HPLC quantification of the dihydrochalcones,aspalathin and nothofagin in rooibos tea (Aspalathus linearis) as affected by processing

An HPLC method was developed for determination of the C-glucoside dihydrochalcones, aspalathin and nothofagin, in rooibos tea. Gradient separation of the phenolic fraction was achieved on a reversed-phase C₁₈ column. The polyphenolic fraction was prepared by extraction of the phenolic compounds with hot water, followed by liquid-liquid extraction with ethyl acetate. The method was applied to unprocessed, partially oxidized (unfermented) and fermented rooibos tea as well as tea dried in the sun and under controlled conditions. Aspalathin and nothofagin oxidation occurred as soon as the tea leaves were comminuted which resulted in browning as indicated by CIELAB parameters. The drying method had no effect on the degree of oxidation of aspalathin and nothofagin.     

Effect of Vitamin D3 Fortification and Saskatoon Berry Syrup Addition on the Flavor Profile,Acceptability, and Antioxidant Properties of Rooibos Tea (Aspalathus linearis)

The unique characteristics and healthful reputation of caffeine‐free rooibos tea (RT) make it an ideal carrier for vitamin D₃ supplementation, and a potential base for the addition of Saskatoon berry syrup (SBS), a natural flavor additive. The objective of this study was to determine the effect of vitamin D₃ fortification and SBS addition on the flavor profile, consumer acceptability, and antioxidant properties of RT. Six formulations (RT, RT with SBS, RT with SBS and vitamin D₃, RT with vitamin D₃, green tea [GT], and GT with SBS) were evaluated by 12 trained panelists and 114 consumers. The formulations were also assessed for antioxidant capacity, physical characteristics, and untargeted phytochemical content. Sensory results revealed that the mean intensity values for berry and sweet attributes were significantly higher (P < 0.05) while bitter and astringent attributes were significantly lower when SBS was added to RT samples compared to those without syrup. Acceptability of flavor, aftertaste, and overall acceptability were also significantly higher for the RT with SBS. The addition of SBS to RT significantly increased the antioxidant capacities which may increase the related health benefits of RT. SBS contributed several polyphenols, particularly flavonoids, to the tea. Vitamin D₃ added to RT formulations did not significantly affect the sensory attributes, acceptability, or antioxidant content. For the development of a functional vitamin D₃ fortified iced‐tea beverage that can be consumed as part of the daily diet, SBS could be a favorable flavoring additive that may provide additional health benefits.     

Lipid and protein stability and sensory evaluation of ostrich (Struthio camelus) droëwors with the addition of rooibos tea extract (Aspalathus linearis) as a natural antioxidant

The effect of rooibos tea extract (RBTE 0%, 0.25%, 0.50%, 1.00%) as a natural antioxidant on the lipid and protein stability of ostrich droëwors (traditional South African dried sausage) after a 15 day drying period was investigated. The lipid stability of the droëwors increased with 0.25% RBTE having lower TBARS. The protein stability of the droëwors did not differ (P ≥ 0.05) between treatments. The heme–iron content did not differ (P ≥ 0.05) between the treatments and increased from day 0 to day 15. Drying resulted in a decrease in the total moisture content by 45% and a corresponding increase in all other components. There were no differences between the moisture, fat and ash contents between treatments within a specific day. The droëwors had high concentrations of oleic acid, palmitic acid and linoleic acid. The addition of RBTE also improved the sensory attributes and can thus be added and marketed as a natural flavourant from ‘out of Africa’ for a traditional South African meat product.     

An investigation of rancidity inhibition during frozen storage of Wels catfish (Silurus glanis) fillets by previous ascorbic and citric acid treatment

The effect of preliminary ascorbic and citric acid (AA and CA, respectively) soaking treatments on the rancidity development in Wels catfish ( Silurus glanis ) fillets during further frozen storage (−18 °C; up to 6 months) was studied. Rancidity development was measured by biochemical quality indices (formation of free fatty acids, peroxides and secondary oxidation products) and compared with sensory analysis (appearance, rancid odour and consistency) and general chemical analyses (pH, expressible moisture and heme iron contents). When compared with control samples, AA- and CA-treated samples showed a lower ( P  < 0.05) formation of primary and secondary lipid oxidation compounds that was corroborated by a longer ( P  < 0.05) shelf-life time as a result of a lower rancid odour formation. According to these results, control samples showed a higher ( P  < 0.05) heme iron breakdown (months 3–6) and a lower ( P  < 0.05) water-holding capacity (higher expressible moisture value) (month 6).     

