Nutrients in fresh produce vs frozen or canned

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Nutrients in fresh produce vs frozen or canned

Postby hatshepsut » Sat Mar 15, 2008 12:17 pm

Hello.

I like to shop for vegetables once a week. Over the period of a week, some produce necessarily sits longer than others before cooking or use. I've wondered how much of the food value of the produce is lost as it ages. Also, should some produce be used more quickly than others?

I'm new. If this has been answered before, please direct me to the post.

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Re: How long do nutrients survive in fresh produce?

Postby JeffN » Tue Mar 18, 2008 8:46 am

hatshepsut wrote:Hello.

I like to shop for vegetables once a week. Over the period of a week, some produce necessarily sits longer than others before cooking or use. I've wondered how much of the food value of the produce is lost as it ages. Also, should some produce be used more quickly than others?

I'm new. If this has been answered before, please direct me to the post.

Hatshepsut


Hi,

I do not think there is any one simple answer as it will depend on so many variables including which nutrient, and which food we are talking about.

Below is a summary review from a recent study that looked at this issue.

My simple rule at home is "simple," as look as the fresh produce is still "fresh" and firm, and not wilting, or turning color, then I will use it.


In Health
Jeff Novick, MS, RD

A Nutritional Comparison of Canned, Fresh and Frozen Fruits and Vegetables

J Sci Food Agric 87:930 – 944 (2007)

The 2005 Dietary Guidelines urge Americans to increase their fruit and vegetable intake regardless of type (fresh, frozen, canned and dried), yet Americans are far from meeting fruit and vegetable goals. Exclusively recommending one form of fruits or vegetables over another ignores the benefits that each form provides and limits consumer choice.
Specific Key Study Findings Include:

* A diet should include a variety of fruits and vegetables. Fresh, frozen and canned each contain important nutrients and contribute to a healthy diet.

* For some nutrients canned products were higher than fresh.

* By the time food is consumed, fresh, frozen and canned fruits and vegetables may be nutritionally similar.

Canned

* The canning process locks in nutrients at their peak of freshness and due to the lack of oxygen during the storage period, canned fruits and vegetables remain relatively stable up until the time they are consumed and have a longer shelf-life.

Fresh

* Eat fresh fruits and vegetables as soon as possible. Some fresh vegetable, such as spinach and green beans, lose up to 75% of their vitamin C within 7 days of harvest, even when held at the recommended refrigerator temperature.

Frozen

* Frozen products are also packed at their peak of freshness. Frozen fruits and vegetables may be more nutritious in some cases if stored for short periods of time under well-controlled temperatures.
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Postby JeffN » Tue Mar 18, 2008 8:50 am

Executive Summary

Nutritional comparison of fresh, frozen, and canned fruits and
vegetables

Joy C. Rickman, Diane M. Barrett, PhD, Christine M. Bruhn, PhD, Department of Food Science and Technology, University of California- Davis, Davis, CA. 95616


Recent and classical literature was reviewed to obtain current information on the nutrient value of fresh, canned and frozen foods with an emphasis on fruits and vegetables.

Research that has undergone the scrutiny of peer review and the USDA nutrient database served as the source of information. The literature indicates that by the time they are consumed, fresh, frozen and canned fruits and vegetables may be nutritionally similar, depending on the post harvest handling and processing treatments.

Loss of nutrients in fresh products may be more substantial than commonly perceived. Storage and cooking can lead to overall losses of up to half of the original nutrient content prior to consumption. Depending on the commodity, freezing and canning processes may preserve nutrient value. While the initial thermal treatment of canned products can result in loss, nutrients are relatively stable during subsequent storage due to
the lack of oxygen. Frozen products lose fewer nutrients initially because of the short heating time in blanching, but they lose more nutrients during storage due to oxidation.

Vitamin C, a water-soluble nutrient, is sensitive to heat, light, and oxygen. If fresh products are held at the appropriate temperature and consumed in a short period of time, they have more vitamin C than commercially canned products. However vitamin C degrades rapidly after harvest, and depending on commodity, as much as 77% of the nutrient (in green beans) may be lost in 7 days storage at 4°C (39°F). Vitamin C is lost when frozen vegetables are blanched, but some fruits have ascorbic acid added to prevent browning, so the nutrient level may be higher in the frozen than the fresh fruit. Between 10 to 90% of vitamin C is lost during canning, however the nutrient changes little during storage of canned products and little is lost during reheating because the heating time is short.

