Nutritional comparison of fresh,frozen, and canned fruits and vegetables II. Vitamin A and carotenoids,vitamin E,minerals and fiber

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 postharvest treatments, inclusion of a wide variety of fruits and vegetables in the diet is encouraged. Copyright © 2007 Society of Chemical Industry     

Nutritional content of fresh and canned peaches

BACKGROUND: The objective of this study was to assess whether canned peaches could deliver nutrient levels comparable to fresh peaches. Fresh freestone peaches, fresh cling peaches and canned cling peaches were analyzed for vitamins A, C and E, folate, antioxidants, total phenolics and total carotenoids to assess how these nutrients were affected by the canning process and whether storage further changed these components. RESULTS: The vitamins and phytochemicals measured in this study were found to be present in canned cling peaches versus fresh freestone at statistically significantly higher levels (vitamin C, antioxidants and folate); higher but not statistically different levels (vitamin A); or lower, but not statistically different levels (vitamin E, total phenolics and total carotenoids). There were no statistically significant changes in nutrient content during storage for 3 months. CONCLUSIONS: The nutritional content of canned peaches has been shown in this study to be comparable to that of fresh peaches. There were no statistically significant decreases in those nutritional parameters measured in this study between fresh freestone peaches and canned cling peaches. Vitamins A and E along with total carotenoids decrease immediately upon processing, but appear to stabilize after the processing step, showing minimal additional changes upon storage for 3 months. This study shows that canned peaches can provide comparable nutrient levels to the consumer as fresh peaches, meaning that consumers can enjoy peaches year round without worrying about loss of nutrients in their diet. © 2012 Society of Chemical Industry     

Effect of Processing Method and Storage Time on the Nutrient Composition of Fiddlehead Greens

The effect of processing method (freezing vs canning) and storage time (day 1 or 10 months) on the proximate composition and the vitamin and mineral content of fiddlehead greens was examined. Comparisons were made between the nutrient composition of raw and processed fiddlehead greens. The protein, ash and water soluble vitamin (niacin, thiamin, riboflavin, vitamin C) content of the fiddle-heads decreased with processing. These losses were most likely the result of leaching and heat processing. Losses of water soluble vitamins, particularly niacin, was the greatest in canned fiddlehead greens. The mineral content (K, Mg, P) was substantially reduced by processing. Storage for up to 10 months resulted in a significant decrease in the moisture, crude fiber, and α-carotene content of frozen and canned fiddlehead greens.     

NUTRITIVE CONTENT OF CANNED TOMATO JUICE AND WHOLE KERNEL CORN

Most of the information on the nutritive value of canned foods in the technical literature was obtained 25–30 years ago. A resurvey of the nutrient content of canned tomato juice and canned whole kernel corn has been carried out on a nation-wide basis with sampling methods directly comparable to the older survey procedures. Although there have been extensive changes in varietal types and processing methods during the past 30 yr the mean nutritional values for these products have changed very little. Comparison of the nutrient values for these products listed in USDA Handbook No. 8 reveals no differences that could not be attributed to seasonal variations. A possible exception is the ascorbic acid content of tomato juice, which for the 1969 season was found to be somewhat lower than the listed value. While sample-to-sample variation is small in terms of the RDA of most nutrients, it can be critical in terms of the regulatory requirements proposed for nutritional labeling. Under this proposal canners would have to grossly "under declare" some nutrients such as ascorbic acid in order to ensure compliance. The indication is that mean values derived from adequate sampling programs are relatively stable although the population may encompass wide ranges of variability. For this reason, nutrient labeling declarations based upon properly constituted average values provide the most practicable solution to the inherent technical problems in the proposed nutritional labeling regulation     

Effects of Different Processing Methods on the Micronutrient and Phytochemical Contents of Maize: From A to Z

Maize is a staple human food eaten by more than a billion people around the world in a variety of whole and processed products. Different processing methods result in changes to the nutritional profile of maize products, which can greatly affect the micronutrient intake of populations dependent on this crop for a large proportion of their caloric needs. This review summarizes the effects of different processing methods on the resulting micronutrient and phytochemical contents of maize. The majority of B vitamins are lost during storage and milling; further loss occurs with soaking and cooking, but fermentation and nixtamalization (soaking in alkaline solution) can increase bioavailability of riboflavin and niacin. Carotenoids, found mainly in the kernel endosperm, increase in concentration after degermination, while other vitamins and minerals, found mainly in the germ, are reduced. Mineral bioavailability can be improved by processing methods that reduce phytic acid, such as soaking, fermenting, cooking, and nixtamalization. Losses of micronutrients during processing can be mitigated by changes in methods of processing, in addition to encouraging consumption of whole‐grain maize products over degermed, refined products. In some cases, such as niacin, processing is actually necessary for nutrient bioavailability. Due to the high variability in the baseline nutrient contents among maize varieties, combined with additional variability in processing effects, the most accurate data on nutrient content will be obtained through analysis of specific maize products and consideration of in vivo bioavailability.     

