Texture of French fried potato: Quantitative determinations of non-starch polysaccharides

Contents of high, intermediate and low molecular weight, non-starch polysaccharides of low specific gravity (LSG: 1.062–1.070) potatoes were determined to be 32.3, 28.9 and 32.2%, respectively. Respective figures for high specific gravity (HSG: 1.102–1.106) potatoes were 42.3, 22.2 and 29.1%. Frying caused severe degradation of high molecular weight polysaccharides (MWP) and reduced the original levels in LSG potatoes from 32.3% to 21.3% (34% degradation) and in HSG potatoes from 42.3% to 37.8% (10.6% degradation). HSG fries, therefore, had almost twice the levels of high MWP than LSG fries (37.8 VS 21.3%). Contents of intermediate and low MWP in HSG fries (25.3 and 30.3%, respectively) were lower than those in LSG fries (34.2 and 37.6%, respectively). These differences are suggested to be one of the important factors governing the textural qualities of french fries.     

Objective measurement of texture variables in raw and processed French fried potatoes

The five most important variables encountered in french fry production and texture measurement are: specific gravity, raw potato storage, raw potato firmness, freezing of fried product, and cooling of hot french fry slices. Shear force curves are presented to illustrate the effects of these variables. A double maximum cruts shear peak is exhibited by properly processed french fried potatoes when they are hot. Bursting of the crust is less evident with less desirable fries and with frozen and reheated samples. Shear press punch tests proved to be best for analyzing raw potato firmness. In order to determine and study the texture variations within a potato, Durometer³ tests were conducted on concentric zones and sections from bud to stem end of most firm and least firm raw tubers. Higher resistance to penetration was encountered in the most firm potatoes. Durometer values vary directly with solids within a tuber which can be explained by certain morphological conditions. Because of turgidity, however, solids and Durometer values vary inversely between firm and non-firm tubers. A table is presented which lists the texture inferences derivable from changes which occur in the french fried potato shear force curves.     

Pectic substances and the texture of french fried potatoes

French fries made from low specific gravity potatoes are poor in texture and soggy in appearance. High specific gravity potatoes, on the other hand, produce mealy, firm and good-textured french fries. A comparison of raw potatoes of high and low specific gravity for protopectin, the degree of esterification, water-soluble pectins and divalent cations revealed no significant differences. Low specific gravity potatoes, however, were found to contain significantly higher levels of free calcium and lower degree of esterification of water-soluble pectins. Similar comparisons of french fries made from these potatoes showed that low specific gravity fries had a higher degree of protopectin de-esterification, greater breakdown of protopectin and higher levels of free calcium. It was concluded that protopectin of low specific gravity potatoes possesses fewer and/or weaker cross linkages, is poorly polymerized, and a substantial percentage of it breaks down on frying. This weakens the cell wall and results in a french fry of poor texture.     

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.     

Effects of various chemical blanchings on the texture of French fries

Trial blanching with CaCl₂, MgCl₂ and Ca-citrate improved the texture of low specific gravity fries. For overall textural improvement, CaCl₂ was considered most effective. Best results were obtained by blanching for 15 minutes at 158 F in 0.5% calcium chloride salt solution.     

Objective measurements of french fried potato quality. Laboratory techniques for research use

Processing French fried potatoes on a laboratory scale presents many problems. These problems involve sampling, elimination of variables such as those due to specific gravity, freezing, and frozen storage. Techniques are presented for sampling, slicing, blanching, frying, agitation, draining, freezing, elimination of sublimation in storage and reheating. In order to prevent degradation of texture resulting from slow freezing, a simplified liquid nitrogen freezer was constructed. Modifications were made on a standard, electronic, recording shear press to increase its suitability for objective texture studies and interpretation of the results. A standardized method for use of this modified shear press is described in detail for research evaluation of French fry texture.     

Detection of potato virus M in tubers,sprouts, and leaves of potato by the French bean test

Summary A simple French bean test was found useful in detecting potato virus M (PVM) in tubers, sprouts, and leaves of potato. Intact primary leaves of several bean cultivars were highly susceptible to the selected isolates of PVM fromKing Edward, Bintje, Fortuna, andUp-to-Date. Distinctive brown local lesions were formed 3 days after PVM inoculation. Certain factors, including leaf age, virus inactivation in sap, and relative virus infectivity in leaf and different parts of tuber, were studied by the French bean test. PVM was detectable by inoculating bean half-leaves directly with freshly cut pieces of tubers.

