Cellulose, Hemicellulose and Lignin Content of Raw and Cooked Spanish Vegetables

The content in NDF, ADF, cellulose, hemicellulose, and lignin of 22 raw and 19 cooked vegetables (14 boiled, and 5 fried) widely consumed among the Spanish population was determined according to the method of Van Soest. Cooking generally increases the NDF, ADF and cellulose content on a dry weight basis. Normal size servings of the vegetables were prepared and their NDF, cellulose, hemicellulose and lignin contents calculated. We observed that, with vegetables of common use, a total amount of 15–20 g/day of these fiber components can be obtained; according to current knowledge this implies beneficial physiological effects for a broad human pathology.     

The effect of cooking on Brassica vegetables

Assessing antioxidant intake requires a food antioxidant database. However, cooking may affect antioxidant content due to antioxidant release, destruction or creation of redox-active metabolites. Here, effects of boiling, steaming and microwaving of broccoli, cauliflower, cabbage and choy-sum (Chinese cabbage) were explored by measuring antioxidant contents of raw and cooked vegetables. Cooking water was also tested. For all cooked vegetables, antioxidant content was highest in steamed > boiled > microwaved, and decreased with longer cooking time, regardless of method. All steamed vegetables had higher antioxidant contents than had matching raw vegetables. Effects were variable for boiling and microwaving. Microwaving caused greater antioxidant loss into cooking water than did boiling. Marked losses of anitoxidants occurred in microwaved cabbage and spinach. To assess food antioxidant content/intake accurately, cooking effects need detailed study. Steaming may be the cooking method of choice to release/conserve antioxidants. The cooking water is a potentially rich source of dietary antioxidants.     

The comparative evaluation of the nutrient composition and sensory attributes of four vegetables cooked by different methods

The following four vegetables; beans (Phaseolus vulgaris var. vulgaris), brinjal (Solanum melongena var. esculentum), knol‐khol (Brassica oleracea var. caulorapa) and radish (Raphanus raphanistrum satvius) were processed either by conventional, pressure or microwave cooking methods and were analysed for their nutritional and sensory profile. Raw samples were used as controls. Microwave cooking resulted in greater moisture loss when compared with vegetables cooked by other methods. The protein, fat, total ash, calcium, phosphorus, iron, and dietary fibre contents of the vegetables did not differ significantly in raw or cooked vegetables. Ascorbic acid was destroyed to the greatest extent by pressure cooking followed by microwave and conventional method. The sensory attributes of cooked vegetables, as evaluated by a paired preference test, revealed that there were no significant differences between cooked radish and knol‐khol but, in the case of beans and brinjal, microwave and conventionally cooked samples were preferred over pressure cooked ones.     

Cooking loss and juiciness of pork in relation to raw meat quality and cooking procedure

The study comprised two experiments with the aim to investigate the influence of raw meat quality and cooking procedure on cooking loss and juiciness of pork. The first experiment determined the cooking loss at 60, 70 and 80 °C centre temperature of 10 raw meat qualities (defined according to ultimate pH, drip loss, breed and rearing conditions) when cooked as steaks on a pan or as a roast in oven at a oven temperature of 90 or 190 °C. The differences in cooking loss between the raw meat qualities and the cooking procedures did decrease as the centre temperature increased and were almost negligble at 80 °C. Low water holding capacity (WHC) and low pH resulted in high cooking loss while no difference in cooking loss was observed between meat having medium or high WHC and pH. In the second experiment four raw meat qualities (standard, Duroc, low pH and heavy carcass weight) chosen from the first experiment to ensure a wide variation in cooking loss, were cooked in oven at 90 or 190 °C oven temperature. Juiciness was assessed three times during the chewing process. The results suggested that juiciness experienced initially in the chewing process depended only on the water content of the meat, whereas juiciness experienced later in the chewing process was determined by a combination of the water and intramuscular fat contents and the saliva production during chewing.     

Snap Bean Texture Softening and Pectin Solubilization Caused by the Presence of Salt during Cooking

Special procedures were used to separate the effects on softening and pectin solubilization of the presence of salt during cooking from the effects of salt apart from cooking. The effects of the presence of salt during cooking, calculated with respect to corresponding distilled water cooked beans, were greater with processing conditions of lower blanch temperature and shorter cook times, consequently they were greater with higher canned bean firmness and lower liquor pectin. Neither softening nor pectin solubilization had a significant relation to the reduction in pH induced by NaCl. The softening due to salts was seen with NaCl, KCl, and, to a lesser extent, with CaCl₂, and it may be the result of accelerated degradation of pectins.     

