Frozen Carrots Texture and Pectic Compotients as Affected by Low-Temperature-Blanching and Quick Freezing

Carrots preheated for 2 hr at 60°C and then cooked became firmer than raw or cooked carrots. After preheating, the amount of high methoxyl pectin decreased, and low methoxyl pectin increased. Firmness of carrots decreased through freezing then thawing, but preheated carrots retained firmer texture than those blanched in boiling water. Quick-freezing resulted in better texture than slow-freezing. Loss in texture was accompanied by release of pectin. Slow-freezing accelerated release of pectin as compared to quick-freezing. Preheated carrots were slower in release of pectin. The degree of esterification of pectin substances in raw carrots decreased during preheating, freezing and thawing. Cell damage in quick frozen carrots was slight. Optimum preheating occurred with 30 min at 60°C or 5 min at 70°C. Preheating and then quick freezing were effective in improving texture of frozen carrots.     

Molecular Composition of Onion Pectic Acid

ABSTRACT: Pectin was extracted, then pectic acid was purified without autolysis. It contained 93.7% uronic acid and 6.3% neutral sugar. Using exopolygalacturonase, exopolygalacturonate lyase and endopolygalacturonase, the molecular composition of onion pectic acid was determined; the proportion of galacturonic acid residue from the nonreducing end to rhamnogalacturonan (RG) was 9.7%, while that of the reducing end to RG was 46.7%. From RG to RG, the proportion of galacturonic acid residue was 41.0%, and the RG region was 2.6%.     

Quality Improvement and Evaluation of Hypoallergenic Rice Grains

The color of hypoallergenic rice grains, produced by an enzymatic process was improved by treatment with diluted hydrochloric acid and washing with water. The acid-treated grains were steamed at the surface layer to prevent breakage. Textural evaluation showed the cooked hypoallergenic rice grains had a favorable stickiness/hardness ratio.     

RHYTHMIC AND IRREGULAR MOVEMENT OF THE FIRST MOLAR WHILE EATING FOODS WITH DIFFERENT TEXTURES

The three-dimensional movement of a tooth, any tooth, while naturally eating, was measured by an apparatus developed in our laboratory. The movement of the first molar on the usually used side is reported here. The mastication movements are divided into two parts, namely the rhythmical chewing period during which there are mastication pressure loads on the molar and the irregularly pulsated moving period in preparation for the swallowing followed by the rhythmical one during which there is no more pressure on it. The amplitudes of the up and down movements of the molar are 10–22mm for the rhythmical chewing period which are bigger than those for the irregularly moving period. The rhythmical chewing periods are distributed around 10–40 s depending on 14 kinds of food texture, and also on the size of the food, in a fairly similar manner for the participants. The period is longer for tough foods and bigger samples. The irregularly pulsated moving periods are widely distributed, 2–45s, and depend both on the food texture and on the participant. The irregular moving periods are longer for foods which scatter in the mouth or adhere to the teeth when chewing. The ingestion difficulty of the food was divided into two groups. One is where it is difficult to break down the food with the teeth and the other is where it is difficult to prepare for swallowing.     

Histological Changes in High-Pressure-Frozen Carrots

Histological changes in carrots frozen using a computer-programmed high pressure pilot unit for food processing were examined by light microscope. When raw carrots were frozen at 50 MPa, – 15°C; 100 MPa, –15°C; 150 MPa, –25°C; 200 MPa, –28°C, they were extremely damaged due to volume expansion by the formation of ice I. Conversely, carrots pressurized at 100 MPa, – 10°C (between liquid phase and ice I) and 200 MPa at –20°C (liquid phase) were not damaged because they were frozen rapidly during pressure reduction. They were not damaged even after pressurizing-then-immersing in LN₂. Carrots frozen at 240 MPa, –28°C and at 280 MPa, –25°C, were also not damaged, although ice III formed. The structure of carrots frozen at 400 MPa, –20°C (ice V) was comparatively intact. When carrots were preheated at 60°C for 30 min and frozen at 100 MPa, –15°C or at 400 MPa, –20°C, damage was reduced further.     

Chinese Cabbage Midribs and Leaves Physical Changes as Related to Freeze-processing

Differences were investigated in texture, drip and pectic composition of raw or blanched Chinese cabbage midribs and leaves after conventional (F) or program freezing (PF). Softening of tissues and amount of drip were least to greatest: PF-5°C/min < PF-2°C/min < F-35°C < F-20°C, respectively. Freezing-thawing accelerated release of pectin but the freezing rate did not affect pectin release much. Total pectin in raw midribs was less than in raw leaves. The leaves contained more low methoxyl pectin than midribs, but the high methoxyl pectin was almost the same. Cell damage in frozen-thawed midribs and leaves by light-and electron-microscopy appeared extensive.     

Relationship Between Pectic Compositions and the Softening of the Texture of Japanese Radish Roots During Cooking

The pectins of Japanese radish roots were fractionated by successive extraction with three reagents: diluted HCI, sodium acetate buffer, and sodium hexametaphosphate solutions. The tissue, softened by thermal maceration, contained more HCl-soluble pectin (pA) than the sodium acetate buffer soluble pectin (pB). The degree of esterification (DE) of pA was higher than that of pB. With CaCI₂, pB formed some precipitates, but pA did not. The elution patterns of pA and pB by DEAE-cellulose column chromatography were different. A clear relationship between other dietary fiber (hemicellulose, cellulose and lignin) and softening of roots was not observed. The composition of pectins, especially DE, appeared to have an effect upon the texture of the Japanese radish softened during cooking.     

Texture and Pectic Composition Differences in Raw, Cooked and Frozen-Thawed Chinese Cabbages due to Leaf Position

Differences in texture of raw, cooked and blanched-frozen-then-thawed Chinese Cabbages and their leaf positions (10, 20, 30, 40, or 50th midribs from the outside) were investigated. Firmness and rupture strain of raw midribs were low, but increased after short cooking time. Crispness of tissues decreased and elasticity increased. The 20–30th midribs were slowest to soften during cooking, while the inner midribs from the 40th were more readily softened. The 40th contained more high methoxyl pectin than did the 20th. Therefore, they were more quickly softened because of pectic release by transelimination. After freezing-thawing, firmness decreased and rupture strain increased. Midribs with firmer texture contained more pectin. After freezing-thawing, amounts of pectin in midribs decreased.     

Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Proteinaceous surfactants were prepared by applying the “one-step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n-alkyl esters of L-leucine as lipophiles. Each of the hydrophile-lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone-1M carbonate (pH 9) containing 2 mM 2-mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L-leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low-molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C₄–C₆ alkyl esters of leucine showed greater whippability, whereas the incorporation of the C₁₀–C₁₂ alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.