The Effect of Domestic Preparation of Some Potato Products on Acrylamide Content

The influence that food heating has on the concentration of acrylamide in home-cooked potato dishes prepared by high-temperature, such as pan-frying, deep-frying, roasting and microwave heating was analyzed. The experiment was performed with commercially available deep-frozen par-fried French fries and deep-frozen par-fried potato products other than French fries (cubes, wedges, noisettes, pancakes). Acrylamide was found in all deep-frozen par-fried French fries and other deep-frozen par-fried potato products before domestic preparation. The mean level of acrylamide content in all frozen potato products before preparation was found to be 322 μg/kg. Potato products were then prepared at 180 °C for 3 min and at 220 °C for 10 min. After domestic preparation (roasting, pan-frying, deep-frying and microwave heating) it was found that the level of acrylamide in all products increased. Acrylamide content in the analyzed samples significantly increased as the temperature and time of processing increased. The statistical analysis showed significant differences (P < 0.05) for acrylamide content as a function of food preparation. The level of acrylamide increased with the increased heating temperature and heating time. Additionally, the preparation method of roasting was significantly lower in acrylamide content (P < 0.05) than the preparation method of microwaving although both preparation methods used the same conditions (time and temperature). These results suggest that microwaving might be more favourable to the formation of acrylamide than conventional heating methods, such as roasting.     

Determination of blanching conditions for frozen par-fried potatoes

A procedure is presented for determining systematically the optimum blanching conditions required for potatoes from low temperature storage that are to be used for frozen French fries. Processing includes a low-temperature blanch for partial cooking and leaching of excess sugar followed by a brief immersion in glucose solution, if needed, for uniform coloring during finish frying. The glucose solution, or plain water if additional glucose is not required, should be of high temperature if other processing steps do not provide sufficient heating for complete enzyme inactivation. The potatoes are then par-fried and frozen.     

Frying Stability of Moringa stenopetala Seed Oil

The frying performance of Moringa stenopetala seed oil (extracted with cold press or n-hexane) was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175 °C for 5 consecutive days (5 fryings per day). The chemical changes occurring in oils were evaluated. Free fatty acid content, polar compounds, colour and viscosity of the oils all increased, whereas the iodine value, smoke point, polyunsaturated fatty acid content, induction period and tocopherol content decreased. The effect of the oil on the organoleptic quality of these fried foods and the theoretical number of frying operations possible before having to discard the oil was also determined. The analytical and sensory data showed that the lowest deterioration occurred in cold press produced oil.     

Processing conditions influencing the physical properties of French fried potatoes

Summary Achieving optimal colour and texture in French fries requires careful control of the unit operations that convert the raw potatoes into fries. The effects of variation in blanching, drying and finish frying conditions on puncture properties (peak force and peak deformation) and Hunterlab L (lightness) values of French fries were investigated. Fries blanched by low-temperature long-time (LTLT) conditions had larger peak force, peak deformation and L value than fries processed by standard conditions. High-temperature short-time (HTST) blanching increased lightness but decreased peak force and peak deformation. For drying, the colour and textural quality of French fries processed by standard conditions were better than those processed by the drying alternatives. For finish frying, LTLT conditions increased peak force whereas HTST conditions increased lightness. Therefore, a compromise has to be made in processing conditions to optimise both colour and textural quality. Even after finish frying, compositional differences within potato tubers influenced texture, both between and within French fries.     

Moisture Content and Oil Uptake in Potatoes (Cultivar Satina) During Deep-Fat Frying

In this study, the effect of ultrasonic sound (at 20- and 40-kHz frequency for 15 min) and drying (at 60 °C for 15 min) pretreatments on the moisture content and oil uptake of potato slices (cultivar Satina) during deep frying were studied. The potato slices were fried at temperatures of 170 and 190 °C for 5, 7 and 10 min. Samples pretreated with ultrasound at 20 kHz had higher moisture contents than those receiving the 40-kHz pretreatment. The highest moisture content was obtained at 20 kHz and frying at 170 °C for 5 min. On the other hand, samples pretreated with ultrasound at 40 kHz had higher effective water diffusivity coefficient and activation energy than those pretreated at 20 kHz. The highest effective water diffusivity coefficient was obtained at 40 kHz and frying at 190 °C for 5 min, whereas the highest activation energy belonged to pretreatment with 40 kHz and frying at 170 °C for 10 min. The range for effective water diffusivity coefficient was 6.95?×?10^?8 to 8.80?×?10^?8 m² s^?1 and that for activation energy was 13.161 to 16.307 kJ mol^?1. In addition, samples pretreated at 40 kHz had a lower oil uptake than those pretreated at 20 kHz. The highest oil uptake took place at 20 kHz, with frying at 170 °C for 10 min. Regression analysis revealed that an exponential model was best for predicting variations in moisture content and oil uptake of potato slices.     