Among B vitamins, thiamin, B6 and riboflavin are sensitive to heat and light, resulting in loss in canned products. Since these nutrients are also water soluble, from 20-60% is lost in the blanching step prior to freezing. Water soluble polyphenolic compounds, found primarily in the skins of peaches, pears and apples, are lower in products canned without the skin compared to fresh, however if juice is included, such as in canned cherries, levels are higher in the canned than fresh products. Mineral and fiber content are similar in fresh, canned and frozen fruits and vegetables.

Fat soluble nutrients, including vitamin A, E, and carotenoids including lycopene are sensitive to heat, light, and oxygen. Since these nutrients are fat soluble, little is lost in blanching. Nutrient loss varies by commodity. For example, cooked fresh green beans contained higher levels of beta- carotene than cooked frozen and cooked canned green beans, however cooked frozen green peas contained higher levels of beta-carotene than
cooked fresh and cooked canned. Compared to fresh tomatoes, canned tomato products have been reported to have high levels of beta-carotene, a precursor of vitamin A. Processed tomatoes are also reported to have higher lycopene content than fresh, likely due to the heat-induced release of this nutrient from its cellular matrix.

Protein and carbohydrates as well as fatty acid composition is not significantly affected by canning for freezing. For example, the level of Omega 3 fatty acids in fish is not adversely affected by canning or freezing.

The literature review is complicated by variations in experimental procedure and method of reporting. Some studies measure the same cultivar, grown under controlled conditions, and evaluated as fresh, canned, or frozen. This approach provides data on the effect of
processing treatment. Others obtain samples from the supermarket, measuring what the consumer has available, but increasing nutrient variability due to cultivar, growing conditions, and handling practices. Further, changes in moisture content during storage, cooking, and processing can misrepresent changes in nutrient content expressed as
percent of product weight. Nutritional comparison would be facilitated if future research would express nutrient data on a dry weight basis to account for changes in moisture.

The nutritional comparison of fresh, canned and frozen products indicates that each can contribute to a health diet. Exclusive recommendations of fresh produce ignore the nutrient benefits of canned and frozen products and limits consumer choice.
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Re: How long do nutrients survive in fresh produce?

Postby JeffN » Fri Mar 28, 2014 5:14 pm

Cookings Influence on Antioxidant Levels of the Potato

Postby JeffN » Thu Nov 19, 2009 4:51 pm
Enjoy your cooked potatoes!

In Health
Jeff


Phenolic Content, Composition, Antioxidant Activity, and Their
Changes during Domestic Cooking of Potatoes

J. Agric. Food Chem. 2009, 57, 10231–10238 10231
DOI:10.1021/jf902532q

Potatoes in the diet contribute significantly to antioxidant daily intake worldwide. The influence of different domestic cooking conditions, boiling, microwaving, and baking, on total phenolics (TP),vantioxidant capacity, phenolic composition, and tryptophan content was studied using eight commercial potato varieties. The antioxidant capacity was detected by the methods of oxygenvradical absorbance capacity assay (ORAC) and the 2,2-diphenyl-1-picrylhydrazyl free radicalv(DPPH•) assay. The phenolic composition and tryptophan content were determined using high performance liquid chromatography coupled with a diode array detector (HPLC-DAD), whereasvphenolics and tryptophan were identified by means of HPLC-mass spectrometry, HPLC-DAD, andvauthentic standards. Antioxidant capacity was influenced by potato variety and cooking conditions;vhowever, cooked potatoes retained 68-97% ORAC value depending on cooking procedure and variety. Chlorogenic acid and its isomers dominated the phenolic composition of each variety involved in this study. ORAC and TP were highly and positively correlated (r = 0.9119). Norkotahvranked highest in chlorogenic acid content and antioxidant value. Principal component analysis showed different cooking processes did not influence the trend of the antioxidant profile of the eight potato varieties, but specific compounds exert influence on the antioxidant capacity. The results imply that the potato varieties rich in antioxidant components could be good antioxidant sources as activities are not greatly affected by different cooking conditions.


