A Comparative Study of Physicochemical and Flavor Characteristics of Chicken Nuggets during Air Frying and Deep Frying

Chicken nuggets were air-fried and deep-fried for various times at the same temperature. The moisture content, oil content, color, texture, volatile compounds, and lipids degradation of the chicken nuggets were investigated. The evolution rate of the moisture content, oil content, color, and texture were much higher during deep frying than during air frying. Air frying required more time to produce similar quality attributes as those of deep-fried chicken nuggets. On average, the oil content of the air-fried chicken nuggets was 25% lower than that of the deep-fried chicken nuggets. Of the 74 volatile compounds identified in the fried chicken nuggets, aldehydes, hydrocarbons, and heterocycles were the main flavor contributors. The total amount of volatile compounds and aldehydes detected in the air-fried chicken nuggets was much lower than that in the deep-fried samples, but the number of heterocycles produced by the Maillard reaction was higher during air frying. Sensory evaluation revealed that the air-fried chicken nuggets had lower oiliness and crispness, and 9 min was the optimal frying time to obtain air-fried chicken nuggets with similar sensory attributes (color, odor, juiciness, and overall acceptance) as those of the best deep-fried chicken nuggets. Air frying was a healthier frying method for the production of fried chicken nuggets, which could reduce oxidative degradation of lipids in chicken nuggets.     

EFFECTS OF HYDROCOLLOIDS ON APPARENT VISCOSITY OF BATTERS AND QUALITY OF CHICKEN NUGGETS

The effect of different types of starches and gums on batter consistency and the effect of batter consistency on quality parameters of deep-fat fried chicken nuggets were determined in this study. Consistency of batter was correlated with coating pickup and oil content of the product. Addition of different starch and gum species to batter was found to be effective for both viscosity development and quality attributes of deep-fat fried chicken nuggets. Hydroxypropyl methylcellulose gum (HPMC), xanthan gum, and pregelatinized starch provided the highest consistency to the batters. Amylomaize starch addition to the batter formulation provided about 50% increase in texture of nuggets as compared to the control. Chicken nuggets coated with batters containing HPMC, xanthan, or guar gum had the lowest oil content. HPMC reduced oil content by about 54%, while the reduction in oil content was 40% and 33% in the case of xanthan and guar gum addition, respectively.     

EFFECTS OF HYDROCOLLOIDS ON APPARENT VISCOSITY OF BATTERS AND QUALITY OF CHICKEN NUGGETS

The effect of different types of starches and gums on batter consistency and the effect of batter consistency on quality parameters of deep-fat fried chicken nuggets were determined in this study. Consistency of batter was correlated with coating pickup and oil content of the product. Addition of different starch and gum species to batter was found to be effective for both viscosity development and quality attributes of deep-fat fried chicken nuggets. Hydroxypropyl methylcellulose gum (HPMC), xanthan gum, and pregelatinized starch provided the highest consistency to the batters. Amylomaize starch addition to the batter formulation provided about 50% increase in texture of nuggets as compared to the control. Chicken nuggets coated with batters containing HPMC, xanthan, or guar gum had the lowest oil content. HPMC reduced oil content by about 54%, while the reduction in oil content was 40% and 33% in the case of xanthan and guar gum addition, respectively.     

Kinetic modeling of mass transfer during deep fat frying of shrimp nugget prepared without a pre-frying step

The objective of this study was to evaluate the effect of different batter formulation on mass transfer during deep fat frying of shrimp nuggets prepared without a pre-frying step. The effects of soy and corn flour (5, 10%) addition to the batter formulation, frying temperature and time on mass transfer were determined. The results showed an interaction effect of these processing conditions on mass transfer. The most reduction in fat absorption was observed when samples were coated with batter contained 10% soy flour and fried at 190 °C. The first order kinetic based on the Fick's law were used to describe moisture transfer data. The effective moisture diffusivity ranged between 2.05 × 10⁻⁸ and 5.71 × 10⁻⁸ m²/s with R² between 0.91 and 0.98, and fat transfer rate constant was between 3.5 × 10⁻³ and 7.8 × 10⁻³ s⁻¹ with R² from 0.82 to 0.99. Activation energy obtained from the Arrhenius plot for the effective moisture diffusivity ranged between 18.42 and 23.84 kJ/mol.     

