Effect of processing on the amino acid content of New Zealand spinach (Tetragonia tetragonioides Pall. Kuntze)

The aim of this work was to evaluate the effect of processing on the amino acid content and protein quality of New Zealand spinach (Tetragonia tetragonioides Pall. Kuntze). In this research, fresh and cooked New Zealand spinach as well as two frozen products prepared for consumption, one obtained using the traditional method (blanching–freezing–storage–cooking) and the other a convenience food product obtained using a modified process (cooking–freezing–storage–defrosting and heating in a microwave oven), were analysed. Glutamic acid was the dominant amino acid in fresh New Zealand spinach, and the limiting amino acids were cystine and methionine. Technological and culinary processing caused a significant increase in amino acid content in 100 g of edible portion, with the exception of methionine and cystine in frozen products prepared for eating. Changes in amino acid content expressed in g/16 g of N (which corresponded to 100 g tissue protein) were not significant, with the exception of the lower glutamic acid content in the frozen product obtained using traditional processing method.     

Effect of different technological and culinary treatments on iron retention,nutritional density and recommended dietary intake in fourteen vegetable species

The present work determined iron content in fourteen species of vegetable prepared for consumption. The experimental material consisted of raw and boiled raw vegetables and two types of frozen product: one traditionally produced (blanching before freezing); the other obtained using the modified method (boiling before freezing), having the characteristics of a ready‐to‐eat convenience product. Nutrient density (ND) and recommended dietary intake (RDI) were established on the basis of iron content. The highest iron content was found in pea seeds (2.03 mg per 100 g fresh weight) and the lowest in root vegetables (0.38–0.60 mg). Iron retention was similar in all pea, broad bean, New Zealand spinach, kale, white cauliflower, celery and red beet products. In the remaining products, the significantly lowest retention was found in the traditionally frozen product (Sample C) and the highest in the ‘convenience’ frozen product (Sample D). The above‐mentioned order also applied to ND and RDI values. Only in the ND of parsnip calculated for women did any value fall below 100%.     

Effect of freezing and canning on the content of selected vitamins and pigments in seeds of two grass pea (Lathyrus sativus L.) cultivars at the not fully mature stage

Seeds of the grass pea (Lathyrus sativus L.) cultivars Derek and Krab, with a dry matter content of about 33%, were used for freezing and for canning. The content of vitamins C, B1, and B2 and of carotenoids, beta-carotene, and chlorophylls was determined in raw and blanched material, in frozen products after 6-month storage before and after cooking to consumption consistency, and in canned products after 6-month storage. In comparison with the cultivar Krab, raw seeds of Derek contained 45% more vitamin C, 14% more total chlorophylls, 13% less thiamine (vitamin B1), and 7% less riboflavin (vitamin B2). The level of carotenoids was similar. Blanching of seeds led to a statistically significant decrease only in the content of vitamin C. Freezing and frozen storage significantly lowered the level of vitamin C and chlorophylls. The cooking of frozen seeds and the production of canned products and their storage resulted in a statistically verified reduction in the content of components analysed in all the samples. Greater losses were found in products prepared from seeds of the cv. Krab. After cooking, frozen seeds contained more of all the analysed components than the canned products.     

Impact of the industrial freezing process on selected vegetables -Part II. Colour and bioactive compounds

In the present study, the impact of the different steps (i.e. blanching, freezing, storage following the industrial freezing process and the final cooking prior to consumption) of the industrial freezing process was evaluated on colour, chlorophylls, lutein, polyphenols and ascorbic acid content of asparagus, green beans and zucchini. In addition, the domestic boiling of raw samples was compared with the boiling of frozen storage vegetables.Results showed that the blanching treatment retained phytochemicals in all studied green vegetables and the frozen storage up to 2 months did not negatively affected phytochemicals, in particular lutein and flavonoids in almost all samples. On the contrary, colour significantly changed during blanching and frozen storage. The changes of b* (yellowness) and the shift of H° (hue angle) were not coherent with the increase of pheophytin. In addition, the greenness (− a*) was found to increase with the exception of boiled samples in all vegetables. Generally, in boiled frozen vegetables there was a better or comparable retention of bioactive compounds with respect to raw ones, and this was especially true for green beans and zucchini. Colour changes after cooking did not exhibit the same trends among vegetables, being more remarkable for frozen asparagus in comparison with those boiled from raw, but overall comparable for green beans and zucchini.In conclusion, the overall results of the present study suggest that, when the industrial freezing process is well performed, the boiled frozen vegetables do not have a lower nutritional value than the fresh ones.     

