The effect of light on the vitamin B2 and the vitamin A content of cheese

Edam type cheese was exposed to sunlight at ambient temperature and to fluorescent light at 5 °C. The loss of vitamin B₂ (riboflavin) and vitamin A was monitored in both the surface and inner layers of the cheese and the results compared with control samples kept in the dark. The loss of riboflavin when exposed to sunlight was shown to be primarily a surface effect but losses of vitamin A were similar throughout the cheese. When exposed to fluorescent light at 5 °C and monitored at intervals for 10 days the loss of riboflavin was still greatest at the surface but a trend to lower values than the control was evident throughout the cheese. Vitamin A losses followed a different pattern in both sunlight and fluorescent light. There was a heavy initial loss throughout the cheese. Under fluorescent light this was followed by a period in which further loss was mainly in the surface layer. Vacuum packaging reduced the loss of riboflavin but had no effect on the loss of vitamin A.     

Kinetic modelling of vitamin C loss in frozen green vegetables under variable storage conditions

A systematic kinetic study of l-ascorbic acid loss of four green vegetables was conducted in the temperature range of freezing storage. The temperature-dependence of vitamin C loss in the −3 to −20 °C range was adequately modelled by the Arrhenius equation and activation energy ranged from 98 to 112 kJ/mol for the four frozen green vegetables. The developed models were validated in fluctuating time–temperature conditions, in order to establish their applicability in the real marketing path of the commercial products. Based on the models, the nutritional level can be estimated, at any point of the freezing chain, when the full time–temperature history is available. Comparison among different green vegetables showed that the type of plant tissue significantly affects the rate of vitamin C loss. Frozen spinach was found to be the most susceptible to vitamin C degradation, peas and green beans demonstrated a moderate retention, whereas okra exhibited a substantially lower loss rate.     

Effects of Processing and Storage on the Water-Soluble Vitamin Content of Human Milk

Effects of four heat treatments (62.5°C, 30 min; 72°C, 15 sec; 88°C, 5 sec; and 100°C, 5 min) and frozen storage (?20°C, 4 wk) on water-soluble vitamin content of composite samples of mature human milk were determined. No changes in riboflavin, biotin, and total pantothenic acid content were observed after any of the treatments. Heating at 100°C for 5 min decreased thiamin, vitamin B₁₂, and vitamin C contents. Vitamin Bs content was reduced by heating at 88°C and 100°C. Free folate was not affected by heating while total folate concentration was decreased similarly by all heat treatments. During frozen storage at ?20°C, niacin and free pantothenic acid concentrations were reduced; riboflavin, vitamin Bs, biotin, total pantothenic acid, vitamin C, and vitamin B₁₂ were unaffected; while measurable thiamin and free folate concentrations increased. Overall, the two lower temperature treatments were less detrimental to the water-soluble vitamins in human milk.     

Vitamin C losses in some frozen vegetables due to various cooking methods

Frozen spinach, peas, green beans and okra were commercially cooked in three different stewpans (double based stainless steel, teflon, pyrex) with and without thawing. The vitamin C levels were effected both by cooking methods and stewpans. Frozen peas were found to be the least (3.5% loss), and frozen green beans were found to be the most (19.6% loss) effected vegetables by thawing. In all of the stewpans, double based stainless steel pan retained more vitamin C than the others. While boiling spinach, peas, green beans, and okra without thawing resulted 46.5, 25.2, 18.2, and 21.6% vitamin C loss in double based stainless steel pan, boiling them in pyrex pan resulted 58.5, 36.0, 42.1, and 28.2% vitamin C loss, respectively. Besides, the losses in cooking processes were accelerated in thawed vegetables with the same tendency; that is more destruction occurred in samples boiled in pyrex pan (60.3% loss in spinach, 40.8% loss in peas, 48.4% loss in green beans, and 41.6% loss in okra). According to the results, it was found that thawing before cooking is useless and causes more vitamin C loss. Therefore, frozen vegetables must not be thawed before cooking. In order to prevent vitamin C from destruction, using double based stainless steel pan, minimum amount of water and cooking of frozen vegetables are recommended.     