Changes in anthocyanin,flavonoid and phenolic acid concentrations during development and storage of coloured potato (Solanum tuberosum L) tubers

Changes in the anthocyanin concentration of coloured potato tubers have been investigated in cultivars with coloured skin and coloured or white flesh. The biosynthesis of anthocyanins coincided with tuber initiation in cultivars with intensely coloured mature tubers and, after a slight increase as the smaller tubers increased in size, anthocyanin concentrations remained relatively constant. Thus, because tubers were increasing in weight, anthocyanin was being synthesised to maintain a more or less constant concentration. In cultivars with less coloured tubers, the developing tubers remained white for a longer time, with anthocyanin concentrations increasing gradually up to a maximum at a certain tuber weight depending on the cultivar. The concentration of flavonoids was lower than that of anthocyanins but followed a similar pattern. Phenolic acid levels were about twice those of the anthocyanins and reached their maximum at a slightly lower tuber weight than anthocyanins and flavonoids. During cold storage (4°C) the anthocyanin concentration in coloured tubers increased, whereas tubers stored at higher temperatures did not show this increase. The increased colour in cold‐stored tubers is discussed in terms of its relationship to ‘cold sweetening’ and the increased concentration of sugars in cold‐stored tubers. The distribution of anthocyanins altered during tuber development and also during cold storage. In very small developing tubers the anthocyanins appeared first at the stem end of the tuber whilst the bud end remained white. As the anthocyanin concentration increased during tuber development, it increased over the whole tuber, but the concentration at the stem end was always higher than that at the bud end, until the tuber reached maturity, when the concentration became approximately equal at both ends. After cold storage, tubers had a higher concentration of anthocyanin in the bud end than the stem end; the opposite to that found in developing tubers. © 1999 Society of Chemical Industry     

Effectiveness of a natural Rosemary (Rosmarinus officinalis) extract on the stability of filleted and minced fish during frozen storage

 The objective of this study was to evaluate the effect of adding a natural Rosemary (Rosmarinus officinalis L.) extract to filleted and minced frozen fish and to compare the fat stability of the samples with that of the controls. Horse mackerel (Trachurus trachurus), a relatively fatty fish, and Mediterranean hake (Merluccius mediterraneus), a low-fat fish, were used. Fat stability evaluation was done by comparing the changes of the malondialdehyde (MDA) content and the percentage of polyunsaturated fatty acid (PUFAs) degradation that occurred during frozen storage at –18°C for 120 days. Total volatile bases-N (TVB-N) were also measured to assess for quality. The results showed that the natural antioxidant extract retarded the oxidation process throughout storage. The control samples of both filleted and minced frozen fish of both species showed a significant reduction (^* P <0.05) of PUFAs until day 50 of storage, while the oxidation was gradual but slower in the treated samples. Fillets and minced samples of both species treated with antioxidant contained significantly (^* P <0.05) less MDA compared with the controls during storage. Received: 2 December 1996     

Dynamic changes in flavonol glycosides during production of green,yellow, white,oolong and black teas from Camellia sinensis L. (cv. Fudingdabaicha)

Flavonol glycosides with low thresholds are important flavour substances in tea leaves. This study monitored the dynamic changes in flavonol glycosides during the production of different teas. The fresh leaves of cv. Fudingdabaicha with 15.77 mg g⁻¹ of total flavonol glycosides (TFG) were respectively processed into green, yellow, white, oolong and black teas. A reduction of TFG was observed for different teas, amongst which black tea contained the lowest level of TFG (9.83 mg g⁻¹), followed by oolong tea (11.96 mg g⁻¹), while green, yellow and white teas contained similar levels of TFG (~13.70 mg g⁻¹). Fixation was crucial to maintain the stability of flavonol glycosides due to its inactivation effect on enzymes at high temperature. Principal component analysis results indicated that flavonol glycosides were vulnerable to fermentation, and the stabilities of flavonol glycosides were related with aglycone and glycoside moiety.     