Evaluation of the amino acid content and sensory value of flageolet bean seeds (Phaseolus vulgaris L.) as affected by preprocessing methods before freezing

The aim of the work was to evaluate the content of amino acids in flageolet bean seeds, prepared for consumption from frozen products obtained using different methods. One of the frozen products was obtained using the traditional method (blanching–freezing–frozen storage) and then cooked. The other was obtained using the modified technology (cooking–freezing–frozen storage), followed by defrosting and heating in a microwave oven. The culinary and technological processing applied brought about a pronounced decrease in tyrosine content (35–47% in 16 g N). The content of the remaining amino acids decreased or increased in relation to the raw material within the extremes of ?15% to +17%. Sulphur amino acid was the limiting amino acid. Product obtained using traditional method had the higher quality protein (EAA index 144–166) of seeds prepared for consumption. In sensory test products, blanched before freezing were evaluated a bit higher than those cooked before freezing (ready‐to‐eat).     

Retention of mineral constituents in frozen brassicas depending on the method of preliminary processing of the raw material and preparation of frozen products for consumption

The content of ash, P, K, Ca, Mg, Na, Fe, Zn, Mn, Cu, Cr and Ni was determined in four species of brassicas: Brussels sprouts, broccoli, and green and white cauliflowers. The investigation covered the raw material, the material blanched or cooked before freezing and frozen products after 12 months of refrigerated storage and prepared for consumption. Frozen products were obtained by the traditional method of freezing the blanched material or by the modified method of freezing the cooked material. The processing of vegetables before freezing (washing, grinding, blanching or cooking) caused statistically significant decreases in most constituents analysed. Blanching did not basically change the content of sodium and calcium; or that of chromium in both types of cauliflower; copper and nickel in white cauliflower; and nickel and phosphorus in Brussels sprouts. Cooking in brine, however, caused increases in the content of ash, sodium and calcium in white cauliflower, decreases in the content of potassium and iron and, in some species, of the remaining constituents. In comparison with the traditional method, a greater content of most analysed elements was found in frozen products obtained by the modified technology and prepared for consumption. However, no significant differences were noted in the level of chromium in all the samples; in the level of calcium in broccoli and green cauliflower; of nickel in broccoli; of nickel, copper and zinc in white cauliflower; and of copper in green cauliflower.     

Effect of preliminary and culinary processing on amino acid content and protein quality in frozen French beans

The aim of the study was to evaluate the content of amino acids and protein quality of French bean pods. The investigated material consisted of the raw vegetable, fresh pods cooked to consumption consistency, and two kinds of frozen products stored for 12 months at ?20 °C and then prepared for consumption: frozen beans obtained using the traditional method (blanching before freezing) and frozen products of the ready‐to‐eat type (cooking before freezing). A comparison of the amino acid content in the product prepared for consumption showed that the lowest quantities were found in French beans obtained using the traditional method; products obtained using the modified technology and beans cooked directly after harvest had similar levels of most amino acids. The content of amino acids in 16 g N was less varied than in 100 g of the product. The protein in all the three products prepared for consumption as well as that in fresh bean pods hardly differs, as confirmed by the values in the essential amino acid index (EAA). The first limiting amino acid was methionine with cystine and the second was lysine.     