Sensory quality of French fries prepared from BelRus and Russet Burbank potatoes

Frozen par-fries were processed in January, February, and March using BelRus and Russet Burbank potatoes which were obtained from the same source and held under the same storage conditions. At each processing date, total solids of the raw tissue were determined and the par-fries were analyzed for fat content. Samples were finish-fried and presented to panels for evaluation of sensory qualities. The color, flavor, and textural properties of frozen French fries prepared from BelRus potatoes, which were considerably higher in total solids content and absorbed less vegetable oil, were significantly preferred by sensory panels to French fries processed from Russet Burbank potatoes.     

Some storage characteristics of potato cultivar Atlantic

The cultivars Atlantic, Kennebec and Katahdin were compared as to their storability and cooking qualities for the storage seasons 1974–75 and 1975–76. The studies show Atlantic was equal to Katahdin and Kennebec with regard to storability, except that at storage temperatures above 40°F (4.5°C) for 6 months, sprouting was excessive. Storage losses due to Fusarium tuber rots from natural infection were higher in Atlantic than either Katahdin or Kennebec. The processing quality for chips and French fries of Atlantic was equal or slightly better when compared to the other varieties tested.     

Properties of Frozen Wheat Doughs at Subzero Temperatures

The subzero properties of wheat doughs were measured by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) over the temperature range −90 to +40 °C and by¹H-nuclear magnetic resonance (NMR) T₂relaxation over the range −45 to 0 °C. The experiments revealed two transitions in the dough: one independent of frequency at −10 °C (attributed to ice melting) and one dependent on frequency at −30 °C (attributed to a glass transition). The glass transition temperatures measured by DMTA moved to higher temperatures during frozen storage when the optimal water content of dough was used. A reduction in the water content eliminated this phenomenon. A similar effect of water reduction was observed by NMR studies, in which amplitude ratios and decay times were used to calculate the phase transitions. However, the glass transition recorded by NMR was independent of frozen storage with optimal water content. The changes of water state in frozen doughs were studied by ultracentrifugation (the amount of liquid phase) and NMR (freezable water based on liquid amplitude ratios). Frozen storage increased the liquid phase in dough with optimal water content. Thus, ice crystals are growing during frozen storage resulting in the concentration of polymers and a higher glass transition observed by DMTA. The increase of liquid phase during storage was substantially lower when the water content of dough was decreased. Ice crystals» growth can be minimised by reducing water content. The experiments were carried out with four different flours. The measurement of glass transition temperature by DMTA, DETA or NMR did not reveal great differences in doughs made from different flours. The amount of liquid phase was strongly flour dependent.     

Physical properties of estolides and their ester derivatives

Vegetable oil based lubricants have good lubricity and biodegradability but often fail to meet viscosity requirements at cold temperatures. These properties for a lubricant are often evaluated by pour point (PP), the minimum temperature at which a liquid will pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes a fluid that has little viscosity change over a wide temperature range. In order to develop better quality vegetable based lubricants, pour point, melting point and viscosity (40 and 100°C) were determined for a series of esters (methyl, butyl, decyl, oleyl, 2-propyl, 2-ethylhexyl, C18-Guerbet and C24-Guerbet) of meadowfoam, crambe and oleic fatty acids and estolides. Oleic estolide esters had the lowest melting points of all derivatives studied. Of the oleic estolide series the 2-ethylhexyl and C18-Guerbet esters had the lowest melting points, −34 and −43°C, respectively. Similar melting point trends within the series of esters were observed for both fatty acids and estolides. Pour points of the oleic estolides were also determined on a series of both free acid estolides and their 2-ethylhexyl esters. The series compared the effect of oligomerization on pour point. Pour points of oleic estolides were 5–10°C higher than the corresponding derivative's melting point. The extent of oligomerization (estolide number, EN) played a significant role in the pour point with higher oligomerization giving higher pour points (EN of 2.96 had a PP of 0°C; EN of 1.1 had a PP of −27°C). In a similar fashion, viscosity increased with higher oligomerization and free acid estolides were generally several hundred centistokes (cSt) more viscous than the corresponding esters. Viscosity index ranged from 151 to 238 with the fatty acid esters giving slightly higher indices than estolide esters. Hydrogenation of the estolides resulted in a dramatic increase in the pour point but only changed viscosity slightly.     