Comparison of Nutrient Density and Nutrient-to-Cost between Cooked and Canned Beans
Food and Nutrition Sciences
Vol.2 No.2(2011), Paper ID 4521, 4 pages
DOI:10.4236/fns.2011.22009

ABSTRACT

Consumption of nutrient rich foods such as beans and peas is recommended because these foods provide key nutrients and relatively little energy. Many consumers are unfamiliar with dried beans or do not have the time to prepare them. The purpose of this study was to compare nutrient density and nutrient-to-cost among dried cooked, canned (liquid and solids), and canned/drained black, garbanzo, kidney, lima, pinto, white beans, and black-eyed peas. Prices were obtained from 60 grocery stores in January 2009. Nutrient content per 100 g was calculated using the U.S. Department of Agriculture Nutrient Database for Standard Reference, Release 22, and Nutrition Data System for Research (for canned/drained). Nutrient density scores were estimated using the Nutrient Rich Food Index 9.3 (NRF9.3). Nutrient-to-cost ratio (NTCR) was computed as the NRF 9.3 score (per 100 kcal) divided by the cost per half-cup servings per package (12) or per can (3.5). Compared to canned beans, dried cooked beans were significantly more energy dense, contained more protein, fiber, iron, potassium and magnesium; and less sodium than canned beans (p < 0.05 for all). Canned/drained beans contained more sodium than cooked beans (p < 0.05). NRF9.3 scores were 7.3, 2.8, and 4.8 for cooked, canned, and canned/drained beans, respectively. NTCR for cooked, canned, and canned/drained beans was 63.4, 8.9, and 15.2, respectively. Results highlight the benefits of choosing dried beans and also illustrate that canned beans, when drained, provide a healthy alternative. Beans, regardless of type/form, are a nutrient rich food and should be encouraged as part of an overall healthy diet.


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Jeff
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Re: How long do nutrients survive in fresh produce?

Postby JeffN » Fri Mar 28, 2014 6:20 pm

NUTRITIONAL CONSEQUENCES OF MINIMAL PROCESSING OF FRUITS AND VEGETABLES
Journal of Food Quality
Volume 10, Issue 3, pages 179–193, August 1987

ABSTRACT
Consumption of fresh or minimally processed fruits and vegetables is increasing due to consumer concern about the effects of processing on nutrients in foods. Relatively little information is available in the literature regarding specific storage and handling techniques that have an impact on nutritional value for fruits and vegetables. Commonly used technologies such as low temperature and controlled atmosphere storage affect vitamin content. The information about other operations such as preparation for the table and irradiation on vitamin losses is fragmentary and may not reflect current practices. It appears that conditions that preserve sensory quality of fruits and vegetables also maintain nutritional value.


A comparison of the vitamin C content of fresh and frozen vegetables
Food Chemistry
Volume 62, Issue 1, May 1998, Pages 59–64

Abstract

This study, using vitamin C (ascorbic acid) as ‘marker’, allowed a direct comparison of the nutritional quality of freshvegetables at various stages of distribution and storage, with the same vegetable commercially quick-frozen and stored deep frozen for up to 12 months. The nutrient status of frozen peas and broccoli was similar to that of the typical market-purchased vegetable and was superior to peas that have been stored in-home for several days. Fresh peas and broccoli retained their quality for up to 14 days when stored under chill conditions. The nutrient status of frozen whole green beans and frozen carrots, with no loss on freezing, was similar to the fresh vegetable at harvest. Frozen spinach also compared reasonably well with the harvested fresh vegetable and was clearly superior to all market produce.



β-Carotene and Ascorbic Acid Retention in Fresh and Processed Vegetables
Journal of Food Science
Volume 64, Issue 5, pages 929–936, September 1999

ABSTRACT:
Broccoli, carrots, and green beans (grown in 2 consecutive years) were randomly divided into 3 treatments: fresh-refrigerated (F-R), frozen (FZ) or canned (C) (carrots only). FZ or C vegetables were processed within 24 h and stored for up to 1 yr. F-R vegetables were held at 4 °C for 3 wk (broccoli and green beans) or 6 mo (carrots). Trans b-carotene (Tb-C) and total ascorbic acid (AA) were determined at specified times, before and after microwave cooking. Vitamin content differed between years due to environmental conditions. Blanching resulted in AA loss, but retention remained stable after freezing broccoli and green beans. F-R green beans lost >90% AA after 16 d storage. Linear decreases in AAwere found in most F-R or FZ vegetables. Tb-C decreased slightly during freezer storage. Reductions in Tb-C occurred in canned carrots. Microwave cooking had minimal effects on AA or Tb-C.