Content of amino acids in raw and frozen broad beans (Vicia faba var. major) seeds at milk maturity stage,depending on the processing method

The aim of the present work was to evaluate the amino acid content in products obtained from broad bean seeds, at the milk maturity stage, and the quality of the protein in broad beans. The investigation included raw seeds, fresh seeds cooked to consumption consistency and two kinds of frozen products prepared for consumption: which were obtained using the traditional method (blanching the seeds before freezing) and the ready-to-eat type (cooking the seeds before freezing). Compared with the raw material, a similar (α = 0.01) content of amino acids in 100 g of the product was found in cooked fresh seeds. The seeds obtained from the ready-to-eat frozen product prepared for consumption contained higher amounts of all the amino acids than the traditional frozen product, and contained higher levels of some amino acids than were found in the product cooked from fresh seeds. Expressing the results per 16 g of N, the differences in the content of amino acids were much smaller. The limiting amino acid was cysteine with methionine (CS 74-86), the EAA index varying within the range 109–118.     

Amino acid profile of raw and as-eaten products of spinach (Spinacia oleracea L.)

The aim of the work was to evaluate the amino acid composition of fresh spinach and spinach products prepared for consumption. The investigation included fresh and cooked spinach and two kinds of frozen product: one obtained using the traditional method (blanching-freezing-refrigerated storage) and then cooked; and the other, of the ready-to-eat type, obtained using the modified method (cooking-freezing-refrigerated storage) and then prepared for consumption in a microwave oven. In 100 g of edible parts of the as-eaten products, the content of amino acids exceeded that in the raw material from which they were obtained, except for sulphur amino acids and tyrosine. In the as-eaten products, the content of amino acids in protein calculated in 16 g N was similar to that in the raw material, except for lower tyrosine and higher arginine content in the traditional frozen product prepared for consumption. Cystine with methionine was the amino acid limiting the quality of protein in the investigated samples, except for the traditional frozen product prepared for consumption, where the Chemical Score (CS) index was 100.     

Effect of pretreatment and conditions and period of storage on some quality indices of frozen chive (Allium schoenoprasum L.)

Chive leaves for freezing contained 13.9 g dry matter, 133 mg vitamin C, 4.7 mg β carotene, 121 mg chlorophylls (a+b), 40.4 mg nitrates, and 0.19 mg nitrites in 100 g of edible parts. Blanching of the raw material before freezing reduced the level of dry matter by 22%, vitamin C 29%, β carotene 20%, chlorophylls 21%, and nitrates 26%, while that of nitrites increased three times. Freezing and 12-month storage of frozen material caused further losses in the analysed constituents except dry matter. Losses were distinctly higher on freezing non-blanched chive, a further enhancement of losses being observed with a storage temperature at −20°C. After a 12-month storage of frozen chive, the preserved content of vitamin C ranged from 11 to 66%, β carotene 37 to 65%, chlorophylls 65 to 75%, and nitrates 58 to 81%. If the blanching is omitted and the storage temperature is −20°C, a good preservation of vitamin C is not possible even for a period of 3 months. In contrast, the pretreatment of blanching ensures its good preservation at −20°C and at −30°C, and also yields a very good conservation of all the constituents analysed.     

Changes in the level of vitamin C,beta-carotene,thiamine, and riboflavin during preservation of immature grass pea (<Emphasis Type="Italic">Lathyrus sativus L</Emphasis>.) seeds