Frying stability of Moringa stenopetala seed oil

The frying performance of Moringa stenopetala seed oil (extracted with cold press or n-hexane) was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175 degrees C for 5 consecutive days (5 fryings per day). The chemical changes occurring in oils were evaluated. Free fatty acid content, polar compounds, colour and viscosity of the oils all increased, whereas the iodine value, smoke point, polyunsaturated fatty acid content, induction period and tocopherol content decreased. The effect of the oil on the organoleptic quality of these fried foods and the theoretical number of frying operations possible before having to discard the oil was also determined. The analytical and sensory data showed that the lowest deterioration occurred in cold press produced oil.     

The effect of soil temperatures on brown center development in potatoes

A study was conducted to determine the effect of different soil temperatures on the development of brown center in potatoes,Solanum tuberosum L. cv Russet Burbank. Plants were grown in 19 liter (5-gal) nursery pots under warm conditions, previously shown to be non-inductive to brown center development, until shortly after tuber formation. They were then moved to a cool growth room and grown in 4 soil temperature regimes until harvest. Soil temperatures of 10°C (50°F) and 15°C (60°F) produced greater development of brown center than either 4°C (40°F) or 21°C (70°F).     

Effect of Cooking and Processing on CIPC Residue Concentrations in Potatoes and Processed Potato Products

Residue concentrations of the sprout suppressant chlorpropham (or CIPC) were determined in raw and cooked potatoes and processed potato products, 48 h after CIPC aerosol treatment and after 30 days of subsequent storage at 4 or 12 °C. In the raw (uncooked) tuber, 48 h after CIPC treatment, the CIPC residue in the peel was 4.7 mg kg^-1, while in the peeled tuber it was 0.1 mg kg^-1. Boiling resulted in a decrease in residue concentration in the peel, but no significant differences in the residue concentration of the peeled tuber were observed. Pressure cooking resulted in a significantly increased residue concentration in the peel, but no significant change in the peeled tuber, whereas microwave cooking also did not increase the residue concentration in the peel significantly compared with that in raw tubers. Also the trend towards increases in residue concentration in microwave-cooked peeled tubers was not significant. The CIPC residue concentration detected in peeled tubers was 0.4–0.7 mg kg^-1 after boiling, 0.4–1.5 mg kg^-1 after pressure cooking and 0.4–3.8 mg kg^-1 after microwave cooking. The highest values were always found for tubers stored for 30 days at 4 °C. Processed products such as crisps, French fries, dehydrated sliced potatoes and starch contained different concentrations of CIPC residue, which was also detected in the cooking water and frying oil. The highest residue concentrations detected were 0.7, 4.7, 1.3 and 0.2 mg kg^-1 in crisps, French fries, dehydrated sliced potatoes and starch, respectively. The highest CIPC residue concentration observed in raw potatoes was much lower than the maximum residue level of 10 mg kg^-1 prescribed by the European Union.     

Payette Russet: a Dual-Purpose Potato Cultivar with Cold-Sweetening Resistance,Low Acrylamide Formation,and Resistance to Late Blight and Potato Virus Y

