Effect of deep-fat frying on ascorbic acid, carotenoids and potassium contents of plantain cylinders

The influence of thermal treatment (frying of plantain) on the micronutrients ascorbic acid, potassium and carotenoids is evaluated. Cylinders (diameter 30 mm, thickness 10 mm) of plantain (Musa AAB 'barraganete') were fried at four thermal treatments (120-180 degrees C and from 24 to 4 min) to obtain products with approximately the same water content (approximately 0.8+/-0.02 kg/kg1) and fat content (approximately 0.15+/-0.06 kg/kg). The thermal study used the cook value and the mean cook value as indicators of the effect of several different treatment temperatures and times on quality. Deep-fat frying had no significant effect on carotenoid contents at any frying conditions, and on potassium content, except at 120 degrees C and 24 min (loss 相似文献   

The optimization of the deep-fat frying process of coated zucchini pieces by response surface methodology

The effect of Carboxymethyl cellulose (CMC) gum in three concentrations of 0.5, 1, and 1.5% (w/v) was investigated on the oil uptake and qualitative properties (moisture content, color, and overall acceptance) of zucchini during frying at 150, 165, and 180°C for 1, 3.5, and 6 min. To determine optimum conditions of frying operation, the response surface methodology (RSM) was used. Based on the modeling performed, the lowest oil uptake (1.93%) was determined for the coated samples with concentrations of higher than 0.75% of CMC gum and fried at temperatures less than 157.5°C for 2.25 min. The optimization results of RSM showed that oil uptake of zucchini coated with CMC gum during frying is decreased significantly (p < 0.05) with the reduction of operation time and temperature, and concentration of CMC gum. Optimum conditions for decreasing oil uptake of coated zucchini pieces were 153.46°C, 0.5%, 1.03 min for temperature, concentration and time, respectively.     

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod 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±5°C for 5 consecutive days. The chemical changes occurring in the oils were evaluated. Free fatty acid content, peroxide value, specific extinction at 232 nm, polar compounds colour and viscosity of the oils all increased, whereas the iodine values, smoke points, polyunsaturated fatty acid content, induction period and tocopherol concentration decreased. The effect of the oils on the organoleptic quality of these fried foods was also determined by expert panellists. The analytical and sensory data showed that the lowest deterioration occurred in cold pressure produced oil and the highest in n -hexane extracted oil. Therefore, cold pressure oil appears to be the most appropriate for frying. Potatoes and cod were also fried in virgin olive oil in order to have a direct comparison between the different oils. The results clearly indicated that virgin olive oil has the highest resistance to thermal deterioration during frying compared with the other two oils.     

Loss Of Ascorbic Acid Due To Wilting In Some Green Leafy Vegetables

Summary

The ascorbic acid content of 12 varieties of leafy vegetables was determined. Infresh leaves, the ascorbic acid content varied from 276 mg/100 g fresh weight inTrigonella foenum-graecum to 58 mg/100 g in Polygonum plebeium.

The ascorbic acid content in the leafy vegetables stored open (uncovered) inthe laboratory (25-35 °C) for 24 hours decreased, the loss varying from 28.0 to 48.3 per cent. Contrary to this, the loss of ascorbic acid during storage in theleaves covered with a wet cloth was much less, ranging from 1.6 to 10.4 per cent.

Estimations of moisture and ascorbic acid content of T: foenum-graecum andP.plebeium at different intervals during wilting until the leaves reached the airdrystate indicated a positive correlation of ascorbic acid content with the mois-turecontent of the leaves.     

