The effect of cooking methods on the lipid composition of potatoes

The effect of boiling and baking in either a convential or microwave oven on the lipid content of potatoes was investigated. The crude lipid content of potatoes was lowered significantly by all methods of cooking. The loss was highest in potatoes cooked in a microwave oven, least in boiled tubers, and intermediate in tubers baked in a conventional oven. Similar trends were observed for both cortex and pith tissues. Generally, the phospholipid content followed the same trend as the crude lipid, the exception being the cortex tissue of tubers baked in the conventional oven, in which the greatest loss of phospholipid occurred. Cooking did not significantly alter the fatty acid composition of tubers. A possible relationship between the degree of cell rupturing, known to be influenced by different mechanisms of heat transfer, and the amounts of tuber lipid associated with different cooking methods was discussed.     

Sensory and cooking quality of individually film wrapped potatoes

Newly harvested Russet Burbank potatoes were cured for 3 weeks at 15.5 C. The cured potatoes were individually film wrapped either immediately, or stored at 7.2 C for 12 weeks and then film wrapped. The film wrapped potatoes stored at 20 C were compared with nonwrapped potatoes stored at 7.2 C or 20 C for cooking time and various sensory characteristics. The sensory and cooking characteristics of the film wrapped potatoes stored at 20 C were better than the baking characteristics of nonwrapped potatoes stored at 20 C but not at 7.2 C. Individual film wrapping of potatoes significantly preserved the baking and cooking quality of potatoes during storage at 20 C, 60% RH.     

Storage temperature for maintenance of internal quality in Idaho Russet Burbank potatoes

Idaho-grown Russet Burbank potatoes treated with a sprout inhibitor were stored at 42 F, 45 F, and 48 F for 11 months. Monthly quality evaluations showed that tubers stored at 42 F were less mealy, contained more reducing sugars, and were yellower in color than those stored at 45 F or 48 F. The latter two treatments were not significantly different in mealiness and were generally similar in yellowness of color. Tubers stored at 48 F had less reducing sugars than those stored at 45 F. Although all treatments resulted in a gradual darkening of the potatoes during storage, differences in grayness among the three storage treatments were minor from a practical standpoint. It is suggested that a storage temperature no lower than 45 F be used to maintain the internal quality of Russet Burbank potatoes.     

Reducing chilling injury of potatoes by intermittent warming

Potato tubers held continuously 19 weeks at 32 F developed chillinginjury symptoms early during storage and the symptoms worsened with time in storage. Early symptoms included browning and surface mold on skinned areas. By 11 weeks mahogany browning, blackheart, and hollow heart, bluish skin discoloration and sinking of intact skin were visible in daylight. And under ultraviolet light, yellow fluorescence was visible in halos, washes, or spots around or near internal tuber tissues discolored by other chilling-injury symptoms. Some damage at 32 F became visible after subsequent holding of tubers for 1 week at 60 F. Tubers accumulated high amounts of reducing and total sugar at 32 F and respiration, measured at 60 F as CO₂ evolved, was progressively stimulated by time at 32 F. Sugar build-up, respiration-rate increase, and chilling injury seemed to show no cause-and-effect relationship but appeared as separate phenomena each caused by the stress of holding tubers at too low a temperature. Moving potatoes to 60 F for 1 week after every 3rd week to interrupt storage at 32 practically eliminated all forms of chilling injury except skin browning and surface mold which were greatly reduced. Sugar content and respiration rates in tubers intermittently held at low and high temperatures were higher after periods in low temperature and lower after periods at 60 F, and in general were maintained at levels much lower than in potatoes held continuously at 32, 36, or 40 F. In all treatments sugar content was higher than desirable for chipping type potatoes. Holding potatoes at 60 F for 1 to 4 weeks before placing them at 32 F reduced skin browning and surface mold but had no effect on other forms of chilling injury, sugar accumulation, or respiration rates in tubers as measured after 15 to 19 weeks continuously at 32 F. Practically no chilling-injury symptom except for very little mold growth and browning of skinned areas developed in tubers held in 36 or 40 F.     