Controlling Temperature and Water Loss to Maintain Ascorbic Acid Levels in Strawberries During Postharvest Handling

‘Chandler’, ‘Oso Grande’ and ‘Sweet Charlie’ strawberries were stored for 8 days at 1 or 10°C, or 4 days at 20°C, either unwrapped or wrapped in PVC film to retard were conducted during the 1 water loss. Total ascorbic acid (AA) content was expressed on a dry weight basis to correct for water loss differences between treatments. Loss of AA was low and did not differ between wrapped treatments at 1 and 10°C, but was much greater at 20°C. Wrapping reduced AA loss by 5-fold at 1 and 10°C and by 2-fold at 20°C. The effect was not due to modification of O₂ and CO₂ levels in wrapped treatments, which was minimal. The results indicate that water loss had a greater effect on AA levels than temperature. Combining wrapping with storage at 1 or 10°C reduced AA loss by 7.5-fold compared to unwrapped strawberries stored at 20°C.     

Freezing, thawing and cooking effects on quality profile assessment of green beans (cv. Win)

Results are presented of the effect of freezing followed by thawing (air and water immersion, both at environmental temperature) and cooking (traditional boiling in a covered pot) on quality profile (in terms of objective texture, colour, chlorophylls and pheophytins and sensory attributes) and structure of green beans (cv. Win). Freezing was carried out at three different rates by forced convection with liquid nitrogen vapour. Kramer shear cell (KSC) and Warner–Bratzler (WB) tests were used for objective assessment of the texture. The highest parameter values occurred in beans frozen at the highest rate and air-thawed at the slowest rate. Also, minimum alteration of the rheological behaviour of cooked beans was achieved by freezing at the highest rate. The best parameter for assessing the texture of frozen green beans after thawing and cooking was the Warner–Bratzler slope (S _WB). Coefficients of softening estimated for S _WB in the thawed beans showed that the texture of the beans frozen at −24 °C was almost four and almost five times softer than that of the beans frozen at −70 °C, for air and water thawing respectively. Frozen and thawed green beans were darker than fresh control, whereas freezing prior to cooking produced lighter-coloured beans than direct cooking. The freezing rate affected colour parameters differently depending on the process that followed. When beans were thawed, increasing the freezing rate produced lighter-coloured beans, whereas when beans were cooked, increasing the rate produced darker-coloured beans. No difference was found in sensory assessments between cooked samples frozen at −24 °C, −35 °C and −70 °C, which probably reflects the panellists' mixed preferences for quickly and slowly frozen samples. Scanning electron microscopy (SEM) revealed different degrees of mechanical damage to tissue structure, which accounted for the rheological behaviour of the beans.     

Vitamin Retention, Color and Texture in Thermally Processed Green Beans and Royal Ann Cherries Packed in Pouches and Cans

Thiamin (B-1) ascorbic acid (AA) and vitamin B-6 (B-6) were determined in pouched and canned green beans immediately after processing and after storage at 24–26°C or 38°C. AA and B-6 were also determined in pouched and canned cherries before and after storage at 24–26°C. There was significantly more B-1 and AA in drained pouched green beans, and more AA in drained pouched cherries than in canned ones. B-6 values in the solids of the pouched and canned products were not significantly different. These three vitamins were significantly reduced in drained pouched and canned green beans after storage at 38°C. B-6 was significantly reduced in the stored cherries. Compared to canned, the pouched products were brighter and firmer in texture.     

Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolus vulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AAS_IVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AAS_IVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.     

The peroxidase enzyme activity of some vegetables and its resistance to heat

The peroxidase enzyme activities of some fresh vegetables (cabbage, leeks, carrot, spinach, celery, squash, potatoes, onions and green beans) were determined. The peroxidase activities of cabbage and green beans were high. Onions showed very little peroxidase activity. The vegetables were blanched in hot water at 75°G, 85° and 95°C. Peroxidase inactivation was faster at the higher temperature blanch. Blanching of green beans, potatoes and squash at 75°C for 30 min was not sufficient for complete inactivation of peroxidase enzyme. Peroxidase enzyme inactivation was also affected by the type of vegetable and the size of vegetable pieces.     

