The influence of oil type and frying temperatures on the texture and oil content of French fries

The purpose of the present study was to determine the effects of the frying medium and temperatures on fat content and texture of French fries. The material taken for the study consisted of seven types of vegetable oil: refined sunflower, rape, soy, olive oil, palm, partially hydrogenated rape oil (modified oil I) and a blend of vegetable oils (modified oil II). The French fries prepared from Asterix potato variety were fried at oils heated to 150, 160, 170, 180 and 190 °C. The length of frying (12, 10, 8, 6.5 and 4.5 min, respectively) depended on oil temperature. Fat content and the texture of French fries were determined. The type of frying medium significantly affects the texture of French fries. Temperature influenced both the fat content and texture of product. The increase of frying temperature decreased fat uptake and hardness of French fries. French fries fried in rape oil exhibited the most delicate texture and the lowest oil absorption when compared with French fries fried in other types of oil under investigation. Copyright © 2005 Society of Chemical Industry     

Changes of polysaccharide content and texture of potato during French fries production

The purpose of the present study was to determine the changes in non-starch polysaccharide and lignin contents of potato during French fries production and also the relationship between the texture of the finished product and half-products, as a result of processing at each stage under investigation. The samples for laboratory studies were taken from potato tubers, strips and French fries collected from nine locations of a technological line. The greatest changes in non-starch polysaccharide content and texture of potatoes resulted from blanching and frying. The texture of French fries was mainly affected by pectin and cellulose. The texture of French fries can be predicted from the measurements of the texture of potato strips after blanching.     

11种煎炸油煎炸薯条挥发性成分的组成北大核心CSCD

利用顶空固相微萃取与气质联用相结合的方法测定了11种煎炸油煎炸薯条的挥发性物质组成,并对薯条进行感官评定。结果表明:11种煎炸油煎炸薯条共鉴定出包括醛类、含氧杂环类、含氮杂环类、酮类、醇类、酸类、烃类、含硫化合物和酯类化合物共80种挥发性物质,其中醛类化合物是煎炸薯条中主要的挥发性物质。棕榈油煎炸薯条鉴定出的挥发性物质种类最多,亚麻籽油煎炸薯条的最少,且通过分析11种煎炸油煎炸薯条的醛类物质发现,葵花籽油和棉籽油煎炸薯条中多不饱和醛含量较高,其中(E,E)-2,4-癸二烯醛含量最高,是薯条呈现油脂香的主要物质;高油酸菜籽油和高油酸葵花籽油煎炸薯条中单不饱和醛含量较高,其中高油酸葵花籽油煎炸薯条中2-十一烯醛含量最高;亚麻籽油煎炸薯条中(E,E)-2,4-庚二烯醛含量最高,呈现出消费者不期望的脂肪味和油腻味。感官评定结果显示,棕榈油煎炸薯条品质最好,猪油煎炸薯条品质最差。     

The effects of enzymes on fat content and texture of French fries

The purpose of the present investigation was to study the changes in the microstructure of potato cells during French fries processing with the use of enzymes and to find the impact of the enzymes on fat content and texture of French fries. The samples for laboratory studies were of potato strips and French fries, collected from five locations of the technological line.     

The influence of frying medium degradation on fat uptake and texture of French fries

The purpose of the present investigation was to study the influence of the degree of degradation of different kinds of oils used as a frying medium on fat uptake and texture of frozen pre‐fried French fries. As has been found, the degradation degree of the frying medium depends on the kind of oil and processing time. Liquid hydrogenated rapeseed oil exhibited the best thermo‐oxidative stability among the oils under investigation. The kind of oil influenced fat uptake and the texture of French fries. The lowest fat uptake was observed with French fries fried in solid oil. Some correlations between fat uptake and changes in fatty acid content were found in the frying medium during frying. Fat absorption increased with increasing unsaturated fatty acids and decreasing saturated fatty acid content. The texture of French fries fried in hydrogenated oils was harder than that exhibited by French fries fried in liquid rapeseed oil. The hardness of French fries fried in liquid oils decreased during frying while the hardness of French fries fried in solid oil increased. Some correlations between the texture of French fries and iodine value and fatty acids content of frying media were found. The hardness of French fries increased with increasing content of saturated fatty acids and decreasing unsaturated fatty acids and trans isomer fatty acid content. Copyright © 2005 Society of Chemical Industry     

