We thank Monika Möhler, Kurt Ehm, Wolfgang Meyer, and Erhardt Sonnenkalb for providing fruit samples, Ruth Richter and Matthias Hinz for technical assistance, Stefanie Peschel for useful discussion, Dieter Reese for building experimental equipment
Abstract
A consistent preference by the meadow vole, Microtus pennsylvanicus, for the roots of certain inbred carrot lines and hybrids observed in field plantings suggested the possibility of using these animals to evaluate carrot breeding material for nutritive value and culinary quality. In a preliminary field test, 50 carrot lines representing the full range of feeding damage were planted in a confined feeding experiment. Lines showing no damage and severe damage were selected for controlled feeding trials and further evaluation.
In laboratory ad libitum feeding tests, all carrot diets were inferior to control diets. There was no relationship between vole preference and the nutritive value of the carrots as measured by the growth response of weanling voles. However, vole preference showed a significant positive correlation with the sucrose content of the roots while a significant negative correlation was found between preference and total reducing sugars. Neither growth response nor vole preference was correlated with crude fiber, protein, or total carbohydrates. No correlation was found between taste panel scores for overall rating of carrot samples and ad lib. feeding indexes by the voles.
Sweetpotato resin glycosides were purified by HPLC methods. Most allelopathic potential could be explained by these compounds. Fifty percent inhibition (I50) of seed germination was obtained for redroot pigweed at 160 ppm, for velvetleaf at 13 ppm and for prosomillet at 11 ppm. Seed of the congeneric species I. purpurea was not sensitive. Growth of yellow nutsedge was drastically reduced, the I50 for shoot growth was 30 ppm, for number of roots 36 ppm, and for total root length 19 ppm. The glycosides accounted for approximately half of the total fungicidal activity of all extract fractions when tested on Fusarium oxysporum pv. batatae. At 2 mg per ml, the glycosides inhibited hyphal growth by 31%. This concentration is less than 10% of the glycoside concentration in dry periderm tissue of `Regal'. The purified glycosides were incorporated into a meridic diet for diamondback moth larvae. All observed antibiosis was caused by the glycosides; the LD50 was 7.2 mg per ml diet. At that concentration the surviving larvae showed a weight decrease of 46%.
Carrots contribute ≈14% of the total Vitamin A to the human diet in the United States due to the presence of the provitamin A carotenoids α- and β-carotene. We have described a recessive gene (rp) that inhibits carotenoid biosynthesis in carrot by 93%, resulting in whitish-yellow roots. The rp mutation is also associated with relatively high levels of a tocopherol (Vitamin E, 0.61±0.15 mg α-tocopherol/100 g FW). Vitamin E is a powerful antioxidant that must be obtained from the diet. The biosynthesis of a tocopherol in carrot has not been studied in any detail; however, the rp gene may provide clues as to its mechanism. The production of carotenoids and tocopherols is biosynthetically linked by their common precursor, geranylgeranyl diphosphate (GGDP). GGDP is converted into phytoene by phytoene desaturase to produce carotenoids and combined with homogentisic acid to produce tocopherols. Carotenoid and tocopherol profiles for various carrot genotypes are presented alongside a model describing the potential relationship between root carotenoids and tocopherols in carrot. The presence of significant amounts of tocopherols in carrot could significantly raise the nutritional profile of this vegetable.
The origins, demise and current status of some common misconceptions about the role of fruit and vegetables in human nutrition are discussed. Most, but not all, of the misconceptions were held by the public. The early widespread belief that tomatoes were poisonous was gradually overcome, and today the tomato is one of the most versatile and widely used foods in the diet. Recent reports suggest that consumption of tomatoes and tomato products has the potential to reduce the risk of certain cancers. Our current awareness of the potential of spinach in nutrition and health evolved from an early misconception that its only important nutritive value was as a source of iron. The connection between foods from the nightshade family and arthritis and the connection of cherries and gout relief are discussed briefly. The misconception that a wide variety of fruit and vegetables was not needed in the human diet was rejected long ago. Today fruit and vegetables are considered essential for their intrinsic nutritive value and for their potential health functionality because of the phytochemicals they contain.
Fruits and vegetables are rich sources of the micro mineral elements and vitamins often lacking in diets based on cereals, grain legumes, and starchy roots and tubers, but void of animal products. When embarking on a breeding program to improve nutritional compounds, the way the fruit or vegetable is consumed in mixed diets must be considered. To alleviate nutritional problems, the nutrients must not only be present in the plant parts consumed, but also absorbed efficiently in the body. In some cases, it may be necessary to modify compounds to improve absorption as well as increase the concentration. Breeding to improve nutritionally related traits can be approached in a manner similar to that for other traits; i.e., identification of genetic variability, selection for enhanced levels using either individual phenotype or family mean values, and testing for field performance. In addition to improving amount and availability, avoidance of undesirable correlated responses due to genetic or physiological linkages between the trait of interest and other traits deleterious to either plant growth or the consumer is critically important during selection. The growing number of molecular marker-based linkage maps should prove especially useful for identifying genes of interest and employing marker-aided selection. When insufficient variability for amount or type of compound is present in the gene pool, strategies using transgenic plants may be useful.
The authors are grateful to Dr. Masahiro Mii, Faculty of Horticulture, Chiba University, for his advice and critical reading of this manuscript. This research was supported by Diet and Cancer Prevention: Exploring Research Technology, Miyazaki
Dry edible beans (Phaseolis vulgaris) represent an inexpensive way to incorporate protein into the diet as a food ingredient, but beans contain unpleasant flavors and several anti-nutritional factors that limit their use without first processing with long heat treatments. `Great Northern' bean flour was processed using either static or specially designed dynamic (continuous) processing methods. The dynamic process treated flour slurries at temperatures up to 124°for 20 sec. The slurries were quick-frozen and freeze-dried after frozen storage periods of 0, 8, 24, 120, or 504 hr. The flours were analyzed for sensory properties, emulsifying activity, foaming properties, and trypsin inhibition. The heat treatments improved sensory attributes of the flour. The foam capacity and foam stability decreased in heat-treated flours. Trypsin inhibitor activity was at a minimum level immediately following thermal processing, but increased with time in frozen storage prior to drying. Minimal thermal processes cannot be relied upon to inactivate trypsin inhibitors.
Abstract
The cowpea, Vigna unguiculata (L.) Walp., has been cultivated since Neolithic times, and it is one of our most ancient food plants. Cowpeas are important in world agriculture with more than 12 million acres (5 million hectares) produced annually. The seed, leaves, and shoots provide a significant portion of the dietary protein in the stable cereal diets of people in many of the developing nations. Although the cowpea is an excellent forage and green manure plant and was once an important agronomic crop in the United States, there is only limited agronomic use of the crop in this country at present. However, the cowpea has long been valued in the South as an edible table legume, and an extensive industry now exists to supply the cowpea products that are consumed nationwide.
Abstract
The selection of olive (Olea europaea L.) cultivars goes back to early biblical times. The main objectives were high oil content and regional adaptability. Subsequently, olive cultivars were selected also on a size basis for table consumption. In the last hundred years, form and size of green table olives became even more important than their oil content, but still, the minimum oil content was not lower than 7 to 8% oil of fresh wt for green ripe fruit. Selection for low-oil-content olives has not been attempted in the past. However, with diet consciousness and increased awareness of public health, the development of low-oil-content olive, particularly for dietetic use is of interest. This release describes a new olive named ‘Kadesh’ with extrem ely low oil content, yield stability, and relatively easy rooting (1).