Acrylamide in crisps: Effect of blanching studied on long-term stored potato clones

Acrylamide, a probable carcinogen, is formed via the Maillard reaction between reducing sugars and the amino acid asparagine during heating of carbohydrate-rich foods. Potatoes contain high levels of these precursors, and thus potato crisps can contain high levels of acrylamide. In this study, the effect of blanching on the concentration of precursors and acrylamide content was studied in three potato clones stored at 4 °C or 8 °C. After 6, 12 and 18 weeks of storage, potatoes were sliced and blanched for 3 min in water at 80 °C and deep-fat fried for 3 min at an initial frying temperature of 180 °C and a final frying temperature of 160 °C. Blanching reduced the acrylamide content by 51–73%. Interestingly, blanching affected the levels of the precursor sugars and asparagine, but not the acrylamide content to the same extent. The reduction of precursors was 17–66%. This may be due to restriction of the transport of precursors to the surface, as the availability of precursors for reactions is crucial for acrylamide formation. In conclusion, blanching was an efficient way to reduce acrylamide content in potato crisps, in addition to using potatoes low in asparagine and reducing sugars.     

Impact of baking time and temperature on nutrient content and sensory quality of sweet potatoes

Sweet potatoes are a valuable economic asset to Louisiana. The impact of baking time and temperature on cook loss, vitamin C content, total sugars content, and sensory quality of sweet potatoes were compared when baked at 325°F, 375°F, and 425°F for 60, 45, and 30 minutes respectively. The 325°F sample had a significantly lower vitamin C content and a significantly higher total sugars content compared to the other two samples. However, the 425°F sample had a significantly lower percent cook loss compared to the other two samples. The 425°F sample had a significantly lower cook loss and total sugars compared to the 325°F samples. Untrained consumer panelists perceived the 425°F sample to be significantly less tender and less liked than the other two samples. These results have important implications for chefs, the food industry, and nutritional feeding programs.     

Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160°C, 180°C and 200°C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography–mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Application of starch-albumen powder as breading material in fried foods: An optimization study

The potential of using starch-albumen powder (SAP) as solid coating powder for fried food application was studied. Egg albumen was mixed with 10–30% dried starch and dried at 40–60°C air velocity of 4.5 m/s to produce SAP. SAP was used to coat wet yam chips prior to frying at 180°C for 3 min. The drying temperature and starch content in SAP significantly affected the oil uptake and moisture of fried chips. The increased amount of albumen (or reduced starch) content significantly reduced oil uptake. The sensory attributes influenced the overall acceptability of the fried chips in the order of taste > flavor > texture > appearance. To minimize oil uptake and moisture content and maximize acceptability of the fried chips, SAP dried at temperature of 40°C with starch content of 11.3% should be used. The study further indicates the potential of using SAP as coating in some other food products.     

Changes in ascorbic acid,beta‐carotene and sensory properties in Sundried and stored Amaranthus hybridus vegetables

Amaranthus hybridus was grown as a leafy vegetable in Dar‐Es‐Salaam, Tanzania. Freshly harvested leaves were analyzed for moisture content, beta‐carotene and reduced ascorbic acid. The leaves from the four sites were bulked, blanched and sundried with shade provision drier. The dried samples were stored in polythene bags at 22°C, 28°C and room temperature (30°C to 32°C). At the beginning and thereafter every month during storage, the vegetables were analyzed for beta‐carotene and ascorbic acid and subjected to sensory evaluation in comparison with fresh cooked leaves.

Sundrying of the amaranth leaves resulted in significant reductions (P < 0.05) in the levels of ascorbic acid and beta‐carotene, of 87.4% and 16.3% respectively. After storage of the dried vegetables for three months, the retention at 22 ° C, 28 ° C and room temperature of ascorbic acid and beta‐carotene were 42, 40 and 36 mg/100g and 32.4, 29.5 and 27.4 mg/100 g dwb respectively. Sensoric quality evaluation of amaranth leaves showed that significant differences (P < 0.05) existed in appearance and colour, flavour, texture and overall acceptability, although the dried vegetables were still acceptable in all the sensory characteristics tested. The study established that the vegetables could be dried to produce an acceptable product which maintained its eating quality for up to three months in storage.     