2种加工方法对美国引进薯条加工型品种感官品质的影响

目的以从美国引进的薯条加工型品种或品系为实验对象,比较漂烫预油炸加工法和直接油炸加工法2种加工方法对其感官品质的影响。方法采用漂烫预油炸加工法和直接油炸加工法对其加工,采用感官评价的方法比较2种加工方法对薯条感官品质的影响。结果漂烫预油炸法与直接油炸法相比,在外观指标和总体评分上均有显著性差异(P0.05),而在其他指标均无显著性差异,且2种方法对外观、湿度、外壳和内部表现4个指标的影响趋势大致相同。结论漂烫预油炸方法与直接油炸方法相比,改进了外观色泽,但并未改变薯条的其他加工性状,在加工薯条品种筛选的过程中推荐使用该方法。     

Correlation between instrumental and sensory ratings by evaluation of some texture reference scales

The objective of this study was to investigate instrumental–sensory relationships of some texture scales using argentine foods as references. Textural characteristics of these foods were instrumentally investigated by the texture profile analysis technique. Principal component analysis (PCA) was used to describe the main attributes of the food samples. High Pearson’s correlation coefficients were found between hardness and fracturability (r = 0.94; P < 0.0001), hardness and gumminess (r = 0.71; P < 0.0001) and springiness and cohesiveness (r = 0.85; P < 0.0001). PCA identified two significant principal components, which accounted for 81.2% of the variance in the instrumental data. Additionally, a trained panel described the texture characteristics of the food samples according to the standard reference scales. The correlation curves showed nonlinear relationships (R² between 85.6% and 99.9%) which were used to predict sensory attributes of other food samples. Some texture attributes like hardness and fracturability were accurately predicted by mechanical properties, while others like cohesiveness and adhesiveness were less representative.     

襄阳牛肉面质地感官与仪器分析的相关性研究

目的 明确襄阳牛肉面质地的感官与质构特性以及关键评价指标,并探讨感官与质构特性之间的关联性。方法 采用感官评分法对12种不同品牌襄阳牛肉面质地特性进行感官评定,同时使用质构仪开展面条的拉伸实验、剪切实验以及质地剖面分析(texture profile analysis, TPA)等质构特性测定,进一步采用偏最小二乘法回归(partial least squares regression, PLSR)对感官和质构特性进行关联性分析。结果 襄阳牛肉面整体呈现爽滑劲道的感官特性,有弹性、质地较硬且略黏的质构特性。感官指标的适口性、黏性以及韧性对面条质地感官评分影响显著,不同品牌襄阳牛肉面质地的感官评分和质构指标之间均存在较强相关性,剪切硬度、剪切韧性与感官评分值、适口性(软硬度)呈现显著相关性(P<0.05)。分析结果表明影响面条感官评分和适口性的关键质构指标是剪切硬度、剪切韧性以及最大拉伸强度。结论 襄阳牛肉面质地的感官评分和质构指标剪切硬度、剪切韧性以及最大拉伸强度之间存在显著关联性。本研究为构建襄阳牛肉面的感官性状评价体系奠定了基础。     

鱼糕质构的仪器分析与感官评定间的相关性

质构是鱼糕品质的决定性因素,为了建立一种客观的品质评价方法,对目前市场上不同品牌鱼糕的感官评定结果与仪器分析结果的相关性进行研究,以期为定量表达鱼糕的感官质构特性提出理论依据。选用了10种市售销量大的鱼糕,进行感官评定,并使用物性分析仪进行质地剖面分析。进而运用主成分分析法与相关性分析法对感官评定与仪器分析的测定结果进行讨论。结果表明,二者之间具有一定的相关性。为进一步评价鱼糕的质构特性,以仪器分析指标为自变量,感官评定指标为因变量,进行逐步回归分析,建立具有统计意义的鱼糕质构特性的预测方程。     

Development and experimental validation of a frying model to estimate acrylamide levels in French fries

ABSTRACT:  In this study, a numerical model was developed to simulate frying of potato strips and estimate acrylamide levels in French fries. Heat and mass transfer parameters determined during frying of potato strips and the formation and degradation kinetic parameters of acrylamide obtained with a sugar–asparagine model system were incorporated within the model. The effect of reducing sugar content (0.3 to 2.15 g/100 g dry matter), strip thickness (8.5 × 8.5 mm and 10 × 10 mm), and frying time (3, 4, 5, and 6 min) and temperature (150, 170, and 190 °C) on resultant acrylamide level in French fries was investigated both numerically and experimentally. The model appeared to closely estimate the acrylamide contents, and thereby may potentially save considerable time, money, and effort during the stages of process design and optimization.     