---

Zusammenfassung Sieben aus Kanada und den Niederlanden stammende Isolate des Kartoffelvirus M (PVM) wurden in dieser Untersuchung gebraucht, um den Wert des Brechbohnen (Phaseolus vulgaris L.)-Testes für die praktische Verwendung beim Nachweis des PVM zu ermitteln. Die Inokulation erfolgte durch Abreiben jeder Blatth?lfte (nach Best?ubung mit Karborund, 600 Mesh) von voll ausgewachsenen Prim?rbl?ttern mit einem Baumwollappen, der vorher in ein Inokulum (mit 0,057M Phosphatbuffer, pH 8,5, verdünnt) getaucht worden war. Intakte Bl?tter und gepflückte Bl?tter. Die Empfindlichkeit der Prim?rbl?tter der Bohne nahm durch das Pflücken vom Stengel ab. Bohnensorten und Virusisolate. PVM-Isolate vonKing Edward, Bintje, Fortuna undUp-to-Date führten bei den folgenden Bohnensorten zu Lokall?sionen:Red Kidney, Bataaf, Prinsesco, Processor, Saxa, Walcherse Witte undWagenaars. Imuna, Noordhollandse Bruine undPinto UI 114 waren resistent gegen PVM (Tabelle 1).Alter des Blattes. Die Empf?nglichkeit der Bohnenbl?tter ?nderte mit zunehmendem Alter. Die gr?sste Empf?nglichkeit wurde 11 Tage nach der Saat beiRed Kidney, Bataaf, Processor undWalcherse Witte erreicht und 12 Tage nach des Saat beiWagenaars (Abb. 1). Verdünnungsendpunkt. PVM wurde in allen Knollenteilen bis zu einer Verdünnung von 10⁻³ entdeckt, nicht aber bei Verdünnung von 10⁻⁴, w?hrend PVM im Blatt bis zu einer Verdünnung von 10⁻⁴, aber nicht von 10⁻⁵ gefunden wurde (Tabelle 2). Langlebigkeit des Virus. Die Langlebigkeit des PVM war in den Knollenextrakten stets gr?sser (48 Std.) als in jenen von Blattextrakten (24 Std). bei 21–22°C (Abb. 2). Die Infektiosit?t von Blattmustern, tiefgefroren bei −15°C, nahm nicht stark ab, wie dies bei Saftmustern, aufbewahrt bei 22°C, der Fall war (Tabelle 3). Nachweis des PVM direkt in der Knolle. PVM wurde festgestellt in Augen, Rinde, Keim und Mark der Knollen, die w?hrend 8 Monaten bei 4°C gelagert wurden (Tabelle 4). Die Nachweisrate von 84% wurde durch direkte Inokulierung von halben Bl?ttern vonRed Kidney-Bohnen mit Knollenstücken erzielt (Tabelle 5). Daraus wurde geschlossen, der Bohnentest zur Erfassung des PVM in Knollen, Keimen und Bl?ttern der Kartoffel sei von praktischem Belang. Ferner wurde angenommen, dass der Bohnentest auch nützlich sein k?nnte bei der Auslese von Kartoffellinien bei der Untersuchung ihrer Resistenz gegen PVM und beim Auslesen von virusfreien Pflanzkartoffeln im Hinblick auf die nachfolgende Weitervermehrung.