Payette Russet is a full season, russet-skinned potato cultivar notable for its cold-sweetening resistance and associated low acrylamide formation, making it ideally suited for processing into French fries and other potato products. Low asparagine and reducing sugar concentrations in Payette Russet tubers contribute to an 81 % reduction in acrylamide content in French fries relative to cultivars Ranger Russet and Russet Burbank following eight months storage at 9 °C. In three years of evaluations in the Western Regional Potato Variety Trials, average yield of Payette Russet was intermediate between Ranger Russet and Russet Burbank, but Payette Russet had the highest U.S. No. 1 yield when averaged across all eight trial locations. Acceptably low tuber glucose concentrations (<0.10 % glucose FWB) were maintained in Payette Russet following up to nine months storage at temperatures as low as 5.6 °C with consistently acceptable French fry color scores obtained (USDA value ≤2.0). Reducing sugars are also maintained uniformly throughout Payette Russet tubers, resulting in a low incidence of sugar ends and reduced mottling in French fries relative to standard processing cultivars. Long tuber dormancy also benefits long-term storage for processing. With its russet skin, Payette Russet could also be used for fresh-pack, and its assemblage of disease resistances makes it especially suitable for organic production, or for use by growers and companies seeking greater sustainability in their production. Payette Russet is resistant to foliar and tuber late blight, common scab, and has extreme resistance to PVY conferred by the presence of the Rysto resistance gene. Payette Russet also has a moderate level of resistance to Verticillium wilt, early blight, and corky ringspot. It is susceptible to Fusarium dry rot (F. sambucinum), therefore production and storage management guidelines are provided to minimize tuber infection. Payette Russet displays a low incidence of second growth and growth cracks, especially relative to Russet Burbank, and is intermediate between Ranger Russet and Russet Burbank for incidence of hollow heart/brown center. Blackspot bruise expression for Payette Russet is similar to Russet Burbank and reduced relative to Ranger Russet. Payette Russet was more susceptible to shatter bruise, internal brown spot, and tuber weight loss in storage relative to the industry standard cultivars. Payette Russet was released in 2015 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Northwest (Tri-State) Potato Variety Development Program.     

A rapid method of analysis for oil,potato solids and moisture in frozen French fries

A method of analysis for oil, potato solids and moisture in frozen French fries is described. This procedure can be completed in 4–5 hr and oil analysis can be finished within 2–3 hr making it useful for industrial quality control laboratories. The rapid procedure correlates closely with the more rigorous procedure of vacuum drying and Soxhlet extraction and compares favorably for accuracy.     

Auxin Modulates Gibberellin-Induced Effects on Growth,Yield, and Raw Product Recovery for Frozen Processing in Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

Tuber shape phenotype is an important determinant of raw product (≥7.6-cm-long French fries) recovery for frozen processing. Tuber length-to-width (L/W) ratios ≥1.8 translate to maximum yield of raw product; however, some cultivars produce tubers with much lower L/W ratios. While gibberellin (GA) can be used to elongate tubers, it also decreases tuber size and can thereby attenuate raw product recovery. We investigated the utility of GA and naphthaleneacetic acid (NAA) combination treatments for modifying tuber set, size, and shape to increase yield of raw product from ‘Payette Russet’ and ‘Alturas’; two late-season frozen-processing cultivars that often produce tubers with undesirably low L/W ratios. Models describing L/W ratio and fry yield by tuber size class were developed to translate total U.S. No. 1 tuber yields (>113 g) into yield of raw product. Increases in the L/W ratios of 113–284-g tubers had a greater effect on recovery of French fries (% fresh wt) than for tubers >284 g. Undersize (<113 g) and oversize (>340 g) tubers yielded 0 and 96% fries, respectively, regardless of L/W ratio. GA applied as a seed treatment effectively hastened emergence and altered tuber shape by increasing the L/W ratios of ‘Alturas’ and ‘Payette Russet’ tubers, enhancing total fry yield for the 113–340-g tubers by 24–46%, depending on concentration and application technique (dip, spray, in-furrow). However, GA also decreased apical dominance and shifted tuber size distribution away from >284-g tubers toward higher yields of <170-g tubers, erasing the gains in fry yield when all size classes (>113 g) were considered. When combined with GA, NAA maintained apical dominance, attenuated the shift in tuber size distribution, had no effect on the GA-induced increase in tuber L/W ratio, and only partly moderated the GA-induced stimulation of plant emergence. Raw product yield from ‘Payette Russet’ increased 12–39% in spray application trials by using NAA to confine the effect of GA to tuber shape and limit the loss of U.S. No. 1 tubers to undersize. Increases in tuber L/W ratio with GA/NAA seed treatments translated to increased yield of fries only when the relative concentrations were adjusted to minimize loss of >284-g tubers and gain in undersize tubers, as dictated by cultivar sensitivity to GA. ‘Alturas’ was less sensitive to GA than ‘Payette Russet’ for shifts in tuber size distribution but not shape, resulting in 17% increase in raw product with GA alone in pre-plant seed spray application studies. GA/NAA combination treatments provide an effective approach to manipulate tuber size distribution and enhance the yield of raw product for frozen processing in cultivars with a rounder tuber shape phenotype.     