Effect of inulin and Lactobacillus paracasei on sensory and instrumental texture properties of functional chocolate mousse

BACKGROUND: This study evaluated the effect of a potentially probiotic bacteria (Lactobacillus paracasei subsp. paracasei LBC 82), added solely or together with the prebiotic ingredient inulin on instrumental texture attributes and sensory properties of a functional chocolate mousse during storage at 4 ± 1 °C for up to 28 days. RESULTS: The addition of Lactobacillus paracasei resulted in a firmer and more adhesive chocolate mousse. This effect was intensified with the presence of inulin in the synbiotic formulation (5.24 N and ? 0.956 N, respectively, for firmness and adhesiveness after 28 days of storage) (P < 0.05). L. paracasei population did not vary (P > 0.05) during storage (always between 7.27 and 7.35 log cfu g^?1), both for the probiotic and the synbiotic mousses. Synbiotic mousse differed from control and probiotic mousses during storage with respect to the color attribute. Moreover, both probiotic and synbiotic mousses presented taste, aroma and texture perceptions which were different from one another and from the control mousse after 14 and 21 days of storage. CONCLUSION: The use of inulin, together with the potentially probiotic strain of Lactobacillus paracasei subsp. paracasei, is advantageous, conferring potentially symbiotic potential to the chocolate mousse, as well as favorable texture and sensory properties. Copyright © 2008 Society of Chemical Industry     

Influence of the frying temperature on acrylamide formation in French fries

It is well established that high oil temperatures during frying strongly increase acrylamide formation in French fries, but it is less clear, which temperature or rather which part of a temperature profile is relevant and if rules or regulatory measures should be established in respect of frying temperature, on which temperature they should refer. In most fryers, the oil temperature strongly drops on adding the potato sticks and may not fully recover up to the end of the frying process (depending on the amount of potato added in relation to the volume of oil and the heating power of the fryer). Since acrylamide is formed towards the end of frying, the temperature during the second half of the process is more important than that regulated by the thermostat. The profile of the frying temperature was optimized regarding product quality (crispness, flavor) and acrylamide formation. An initial temperature of 170–175 °C dropping to 140–145 °C and a virtually isothermal frying at 160 °C resulted in products of similar quality and acrylamide content. At initial temperatures below 160 °C and with main frying temperatures below 140 °C, crispness and the flavor of the French fries suffered: the sticks dried out and became oily. Isothermal frying at 167–170 °C resulted in approximately doubled acrylamide content compared to conditions that were optimal in respect of culinary quality and low acrylamide formation, showing that rules on the initial temperature alone are inadequate to ensure low acrylamide contents. Optimized fryers should program temperature: allowing an initial temperature drop, but then efficiently heating to prevent the temperature dropping below a given limit; after the end of frying, the initial temperature must be restored before frying the next portion.     

Provenance of the oil in par-fried French fries after finish frying

Frozen par-fried French fries are finish-fried either by using the same type of oil used for par frying, or a different type. The nutritive quality of the final oil contained in the product depends on the relative amounts and the fatty acid (FA) composition of the oils used for par frying and finish frying. With the aim of understanding the provenance of the oil in the final product, par-fried French fries-either purchased ready or prepared in the laboratory-were finish fried in oils different from the ones used for par frying. The moisture content, oil content, and FA compositions of the par-fried and finish-fried products were experimentally determined, and the relative amounts of each of the oils present in the final product were calculated using the FAs as markers and undertaking a mass balance on each component FA. The results demonstrate that 89% to 93% of the total oil in the final product originates from the finish-frying step. The study also shows that a significant proportion of the oil absorbed during par frying is expelled from the product during finish frying. Further, the expulsion of par-frying oil was found to occur in the early stages of the finish-frying step. Experiments involving different combinations of par-frying and finish-frying oils showed that the relative proportions of the 2 oils did not depend on the individual fatty acid profiles. This study concludes that any positive health benefits of using an oil having a favorable FA profile for par frying, can potentially be lost, if the oil used for finish frying has a less favorable composition. PRACTICAL APPLICATION: This paper estimates the relative amounts of oil in French fries that have been fried in 2 stages-a par-frying step and a finish-frying step-which is commonly practiced in food service establishments as well as homes. The 2 key conclusions are: (1) nearly 90% of the oil content of the final product is the one used for finish frying; that is, a processor may use very good oil for par frying but if the oil used for finish frying is inferior, its effect will dominate. (2) The paper also shows that a significant proportion of the oil used by the processor gets expelled during finish frying.     