Color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree during storage at room temperature: Effect of pH, potassium sorbate, ascorbic acid and packaging material

The color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree of pH 4.00 and 5.00 containing potassium sorbate (KS), ascorbic acid (AA) or their mixture, packaged in polyethylene and in polyvinyl chloride-polyvinylidene chloride copolymer (PCPC) bags, was analyzed throughout the storage at 25 °C. Color changes were measured through lightness (L), redness (a), yellowness (b). Changes in a and b were mathematically modeled. In general, lightness, redness and yellowness diminished with storage time. The presence of KS diminished color loss of purees packed in PCPC bags and increased the discoloration of purees contained in polyethylene suggesting, in the first case, that KS oxidation diminished the available oxygen protecting carotenoids oxidation, and in the second case, the existence of a coupled oxidation between KS and carotenoids helped by the oxygen presence. Addition of AA to a puree of pH 4.00 containing KS and packed in polyethylene minimized the losses of redness and yellowness; probably as a consequence of the antioxidant action of AA. The increase in pH from 4.00 to 5.00 in the presence of KS significantly minimized color degradation of puree packed in PCPC. From the point of view of improving color stability, a convenient formulation could be a puree of pH 5.00 preserved with KS and packed in PCPC.     

Changes in composition of lipids,free amino acids and organic acids in rice-bran-fermented- sardine (Etrumeus teres) during processing and subsequent storage

Changes in composition of lipids, free amino acids and organic acids in rice-bran-fermented sardine—one of the traditional marine products of Japan—were investigated. The moisture content decreased rapidly during pre-curing and then slowly during rice bran fermentation. The salt content of the finished product was about 234 g kg⁻¹ on a dry weight basis. The pH decreased from 6.1 in the raw sardine to 5.3 in the finished product. Total volatile basic nitrogen increased up to 1.0 g kg⁻¹ after 2 months of rice bran fermentation and then remained almost unchanged. Most free amino acids except histidine and taurine increased during rice bran fermentation. The histamine content increased to 0.75 g kg⁻¹ at 2 months of rice bran fermentation and subsequently decreased gradually. Certain polyamines also accumulated on relatively lower levels. Lactic acid (8.14 g kg⁻¹ at 2 months of rice bran fermentation) was a prominent organic acid produced during processing. Considerable decompositions of triglyceride and phospholipids occurred accompanied by production and accumulation of a correspondingly high concentration of free fatty acids. The peroxide value and the amount of thiobarbituric acid reactive substances in the extracted total lipids decreased gradually during rice bran fermentation. It was concluded that lipid oxidation was restricted during rice bran fermentation although remarkable proteolysis occurred. The present traditional manufacturing process seems to be applicable to the technology of processing and subsequent preservation of fish products in the developing countries.     

鲜切红菜薹中有机酸和花青苷在货架贮藏过程中的变化

为探讨货架温度（8±1）℃下鲜切蔬菜中有机酸和花青苷在贮藏过程中的变化趋势,本实验以红菜薹（Brassica campestris L.ssp.chinensis L.var.purpurea Bailey）为材料,采用高效液相色谱/液相色谱-质谱联用（HPLC/HPLC-MS）技术,对红菜薹中有机酸和花青苷的成分和含量进行了鉴定和分析,并对在货架温度下经鲜切处理的红菜薹中有机酸和花青苷在货架期内（7 d）的变化情况进行了观测。结果表明:供试红菜薹中检测出7种有机酸和11种花青苷。其中,苹果酸与柠檬酸是红菜薹中最主要的有机酸（91.49%）;矢车菊-3-p-香豆酰-丙二酰-葡萄糖苷-5-葡萄糖苷和矢车菊-3-阿魏酰-丙二酰-槐糖苷-5-葡萄糖苷是红菜薹中最主要的两种花青苷（65.02%）。鲜切红菜薹中总有机酸含量在货架期内显著下降（p<0.05）,而总花青苷含量呈现先平缓下降后显著上升的趋势（p<0.05）。因此,鲜切红菜薹中所含各有机酸的组分除琥珀酸和富马酸以外在贮藏过程中均呈现不同程度的消解与损失;各花青苷组分在贮藏过程中则大多呈现不同程度的增长。      