Evaluation of soybean oil quality during conventional frying by FTIR and some chemical indexes

Conventional deep fat frying is a common food preparation technique in Mauritius. The deterioration of soybean oil, commonly used in conventional frying, has been studied during frying of potato chips. The oil was subjected to continuous frying at 180 degrees C for a total of 600 min. The quality changes in soybean oil were evaluated at 90 min interval by Fourier transform infrared (FTIR) spectroscopy and some routine chemical parameters, namely peroxide value, iodine value and free fatty acid. An increase in hydroperoxide and free fatty acid concentration has been observed during the frying process by FTIR technique and the chemical parameters, peroxide value and free fatty acid respectively. A significant decrease in triglyceride ester linkage was observed by FTIR. The linear decrease noted for iodine value (P < 0.01) indicated a general loss of unsaturation. Furthermore, FTIR studies showed a loss of cis double bonds along with an increase in trans unsaturation. The formation of unsaturated aldehyde has also been observed during the frying process by FTIR technique.     

Impact of heat processing on the nutritional content of Gryllus bimaculatus (black cricket)

Insects are increasingly suggested as a potential novel solution to global nutrition challenges. However, limited research is available on the impact of processing methods on the nutritional content of edible insects. This trial examines the effect of heat processing on the nutritional profile of the black cricket, Gryllus bimaculatus. Adult black crickets were killed by freezing and then dried at either a low (45°C) or high (120°C) temperature followed by nutritional analysis of protein and micronutrient content. An additional set of samples was either freeze‐dried or dried at 32, 45, 72 or 120°C followed by nutritional analysis of lipid content. Analysis showed that percentage protein content was significantly higher in crickets dried at 45°C, a difference of roughly 1% of the total weight. Similarly, calcium content was also significantly higher in crickets dried at 45°C, although no other measured micronutrients were affected. Additionally, the fatty acid content was significantly influenced by higher temperature processing. Freeze‐drying black crickets conserved significantly more of the long‐chain polyunsaturated fatty acids than drying at 120°C. Insects hold potential as a source of essential nutrients and fatty acids; however, consideration must be given to heat processing at high temperatures as this may affect the nutritional profile.     

The effect of the germination temperature on the phytochemical content of broccoli and rocket sprouts

This study investigates the effect of different germination temperatures (10, 20 and 30?°C) on the phytochemical content as well as reducing and antioxidant capacity of broccoli and rocket sprouts. In both seeds and sprouts, the total glucosinolates and ascorbic acid contents did not differ between vegetables, while broccoli exhibited exceptionally higher polyphenols and greater reducing and antioxidant capacity compared to rocket. In both species, an increase in germination temperature positively affected the glucosinolate content. Ascorbic acid increased during germination without a difference among the three tested temperatures. The phenol content in broccoli sprouts increased when they were grown at 30?°C, but the amount decreased at the highest temperatures in rocket. The reducing and antioxidant capacities increased with germination, and higher indexes were detected at 10?°C, particularly in rocket. Different germination temperatures differentiate the health-promoting phytochemical content and antioxidant properties in broccoli and rocket sprouts.     

烹调对蔬菜中Vit C的影响

为了解蔬菜在通常烹调加工条件下Ｖｉｔ Ｃ的损失情况，将市售新鲜蔬菜洗净切好，经不同烹调方法和时间处理，用２，６二氯酚靛酚滴定法测定烹调前后还原型Ｖｉｔ Ｃ的含量，结果显示，随着炒菜时间的延长Ｖｉｔ Ｃ的损失增加，３分钟员失３３。６８％，１０分钟平均损失增至４４．６３％，高温煲汤亦会造成Ｖｉｔ Ｃ的损失，煲汤１小时相当于炒３分钟的损失量，而汽中蔬菜Ｖｉｔ Ｃ含量仍占汤菜Ｖｉｔ Ｃ总含量的３４．３３％     

Nutritional composition of freshly harvested and stored Latvian potato (Solanum tuberosum L.) varieties depending on traditional cooking methods