Dietary Fiber in Processed Lentils

Effect of soaking (distilled water, 0.1% citric acid (CA) and 0.07% sodium bicarbonate (SB) solutions), and cooking (distilled water) was studied on dietary fiber components of lentils. A high increase of protopectin, total pectic substances (PS), and dietary fiber (DF) was observed in soaked lentils (dry matter basis). Soaking in CA and in SB solutions led to an appreciable increase of hemicellulose (HMC) and neutral detergent fiber, but not in lentils soaked in water. Cooking the previously soaked lentils, reduced the amount of DF, due to a drastic loss of HMC, although cellulose and lignin increased. PS content of cooked lentils, previously soaked in CA and SB was still higher than in raw lentil.     

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.     

Fiber Contents of Selected Raw and Processed Vegetables, Fruits and Fruit Juices as Served

Pectin and neutral detergent fiber (NDF) contents were investigated for commercially processed foods as served: 10 vegetables, 10 fruits, and 8 fruit juices. Fiber content of fruits ranged from 0.7%?4.5% NDF and 0.28%?0.48% pectin; juices ranged from 0.1%?0.22% NDF and 0.2%?0.39% pectin. Fiber in frozen, canned and cooked vegetables ranged from 1%?4.4% NDF and 0.5%?1% pectin. In general, there is no evidence that any of the food preparation methods was superior. There appears to be no great loss of fiber when food is prepared by typical home methods or commercial processing.     

Effect of different cooking methods on the content of vitamins and true retention in selected vegetables

This study evaluated the effect of different cooking methods including blanching, boiling, microwaving and steaming on the content of vitamins in vegetables. True retention was estimated using the yield expressed as a ratio of the weight of the cooked sample to the weight of the raw sample. The retention of vitamin C ranged from 0.0 to 91.1% for all cooked samples. Generally, higher retention of vitamin C was observed after microwaving with the lowest retention recorded after boiling. Cooked vegetables were occasionally higher contents of fat-soluble vitamins, including α-tocopherol and β-carotene, than that of their fresh counterparts, but it depends on the type of vegetables. Microwave cooking caused the greatest loss of vitamin K in crown daisy and mallow; in contrast, it caused the least loss of vitamin K in spinach and chard. Cooking may cause changes to the contents of vitamins, but it depends on vegetables and cooking processes.     

Effect of cooking method on carnosine and its homologues, pentosidine and thiobarbituric acid-reactive substance contents in beef and turkey meat

Commercial samples of beef and turkey meat were prepared by commonly used cooking methods with standard cooking times: (1) broiled at 200 °C for 10 min, (2) broiled at a medium temperature (140 °C) for 10 min, (3) cooked by microwave (MW) for 3 min and then grilled (MW/grill) for 7 min, (4) cooked in a domestic microwave oven for 10 min, and (5) boiled in water for 10 min. The raw and cooked meats were then analysed to determine the carnosine, anserine, homocarnosine, pentosidine, and thiobarbituric acid-reactive substance (TBARS) contents. It was observed that boiling beef caused a loss of approximately 50% of the carnosine, probably because of the high water solubility of carnosine and its homologues; cooking by microwave caused a medium loss of the anti-oxidants of approximately 20%; cooking by MW/grill led to a reduction in carnosine of approximately 10%. As far as the anserine and homocarnosine contents were concerned, a greater loss was observed for the boiling method (approximately 70%) while, for the other cooking methods, the value ranged from 30% to 70%. The data oscillate more for the turkey meat: the minimum carnosine decrease was observed in the cases of MW/grill and broiling at high temperature (25%). Analogously, the anserine and homocarnosine contents decreased slightly in the case of MW/grill and broiling at a high temperature (2-7%) and by 10-30% in the other cases. No analysed meat sample showed any traces of pentosidine above the instrumental determination limits. The cooked beef showed an increased TBARS value compared to the raw meat, and the highest values were found when the beef was broiled at a high temperature, cooked by microwave or boiled in water. The TBARS value of the turkey meat decreased for all the cooking methods in comparison to the TBARS value of the fresh meat.     

BETWEEN-SPECIES DIFFERENCES IN FRACTURABILITY LOSS: COMPARISON OF THE THERMAL BEHAVIOR OF PECTIC AND CELL WALL SUBSTANCES IN POTATO AND CHINESE WATERCHESTNUT1

This study was undertaken to determine how the mode of chemical changes taking place during the cooking of two chemically similar vegetables (potato and waterchestnut) might explain the tremendous between-species differences in cooked tissue fractura bility as determined by Instron Texture Profile Analysis. Although pectin breakdown and depolymerization by heat weakens the cell wall structure, loss of cell wall physical strength does not necessarily coincide with pectin depolymerization. Potato phosphate-soluble pectin (PSP) showed a more rapid rate of depolymerization than waterchestnut PSP as proven by both chemical and gel chromatographic studies. The unique composition (e.g., neutral sugar content) of the cell wall microstructure of a given vegetable species is the major determinant of the resistance of that plant tissue to fracturability loss during cooking. Based on GLC analyses of cell wall components, cell wall models have been proposed to illustrate the possible structural differences between potato and waterchestnut tissue. It appears that the cell wall character of edible plant tissue for a given species is determined genetically.     