Fatty acid components of fried foods and fats used for frying

Oxidation of fat is accelerated at temp as high as those used for frying. The extent of this oxida-tion has been studied by frying two kinds of foods (chicken or potatoes) in cottonseed oil and in lard. Fat samples, taken prior to use and follow-ing 5 and 10 hr of frying (both for chicken and potatoes) were esterified. Subsequent quantita-tive assays of methyl esters by gas chromatogra-phy showed that the linoleic acid content had decreased from 57-49% after cottonseed oil had been used 10 hr for frying. This decrease was present regardless of whether chicken or potatoes were fried. There was no change in the linoleic acid content of lard after chicken was fried, but a decrease from 11.3-5.8% was noted when pota-toes were fried for 10 hr. The fatty acid content of the fat extracted from the potatoes and the fat used to fry them, was the same when sampled at 5 hr. However, at the end of the 10-hr frying period, fat ex-tracted from the potatoes had a lower linoleic acid content than fat used to fry them. Results were the same for both cottonseed oil and lard. Fatty acid components of the fat extracted from the chicken seemed to be affected as much by the fatty acid composition of the chicken itself as by fat used for frying. Whether the chicken was cooked in fat used 5 or 10 hr made little differ-ence. Journal Paper No. 1130, Mississippi Agricultural Experiment Station. A portion of the work in this paper is taken from a thesis sub-mitted in partial fulfillment of the requirements for the Master of Sci-ence degree at Mississippi State University in January, 1963.     

Carbon dioxide blanketing impedes the formation of 4‐hydroxynonenal and acrylamide during frying. A novel procedure for HNE quantification

Acrylamide and 4‐hydroxynonenal (HNE) are among the most detrimental compounds formed during high temperature processing of food. The effect of carbon dioxide blanketing (CDB) on the formation and accumulation in food of these compounds during deep‐fat frying was investigated. French fries were fried for 7 h daily and for 7 days in canola oil at 185 ± 5°C without and with CO₂ protection. The amount of acrylamide and HNE accumulated in the French fries were analyzed. Compared to standard frying conditions (SFC), frying under CDB reduced the amount of HNE by 62%. On the 3rd day of frying, the amount of acrylamide in fries fried under SFC was 3.3 times higher compared to frying with CO₂ protection. Frying with carbon dioxide protection is an effective and practical way to impede formation of toxic components during deep‐fat frying. To assess formation of HNE a simple, sensitive and reliable procedure for HNE analysis in frying oils and fried products was developed and evaluated. Practical applications : The toxicity of HNE and acrylamide, coupled with the increasing consumption of fried foods necessitates that measures be taken to reduce their formation and subsequent accumulation in fried foods. The frying method proposed in this study is very effective and requires only a simple modification to the fryer. Developed rapid and simple procedure for HNE analysis allows more accurate quantification.     

Functionality of Coatings with Salep and Basil Seed Gum for Deep Fried Potato Strips

We investigate the efficiency of using a coating made from novel hydrocolloid basil seed gum (BSG), salep, and a mixed solution of BSG and salep as well as oil origin (canola or palm olein) to reduce oil absorption in deep‐fried potato strips. We also evaluate the coating pick up, its effect on moisture content, frying yield value of fried potatoes and flow behavior of the coating suspensions. Flow curves show that all the studied suspensions are pseudoplastic and have shear thinning characteristics. The most effective coating formulations were 0.5 % BSG and 1.5 % salep. For these formulations, maximum oil uptake reduction was 28.8 and 28.7 % for potato strips compared to uncoated samples; the increase in moisture content was 29.1 and 17.5 %, respectively. Furthermore, the increase in moisture content resulted in an increase in frying yield up to 16.62 % for 0.5 % BSG. The oil type significantly (p < 0.05) influenced oil uptake.     