Monitoring of the vitamin C content of frozen green beans and Padrón peppers by HPLC

HPLC (using a C18 column, water at pH 2·2 as mobile phase, and UV detection) was used to monitor the vitamin C content of deep-frozen (-22°C) green beans and Padrón peppers over 12 months. Unblanched beans and peppers lost ⩾97% of their vitamin C within 1 month of freezing, whether or not they were contained in bags sealed under vacuum. Blanching reduced the beans' vitamin C content by 28%, but limited further decreases to between 3 (vacuum sealed) and 10% (no vacuum) in 12 months. These results confirm the utility of blanching in the preservation of vegetables by deep-freezing. © 1998 SCI.     

Canning Quality Evaluation of Pinto and Navy Beans

Thermal processing of pinto and navy beans at 121.1°C for 16 or 14 min in a still retort gave similar sterilization value (F_o= 10) as the processing at 115.6°C for 45 min. The 121.1°C/16 or 14 min process produced beans with greater firmness than the 115.6°C/45 min process. The addition of CaCl₂ and EDTA improved firmness and color of canned beans. Calcium chloride also reduced clumping and splitting of the canned beans. Sensory evaluation showed that the acceptability of canned beans was reduced when CaCl₂ was increased up to 10 mM. High correlation between firmness and soluble pectin in various bean cultivars implied that soluble pectin content could be used as a parameter for screening bean cultivars with desirable firmness.     

Nutritional properties of oat‐based beverages as affected by processing and storage

Oat‐based beverages enriched with vitamins and minerals were produced with common hydrothermal treatments and stored at 22 °C for 64 weeks. The effects of decanting on the retention of native vitamins, minerals and fatty acids, and different UHT holding time (5 s or 20 s) at 140 °C on vitamins were investigated. Fatty acid profile, vitamin retention and dissolved oxygen concentration were monitored during storage. The decanting process caused a 47% increase of vitamin B₆ and a 45–74% loss of phosphorus, zinc, calcium and iron. The steam‐injection UHT treatment caused a 60% loss of vitamin D₃ for both holding times and a 30% loss of vitamin B₁₂ for 20 s. During 1 year of storage, oleic and linoleic acids were stable, whereas linolenic acid decreased only slightly, even in the iron‐enriched variety. The dissolved oxygen concentration increased to a low value of 0.71 mg L^?1 and reached a balance after 16 weeks. Most enriched vitamins except vitamins A, D₃ and B₁₂ were stable during ambient storage. Oat‐based beverages with highly retained vitamins can be manufactured by adding vitamins prior to direct UHT treatment with a shorter holding time. Additionally, iron enrichment of such beverages, without affecting the fatty acid profile, can be achieved by filter sterilisation. Copyright © 2007 Society of Chemical Industry     

Trials to Reduce Nitrate and Oxalate Content in Some Leafy Vegetables. 2. Interactive Effects of the Manipulating of the Soil Nutrient Supply,Different Blanching Media and Preservation Methods Followed by Cooking Process

Experiments were carried out to find ways to prevent undesirably high nitrate contents in lettuce and high nitrate and oxalate contents in spinach. Treatments included manipulating the soil nutrient supply and the effects of processing and cooking on the reduction of nitrate and oxalate contents, and the maintenance of vitamins and minerals in the spinach. Best lettuce and spinach qualities, ie highest vitamin and mineral contents with lowest nitrate and oxalate levels, were achieved by fertilising them either with farm yard manure (FYM) or Ca(NO₃)₂+(NH₄)₂SO₄(1: 1)+N-serve (nitrification inhibitor), at the rate of 178·5 kg N ha^-1. High spinach yields were also obtained by fertilisation with urea at 178·5 kg N ha^-1, but resulted in high nitrate and oxalate levels. Losses of vitamins A, B₁, B₂, niacin and C as well as minerals Ca, Fe, Mg, Na, K and P from spinach were smaller following freezing compared with canning, especially when 0·1% calcium citrate and 0·01% sodium ascorbate solutions were used for blanching at ∽77°C for 2 min. © 1997 SCI.     