NUTRITIONAL, PROXIMATE, AND MICROBIAL CHARACTERISTICS OF PHOSPHATE PROCESSED SEA SCALLOPS (PLACOPECTEN MAGELLANICUS)

Sea scallop adductor muscles were used to evaluate six scallop processing methods with regards to changes in moisture content, nutritional equivalency, and total plate counts. Sodium tripolyphosphate (STP) reduced the rate of moisture incorporation, enhanced scallop moisture binding capacity and maintained a degree of antimicrobial capacity. Scallop moisture content increased with processing time. Short processing times using a higher concentrated STP solution performed as well, or better, in binding moisture and reducing bacteria than longer processing times using a lower concentrated STP solution. Increasing moisture content decreased nutrient levels on a per weight basis. Nutrients most affected by increasing moisture content were protein, niacin, calcium, and vitamin B₁₂. Moisture loss due to freeze/thaw or cooking concentrated some nutrients (protein and minerals), while contributing to the loss of water-soluble nutrients. The use of STP lowered scallop drip loss, which in turn, reduced nutrient loss.     

Impact of cooking methods on folates,ascorbic acid and lutein in green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea)

Folates, ascorbic acid (vitamin C) and lutein (antioxidant carotenoid) concentrations were determined after cooking (boiling and steaming) fresh, frozen and canned green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea). The aim of this study was to qualify and quantify the loss of water soluble (folates and ascorbic acid) and lipid soluble (lutein) micronutrients in the cooked products and liquids and the canning liquor. In canned products, folates were found in the canning liquor. Boiling regardless of product reduced plant tissue folates and ascorbic acid but not lutein concentrations. Loss of folates during boiling occurred due to leaching (diffusion) and ascorbic acid due to temperature (heating). Steaming reduced ascorbic acid but not folate or lutein concentrations.     

Storage effects on anthocyanins, phenolics and antioxidant activity of thermally processed conventional and organic blueberries

BACKGROUND: Consumer demand for products rich in phytochemicals is increasing as a result of greater awareness of their potential health benefits. However, processed products are stored for long‐term and the phytochemicals are susceptible to degradation during storage. The objective of this study was to assess the storage effects on phytochemicals in thermally processed blueberries. Thermally processed canned berries and juice/puree were analysed for phytochemicals during their long‐term storage. RESULTS: The phytochemical retention of thermally processed blueberries during storage was not influenced by production system (conventional versus organic). During 13 months of storage, total anthocyanins, total phenolics and total antioxidant activity in canned blueberry solids decreased by up to 86, 69 and 52% respectively. In canned blueberry syrup, total anthocyanins and total antioxidant activity decreased by up to 68 and 15% respectively, while total phenolic content increased by up to 117%. Similar trends in phytochemical content were observed in juice/puree stored for 4 months. The extent of changes in phytochemicals of thermally processed blueberries during storage was significantly influenced by blanching. CONCLUSION: Long‐term storage of thermally processed blueberries had varying degrees of influence on degradation of total anthocyanins, total phenolics and total antioxidant activity. Blanching before thermal processing helped to preserve the phytochemicals during storage of blueberries. Copyright © 2011 Society of Chemical Industry     

加工方式对海带营养品质的影响

目的 研究不同加工方式对海带营养品质的影响。方法 将不同海域、不同时期收割的新鲜海带加工制成干海带、盐渍海带、盐渍半干海带,对四类海带样品进行基本营养成分的测定,同时模拟家庭食用方式对海带制品进行浸泡和熟制处理,测定处理前后碘含量。结果 鲜海带中碘、蛋白质、膳食纤维含量高于其他三种类型海带;干海带的矿物质含量较高;深水海域海带产品的矿物质含量高于浅水海域;成熟期海带产品的碘和蛋白质含量较高。浸泡和熟制处理前后海带中碘流失量达到80%以上。结论 不同加工方式会使海带中营养成分出现不同程度的损失,食用状态下的海带碘含量较低,适量食用海带不会存在补碘过量的风险。     

Computational Fluid Dynamics Modeling of the Thermal Processing of Canned Pineapple Slices and Titbits