**Effect of Freezing and Storage on the Phenolics, Ellagitannins, Flavonoids, and Antioxidant Capacity of Red Raspberries
J. Agric. Food Chem., 2002, 50 (18), pp 5197–5201
DOI: 10.1021/jf020141f

http://pubs.acs.org/doi/abs/10.1021/jf020141f

Abstract

Scottish-grown red raspberries are a rich source of vitamin C and phenolics, most notably, the anthocyanins cyanidin-3-sophoroside, cyanidin-3-(2G-glucosylrutinoside), and cyanidin-3-glucoside, and two ellagitannins, sanguiin H-6 and lambertianin C, which are present together with trace levels of flavonols, ellagic acid, and hydroxycinnamates. The antioxidant capacity of the fresh fruit and the levels of vitamin C and phenolics were not affected by freezing. When fruit were stored at 4 °C for 3 days and then at 18 °C for 24 h, mimicking the route fresh fruit takes after harvest to the supermarket and onto the consumer's table, anthocyanin levels were unaffected while vitamin C levels declined and those of elligitannins increased, and overall, there was no effect on the antioxidant capacity of the fruit. It is concluded, therefore, that freshly picked, fresh commercial, and frozen raspberries all contain similar levels of phytochemicals and antioxidants per serving.



The antioxidant activity and composition of fresh, frozen, jarred and canned vegetables
Innovative Food Science & Emerging Technologies
Volume 3, Issue 4, December 2002, Pages 399–406

Abstract
Regular consumption of dietary antioxidants may reduce the risk of several serious diseases. As vegetables are a major source of antioxidants it is desirable to assess their antioxidant activity and compare different processing and preparation methods. The total antioxidant activity was determined in water- and lipid-soluble extracts from fresh, stored and frozenvegetables. The contribution of individual compounds to total antioxidant activity was estimated. In stored vegetables at ambient or chill temperatures antioxidant activity declined. Blanching and freezing of peas and spinach reduced water-soluble antioxidant activity by 30 and 50%, respectively, thereafter levels remained constant on storage at −20 °C. Samples of frozen peas and spinach purchased from retail outlets had substantially higher antioxidant activity than canned or jarred samples. In a comparison of cooking methods, microwave and boiling for short periods had a negligible effect on total antioxidant activity, but substantial losses occurred after prolonged boiling in water.



Polyphenols and Antioxidant Capacity of Vegetables under Fresh and Frozen Conditions
J. Agric. Food Chem., 2003, 51 (8), pp 2222–2226
DOI: 10.1021/jf020936m

Abstract
The phenolic and oxygen radical absorbance capacity (ORAC) values have been measured in six fresh and frozen vegetables (beet green, spinach, broccoli, carrot, onion, and celery) from the same cultivar by analyzing the whole juice (WJ) and the acetonic extract of the squeezed pulp. To exploit the effect of the acid environment on the stability and recovery of the phenolics, perchloric acid (PCA) was added directly to WJ and to the pulp before the extraction with acetone. In both fresh and frozen vegetables, PCA markedly increased the recovery of phenolics extracted from the pulp, but PCA had no effect on the WJ. Four of six frozen vegetables showed lower phenolic and ORAC values than the fresh vegetables, whereas in the other two cases, values were significantly higher compared to fresh samples. Among the fresh vegetables, beet green showed the highest ORAC and phenolic values; however, when measured in two different cultivars of beet green, the ORAC value showed as much as 4.5-fold variation, whereas total phenolics and flavonoids showed 1.2- and 3.5-fold variations, respectively. The results show that total phenolics and ORAC, compared in fresh and frozen vegetables, represent an index of the mildness of blanching in the industry of frozen vegetables and provide a measure of the gap in antioxidants in the diet of people who consume frozen instead of fresh vegetables. The plant genotype is an important source of variabilty in the ORAC value, which can be conveniently used to increase the intake of antioxidants from vegetables.