Quality changes during storage of sous vide cooked green beans (Phaseolus vulgaris)

 The acceptability and quality of sous vide cooked green beans (Phaseolus vulgaris) were investigated during chilled storage. A suitable heating procedure was established whereby 2.0-kg packages were heat processed at 90°C for 25 min, corresponding to an average pasteurization value, PV_70,10, of 14 min. During storage for up to 25 days at 3°C drip loss, pH, colour (Minolta L ^* a ^* b ^*), texture (Instron) and microbiological stability were examined and sensory characteristics evaluated by a trained sensory panel. No marked changes in texture, drip loss, pH or microbiological counts were observed but a change of colour from green to olive green was observed by both objective and sensory analyses. This detrimental change in colour, which had begun during the first week, was the limiting factor for shelf-life during storage. Subsequent reheating, however, resulted in further colour changes which partially obscured the initial differences observed during the storage period. Storage for more than 1 week resulted in undesirable quality changes in the odour and flavour of the green beans. Therefore, a maximum shelf-life of 8 days at 3°C was recommended. Inoculation trials showed that psychrotrophic Bacillus cereus were able to germinate and grow to levels of 10⁷ g^–1 in the packages at abuse temperatures (7°C and 17°C), whereafter numbers declined. Received: 21 April 1997     

Effect of storage of adzuki bean (Vigna angularis) on starch and protein properties

Differential scanning calorimetry was used to evaluate the effect of storage at 10°C, 20°C and 30°C, and 40% and 65% relative humidity (RH) on adzuki bean starch gelatinisation and protein denaturation temperatures. Storage for 6 months at an elevated storage temperature (30°C) caused increases in the starch gelatinisation onset temperature (T_o) and gelatinisation peak temperature (T_p) for both Bloodwood and Erimo varieties. Storage at 40% RH resulted in higher T_o and T_p values than storage at 65% RH. The T_o of starch from Bloodwood and Erimo beans stored for up to 1.5 months at 10°C and 65% were similar to those of fresh beans.The changes in the salt-soluble protein component were less clear cut than those of the starch. Nonetheless, protein extracted from beans stored at 40% RH exhibited significantly lower T_o and T_p values compared with those stored at 65% RH. This indicates some destabilisation of the protein at the higher RH.These results suggest that detrimental changes occur in starch and, to a lesser extent protein, of adzuki beans stored under unfavourable conditions. On the basis of these results, the best storage conditions to maintain the characteristics of fresh beans are low temperatures (e.g. 10°C) and high RH (e.g. 65%).     

Comparison of Sample Storage Methods for Vitamin B6, Assay in Broiler Meats

Five methods were compared for storage stability of vitamin B₆ in broiler meat samples. Maximum retention of vitamin B₆ was observed in the N₂-packed freeze-dried samples at -34°C (101–103% up to 20 mo). Good retentions occurred in the intact tissues of half birds at -34°C (90% in 16 mo) and in ground meat samples (200g portions) at -34°C (91% up to 12 mo). Significantly lower retentions were found in freeze-dried samples stored at room temperature (85–77% in 1–5 mo, respectively) and for ground meat small portion samples (5g) at -34°C (84–72% in 3–5 mo, respectively).     

Natural fermentation of lentils Influence of time, temperature and flour concentration on the kinetics of thiamin, riboflavin and niacin

