The Change of Total Anthocyanins in Blueberries and Their Antioxidant Effect After Drying and Freezing

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

2006. The change of total anthocyanins in blueberries and their antioxidant effect after drying and freezing

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

Effects of drying on anthocyanins in blueberries

Blueberries are well known for their high anthocyanin content and the health benefits. Fresh blueberries have limited shelf life and thus are kept frozen or processed. Since freezing is expensive, low cost processing methods, particularly drying are being devised. Various drying treatments were compared with regard to drying time and quality of the dried product in terms of anthocyanin and polyphenolic contents as well as antioxidant activity. The drying treatments involved high temperature in a cabinet dryer and low temperature in a heat pump dryer. Freeze drying was used as a reference treatment. Highbush (Vaccinium corymbosum L., cultivars Crunchie, Star, and Sharpe) and rabbiteye (Vaccinium ashei, cultivars Climax, Powderblue, and Brightwell) blueberries were used in this study. Pre-treatments included osmotic dehydration or skin abrasion. The temperature and concentration of the osmotic solution were the mainparameters contributing to the reduction of drying time. Mechanical skin abrasion was more effective than osmotic dehydration in reducing drying time and minimising the loss of anthocyanin and phenolic contents of the blueberries in air drying treatments. The thickness of cuticle and the structure of epicuticular waxes affected the drying rate of different cultivars of blueberries. Liquid chromatography and mass spectrometry (LC/MS) was used to identify different anthocyanins in the blueberry samples. Delphinidin, petunidin, and malvidin were the main contributors to the total anthocyanin content of the fresh and dried samples. Degradation products of anthocyanins were observed in samples where the anthocyanin contents declined as a result of drying treatments. The anthocyanin content and profile, phenolic content, and antioxidant activity of mulberries (Morus nigra), and Makiang (Cleistocalyx nervosum), a Thai native fruit, were also analysed. There was no significant difference between total anthocyanin content of blueberries and mulberries. In contrast, the total phenolic content and antioxidant effect of mulberry were significantly higher than those of blueberries and Makiang. Skin abrasion and high temperature drying resulted in the fastest drying rate and highest anthocyanin retention. Anthocyanin profiles differed in various cultivars of blueberries. Within the same cultivar, amounts of each anthocyanin varied with pre-treatments and drying methods but the distribution of monomeric anthocyanins was similar

Development of microbiological criteria to assess the acceptability of a food lote. An example for milk powder

Milk powder to be consumed without further treatment to inactivate microorganisms was selected to illustrate the process for establishing and applying a microbiological criterion to assess the acceptability of a food lot. Example criteria (size of analytical unit, sampling plan and limits) were specified for mesophilic aerobic colony count and Enterobacteriaceae as indicators of the adequacy of Good Hygienic Practices and forSalmonellaas a food safety criterion. Performance characteristics were determined for each criterion using four values for standard deviation of the microbial counts to illustrate how sampling plan performance depends on the within-lot standard deviation, which is uncertain for any given lot and varies among lots. Methods of analysis were specified. A description of how to interpret the results and examples of actions that could be taken by food business operators and competent authorities are provided