Effect of storage temperature on tuber composition,extrusion force,and Brabender viscosity

Kennebec potatoes were evaluated for the effect of storage temperature and time on tuber composition and on mealiness as measured by extrusion force of baked potato and Brabender viscosity of raw, lyophilized tissue. Potatoes from three specific gravity classes, 1.072, 1.082, and 1.090 (±0.001), were evaluated initially and after storage at 1.7°C for 2 and 3 mo., 7.2°C for 2 and 3 mo., 1.7°C for 2 mo. followed by 7.2°C for 1 mo., and 7.2°C for 2 mo. followed by 1.7°C for 1 mo. There were highly significant differences in mealiness associated with the storage treatments and with specific gravity. Mealiness decreased as temperature decreased. Mealiness estimates of tubers from the storage temperature reversal treatments were intermediate to those of the 7.2°C and 1.7°C treated tubers. Simple correlation analysis showed extrusion force and Brabender viscosity to be significantly and positively related to each other, to total starch and to swollen starch and significantly but inversely related to glucose and to the sum of glucose plus sucrose. Specific gravity and total solids were significantly but less highly positively correlated with both physical measurements. Multiple correlation-regression analysis showed only total starch to be significantly related to mealiness independent of the other compositional variables.     

Internal quality of Russet Burbank potatoes following chilling

Russet Burbank potatoes were chilled at 25 F (?3.8 C), 27.5 F (?2.5 C), or 30 F (?1.1 C) for various periods of time and were then held at 45 F (7.2 C) for one or four weeks before testing. Susceptibility to injury was quite variable between the two crops and among tubers of the same lot exposed to the same treatment. The greatest amount of low temperature breakdown occurred in tubers chilled at 27.5 F (?2.5 C) for 10 hours. Flesh color, reducing sugar content, mealiness, and amount of sloughing in tubers that survived chilling were not markedly different from those in control samples although certain trends were observed indicating that the quality of chilled tubers was beginning to deteriorate. Chilling increased yellowness of flesh color in most treatments and darkness in several. Chilled tubers had a reducing sugar content slightly to moderately higher than the controls. They sloughed less than the controls and tended to be less mealy     

Sensory quality of Ontario potatoes compared with principal varieties grown in Maine

Baked potatoes of five varieties grown at the same location in Maine were evaluated for quality shortly after harvest and after six months’ storage by sensory panels of 16 and 18 members. The Ontario variety was rated significantly poorer (P = 0.05) in flavor than Russet Burbank, Katahdin, and Superior, but did not differ from Kennebec when tested in November. Following storage, however, these differences were not significant. At the 1% level of detection, Ontario tubers were judged significantly less mealy than those of the Russet Burbank, Katahdin, Superior, and Kennebec varieties (Nov. Kennebec excepted) and were grayer (Mar. Superior excepted). Due to the low mealiness ratings and grayness of flesh, tubers of the Ontario variety were considered less desirable for table stock than potatoes of other principal varieties grown in Maine.     

Andover: An early to midseason golden nematode resistant variety for use as chipstock or tablestock

Andover may be used as an early to midseason tablestock and chipstock variety. It has a very rapid emergence and early tuber set. The vine maturity is similar to Superior in the absence of severe stress. In New York trials harvested 90 days after planting, the yields of Andover and Superior are nearly equal, 274 cwt/A. At 120 days, over eight seasons at two Ithaca locations, Andover yielded 87% Atlantic. Andover appears to be susceptible to drought and heat stress which can cause early senescence and reduce late season yields. It has few external and internal defectS. Specific gravity is high for an early variety, being .009 less than Atlantic. Andover has excellent chip color from the field from a range of environments and from 7 C storage. It has good boiling and baking properties. The mealiness of the baked potatoes is especially good. Tuber dormancy is two weeks longer than Atlantic. The reaction to common scab is like that of Monona, which is considered to be resistant. It is also resistant to powdery scab and the golden nematode.     