Carbon nanofiber/poly(vinylidene fluoride-hexafluoro propylene) composite films: The crystal structure and thermal properties with various drawing temperatures

Carbon nanofiber (CNF)/polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) composite film was prepared by solution casting and melt pressing. The resultant 2 % CNF/PVDF-HFP composite films were uniaxially drawn at 50 °C, 75 °C, and 100 °C, respectively. In the SEM images, the morphology of drawn CNF/PVDF-HFP composite film confirmed the orientation of the CNF and the polymer matrix. The WAXD results showed the coexistence crystal phase of PVDF-HFP. The drawn CNF/PVDF-HFP composite film demonstrates improved electrical properties. The DSC thermogram results indicated no change in the melting temperature but slightly increased crystallinity with increasing drawing temperature. Dynamic mechanical analysis and tensile test showed an improvement in the storage modulus and stress at a drawing temperature of 75 °C.     

Growth rate and carbohydrate metabolism of potato tubers exposed to high temperatures

Summary The effect of high tuber temperature (30 °C) on the growth rate and carbohydrate metabolism of tubers was studied with 3 cultivars differing in heat tolerance. Subjecting individual tubers to 30°C for 6 days caused cessation of tuber growth. During this period, non-treated tubers (20°C) on the same plant increased in volume. At 30°C, incorporation of¹⁴C-labelled assimilates into the ethanol-insoluble fraction (mainly starch) as well as the starch content was significantly reduced. In contrast, the incorporation of¹⁴C-labelled assimilates into the sugar fraction was not affected by high tuber temperature. At 30°C the activity of some of the enzymes involved in starch metabolism was depressed. Varietal differences in responses of tuber growth rate and carbohydrate metabolism to high tuber temperature were insignificant. From these preliminary results it is concluded that high soil temperatures may decrease starch content of potato tubers directly by inhibition of the conversion of sugars into starch.     

Cardinal temperatures for germination and early growth of two Lesquerella species

Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as ‘L. pallida aff.’ because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 °C, whereas L. fendleri germinated earlier at 18 °C, but grew faster at 22 °C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 °C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 °C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 °C) and optimal (22 °C) temperatures than non-dormant seeds (>7 °C and 28 °C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.     

Effect of Final Dough Temperature on the Microstructure of Frozen Bread Dough

The effect of final mixing temperature (16 °C and 31 °C) on the structure stability of frozen bread dough was examined by low temperature-scanning electron microscopy and the quality of bread made from them assessed. The presence of ice-crystals were determined in both doughs after freezing, by low-temperature S.E.M. The microstructures showed a slight increase in size and decrease in number of angular voids, representing ice-crystals, after 14 weeks storage at −20 °C. Loaves baked from frozen dough with a final mixing temperature of 31 °C were poorer in both gassing power and overall loaf quality than 16 °C doughs, after 14 weeks storage.     

Effect of quick-freezing temperature on starch retrogradation and ice crystals properties of steamed oat roll

Oat roll is one of the traditional oat wholemeal foods. The purpose of this work was to investigate the effects of quick freezing at −20 °C, −40 °C and −80 °C for 90 min before frozen storage on the quality of frozen steamed oat roll. Quick freezing at −40 °C and −80 °C inhibited the increase of peak gelatinization temperature, enthalpy and the ordered degree of oat roll starch, therefore postponing starch retrogradation. The cross-section microstructure confirmed that reducing the quick-freezing temperature could prevent the increase of ice crystals size, ruptured structures and maintain the integrity of internal structure. As the storage time extend, the ice recrystallization led to an increase in size of ice crystals, while a decrease in their number. Frozen steamed oat roll starch had the highest swelling power at the quick-freezing temperature of −80 °C, that indicated strongest water absorption and binding ability when gelatinized again. Texture analysis demonstrated that hardness increased during frozen storage, quick freezing at −80 °C had the best texture properties. Therefore, declining the quick-freezing temperature could obtain a higher quality of frozen steamed oat roll, by means of delaying the starch retrogradation and minimising the size of ice crystals.