**The Change of Total Anthocyanins in Blueberries and Their Antioxidant Effect After Drying and FreezingJ Biomed Biotechnol. Dec 1, 2004; 2004(5): 248–252. PMC1082901

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1082901

Abstract

This study examined the effects of freezing, storage, and cabinet drying on the anthocyanin content and antioxidant activity of blueberries (Vaccinium corymbosum L). Fresh samples were stored for two weeks at 5°C while frozen samples were kept for up to three months at −20°C. There were two drying treatments, one including osmotic pretreatment followed by cabinet drying and the other involving only cabinet drying. Total anthocyanins found in fresh blueberries were 7.2 ± 0.5 mg/g dry matter, expressed as cyanidin 3-rutinoside equivalents. In comparison with fresh samples, total anthocyanins in untreated and pretreated dried blueberries were significantly reduced to 4.3 ± 0.1 mg/g solid content, 41% loss, and 3.7 ± 0.2 mg/g solid content, 49% loss, respectively. Osmotic treatment followed by a thermal treatment had a greater effect on anthocyanin loss than the thermal treatment alone. In contrast, the frozen samples did not show any significant decrease in anthocyanin level during three months of storage. Measurement of the antioxidant activity of anthocyanin extracts from blueberries showed there was no significant difference between fresh, dried, and frozen blueberries.


Analytical, Nutritional and Clinical Methods
The effect of cooking methods on total phenolics and antioxidant activity of selected green vegetables
Food Chemistry
Volume 93, Issue 4, December 2005, Pages 713–718

Abstract
Effects of microwave and conventional cooking methods were studied on total phenolics and antioxidant activity of pepper, squash, green beans, peas, leek, broccoli and spinach. Total phenolics content of fresh vegetables ranged from 183.2 to 1344.7 mg/100 g (as gallic acid equivalent) on dry weight basis. Total antioxidant activity ranged from 12.2% to 78.2%. With the exception of spinach, cooking affected total phenolics content significantly (p < 0.05). The effect of various cooking methods on total phenolics was significant (p < 0.05) only for pepper, peas and broccoli. After cooking, total antioxidant activity increased or remained unchanged depending on the type of vegetable but not type of cooking.



Stability of 5-methyltetrahydrofolate in frozen fresh fruits and vegetables
Food Chemistry
Volume 92, Issue 4, October 2005, Pages 587–595

Abstract
The stability of 5-methyltetrahydrofolate (5MTHF) in homogenized fresh fruits and vegetables representing samples for the USDA National Food and Nutrient Analysis Program was evaluated. Samples were homogenized in liquid nitrogen and 5MTHF was measured after 0, 2, 7, 30 days and then at 3-month intervals for a total of 12 months storage at −60 ± 5 °C, utilizing extraction by a tri-enzyme treatment, purification by strong anion-exchange solid-phase extraction, and quantification by reverse-phase HPLC. Method validation included analysis of a reference material and interlaboratory analysis of selected samples by HPLC and LC-MS. A canned spinach composite was assayed in each analytical batch to monitor inter-assay precision. No change in 5MTHF content was detected in any of the samples after 12 months. Concentrations ranged from <10 μg/100 g in bananas to >100μg/100 g in spinach. Relative standard deviations were generally <7% within assay and <11% between assays.



Comparison of carotenoid content in fresh, frozen and canned corn
Journal of Food Composition and Analysis
Volume 18, Issue 6, September 2005, Pages 551–559

Abstract
The carotenoid content of fresh, commercially canned and frozen samples of two cultivars, White Shoepeg (WS) and Golden Whole Kernel (GWK) corn (Zea mays), from the same production field was studied. WS and GWK corn samples were harvested daily over a five-day-period and randomly selected for analysis as fresh, frozen or canned. Major carotenoids detected were lutein and zeaxanthin, and to a lesser extent, α-, β-cryptoxanthin, α-, and β-carotene. Fresh GWK corn contained higher amounts of lutein, zeaxanthin and total carotenoids (330, 209 and 702 μg/100 g fresh weight) versus fresh WS corn (5.5, 28.5, and 35.5 μg/100 g fresh weight). In both canned WS and GWK corn, levels of lutein, zeaxanthin, and total carotenoids were similar to their respective fresh counterparts. Detectable levels of zeaxanthin in WS corn increased 67.4% (P=0.042) and total carotenoids in both WS and GWK corn were increased after freezing by 63.3% (P=0.002) and 5.3% (P=0.003), respectively. This work indicates that canning does not decrease carotenoid content in corn and that freezing may increase carotenoid content in WS corn which can further influence bioavailability and health benefits.