Monitoring of Changes in Composition of Soybean Oil During Deep-Fat Frying with Different Food Types

Changes in the composition of soybean oil during deep‐fat frying with wheat dough (WD) and chicken breast meat (CBM) were comparatively investigated using gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy (FTIR). The amounts of saturated fatty acids (FAs) and short‐chain FAs were increased. The amount of unsaturated FAs was decreased as the processing time increased. An increase in the amount of tetradecanoic acid and 9‐cis‐hexadecanoic acid was observed during the CBM frying only. The FTIR spectrum of frying oil was analyzed by extracting the entire information as the area ratios based on vibration absorptions of the specific functional groups. Changes in content of functional groups, namely cis C=C, trans C=C, C=O, C–O, O–H, and C–H, were studied by the FTIR‐based method. Based on the changes in the content of FAs and functional groups, soybean oil fried with CBM degraded more quickly than that fried with WD. Moreover, good linear correlations between the change in contents of functional groups and the mass percentages of FAs were also observed. The FTIR‐based method could be used in real time to monitor the quality of frying oil during the deep‐fat frying.     

DEEP FAT FRYING OF POTATO STRIPS—QUALITY ISSUES

Moisture loss and oil adsorption kinetics, structural properties (apparent density, true density, specific volume and internal porosity), color changes and viscoelastic behavior (compression tests, crispness) were investigated during deep fat frying of french fries. The effect of frying conditions (oil temperature, sample thickness and oil type), drying pretreatment and osmotic dehydration pretreatment on the above properties was also examined. The results showed that oil temperature and thickness of potato strips have a significant effect on oil uptake, moisture loss and color parameters of french fries, while the use of hydrogenated oil in the frying medium does not affect these properties. The porosity of french fries increases with oil temperature increases and sample thickness and it is higher for products fried with hydrogenated oil. Maximum stress and maximum strain increase during frying, while crispness of potato strips is higher for hydrogenated oil, and lower for refined oil. Air drying and osmotic pretreatment increase porosity of fried potatoes but decrease their oil and moisture content. A negative effect on color development with drying time was also observed. Pre-fry drying as well as osmotic pre-treatment increases the maximum stress and maximum strain of french fries during frying. Air drying pre-treatment increases the crispness of potato strips while osmotic pre-treatment does not affect it, with the exception of sugar solutions.     

DEEP FAT FRYING OF POTATO STRIPS—QUALITY ISSUES

Moisture loss and oil adsorption kinetics, structural properties (apparent density, true density, specific volume and internal porosity), color changes and viscoelastic behavior (compression tests, crispness) were investigated during deep fat frying of french fries. The effect of frying conditions (oil temperature, sample thickness and oil type), drying pretreatment and osmotic dehydration pretreatment on the above properties was also examined. The results showed that oil temperature and thickness of potato strips have a significant effect on oil uptake, moisture loss and color parameters of french fries, while the use of hydrogenated oil in the frying medium does not affect these properties. The porosity of french fries increases with oil temperature increases and sample thickness and it is higher for products fried with hydrogenated oil. Maximum stress and maximum strain increase during frying, while crispness of potato strips is higher for hydrogenated oil, and lower for refined oil. Air drying and osmotic pretreatment increase porosity of fried potatoes but decrease their oil and moisture content. A negative effect on color development with drying time was also observed. Pre-fry drying as well as osmotic pre-treatment increases the maximum stress and maximum strain of french fries during frying. Air drying pre-treatment increases the crispness of potato strips while osmotic pre-treatment does not affect it, with the exception of sugar solutions.     