FACTORS AFFECTING TEXTURE OF COCKTAIL SHRIMP*

Texture of shrimp was influenced by pH, cooking time, and length of storage but not by the method of thawing the raw product or the soluble solids contents of the sauce. Shrimp cooked for 2, 5, 10, and 15 min required larger forces to shear than raw shrimp. Larger shear forces were also found with lengthening either the cooking or the storage periods. Shrimps packed in cocktail sauce maintained at pH 6.0 or 8.0 were more tender than those packed at pH 4.0.     

Legume Processing Effects on Dietary Fiber Components

Effects of different processes were studied on neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, and lignin content of legumes. Chick peas, kidney beans, and lentils were soaked and cooked, simulating home processing. Values were recorded on a wet basis as a guide to calculating their contribution to the diet. Decrease in values was more pronounced in pressure-cooked chick peas and kidney beans with cooking liquid removed. In lentils, cooking liquid embedded, no difference between processes was observed. Amounts of dietary fiber components on a dry basis, of interest when legume meal is used as food supplement, increased for chick peas and beans, except for the hemicellulose of beans and lentils, which decreased.     

EFFECTS OF VARIOUS FRESH MEAT STORAGE METHODS ON THE COLOR OF COOKED GROUND PORK

The effects of microbial growth in raw materials on cooked pork color were investigated. In two trials with sow meat held aerobically at 2C for 3 weeks, microbial load reached spoilage levels (10⁷ cfu/g), pH increased to 6.46, and samples cooked to 71C had red exudate, shown by absorption spectroscopy to contain myoglobin and cytochrome c. Samples cooked to 82C also received high panel ratings for red color, due to red, flocculent precipitate in the exudate, but undenatured myoglobin levels were low. In sow meat held frozen or vacuum-packaged at 2C, pH after 3 weeks was 6.03 and 6.18, and plate counts were 10⁴ and 10⁷, respectively, but exudates after cooking were much less red. In five trials with fresh pork legs, total plate counts also reached 10⁷ cfu/g by 3 weeks storage, and pH increased to 6.37, but cooked samples were not red. Higher myoglobin levels in sow meat probably accounted for the red color and level of undenatured myoglobin remaining after cooking of high pH, spoiled samples.     

CARBOHYDRATE TRANSFORMATIONS, COLOR AND FIRMNESS OF CANNED SWEET POTATOES AS INFLUENCED BY VARIETY, STORAGE, pH and TREATMENT

SUMMARY– Two varieties of sweet potatoes were canned at three storage intervals, six buffered pH levels, and two holding times to determine the influence on color, firmness, carbohydrates and other constituents. Color and firmness were improved when the pH was decreased from 8 to 3. There was an increase in brightness of color and firmness by holding peeled sweet potatoes 24 hr in buffers before canning. The sugars and phenolic substances were leached out during holding. Total polyphenols decreased with an increase in pH although tannic and chlorogenic acids were not changed appreciably. There was a decrease in starch and hemicellulose as a result of storage; whereas, water- and Calgon-soluble pectin were not affected. Starch decreased with an increase in pH regardless of other variables. Water-soluble pectin increased when pH was altered up or down from the normal pH of canned sweet potatoes of approximately 6.0. In comparison, Calgon-soluble pectin and hemicellulose reacted inversely to pH. It appeared that pH had a far greater effect on color and firmness than length of post-harvest storage of raw product after curing and other variables because of the direct effect on carbohydrate transformations and discoloration.     

Lipid Oxidation, Volatiles and Color Changes of Irradiated Pork Patties Affected by Antioxidants

Changes were measured in TBARS, color, and volatiles of irradiated (4.5 kGy) pork patties with antioxidants (sesamol, quercetin, rutin, BHT, and rosemary oleoresin) during 7 days storage at 4°C. Irradiation accelerated lipid oxidation of raw pork during storage. However, irradiation before cooking did not influence lipid oxidation of cooked pork during storage. Sesamol, quercetin, and BHT were effective in both irradiated raw and cooked pork during 7-days storage. Rosemary oleoresin and rutin were effective only in irradiated raw pork for 3 days. Hexanal, propanal and higher boiling components were well correlated (P < 0.01) with TBARS in cooked pork. Generation of volatiles was reduced by sesamol and quercetin, but the effects of antioxidants on color changes of raw pork patties were minor and inconsistent.     