Thermal processing of canned fruits is an important preservation technique used to increase the shelf life of canned foods through the inactivation of spoilage microorganisms and enzymes. The objective of this study was to develop a computational fluid dynamics model to investigate the temperature profiles during the thermal processing of canned pineapple products. Two different kinds of products such as canned pineapple slices and titbits were analyzed to investigate the effect of size reduction of the product on the efficacy of heat transfer during thermal processing. The simulation results were validated with the experimental measurements of temperatures. The temperature profile, slowest heating zone (SHZ), and the effects of natural convection and conduction heating on canned pineapple slices and titbits were studied. In the canned pineapple slices, the SHZ was found to lie inside the pineapple slices. In contrast, for the pineapple titbits, the SHZ was present at the bottom of the can. The pineapple titbits were found to achieve a rapid temperature increase owing to the combined effects of buoyancy-induced natural convection and increased surface area available for higher heat transfer. This finding signifies the retention of the nutritive properties of pineapple by preventing the loss of heat-labile nutrients like vitamins without compromising the commercial sterility of the product.     

From apple to applesauce: Processing effects on dietary fibres and cell wall polysaccharides

Modifications in dietary fibre content of apples during industrial processing into applesauce were investigated. Samplings with different post-harvest storage times were performed at five different processing steps (apple sorting, cooking, refining, sugaring and pasteurisation) and the samples examined for their insoluble, soluble and total fibre contents, following the AOAC method. Total fibres were also estimated through preparation of alcohol-insoluble solids and polysaccharide compositions of the various fibre residues were determined. Total fibre content decreased from apple to applesauce from 2.4 to 1.7 g for 100 g of fresh weight and the soluble fraction increased. Fibre loss and soluble/insoluble redistribution occurred during processing. Refining triggered a loss of insoluble polysaccharides whilst cooking and, surprisingly, sugaring led to pectin solubilisation and further degradation due to prolonged heating. These pectic changes, moreover, seemed to be dependent on the post-maturity stage of the apples.     

Nitrate and nitrite nitrogen in fresh, stored and processed table beets and spinach from different levels of field nitrogen fertilisation

Nitrogen fertilisation increased the content of nitrate-N in fresh table beets and spinach but had little or no effect on accumulation of nitrite-N. Interconversion of nitrate to nitrite did not occur when fresh beets and spinach were stored at 35°F . Large quantities of nitrate-N were lost by leaching during the processing of canned beets, spinach and puréed spinach baby food. These processing procedures and storage of the processed products for six months did not give rise to increased amounts of nitrite-N Nitrate- and nitrite-N contents of some commercial products are also reported.     

Effect of Processing on Proximate Composition and Mineral Content of Sea Cucumbers (Parastichopus spp.)

The nutrient content, texture and holothurin content of two sea cucumber species were determined for fresh, dried and canned products. Fresh sea cucumber contained 89–91% moisture, 5–6% protein, 0.3% fat, 3% ash and 0.3% carbohydrate; dried sea cucumber contained 2–6% moisture, 61–70% protein, 2–3% fat, 16–24% ash, and 2–3% carbohydrate. Fresh sea cucumber contained 90 mg of holothurin per 100g of tissue. Canned sea cucumber contained moisture and protein levels similar to those generally found in marine finfish. Processing methods for canned sea cucumber resulted in a significant (P<0.01) decrease in potassium and increase in sodium. No significant differences (P<0.01) were found in the texture of canned products made from fresh-cooked, salted-cooked and cooked-dried raw material.     

国产柑橘罐头感官品质和营养成分分析

目的建立国产柑橘罐头加工品质档案,为企业生产及消费者挑选更优质的柑橘罐头提供参考。方法通过苯酚-硫酸法、3,5-二硝基水杨酸比色法、比色法、分光光度法等对国产柑橘罐头感官品质和营养成分进行分析。结果马口铁的柑橘罐头较玻璃瓶和软包装Vc和黄酮含量高;浙江省产柑橘罐头不完整瓣数比例低,为5.02%,总糖含量较高;河北省产柑橘罐头Vc和类胡萝卜素含量高,分别为43.70、20.78 mg/100 g;包装容量为300～400g的柑橘罐头不完整瓣数比例较低,为10.33%,感官品质较佳;贮藏期较短柑橘罐头较贮藏期较长柑橘罐头可溶性固形物比例高,Vc、黄酮和类胡萝卜素含量高。结论马口铁柑橘罐头对易氧化营养成分的保存率优于玻璃瓶和高阻隔软包装。贮藏时间越短,柑橘罐头感官品质和营养成分损失越少。     

Measurement of Provitamin A Carotenoids in Fresh and Canned Carrots and Green Peas

The influence of thermal processing (canning) on the carotenoid content of carrots (Daucus carota) and green peas (Pisum sativum) was investigated. Carotenoids extracted from fresh and canned vegetables were separated by column chromatography and quantified using spectrophotometric analysis. Canned canots and green peas had a higher carotenoid content than fresh samples. The apparent increase in canned carrots was mainly due to the loss of soluble solids into the brine during processing. However, the increase of carotenoids in canned green peas was due to the loss of carotenoids by enzymatic activity in fresh green peas during extraction procedures.     