Possible causes of variation in acrylamide concentration in French fries prepared in food service establishments: An observational study

Acrylamide is a probable human carcinogen, and its presence in a range of fried and oven-cooked foods has raised considerable health concern world-wide. Dietary intake studies observed significant variations in acrylamide concentrations, which complicate risk assessment and the establishment of effective control measures. The objective of this study was to obtain an insight into the actual variation in acrylamide concentrations in French fries prepared under typical conditions in a food service establishment (FSE). Besides acrylamide, frying time, frying temperature, and reducing sugars were measured and the actual practices at receiving, thawing and frying during French fries preparation were observed and recorded. The variation in the actual frying temperature contributed most to the variation in acrylamide concentrations, followed by the variation in actual frying time; no obvious effect of reducing sugars was found. The lack of standardised control of frying temperature and frying time (due to inadequate frying equipment) and the variable practices of food handlers seem to contribute most to the large variation and high acrylamide concentrations in French fries prepared in a restaurant type of FSE as compared to chain fast-food services, and institutional caterers. The obtained insights in this study can be used to develop dedicated control measures in FSE, which may contribute to a sustainable reduction in the acrylamide intake.     

Evolution of mechanical and optical properties of French fries obtained by hot air-frying

The aim of this study was to analyse the influence of frying technique (air-frying and deep oil-frying) and type of pre-treatment (freezing and blanching) on the evolution of mechanical and optical properties of French fries. The results showed that the chromatic parameters, a* and b*, experimented an increase regardless of the frying method. The increase in a* was significantly higher in deep-oil frying as a result of Maillard's reactions. The texture analysis reported a first stage of initial softening related to starch gelatinization followed by a second stage where the maximum force increased due to the gradual formation of a crust, both stages being faster in deep-oil frying. Pre-frozen potatoes presented the highest value of maximum force parameter independent of the type of frying.     

Effect of pre-drying and par-frying conditions on the crispness of French fries

An experimental design was used to study the effect of pre-drying (to 10, 15 and 20% weight loss) and par-frying conditions (160, 170 and 180 °C) on the crispness of French fries. Par-frying time was adjusted with a software program to obtain equal moisture content and internal texture for all samples. Crispness was evaluated with a sensory panel. Furthermore, samples were analysed with a texture analyser and with confocal scanning laser microscopy (CSLM). Par-frying at 180 °C resulted in a crispier product than at 160 and 170 °C. Pre-drying to 20% weight loss lead to blisters and reduced crispness in comparison with pre-drying to 10 and 15% weight loss. Instrumental texture measurements showed a good correlation with sensory crispness. Large differences in cell structure, such as blisters, could be observed with CSLM. CSLM was useful to explain results from the instrumental and sensory texture evaluation.     

Reduction of acrylamide formation by vanadium salt in potato French fries and chips

The effects of vanadyl sulphate on the formation of acrylamide have been studied in fried potato products, such as French fries and chips. Acrylamide formation was inhibited by 30.3%, 53.3% and 89.3% when the sliced potato strips were soaked in 0.001, 0.01 and 0.1 M vanadyl sulphate (VOSO₄) solutions, respectively, for 60 min before frying. Moreover, 57.7%, 71.4% and 92.5% inhibition of acrylamide formation was observed when chips were soaked in the respective vanadyl sulphate solution before frying. In a separate model reaction, a solution containing an equimolar concentration of l-asparagine and d-glucose showed a significant inhibition of acrylamide formation when heated at 150 °C for 30 min in the presence of vanadyl sulphate (VOSO₄). The results indicate that the binding of VO²⁺ to asparagine and the decrease in the pH of the potato samples resulted in a significant reduction of acrylamide formation in fried potato products.     

岱瞿族大黄鱼质构特性与感官评价的相关性分析

目的 分析养殖大黄鱼质构特性与感官评价的相关性。方法 选择温州不同海域的养殖大黄鱼样品进行肥满度、蛋白质、脂肪、水分、胶原蛋白测定,并进行感官评定和质构剖面分析(textureprofileanalysis,TPA);对结果进行因子和主成分分析,以及相关性分析;再以TPA指标为自变量、感官评价指标为因变量进行逐步回归分析,建立感官预测模型。结果 温州不同海域养殖大黄鱼,在肥满度、脂肪含量、蛋白质含量、质构测定中弹性与咀嚼性指标均存在显著性差异,感官评价指标也存在显著性差异。通过主成分分析得到TPA指标和感官评价指标各1个主成分,累计方差贡献率分别为72.86%和89.97%。相关性结果表明,感官评价结果与TPA测定结果之间存在显著的相关性(r=-0.933～0.808,P<0.05),并建立了色泽、滋味、肉纤维和质地与咀嚼性的预测模型和气味与弹性的预测模型。结论 本研究确定了温州地区养殖大黄鱼品质评价定量指标;大黄鱼感官评价指标受TPA指标中的弹性、咀嚼性影响;本研究的温州大黄鱼感官评价预测模型为大黄鱼品质评价标准体系的科学建立提供了依据。