---

Résumé Dans la présente recherche, l'auteur a utilisé sept isolats du virus M de pomme de terre (PVM) provenant du Canada et de Hollande pour déterminer la valeur du test sur haricot vert (Phaseolus vulgaris L.) dans la pratique de détection du virus PVM. L'inoculation a été réalisée en frottant chaque moitié de feuilles primaires pleinement développées, poudrées avec du carborundum 600, avec un tampon de coton trempé dans l'inoculum dilué dans 0,057M, tamponné de phosphate, de pH 8,5. Feuilles de plantes intactes à feuilles détachées. Lors du sectionnement, la sensibilité des feuilles primaires de haricot diminue significativement de la tige au pétiole. Variétés de haricot et isolats de virus. Les isolats de PVM deKing Edward, Bintje, Fortuna etUp-to-Date provoquent des lésions locales chez les variétés de haricot suivantes:Red Kidney, Bataaf, Prinsesco, Processor, Saxa, Walcherse Witte etWagenaars. Imuna, Noordhollandse Bruine, etPinto UI 114 sont résistants au PVM (Tableau 1). Age de la feuille. La susceptibilité des feuilles de haricot varie avec leur age. La susceptibilité maximum au PVM est obtenue 11 jours après le semis chezRed Kidney, Bataaf, Processor etWalcherse Witte, et 12 jours chezWagenaars (Fig. 1). Point extrême de dilution du virus. PVM est détecté dans toutes les parties du tubercule jusqu'à la dilution de 10⁻³ mais non plus à la dilution 10⁻⁴, tandis que dans la feuille le PVM est détecté jusqu'à la dilution de 10⁻⁴, mais non plus à la dilution de 10⁻⁵ (Tableau 2). Longévité du virus. La longévité du PVM est toujours plus grande dans les extraits du tubercule (48 heures) que dans ceux de la feuille (24 heures) à 21–22°C (Fig. 2). L'infection d'échantillons de feuilles, gelées à −15°C, ne diminue pas fortement comme c'est le cas dans les échantillons conservés à 22°C (Tableau 3). Détection directe du PVM dans le tubercule. Le PVM se détecte dans l'oeil, la couche corticale, le germe et la mo?lle des tubercules conservés 8 mois à 4°C (Tableau 4). Le taux de détection est de 84% lorsqu'on inocule directement des demi-feuilles de haricotRed Kidney avec des fragments coupés de tubercule (Tableau 5). La conclusion est que le test sur haricot est pratique pour la détection du PVM dans les tubercules, les germes et les feuilles de pomme de terre. L'auteur suggère en outre que le test sur haricot peut être pleinement utile dans l'élimination de clones de pomme de terre lors de l'étude de la résistance au PVM, de même que dans la sélection de tubercules de pomme de terre libres de virus en vue d'une multiplication ultérieure.

     

Evaluation of antioxidant activity of methanolic extract from peanut hulls in fried potato chips

Antioxidant activity of methanolic extract from peanut hulls (MEPH) was evaluated in fried potato chips during storage at 25 ^°C and 45 ^°C. Free fatty acids (FFA) and peroxide values (POV) were used as criteria to assess MEPH as an antioxidant. After six months storage at 45 ^°C potato chips treated with 1200 and 1600 ppm of MEPH showed lower values of FFA (0.083, 0.080%) and POV (30.0, 29.0 mEq/kg) than the control samples (FFA 0.377%, and POV 180 mEq/kg). Potato chips treated with BHA and BHT showed POVs of 29.0 and 25.0 mEq/kg whereas FFA values were 0.0086 and 0.074%, respectively, after six months storage at 45 ^°C. These results illustrate that MEPH, at various concentrations, exhibited very strong antioxidant activity which was almost equal to synthetic antioxidants (BHA & BHT). Subjective evaluation studies also showed that potato chips treated with 1200–1600 ppm MEPH after six months storage at 45 ^°C, were organoleptically acceptable.     

Starch and dry matter content of Netted Gem in relation to French fry texture

Studies were made on the relation of French-fry texture to solids content and to starch granule size in stored Netted Gem potatoes. Texture as evaluated both by a sensory panel and by an objective method was positively correlated with the percentages of starch granules in the 31–44 and 22–31 micron ranges. The usual positive correlations of texture with starch content, dry matter content, and specific gravity were in evidence. In limited trials, greater starch viscosiy and swelling power were associated with poorer texture. Heating time required to reach maximum viscosity was also related to texture, the longer heating times being associated with better texture.     

Some aspects of potato appearance and texture. III. Sampling tubers for cation analysis

Individual unpeeled Kennebec tubers were analyzed after being subdiviled in various ways for sampling. The individual portions were wetashed whith a nitric-perchloric mixture and three cations were determined by Atomic Absorption Spectrophotometry. Representative samples of the tubers could be obtained by using subsamples of a blend or by using two opposite sectors cut longitudinally where each sector comprised 1/16th of the tuber. The latter method gave the greatest uniformity among the subsamples. Magnesium was uniformly distributed in the tubers studied, while calcium and potassium were more concentrated in the area external to the vascular tissue and in the stem and the bud ends of the tubers. The inequality of calcium distribution was extremely great.