EFFECT OF STORAGE ON NUTRITIVE VALUE OF FOOD1

With few exceptions, nutrient levels and/or their bioavailability are reduced in foods following harvest, slaughter, or collection. Rate of these losses is usually attenuated by reducing temperature of storage. Initial heat processing to the point of enzyme inactivation, or to the point of microbial sterilization, “stabilizes” the food so that it does not “spoil” but at the same time causes a greater initial reduction in certain nutrients, and a more gradual reduction with extended storage. Initial heat processing and mechanical treatments may also release nutrients so that they become more available, but once released, they are also subject to losses unless stored at low temperatures. Ascorbic acid is undoubtedly the most sensitive to loss and changes to a less active form as the result of time and temperature in storage. In many instances changes in ascorbic acid reflect general changes in quality. Thiamine is the other vitamin which is frequently affected adversely by time and temperature of storage. The A vitamins appear to be lost readily in leafy vegetables, but relatively unchanged in other foods. There is little effect on mineral content of foods, but bioavailability, particularly of iron may be influenced during prolonged storage. Substantial losses in carbohydrates may be encountered as a result of respiratory activity in extended storage at relatively high temperatures. Protein content is rarely affected, but protein availability is readily reduced even in low moisture foods unless they are protected from oxygen and stored at low temperatures. These anticipated changes in nutritive value are of particular significance in nutrient labeling, and must be taken into account when preparing nutrient labels.     

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.     

动物性食品中胆固醇氧化产物的研究进展

动物性食品中的胆固醇氧化产物(Cholesterol Oxidation Products,COPs)的健康效应受到广泛关注。其水平在新鲜动物性食材中均很低,但在储藏加工和家庭烹调中可能有显著增加。文章介绍了水产品、畜产品、蛋制品及乳制品4类食品中影响胆固醇氧化产物形成的因素。研究表明长时间储藏、高温、非适宜的水分活度、与光线和氧气接触等因素均会促进胆固醇氧化产物的形成。烹调中加入油脂的饱和程度和所含抗氧化物质也影响动物性食物烹调后COPs的形成。加入适量的天然抗氧化物质可能有利于减少COPs的生成。     

Chemical composition,antioxidant capacity and functionality of raw and processed Phaseolus lunatus

The nutrients, non‐nutritional components and bioactive compounds, as well as the antioxidant capacity of raw, cooked, tray and drum‐dried Phaseolus lunatus have been quantified. Likewise, the minerals, soluble carbohydrates, total polyphenols and tannins in the soaking and cooking waters were quantified. In addition, the functional properties such as the water and oil absorption indexes and the emulsifying and the foaming capacities were studied. The protein content of the raw beans was 24.98% and decreased, like calcium, magnesium and potassium, with the soaking and cooking processes; these losses are found in the soaking and cooking waters. Drum drying decreased anti‐nutritional factors like trypsin inhibitors (66.09%) and cyanhydric acid (50.36%). Similarly, soluble fiber, available starch, total starch, and soluble sugars diminished, while total and insoluble fiber and resistant starch increased. The content of total polyphenols, tannins and antioxidant capacity decreased with thermal processing, being drum drying the process that least diminished antioxidant capacity. Likewise, the water absorption index was increased by 85% and 161.5% with processing. It was shown that P. lunatus is an important source of nutrients and can be consumed in whole bean form or used as a functional ingredient to be added in the development of new products. Copyright © 2007 Society of Chemical Industry     

Physico-chemical and acceptability of rabadi (a fermented soya flour product) as affected by cooking and fermentation time

Various food‐processing techniques like malting, roasting, soaking, germination, fermentation, etc. are known to enhance nutritive value and acceptability of different food products. The present study deals with the biochemical analysis and acceptability tests of soya flour rabadi, which was made by fermentation before and after cooking at different time intervals. There was a trend towards increase in moisture, ash, total carbohydrate, calcium, total soluble sugars, reducing sugars, non‐reducing sugars, amylase, glutamate oxaloacetate transaminase enzymatic activities and titrable acidity, whereras a trend towards decrease was found in crude protein, fat, fibre, energy, starch, total phenols and glutamate pyruvate transaminase enzyme activity. Major biochemical changes occurred after 8 h fermentation. In sensory evaluation also, samples fermented for 4 and 8 h after cooking got higher scores than all other samples.