Impact of different cooking methods on food quality: Retention of lipophilic vitamins in fresh and frozenvegetables
Journal of Food Engineering
Volume 77, Issue 2, November 2006, Pages 327–333

Abstract
The bioavailability of all-trans-β-carotene from vegetables depends among other things on the molecular linkage and the food matrix in which it is incorporated. It is assumed that cooking can increase the bioavailability by disruption of the plant cell wall and releasing from protein complexes. But it can also lead to isomerization and degradation of all-trans-β-carotene. In this investigation the influence of different domestic cooking methods on the all-trans- and cis-β-carotene as well as the α-tocopherol content in fresh and frozen broccoli and red sweet pepper is examined. While in fresh broccoli all cooking methods lead to a significant release of all-trans-β-carotene and α-tocopherol in the frozen broccoli no change or a decrement occurs. In the fresh and frozen peppers no change or a significant loss of α-tocopherol and all-trans-β-carotene is observed. A slight increase in the cis-isomers of β-carotene can only be found by cooking fresh broccoli.



Review: Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part 1. Vitamins C and B and phenolic compounds
Journal of the Science of Food and Agriculture
Volume 87, Issue 6, pages 930–944, 30 April 2007

Abstract
The first of a two-part review of the recent and classical literature reveals that loss of nutrients in fresh products during storage and cooking may be more substantial than commonly perceived. Depending on the commodity, freezing and canning processes may preserve nutrient value. The initial thermal treatment of processed products can cause loss of water-soluble and oxygen-labile nutrients such as vitamin C and the B vitamins. However, these nutrients are relatively stable during subsequent canned storage owing to the lack of oxygen. Frozen products lose fewer nutrients initially because of the short heating time in blanching, but they lose more nutrients during storage owing to oxidation. Phenolic compounds are also water-soluble and oxygen-labile, but changes during processing, storage and cooking appear to be highly variable by commodity. Further studies would facilitate the understanding of the changes in these phytochemicals. Changes in moisture content during storage, cooking and processing can misrepresent changes in nutrient content. These findings indicate that exclusive recommendations of fresh produce ignore the nutrient benefits of canned and frozen products. Nutritional comparison would be facilitated if future research would express nutrient data on a dry weight basis to account for changes in moisture.



Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fiber
Journal of the Science of Food and Agriculture
Volume 87, Issue 7, pages 1185–1196, May 2007

Abstract
In this second part of our review, we examine the literature for changes in carotenoids, vitamin E, minerals, and fiber due to processing, storage, and cooking of fresh, frozen, and canned fruits and vegetables. While inconsistencies in methodology and reporting methods complicate interpretation of the data, the results show that these nutrients are generally similar in comparable fresh and processed products. The higher levels of carotenoids typically found in canned as compared to fresh products may be attributed to either reporting results on a wet rather than dry weight basis, greater extractability, or differences in cultivars. There are relatively few studies on processing, storage, and cooking effects on vitamin E in fruits and vegetables. Further research is needed to understand nutritional changes in those few fruits and vegetables rich in vitamin E, such as tomatoes. Minerals and fiber are generally stable to processing, storage, and cooking, but may be lost in peeling and other removal steps during processing. Mineral uptake (e.g., calcium) or addition (e.g., sodium) during processing can change the natural mineral composition of a product. Sodium concerns in canned food can be addressed by choosing products with no salt added. Since nutrient content varies considerably by commodity, cultivar, and post harvest treatments, inclusion of a wide variety of fruits and vegetables in the diet is encouraged.