K326烟叶在密集式烤房条件下121烘烤工艺初探

根据卷烟工业开发浓香型特色优质烟叶的要求,为探索烤烟K 326品种在密集式烤房条件下的烘烤工艺,解决烟叶在现有烘烤工艺下烤黄不烤香,烟叶含青量过大,淀粉含量过高等问题,在烤烟三段式烘烤工艺的基础上,调整变黄期干湿球温度和变黄程度指标,对K 326烟叶烘烤工艺进行了改良。结果表明,改良后的烘烤工艺能降低淀粉和叶绿素含量,总糖含量提高6.64%,还原糖含量提高6.26%,增加了中上等烟叶比例,提高了产值,烟叶质量变佳,工业可用性得到提高。     

Inactivation of trypsin inhibitors in sweet potato and taro tubers during processing

In order to understand the extent of elimination of trypsininhibitors during processing of sweet potato (Ipomoea batatas) andtaro (Colocasia esculenta) tubers, a detailed study was conductedusing tubers processed by oven drying, cooking, and microwavebaking. Between 80 and 90% trypsin inhibitor (TI) activity wasretained in sweet potato chips up to 2h at 70 ^°C. Among thefour cultivars of sweet potatoes, RS-III-2 trypsin inhibitors were more heatlabile. Heating at 100 ^°C led to rapid inactivation of TI of sweetpotatoes. Varietal differences in thermal stability were more pronouncedfor the trypsin inhibitors of taro than sweet potatoes. Taro inhibitors werealso more rapidly inactivated than sweet potato TI. Between 17 and31% TI activity was retained in cooked tuber pieces of sweet potatoes,while only 3–10% were retained in taro cultivars. Very effectiveinactivation of trypsin inhibitors of sweet potatoes and taro could beobtained through microwave baking. Flour prepared from taro was devoidof TI activity, while 5–12% TI activity was retained in the flour preparedfrom sweet potatoes. The study clearly established that among the fourtechniques used, microwave baking and flour preparation were the best methods to eliminate TI from sweet potatoes and taro.     

Growth and preharvest stress and processing quality of potatoes

The quality factors influenced by stress conditions are: total dry matter or starch content and distribution of starch, sugar content, types of sugars and distribution, texture, mealiness, flesh color, tuber size and shape, and tuber defects such as growth cracks, and hollow heart. Early stress during growth can cause tubers to become pointed on the stem-end with low starch content and high reducing sugars. Uneven growth due to stress results in growth cracks, or hollow heart and malformed tubers. Varieties differ considerably as to susceptibility. Stress generally causes lower starch content in tubers which results in greater sugar accumulation in storage. Relative maturity is also influenced by stress during growth. Immature and over-mature tubers (from prematurely dead plants) accumulate greater amounts of sugar in storage than tubers properly matured. Stress can also cause poor texture of processed products, such as tough texture of French fries as well as lack of mealiness. Flavor and color of processed products can also be detrimentally influenced by stress.     

The incidence of decay and factors affecting bacterial soft rot of potatoes

The incidence of tuber decay in rail car shipments of potatoes from the State of Washington was determined from 1965 to 1969 inclusive. Reinspection certificates revealed that 7.9% of the rail cars of potatoes shipped during this period were rejected due to tuber defects; tuber decay accounted for 63% of these rejected cars. Percentage of rejections due to tuber decay was greater for Russet Burbank than for Norgold Russet potatoes. Temperature, moisture, and oxygen levels influenced development of bacterial soft rot in freshly harvested potatoes and in potatoes stored for 3 months at 35 F (2 C) previous to treatment. When tuber surfaces were kept dry, no soft rot developed in 11 days over ranges of 50–70 F (10–21 C) and 2–20.5% oxygen levels. Freshly harvested tubers partially immersed in water did not rot when cooled to 40 F (4.4 C) in < 24 hours and held for 8 days under either 20.5 or 4% oxygen levels; however, tubers, rotted when stored similarly but at 50 F or higher temperatures. Partially immersed tubers incubated for 1 day or longer at 70 F developed soft rot in a low oxygen (4%) when later stored for, 8 days at 40 F. When rot occurred, the amount was always greater under lower oxygen levels irrespective of storage temperature. Of various cooling methods tested in rail cars loaded with 100 lb (45.4 kg) sacks of potatoes, prechilling of tubers and icing of cars prior to loading lowered floor temperatures most rapidly. Icing cars after loading lowered floor temperatures the slowest. In a carton shipment, the temperature remained above 68 F (20 C) in cartons after 8 days in transit, even though the wall and floor temperatures had cooled to near 55 F (12.8 C) by the second day. Oxygen level surrounding, tubers in the center of car loads of 100 lb sacks of potatoes was approximately 20.5% after 8 days transit.     