The information about nutritional composition of potatoes at both the ingredient and recipe levels in the Food Composition Data Base (FCDB) of Latvia is insufficient. Therefore, the aim of this research was to determine the nutritional composition and energy content of potatoes prepared by traditional cooking methods before and after storage. Five Latvian potato varieties were selected: Lenora, Brasla, Imanta, Zile and Madara. A two-year research was conducted during two periods: just after harvesting (2007, 2008) and after six months of storage (2008, 2009). The following cooking methods were used: shallow frying (150 ± 5 °C); deep-fat frying (180 ± 5 °C) and roasting (210 ± 5 °C). The weight of the potatoes was recorded before and after frying along with the time and temperature during frying. Chemical analyses were performed to determine the content of reducing sugars, starch, fructose, glucose, sucrose, fibre, fat, protein, moisture, vitamin C and amino acids. The content of the analyzed nutrients differed significantly between both potato varieties and applied cooking methods: differences between potato varieties and cooking methods were found for vitamin C, moisture, reducing sugars, fructose, glucose, sucrose, amino acids, essential amino acids, and energy content, whereas significant differences in starch, fibre, fat and protein content were found between cooking methods.     

The influence of nitrogen and potassium fertilisation on the content of polyphenolic compounds and antioxidant capacity of coloured potato

The effect of fertilisation rates of nitrogen: 0 (control treatment—no soil fertilisation), 40, 80 and 120 kg/ha and potassium: 0 (control treatment), 120, 150 and 180 kg/ha on the content of anthocyanins, phenolic acids and antioxidant capacity in purple–blue potato cv. ‘Blue Congo’ was examined. Anthocyanins and phenolic acids were identified and quantified by LC–MS and UPLC–PDA. Nitrogen was more effective in increasing the anthocyanin content—their quantity in tubers after nitrogen application was twice as much as that found after potassium application. Among phenolic acids, the dominant one was chlorogenic acid, the content of which significantly increased after nitrogen fertilisation at 120 kg/ha, in line with the increase in total concentration of phenolic acids and antioxidant capacity. The adjustment of nitrogen and potassium fertilisation levels during the growth of purple–blue potatoes seems to be an effective way to increase the expression of polyphenolic compounds in these cultivars. Therefore, fertilisation with N at 120 kg/ha and K at 120 and 150 kg/ha is recommended as a way to improve the content of biologically active compounds and antioxidant properties, and consequently, to enhance the nutritional value and the functionality of purple–blue potatoes.     

Formation of trans fatty acids during the frying of chicken fillet in corn oil

To assess effects of heated edible oils on intake of trans fatty acids (TFAs); the formation of TFAs in cooking conditions was investigated by a frying system model, in which chicken fillet was fried in a commercial corn oil at 170?°C, for 12 frying cycles. The main TFAs detected in chicken fillet were trans C18:2 fatty acids (FAs) and trans C18:3 FAs, which exhibited no significant differences among the frying cycles. Besides, the content of trans C18:1 FAs were very low in all samples on different frying cycles. The intake of TFAs was estimated to be 0.06?g/100?g when chicken fillet fried in this process was consumed. These results suggest that an ordinary frying process upon a commercial corn oil has little impact on the daily TFAs intake.     

Pectin methylesterase activity and ascorbic acid content from guava fruit,cv. Predilecta,in different phases of development

The guava pectin methylesterase (PME) specific activity and vitamin C were assayed in samples from different phases of guava fruit development. The PME enzyme from guava was extracted with borate–acetate buffer, 50 mol/l, pH 8.0, in the presence of NaCl 0.3 mol/l. The results showed PME optimum activity at pH 9 and 95°C, and it is a thermostable enzyme. Guava PME retained 96.8% of activity after 300 min in 90°C. Electrophoresis showed that guava PME contained two isoforms, one with 57 kDa molecular mass. The analyses of the different phases of guava maturation showed that ascorbic acid decreases during the maturation process, but PME activity increases with maturation.     