The aim of the work was to evaluate the content of vitamin C, beta-carotene, thiamine, and riboflavin in raw and preserved physiologically immature grass pea seeds. The seeds of the cultivar Krab, differing in their morphology, phytometric traits, and specific gravity were divided into four stages of maturity, which corresponded to the following levels of their dry matter content: I - 25.9, II - 30.1, III - 36.4, and IV 40.6 g/100 g. The evaluation was conducted at the stage of the raw material, the material after blanching, frozen seeds after 6-month storage before and after cooking to the consumption consistency, and canned seeds 6 months after production. With the maturity degree of grass pea seeds the content of vitamin C was reduced by 19%, beta-carotene by 29%, riboflavin by 20%, while that of thiamine increased by 97%. The blanching of seeds led to a statistically significant decrease only in the content of vitamin C. Freezing and frozen storage did not significantly affect the level of the analysed components. The cooking of frozen seeds, the preservation of canned products, and their storage significantly reduced the content of all the analysed components in all the samples. No dependence was found between the magnitude of decreases in the investigated compounds and the degree of seed maturity. After cooking frozen seeds prepared from the raw material at the same maturity degree as the canned product contained 32%-51% more vitamin C, 0%-8% more beta-carotene, 40%-97% more thiamine, and 20%-25% more riboflavin, depending on the degree of seed maturity.     

Content of amino acids and the quality of protein in as‐eaten green asparagus (Asparagus officinalis L.) products

The content of amino acids in fresh green spears and in three as‐eaten products was considered, i.e., in fresh asparagus after cooking and in two products obtained from frozen asparagus stored for 12 months at ?20 °C. One of the frozen products was obtained using the traditional method (blanching–freezing–frozen storage) and then cooked. The other was obtained using the modified technology (cooking–freezing–frozen storage); after the storage period the product was defrosted and heated to consumption temperature in a microwave oven. The limiting amino acid of the first order was methionine with cystine, and of the second order leucine. Essential amino acids constituted 40–43% of the total amino acid content. The dominant amino acids were aspartic acid and glutamic acid. The culinary and technological procedures applied brought about a drastic decrease (50–56% in 16 g N) in tyrosine content.     

Formation of pyrochlorophylls and their derivatives in spinach leaves during heating

The changes of chlorophylls and their derivatives during heating of spinach leaves were studied. Chlorophylls and their derivatives were analyzed by high performance liquid chromatography (HPLC) with photodiode-array detection or positive ion fast atom bombardment mass spectrometry (FAB–MS). No chlorophyll derivatives were detected in fresh spinach leaves. The degradations of both chlorophylls, a and b, fit the first-order model, and the rate constant (min⁻¹) by microwave cooking or blanching was greater than that by steaming or baking. The major chlorophyll derivatives formed during baking and blanching included chlorophyll epimers and pheophytins. Pyrochlorophylls a and b were detected in spinach leaves after steaming for 30 min or microwave cooking for 1 min. Pyropheophytins a and b were not formed until steaming or microwave cooking time reached 30 or 5 min, respectively. Steaming favored the formation of pheophytins a and b while microwave cooking favored that of pyrochlorophylls a and b.     

The amino acid composition of kale (Brassica oleracea L. var. acephala), fresh and after culinary and technological processing

The aim of the investigation was to evaluate the level of amino acids and the quality of protein in fresh and cooked leaves of kale and in two types of frozen product prepared for consumption after 12-months storage at −20 °C. Kale blanched before freezing (the traditional method) was cooked after refrigerated storage, while that cooked before freezing (the modified method) was defrosted and heated in a microwave oven. Both fresh and processed leaves of kale were a good source of amino acids. In all the samples, glutamic acid, proline and aspartic acid were the dominant, while lysine and leucine were the limiting amino acids. Cooked leaves contained 78% of the total amino acid content found in fresh leaves, while the traditional and modified frozen products contained 76% and 78%, respectively. The proportion of essential amino acids in total amino acids was 44% and 43%, respectively for fresh and cooked leaves and 46% for the frozen products. The lowest EAA index was found for the traditional frozen product (99); it was higher for the remaining samples, which were broadly similar to each other (105–106).     