** Anthocyanins Content in Blueberries (Vaccinium corymbosum L.) in Relation to Freezing Duration
Vol. 27, 2009, Special Issue Czech J. Food Sci.

http://www.agriculturejournals.cz/publicFiles/07749.pdf

Abstract
: The changes of total anthocyanins (TA) content in fruit of blueberries in relation to freezing duration are the aim of this study. The samples of 21 chosen cultivars obtained from the research breed station were stored in polyethylene bags in freezing box at temperature –18°C. In ethanolic blueberry extracts TA contents were by spectrophotometric method during the time of 6 months at period of 3 months determined. Significant differences of TA content among the observed cultivars were confirmed. The value interval was 615.8–3206.3 mg/kg. The average TA content in 10 very early, resp. early cultivars was 1655.8 mg/kg, in 5 medium early cultivars 1515.6 mg/kg, in 6 medium late, resp. late cultivars 1431.2 mg/kg. During 6 months of blueberries store in the freezing box the average decrease 16.7% of TA content was observed. The average decrease of TA content in very early, resp. early cultivars was 19.6%, in medium early cultivars 16.5% and in medium late, resp. late cultivars 14%.



**The effect of long-term frozen storage on the nutraceutical compounds, antioxidant properties and color indices of different kinds of berries. Food, Agriculture and Environment (JFAE). 2010, Vol. 8, Issue 1, pages 54-58.

http://world-food.net/the-effect-of-lon ... f-berries/

Abstract

The effects of the Individual Quick Freezing (IQF) process and frozen storage at -18°C up to 10 months, on the nutraceutical compounds, antioxidant properties and color indices of various berries (blueberry, red raspberry and blackberry) have been evaluated. Samples were extracted and analyzed for their total phenolics content, total monomeric anthocyanins, vitamin C, antioxidant activity and color indices. Total anthocyanins and color indices were evaluated by using pH-differential method, total phenolics content was measured using Folin-Ciocalteu procedure, vitamin C content using 2,6-dichlorophenolindophenol method and antioxidant activity using ferric-reducing antioxidant power (FRAP) assay. Blueberry contains the highest amounts of polyphenols, anthocyanins and antioxidant activity among the berries studied. The highest content of vitamin C was found in fresh raspberry. After freezing, no significant difference was observed for investigated nutraceuticals and color of berries, because the IQF is a rapid and non-destroying preservation method. Results showed that the frozen storage up to 4 months did not significantly affect the bioactive compounds and color indices of berries. The degradation of these characteristics was not recorded more than 23% during six months of storage. After 10 months, the content of polyphenols decreased up to 28-47% of the initial value; the total anthocyanins was found in proportion of 80-91%, and the ascorbic acid content was kept at 62-76%. After 10 months of storage the smallest loss of antioxidant activity was recorded for blueberries (approximately 23%) and the biggest loss for raspberries (approximately 37%). The results showed a positive correlation between antioxidant capacity and polyphenols, vitamin C and anthocyanins content. The correlation coefficient between FRAP and the total phenolics was higher than the correlation coefficient between FRAP and total anthocyanins or FRAP and vitamin C for all investigated berries.



**STUDIES INVESTIGATING THE CHANGE IN TOTAL ANTHOCYANINS IN BLACK CURRANT WITH POSTHARVEST COLD STORAGE.
Analele Societatii Nationale de Biologie Celulara . 2011, Vol. 16 Issue 1, p359-363.

http://www.analelesnbc.ro/arhivapdfvol16issue1/55.pdf

Abstract: Anthocyanins are secondary metabolites of plants, distributed in vacuoles in the form of glycosides or acyl-glycosides. These natural pigments have shown diverse physiological effects based on their strong antioxidant properties. Epidemiological studies have shown a positive link between the consumption of anthocyanin-rich foods and reduced risk of cardiovascular, cancer or other age-related diseases. The aim of the present paper was to evaluate the level of total anthocyanins in wild and cultivated black currants (Ribes nigrum) from two different growing area in Romania. Quantitative determination was performed by the pH differential spectrophotometrical method. Wild black currants showed an increased total content of anthocyanin, expressed as cyanidin-3-O-glucoside equivalents, compared to the cultivated ones. Also, the study examined the influence of long-term cold storage of plant materials (freezing) upon anthocyanins content. The results showed an increase in anthocyanin content during long-term storage at -18°C in both investigated samples (11- 52%). The results may be of interest for food manufacturers, as any processing method may influence the content and composition of these pigments and consequently their health benefits.
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Re: Nutrients in fresh produce vs frozen or canned

Postby JeffN » Sun Nov 20, 2016 6:53 am

MSM article

NYTimes: Are Frozen Fruits and Vegetables as Nutritious as Fresh?

