sugar composition of the kernel and the synthesis of α-amylase isozymes during germination.