Application of infusoria Tetrahymena pyriformis culture in quality method of estimation with a help of frozen raw material from Pacific herring fatty

Influence of refrigerated storage on quality of fatty raw material by the example of Pacific herring has been investigated. After freezing and during storage at different temperatures in samples of frozen Pacific herring wedetermined the microbiological parameters, the content of toxic compounds, changes of proteins and accumulation of products of lipids oxidation. In parallel it was determined the quality of frozen herring by method of biotesting using infusorian Tetrachymena pyriformis. It has been established, that during storage of frozen Pacific herring the loss quality of fish raw material takes plase. Results of biotesting completely correlate with the data of chemical analysis under the estimation of fish raw material quality of refrigerated storage.     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

Effect of High Dietary Vitamin E on Lipid Stability of Oven-cooked and Hot-smoked Trout Fillets

ABSTRACT: Supplementing α-tocopheryl acetate (300 and 5000 mg/kg diet) in a trout finishing diet was done to minimize lipid oxidation in oven-cooked fillets and hot-smoked products. Hot-smoked processing did not affect α-tocopherol content of finished products compared with raw fillets. Feeding diets containing 5000 mg vitamin E/kg increased muscle α-tocopherol content that minimized lipid oxidation in (1) oven-cooked fillets produced from fresh and 7-d refrigerated fillets and (2) hot-smoked products following refrigerated storage for 8 wk. Dietary vitamin E did not affect fatty acid composition of products from either cooking method. Oven-cooked fillets produced from 7-d refrigerated, raw fillets and refrigerated, smoked products had lower percentages of omega-6 fatty acids and lower omega-3 fatty acids:omega-6 fatty acids ratios compared with fresh, raw samples.     

Total and soluble oxalate content in legume vegetables used in the preparation of frozen products for consumption

The aim of the investigation was to compare oxalate retention in two types of frozen product prepared for consumption after frozen storage: one obtained using the traditional method (blanching‐freezing‐frozen storage‐cooking) and a convenience food involving cooking‐freezing‐frozen storage‐defrosting and heating in microwave oven. The investigation included three species of legume vegetables: immature (wax‐stage maturity) seeds of broad bean and green pea, and French bean. Fresh broad bean seeds contained 53 mg total oxalates in 100 g fresh matter; pea 38 mg; and French bean 88 mg. Soluble oxalates comprised 53, 58 and 72% of total oxalates. The treatments applied resulted in reduction of the level of total and soluble oxalates, and oxalate to calcium ratio (broad bean and French bean); there was no influence on the level of calcium bound as calcium oxalate; true retention of oxalates was lower than apparent retention (green pea and French bean).     

Effect of preliminary processing, method of drying and storage temperature on the level of antioxidants in kale (Brassica oleracea L. var. acephala) leaves

The levels of vitamin C, polyphenol constituents and Trolox equivalent antioxidant activity (TEAC) were analyzed in raw kale leaves, blanched leaves and dried leaves obtained using air and freeze-drying methods. 100 g of raw kale leaves contained 683 mg vitamin C and 2236 mg polyphenols (identified using the HPLC method); the level of antioxidative activity was 71 μM Trolox/1 g dry matter. Compared with the raw material, blanching before drying brought about significant decreases of 15% in vitamin C, 32% in polyphenols and13% in TEAC. After 12-month storage, air-dried material retained 30-37% polyphenols; 43-57% vitamin C; and 41-50% of the initial TEAC level; the corresponding values for freeze-dried material were 40-47%; 50-65% and 54-66% depending on the type of sample. Freeze-dried kale leaves contained higher levels of antioxidants than air-dried material: polyphenols, vitamin C and TEAC were respectively 36%, 15%and 33% higher.     

Carotenoid Photostability in Raw Spinach and Carrots During Cold Storage

A reverse-phase gradient HPLC method was developed for separating xanthophylls, chlorophylls, carotenes and cisβ-carotene isomers from raw spinach and carrots. The effect of dark and lighted cold storage on pigment stability was studied. Light promoted pigment losses in raw spinach. Degradative losses at 8 days ranged from 60% for violaxanthin to 22% for lutein. Dark, cold storage did not affect carotenoid levels except for all-transβ-carotene which showed an 18% loss at 8 days. In raw carrots, neither lighted nor dark cold storage affected major carotenoids. In spinach, the isomeric distribution of β-carotene showed strong linear correlations between trans and cis forms.