Seed potato quality as influenced by high temperatures during the growth period. 1. Effect of storage temperature on sprout growth

Summary In the Negev area of Israel potatoes are grown in two seasons of the year: spring and autumn. Locally grown seed of cv. Up-to-Date prepared for the autumn season are grown in the spring under high-temperature conditions during the last part of the growth period. The response to storage temperature treatments consisted of different degrees of sprouting. Temperatures that encouraged bud development (12–22°C) shortened the dormant period of the tubers by about a month, and usually there is clear apical dominance. However, increasing length of the apical bud was positively correlated with storage temperature. Partial loss of apical dominance was obtained when the tubers were held at a low temperature (4°C) for at least two months after lifting. After transfer of the tubers to high temperatures for another month, there were 3 or 4 sprouts per tuber. The physiological age of seed tubers developing in the semi-arid region is discussed. Contribution from the Agricultural Research Organization, Beit Dagan, Israel 1979 Series, No 300.     

Techniques for successful field seeding of true potato seed

Crops of potatoes were successfully grown during each of 7 yrs from botanical seed planted directly into fields. During this period a total of 8 ha of direct-seeded potatoes was grown in 27 trials involving several soil types and several planting, cultural, and irrigation methods. Methods of seed production, extraction, treatment, and planting were developed along with methods of weed and insect control and methods of caring for growing seedlings so they would produce good yields of tubers, many of which were of commercial size and quality and very useful in a breeding program.     

Effects of Holding Temperatures on the Development of Zebra Chip Symptoms, ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter Solanacearum’ Titers,and Phenolic Levels in ‘Red La Soda’ and ‘Russet Norkotah’ Tubers

‘Candidatus Liberibacter solanacearum’ (Lso) is the putative causal agent of zebra chip disease (ZC). Late season Lso-infected potatoes that are known to be asymptomatic at harvest may continue to develop symptoms by the time of shipment to consumers. This study observed symptom development, Lso titer changes, and changes in symptom-associated phenolic compounds in Lso-infected yet asymptomatic tubers placed at different holding temperatures. ZC symptoms present in freshly-sliced tubers were more severe in ‘Red La Soda’ or ‘Russet Norkotah’ tubers held at 3 °C than at 6 °C or 9 °C. However, Lso titers showed considerable variability in both cultivars over time and at these holding temperatures. Phenolic compound levels, known to be associated with ZC symptom severity, in tubers kept at 3 °C were greater than those kept at 6 °C or 9 °C and increased over time. These results demonstrate that ZC could develop in tubers kept in cold storage, with those kept at 3 °C having more ZC development than those kept at 6 °C or 9 °C.     