Quality of Lipids of Indian Deep Fat Fried Food Products

A few deep fat fried products of Indian taste were either prepared in the laboratory in heat-abused groundnut oil or collected from commercial establishments along with corresponding frying oils. Quality of lipid extracted from different products or that of frying oils was assessed through different determinations. The study indicates that the quality of the lipid or the fat of a deep fat fried product is governed by the quality of its frying oil; however, both are not same. The study brings out the significance of moisture content of a product in determining the quality of lipid picked up by it from frying oil. When the moisture content of a product is high (45% or more), the quality of its lipid is inferior to that of its frying oil. When the moisture content is low (10% or less), the reverse is the situation. Difference between total lipid and crude fat of a product calculated on moisture free basis is found to be more pronounced in case of products having high moisture contents compared to those having low moisture contents. Products with low moisture content have relatively higher percentage and those with high moisture content, have lower percentage of ?bound”? lipid.     

Formation and distribution of oxidized fatty acids during deep‐ and pan‐frying of potatoes

The formation of cis‐9,10‐epoxystearate, trans‐9,10‐epoxystearate, cis‐9,10‐epoxyoleate, cis‐12,13‐epoxyoleate, trans‐9,10‐epoxyoleate, trans‐12,13‐epoxyoleate and the co‐eluting 9‐ and 10‐ketostearates during eight successive pan‐ and deep‐frying sessions of pre‐fried potatoes in five different types of vegetable oils – namely cottonseed oil, sunflower oil, vegetable shortening, palm oil and virgin olive oil – was followed and quantified both in fried oils and in fried potatoes by GC/MS after derivatization to methyl esters. These oxidized fatty acids were present at relatively low concentrations in the fresh oils and pre‐fried potatoes while they increased linearly with frying time, reaching up to 1140.8 µg/g in virgin olive oil (VOO) and 186.9 µg/g in potatoes pan‐fried in VOO after eight pan‐frying sessions, with trans‐9,10‐epoxystearate predominating in all cases. The formation of polymerized triacylglycerols (PTG) was also quantified in frying oils by size exclusion HPLC. Pan‐frying caused higher oxidized fatty acid and PTG formation compared to deep‐frying. Epoxyoleates and PTG concentrations were increased after frying in polyunsaturated oils, while epoxystearate and 9‐ and 10‐ketostearate concentrations were increased after frying in monounsaturated oils. No specific absorption of the oxidized fatty acids by the fried potatoes seems to occur. The dietary intake of oxidized fatty acids and PTG by the consumption of fried potatoes was discussed.     

Reduction of oil absorption during frying

Because of health concerns, consumers prefer fried food with low oil content and good sensory properties. Oil absorption during frying is affected by pretreatment, frying conditions and material properties. This paper reviews the oil absorption mechanism, influence factors and reduction methods during frying, pre‐drying and coating methods for reducing oil absorption. It is evident that new frying technology, natural coatings, and combination frying, should ultimately lead to the production of healthier fried foods.     

Reduction of fat in fried batter coatings with powdered cellulose

The fat contents of fried batter coatings were reduced significantly (7–28%) when 1% powdered cellulose (fiber length in excess of 100 microns) was incorporated into the batter. In addition, moisture and dry material contents were increased significantly in these coatings. Although fat reductions were observed in both shortening and oil, cellulose had a greater effect in shortening. The decrease in fat and increase in moisture could be due to hydrogen bonds forming between water molecules and cellulose fibers. Results from water and oil retention capacities indicate that powdered cellulose is more hydrophilic than lipophilic. This could also restrict the displacement of water by fat during frying. Presented at the 80th American Oil Chemists’ Society Annual Meeting in Cincinnati, Ohio, May 1989.     