Origin and Nature of Aroma in Fat of Cooked Poultry

SUMMARY: Fat of raw poultry, separated from solid tissue and washed with water at temperatures not exceeding 40°C does not contain cooked poultry aroma and does not develop it when heated. Hence, cooked poultry aroma cannot be derived from the fat alone. Washed and filtered fat from cooked poultry contains characteristic cooked poultry aroma dissolved in it. The aroma of this fat is caused by compounds which dissolve in it during cooking and which apparently stem from nonfat or lean portions of the meat. The ability of fat to dissolve or acquire substances during cooking was demonstrated by showing that fat of cooked poultry contains more sulfur than does fat of raw poultry. Less than 2% of this sulfur build-up occurs as hydrogen sulfide. The magnitude of the sulfur build-up was 8 to 14 times greater in the fat of roasted poultry than it was in the fat of simmered chicken. Authentic amino acids in contact with poultry fat at a typical roasting temperature readily underwent Strecker type degradation. Furthermore, aroma components representing typical amino acid degradation products were found in fat from roasted turkey. These analytical results indicate protein, amino acids and probably also sugars and other water soluble components are invoved in aroma formation. Hence fat contributes to cooked poultry aroma indirectly and passively through its ability to dissolve and retain aroma components formed during cooking. Consequently, the characteristic cooked poultry aroma in fat of cooked poultry is not derived from the fat itself but comes from and is thus dependent on the "lean".     

Enhancement of the nutritional status of beef patties by adding flaxseed flour

Flaxseed flour was used as a functional ingredient in the production of beef patties. Beef patties were produced with five different formulations; the addition of 3%, 6%, 9%, 12% and 15% flaxseed flour. Control samples were formulated with 10% and 20% fat addition. Raw and cooked beef patties were analyzed for moisture, protein, fat, ash, pH, color parameters and fatty acid profiles. Beef patties were evaluated for cooking loss and sensory properties. Fat and ash content of raw patties increased, while moisture and protein content decreased with increased flaxseed flour. The same trend (except fat content) was also observed after cooking. The addition of flaxseed flour did not affect pH values of raw and cooked beef patties. The addition of flaxseed flour improved the cooking loss but, increased the energy value (as kcal/100 g). L and a values of raw beef patties containing flaxseed flour were close to controls with 10% fat. α-linolenic acid content of raw and cooked beef patties increased as the level of flaxseed flour increased. The PUFA/SFA ratio increased from 0.04 in the control with 10% fat to 0.62 in the raw beef patties with 15% flaxseed flour. The n-6/n-3 ratio decreased from 5.76 in the control with 10% fat to 0.36 in the raw beef patties with 15% flaxseed flour. The nutritional status of beef patties was enhanced with minimal composition and sensory changes with 3% or 6% flaxseed flour addition.     

FUNCTIONAL PROPERTIES OF SORGHUM FLOUR AS AN EXTENDER IN GROUND BEEF PATTIES 1

Patties were formulated with 20% fat ground beef and sorghum flour (SF) at 2, 4, and 6% levels (10, 20, and 30% as rehydrated 1:4 with water). Beef patties containing SF had higher pH, greater yield, less total cooking loss, less shrinkage in diameter, and less increase in thickness than those without SF. Water activity of cooked patties was not affected by addition of SF. Fat and water retentions of beef patties increased as the level of SF increased. Hunterlab a values (redness) for raw patties decreased as the level of SF increased, but a values for cooked patties were not influenced by level of SF. Shear force and compression of cooked patties decreased as the level of SF increased. Meat aroma and flavor decreased, but sorghum aroma and flavor of cooked patties increased as the level of SF increased. Tenderness of cooked patties increased as the level of SF increased, but juiciness of cooked patties was not affected.     

Cellulose, Hemicellulose and Lignin Content of Raw and Cooked Processed Vegetables

The NDF, ADF, cellulose, hemicellulose and lignin contents of five frozen vegetables (raw and boiled) and five canned vegetables (two of them fried) have been studied. In general, it was observed that boiling resulted in an increase in the NDF, ADF and cellulose content. There was also a slight increase in hemicellulose values. The lignin contents of most vegetables did not change upon boiling. When the cooking process was frying, a drastic decrease of NDF, ADF, cellulose, and lignin contents occurred, while the amount of hemicellulose changed slightly in the vegetables analyzed.