Repetitive Box Lifting Performance is Impaired in a Hot Environment: Implications for Altered Work-Rest Cycles

This study investigated the effects of environmental temperature on repetitive box lifting (RBL) performance, associated stress hormone and creatine kinase (CK) responses. Ten healthy males performed two experimental trials in a random crossover design. The trials consisted of three 40 min (10 min sitting, 20 min standing, and 10 min RBL) circuits performed in either 23°C or 38°C followed by a 180 min seated recovery period in 23°C. RBL performance (i.e., number of boxes lifted) was reduced (p ≤ 0.05) in 38°C compared to the 23°C trial. Physiological Strain Index was significantly different between trials (38°C: 8.5 ± 1.1 versus 23°C: 7.2 ± 0.7; p ≤ 0.01). Plasma testosterone was elevated (p ≤ 0.05) across both trials and then decreased at 60 min recovery, compared to pre-exercise (PRE) measures, but was higher (p ≤ 0.05) during the 38°C trial. Plasma cortisol increased (p ≤ 0.05) at 60 min during both trials and remained elevated until 120 min in 23°C, and until 60 min recovery in 38°C. Serum CK was greater through 48 hr post compared to PRE values in both trials. Thus, 10 min RBL performance was reduced in 38°C despite the 30-min rest periods between RBL intervals. Plasma testosterone and cortisol were generally higher during the 38°C trial, suggesting a greater stress response. Additional research is needed to determine optimal work:rest cycles for maximizing work performance in thermally oppressive environments.     

Study on combined effects of blanching and sonication on different quality parameters of carrot juice

This study was conducted to evaluate the combined effects of blanching and sonication on carrot juice quality. Carrots were blanched at 100?°C for 4?min in normal and acidified water. Juice was extracted and sonicated at 15?°C for 2?min keeping pulse duration 5?s on and 5?s off (70% amplitude level and 20?kHz frequency). No significant effect of blanching and sonication was observed on Brix, pH and titratable acidity except acidified blanching that decreased pH and increased acidity significantly. Peroxidase was inactivated after blanching that also significantly decreased total phenol, flavonoids, tannins, free radical scavenging activity, antioxidant capacity and ascorbic acid and increased cloud and color values. Sonication could improve all these parameters significantly. The present results suggest that combination of blanching and sonication may be employed in food industry to produce high-quality carrot juice with reduced enzyme activity and improved nutrition.     

An investigation of the antioxidant properties and colour of glasshouse grown tomatoes

The colour and the antioxidant content of five different cultivars of tomatoes (Lycopersicon esculentum L.), grown in glasshouses using commercial hydroponic techniques, were measured in freshly harvested tomatoes and after 2 and 5 days of storage in the dark at 15°C. The two cocktail cultivars of tomatoes, Aranca and Flavourine, were the smallest tomatoes but they contained higher dry matter contents compared with the three standard salad cultivars, Excell, Celero and Dutch Chaser. There were significant differences (P<0.001) in lycopene (the major carotenoid), ascorbic acid and total antioxidant activity in the whole fruit of the five different cultivars evaluated at harvest, while the total phenolic contents were very similar. The lycopene levels of all the cultivars increased significantly (P<0.001) after storage for 2 and 5 days at 15°C. Overall, the total phenolic content of all the cultivars did not change appreciably after storage at 15°C while the levels of ascorbic acid fell by 12.6% when stored for 5 days in the dark. There was a significant difference (P<0.001) in the total antioxidant activity between the five different cultivars when freshly harvested; the highest levels of total antioxidant activity were observed in the two cocktail cultivars, Aranca and Flavourine. Antioxidant activity showed different patterns of change depending on cultivar. An increase in the total antioxidant values could be seen in cultivars Dutch chaser and Excell, after storage for 5 days at 15°C. The total antioxidant activity values of Flavourine and Celero fell on storage while the values for stored Aranca were very similar to the values when freshly harvested.

The skin colour, as shown by Commission Internationale l'Eclairage (CIE) L*a*b* values of each cultivar were markedly different at harvest even though each cultivar was harvested at the same maturity. The a* value of each cultivar increased significantly (P<0.001) when they were stored in the dark, for either 2 or 5 days, at 15°C. Regression analysis showed that overall there was no significant relationship (R²=0.14) between the lycopene content and the a* value of all the tomatoes; however, when examined individually, the two cocktail tomatoes Aranca and Flavourine showed strong correlation—R²=0.96 and R²=0.97, respectively. Overall, the (a*/b*)² was the most reliable indicator of lycopene concentration (R²=0.96) in the tomatoes examined in this study.