Lentils (Lens culinaris, var. vulgaris cultivar Magda-20) were naturally fermented for 96 h at different lentil flour concentrations (79, 150 and 221 g/l) and temperatures (28, 35 and 42°C). During fermentation, samples were taken at 24-h intervals and the changes in thiamin (vitamin B₁), riboflavin (vitamin B₂) and total and available niacin (vitamin B₃) were investigated. Preparation of the lentil flour suspension to be fermented (i.e. the process of mixing the flour and sterilized tap water) caused an increase of the available niacin content in all batches, while changes in thiamin and riboflavin content were related to the conditions in which the preparation of the suspensions was carried out. The whole natural fermentation process (from the raw state to after 96 h of fermentation), either did not affect or produced a slight decrease in the thiamin content of lentils. In contrast, riboflavin, available niacin and total niacin contents increased throughout the 96 h period, which ended with a 35?–?82% increase of riboflavin, a 24?–?91% increase of available niacin and a 20?–?58% increase of total niacin. The temperature during the fermentation procedure had significant effect on the levels of thiamin and riboflavin in fermented lentils. To obtain lentil flours with an improved amount of riboflavin and available niacin with a minimum loss of thiamin, the natural fermentation of lentils should be carried out for 96 h at 42°C and with a lentil flour concentration of 221 g/l.     

Effect of cooking and irradiation on the labile vitamins and antinutrient content of a traditional African sorghum porridge and spinach relish

Irradiation is a potentially useful technology for ensuring the safety and extending the shelf-life of food products in Africa. However, nutritional changes may result. The effects of cooking followed by irradiation (10 kGy) on vitamins B₁ and C, and the antinutritional factors, phytic acid and nitrates, in a ready-to-eat meal of sorghum porridge and spinach-based relish were investigated. Cooking reduced vitamin B₁ and C contents of the spinach relish, and irradiation caused further losses. Cooking did not alter vitamin B₁ content of the sorghum porridge but irradiation decreased it drastically. Cooking did not decrease phytic acid in the sorghum porridge, but irradiation caused a significant decrease. The reduction of antinutritional factors by cooking, followed by irradiation, is promising for the application of this technology to traditional African cereal and leafy vegetable foods. However, ways need to be found to minimise vitamin loss, such as blanching and cooking in minimum water and irradiation at cryogenic temperatures in an oxygen-free atmosphere.     

Quality of fresh‐cut baby spinach grown under a floating trays system as affected by nitrogen fertilisation and innovative packaging treatments

BACKGROUND: Alternative techniques for cultivation of leafy vegetables such as a floating tray system and unconventional gas mixtures for post‐harvest active modified atmosphere packaging (MAP) could be of interest in the minimally processed vegetable industry. RESULTS: The combined effect of three pre‐harvest fertilisation doses (8, 12 or 16 mmol N L^?1) and three post‐harvest MAP conditions (passive, super‐atmospheric or N₂O‐enriched) on the main quality attributes of fresh‐cut baby spinach leaves throughout 10 days at 5 °C was studied. After 8 days of shelf life, spinach leaves fertilised with 8 and 16 mmol N L^?1 and stored under N₂O‐enriched MAP showed the lowest microbial growth, with good sensory quality. Such combined treatments also preserved the total antioxidant capacity sampled at harvest (8 g ascorbic acid equivalent antioxidant capacity kg^?1 f.w.). A decrease of 10–20% in total vitamin C content regardless of N fertilisation and packaging treatment was found during shelf life. Total phenolics content at harvest was 2 g gallic acid equivalents kg^?1 f.w., which was slightly decreased or preserved during shelf life while total chlorophylls were preserved for all treatments assayed around 550 mg kg^?1 f.w. CONCLUSION: No clear effect of fertilisation doses was observed during post‐harvest storage on overall quality of fresh‐cut baby spinach leaves, while N₂O‐enriched atmospheres seems to be a promising alternative to passive MAP for extending shelf life. Copyright © 2010 Society of Chemical Industry     

Thermal Effects on in vitro Protein Quality of Red Kidney Bean (Phaseolus vulgaris L.)

Significant thermal effects on in vitro protein quality of red kidney beans were observed. Beans autoclaved at 121°for 10 and 20 min, and common home-cooked beans had improved protein quality. Uncooked beans, and those autoclaved at 128°for 20 min and at 121°for 90 min had reduced protein quality compared to canned beans and those autoclaved at 110°for 20 min and at 121°for 40 and 60 min. Amino acid scores, essential amino acid index and available lysine (%), corrected for in vitro protein digestibility gave comparable results in evaluation of protein quality. Specific lysine, methionine, cysteine and other amino acid ratios overestimated protein quality.