The differences in nutrient levels between fresh and frozen are so minor that they would be unlikely to have an impact on overall health.

http://well.blogs.nytimes.com/2016/11/1 ... -as-fresh/



Abstract

Mineral, fiber, and total phenolic retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage.
J Agric Food Chem. 2015 Jan 28;63(3):951-6. doi: 10.1021/jf504890k. Epub 2015 Jan 13.

https://www.ncbi.nlm.nih.gov/pubmed/25525668
Abstract

Minerals, total phenolics, and fiber were analyzed in several fruit and vegetable commodities to evaluate the differences between fresh and frozen produce. Magnesium, calcium, iron, zinc, and copper were evaluated in corn, carrots, broccoli, spinach, peas, green beans, strawberries, and blueberries. Each commodity was harvested fresh and split into two batches. Half of each commodity was kept fresh, and the other half was frozen. The nutrient content was analyzed over three storage times per treatment. The retention of nutrients was highly dependent on the commodity, but the majority of the commodities showed no significant difference between fresh and frozen for all analytes (p ≤ 0.05).
PMID 25525668 [PubMed - indexed for MEDLINE]


Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage.Bouzari A, et al. J Agric Food Chem. 2015.
https://www.ncbi.nlm.nih.gov/m/pubmed/2 ... 68/related

Abstract
Four vitamins were analyzed in several fruit and vegetable commodities to evaluate the differences between fresh and frozen produce. Ascorbic acid, riboflavin, α-tocopherol, and β-carotene were evaluated in corn, carrots, broccoli, spinach, peas, green beans, strawberries, and blueberries. Samples of each commodity were harvested, processed, and analyzed for nutrient content at three storage times per treatment. Ascorbic acid showed no significant difference for five of the eight commodities and was higher in frozen samples than fresh for the remaining three commodities. Apart from broccoli and peas, which were higher and lower in frozen vs fresh samples, respectively, none of the commodities showed significant differences with respect to riboflavin content. Three commodities had higher levels of α-tocopherol in the frozen samples, while the remaining commodities showed no significant difference between fresh and frozen. β-Carotene was not found in significant amounts in blueberries, strawberries, and corn. Peas, carrots, and spinach were lower in β-carotene in the frozen samples, while green beans and spinach showed no significant difference between the two storage methods. Overall, the vitamin content of the frozen commodities was comparable to and occasionally higher than that of their fresh counterparts. β-Carotene, however, was found to decrease drastically in some commodities.

PMID 25526594 [Indexed for MEDLINE]
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Re: Nutrients in fresh produce vs frozen or canned

Postby JeffN » Mon Feb 24, 2020 3:57 pm

Fresh vs Frozen: Frozen is much more then just cool :)

Original research article
Selected nutrient analyses of fresh, fresh-stored, and frozen fruits and vegetables
Journal of Food Composition and Analysis
Volume 59, June 2017, Pages 8-17

Highlights

- Consumers’ assumption that fresh produce has much more nutritional value than frozen is incorrect.

- In some situations, frozen produce is more nutritious than its 5-day fresh-stored counterpart.

- The study mimics typical consumer purchasing and storage patterns of produce.

- The study compares key nutrients in fresh, fresh-stored, and frozen produce.

- Fresh produce loses vitamins over time during refrigerated storage.

Abstract
This two-year study compared the status of targeted nutrients in selected fresh and frozen fruits and vegetables. In addition, a novel third category was examined—a “fresh-stored” categorization intended to mimic typical consumer storage patterns of produce following purchase (five days of refrigeration). Broccoli, cauliflower, corn, green beans, green peas, spinach, blueberries, and strawberries of all three categories of freshness were analyzed for their concentrations of l-ascorbic acid (vitamin C), trans-β-carotene (provitamin A), and total folate. Analyses were performed in triplicate on representative samples using standardized analytical methods and included a quality control plan for each nutrient. In the majority of comparisons between nutrients within the categories of fresh, frozen, and “fresh-stored”, the findings showed no significant differences in assessed vitamin contents. In the cases of significant differences, frozen produce outperformed “fresh-stored” more frequently than “fresh-stored” outperformed frozen. When considering the refrigerated storage to which consumers may expose their fresh produce prior to consumption, the findings of this study do not support the common belief of consumers that fresh food has significantly greater nutritional value than its frozen counterpart.

https://www.sciencedirect.com/science/a ... 7517300418
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