Sunflower Oil–Beeswax Oleogels Are Promising Frying Medium for Potato Strips

Sunflower oil–beeswax oleogels at 3% (BWO-3) and 8% (BWO-8) organogelator concentration are prepared to evaluate oleogels as frying medium for potato strip frying against commercial sunflower oil (SO). Rheological and thermal analyses of oleogels prove that the samples are fully solid (20±3 °C) and totally liquid (180 °C), and thermoreversible. Fresh and used (after frying) fat analyses show that free fatty acidity (FFA), peroxide value (PV) and total polar materials (TPM) are enhanced in all samples at the 7th h, but the relative enhancement levels are lower in oleogel samples. Potato strips fried in oleogels absorb significantly less oil (11.97% and 12.07%) than the control sample (15.20%). Potatoes fried in oleogels are also more bright and yellower than the control sample. Textural profile of the fried potatoes indicates that the samples fried in oleogels are harder, springier, and gummier than that of the control sample. Sensory analysis shows that oleogel fried potatoes get higher sensory scores. Also, overall acceptability of potatoes fried in BWO-8 sample is the highest (8.50) among all. The prepared oleogels are found quite promising frying medium in this study. Further studies with other types of oleogels in extended period frying of various foods are suggested. Practical applications: The development of innovative frying techniques to produce healthier products with lower fat and calorie values are still a remarkable research area. Oleogelation is an emerging strategy used for solid-like oil designing and based on the formation of 3D networks by the addition of organogelators. Oleogelation is accepted as a healthy strategy to structure liquid oils into solid consistency, and oleogels have great edible applications in processed foods, and can be used as a frying medium. This work can guide the use of sunflower oil–beeswax oleogels as a frying medium and allow the development of more healthy fried snacks.     

Correction of dietary fat availability estimates for wastage of food service deep-frying fats

Because of the renewed interest in the consumption of hydrogenated fats, reliable estimates of the dietary fat available to the United States population require correction for the considerable amount of deep-frying fats used in food service operations that are discarded after use and thus are not available for consumption. We estimated this fat wastage from food service sources from published data on fat exchange during cooking and on numbers of specific entrees purchased away from the home by United States households. Among food items considered, fat rendered from hamburgers and chicken contributed substantially to the total gross fat available for discard; fried chicken, french fries and doughnuts accounted for a large portion of total fat uptake by foods. To calculate waste frying fat, expressed as a percent of net waste fat, we subtracted fat uptake by foods from the total visible frying fat available for usage and from the level of gross fat available for discard. Dividing the resulting values gave a percent waste frying fat of 60%. For calculation of fat available for consumption, we recommend that contributions from deep-frying fats be reduced by 50% of the total available to correct for wastage. This value is conservative and representative of actual experience of major food service operations and agrees closely with estimates derived from spent grease recovery reported in the United States. Presented at the 1992 AOCS Annual Meeting, May 10–14, 1992, Toronto, Ontario, Canada.     

Content of trans,trans‐2,4‐decadienal in deep‐fried and pan‐fried potatoes

Trans,trans‐2,4‐decadienal is a by‐product of frying oil that is also transferred to fried food. This aldehyde has been found and quantified both in frying oils and fumes generated during frying. Furthermore, it has been reported that 2,4‐decadienal has cytotoxic and genotoxic effects and promotes LDL oxidation. In the present work trans,trans‐2,4‐decadienal was detected directly in fried potatoes (french‐fries). Moreover, the influence of frying conditions (deep‐frying, pan‐frying), the oil type (olive oil, sunflower oil, cottonseed oil, palm oil and a vegetable shortening) and the degree of thermal deterioration (eight successive frying sessions without replenishment) on the production of 2,4‐decadienal in oil and potatoes was studied. The isolation of the aldehyde was performed by methanol extraction, while the identification and quantification was performed by RP‐HPLC. The quantity of trans,trans‐2,4‐decadienal produced during successive pan‐frying demonstrated a peak at the third and fourth frying session. The highest concentration of trans,trans‐2,4‐decadienal was detected in potatoes fried in sunflower oil, and the lowest in olive oil. The quantity of trans,trans‐2,4‐decadienal in fried potatoes decreased during successive deep‐frying at the seventh frying session or remained stable, except for cottonseed oil. The quantity of trans,trans‐2,4‐decadienal in fried potatoes was considered to be dependent on the oil used, on the frying process and, to a lesser extent, on the oil deterioration. In all cases tested, the highest concentration of trans,trans‐2,4‐decadienal was detected during deep‐frying. The unsaturation degree of the frying oil was considered to promote the formation of trans,trans‐2,4‐decadienal. Considering the quantity of 2,4‐decadienal found in french‐fries and in the respective frying medium, direct quantification of 2,4‐decadienal is required in order to make an estimation of intake from french‐fries.     