Effects of Baking and Boiling on the Nutritional and Antioxidant Properties of Sweet Potato [<Emphasis Type="Italic">Ipomoea batatas</Emphasis> (L.) Lam.] Cultivars

The effects of baking and boiling on the nutritional and antioxidant properties of three sweet potato cultivars (Beniazuma, Koganesengan, Kotobuki) cultivated in Turkey were investigated. The samples were analyzed for proximate composition, total phenolic content, ascorbic acid, β-carotene, antiradical activity, and free sugars. The dry matter, protein, and starch contents of the sweet potatoes were significantly changed by the treatments while the ash and crude fiber contents did not differ as significantly. The β-carotene contents of baked and boiled sweet potatoes were lower than those of fresh sweet potatoes; however, the total phenolic and ascorbic acid contents of the baked and boiled sweet potatoes were higher than those of the fresh samples. Generally, the antiradical activity of the sweet potatoes increased with the treatments. Sucrose, glucose, and fructose were quantified as free sugars in all fresh sweet potatoes; however, maltose was determined in the treated samples. In terms of the analyzed parameters, there were no explicit differences among the sweet potato cultivars.     

Effect of storage period, cultivar and two growing locations on the processing quality of french fried potatoes

The source of raw potato tubers and the tubers’ duration of storage have a significant effect on color and texture of french fries. Controlling these variations is crucial to ensuring a consistent, high-quality end product. Russet Burbank and Shepody potatoes grown at two sites in Manitoba, Canada were stored for 9 and 11 months in 1994, and for 1 and 3 months in 1995, to determine the effects of short-term storage period, cultivar, and two tuber-growing locations on fry color and texture. French fry texture was measured by a puncture test, and peak force and peak deformation used as indices of textural quality. Large peak forces and deformations were assumed to be indicative of improved textural quality. Hunterlab L (lightness) value was used to determine fry color, higher values being associated with improved color quality. Fries processed from 11-month-old tubers had improved color and textural quality compared to those processed from 9-month-old tubers. Fries processed after 3 months tuber storage were darker in color but firmer in texture than fries processed from tubers after 1 month of storage. Differences in texture and color between the two cultivars were more evident with prolonged storage; fries processed from Russet Burbank potatoes were superior in texture and lighter in color than fries made from Shepody potatoes. With respect to site, fries processed from potatoes grown at Portage had better texture but darker color than those processed from Carberry potatoes. It was postulated that the calcium content of the soils may be responsible for both these results.     

Impact of different baking processes on bread firmness and starch properties in breadcrumb

The influence the quality and shelf life of baked product has previously been reported to be effected by the time and temperature of the baking process. In this study, dough was baked at 219 °C by using different ovens (conventional, impingement or hybrid) or with doughs of different sizes (large or small) for varying times. During baking the temperature profile at the dough center was recorded. Texture, thermal properties and pasting characteristics of baked product with reference to baking conditions were investigated. Small breads baked in the hybrid oven had the highest heating rate (25.1 °C/min) while large breads baked in conventional oven had the lowest heating rate (6.0 °C/min). When the data are viewed as a function of heating rate in this study, the enthalpy of amylopectin recrystallization, rate of bread firmness and the amount of soluble amylose were all-lower at the slower heating rate. The differences observed in product firmness following storage are potentially a consequence of the extent of starch granule hydration, swelling, dispersion and extent of reassociation; all of which are affected by the heating rate during baking.     

Preconditioning and storage of chemically immature Russet Burbank and Shepody potatoes

Russet Burbank and Shepody potatoes of different chemical maturities (i.e. varying sucrose concentrations) at harvest were preconditioned by holding at 15 C for various durations to lower the concentration of reducing sugars to levels acceptable for processing as french fries out of 8 C storage. In chemically immature tubers (i.e. those harvested with a high sucrose), sucrose declined after harvest and stabilized in storage regardless of the preconditioning period. However, there was a temporary small increase in sucrose after harvest in more chemically mature tubers. The concentrations of the reducing sugars glucose and fructose were low at harvest, usually < 1.0 mg g^?1, but increased rapidly during the first 30 to 45 d of storage in tubers with more than 2.0 mg g^?1 sucrose at harvest. Preconditioning for up to 70 d at 15 C either limited the increase in reducing sugars or lowered them more rapidly during storage than when preconditioned for only 14 d. Fresh weight loss of Russet Burbank and Shepody was greater in physically and chemically immature tubers compared to more mature tubers. Extended preconditioning of Russet Burbank and Shepody resulted in minimal additional weight loss.