Utilization of high‐oleic rapeseed oil for deep‐fat frying of French fries compared to other commonly used edible oils

Changes in chemical, physical and sensory parameters of high‐oleic rapeseed oil (HORO) (NATREON?) during 72 h of deep‐fat frying of potatoes were compared with those of commonly used frying oils, palm olein (PO), high‐oleic sunflower oil (HOSO) and partially hydrogenated rapeseed oil (PHRO). In addition to the sensory evaluation of the oils and the potatoes, the content of polar compounds, oligomer triacylglycerols and free fatty acids, the oxidative stability by Rancimat, the smoke point and the anisidine value were determined. French fries obtained with HORO, PO and HOSO were still suitable for human consumption after 66 h of deep‐fat frying, while French fries fried in PHRO were inedible after 30 h. During the frying period, none of the oils exceeded the limit for the amount of polar compounds, oligomer triacylglycerols and free fatty acids recommended by the German Society of Fat Science (DGF) as criteria for rejection of used frying oils. After 72 h, the smoke point of all oils was below 150 °C, and the amount of tocopherols was reduced to 5 mg/100 g for PHRO and 15 mg/100 g for HORO and HOSO. Remarkable was the decrease of the oxidative stability of HOSO measured by Rancimat. During frying, the oxidative stability of this oil was reduced from 32 h for the fresh oil to below 1 h after 72 h of frying. Only HORO showed still an oxidative stability of more than 2 h. From the results, it can be concluded that the use of HORO for deep‐fat frying is comparable to other commonly used oils.     

Effect of ascorbyl palmitate on the quality of frying fats for deep frying operations

The addition of 0.02% ascorbyl palmitate (AP) reduced color development of frying fat (animal fat/vegetable oil [A-V] shortening) and vegetable oil (partially hydrogenated soybean [V-S] oil) in simulation studies. It also reduced peroxide values, development of conjugated diene hydroperoxides (CDHP) and their subsequent degradation to volatile compounds, such as decanal and 2,-4 decadienal, indicating that AP has the ability to inhibit thermal oxidation/degradation of frying fats and oils. A commercial french fry fat had lower CDHP values compared to A-V fat in simulated studies, and fried chicken oil had lower CDHP values than the V-S oil. Peanut oil had higher thermal stability than the other fats and oils.     

Contamination of Fried Foods by 3-Monochloropropane-1,2-diol Fatty Acid Esters During Frying

In the present work, different foods including banana, potato, cassava, onion, garlic, polenta, rice balls and beef patties were investigated in relation to the possible endogenous formation of 3-monochloropropane-1,2-diol fatty acid esters (bound 3-MCPD) and carry-over of these contaminants from the oil due to fat uptake during frying. For that, the samples were fried in two different types of oil and bound 3-MCPD was determined by using an indirect method based on acid transesterification and gas chromatography coupled to mass spectrometry analysis. The compounds were not detected in the fried foods when corn oil containing non-significant levels of bound 3-MCPD (<0.05 mg kg^?1) was used, indicating no endogenous formation during frying. On the other hand, when the same foods were fried in palm oil containing 1.64 mg kg^?1 of bound 3-MCPD, the mean concentrations ranged from 0.12 to 0.25 mg kg^?1, indicating a clear carry-over of the contaminants. In this case, a good correlation was observed between the levels of the compounds in fried samples and water loss/fat uptake.