Storage stability of jackfruit (Artocarpus heterophyllus) powder packaged in aluminium laminated polyethylene and metallized co-extruded biaxially oriented polypropylene during storage

Total colour difference (ΔE), rates of adsorbed moisture and sensory attributes of drum-dried jackfruit powder packaged in aluminium laminated polyethylene (ALP) and metallized co-extruded biaxially oriented polypropylene (BOPP/MCPP) pouches stored at accelerated storage (38 °C, with 50%, 75% and 90% relative humidity (RH)) were determined over 12 weeks period. The changes in total colour followed zero order reaction kinetics. Packaging materials, storage temperature and RH values significantly (p < 0.05) influenced the rates of adsorbed moisture of jackfruit powder. There was a significant (p < 0.05) decrease in the intensities of the fruity odour, taste and increase in the lumpiness of the jackfruit powder stored at 38 °C with 90% RH. The shelf life of jackfruit powder stored at 38 °C and 90% RH was limited by overall acceptability and the intensity of fruity odour, taste and lumpiness at week 8 of storage. Jackfruit powder stored at 28 °C remained stable and acceptable throughout the storage period for all RH values. The powder packaged in ALP significantly (p < 0.05) reduced total colour change, rates of adsorbed moisture, lumpiness intensity of jackfruit powder and was rated higher in terms of overall acceptability over BOPP/MCPP. Results of this study suggested that ALP packaging with storage conditions of 28 °C and RH less than 75% was better suited for keeping jackfruit powder.     

Relation between types of packaging,frozen storage and grilling on cholesterol and fatty acids oxidation in Atlantic hake fillets (Merluccius hubbsi)

Two different commercial samples of frozen and packaged, in low and high-oxygen permeability packaging, Atlantic hake fillets were stored at −18 °C for 4 months and the intensity of lipid oxidation, as well as the formation of cholesterol oxidation products (COP), during storage and subsequent grilling were studied. Raw fillets at the initial time of storage showed low total COP levels, however, after 120 days of storage the concentrations were raised significantly, under both packed conditions. During freezing and subsequent grilling there was a significant decrease (p < 0.02) in the contents of the cholesterol and polyunsaturated fatty acids in all the hake samples. Correlations were found between the cholesterol and fatty acid parameters and cholesterol oxides formation during storage and heat treatment. The commercial frozen storage with a low-oxygen permeability packaging was more effective in preventing lipid oxidation than high-oxygen permeability packaging, with less accented cholesterol degradation as well as cholesterol oxides formation.     

Effects of feeding regimen and chilled storage on water‐holding capacity,colour stability,pigment content and oxidation in red deer (Cervus elaphus) meat

The effects of feeding regimen on carcass characteristics, meat colour and lipid stability, pigment content and water‐holding capacity of M. longissimus were studied in 16 male red deer. All animals were farm raised; eight were grazing pasture and eight were fed a pelleted commercial feed mixture for 10 weeks prior to slaughter. The pellet‐fed deer had significantly higher live weight, carcass weight, dressing yield (g kg^?1) and fat content than the pasture group. Carcasses from the pellet‐fed deer had higher temperatures over 0–10 h post mortem than carcasses from the grazing animals, probably due to an insulating fat cover. Ultimate pH values were lowest in meat from the pellet‐fed deer. The meat from the grazing deer had significantly better colour stability at 1 day post‐slaughter and after 1, 3 and 6 weeks of refrigerated storage (?1.5 °C) in vacuum bags. After 3, 6 and 12 weeks of refrigerated storage the meat from the pellet‐fed deer had significantly higher drip loss. No difference was found in the amount of oxidation products (thiobarbituric reactive substances, TBARS) when comparing the treatment groups, although the amount of TBARS increased during storage. Muscle pigment content was significantly higher in grazing deer than in the pellet‐fed group. It was not possible to confirm a correlation between lipid and pigment oxidation in the meat, and the pigment content of the meat samples did not seem to have an influence on colour stability or oxidation product formation. Copyright © 2005 Society of Chemical Industry     

Rancidity development during the frozen storage of farmed coho salmon (Oncorhynchus kisutch): Effect of antioxidant composition supplied in the diet

A commercial diet including synthetic antioxidants (BHT–ethoxyquin mixture) (diet I) was provided to coho salmon (Oncorhynchus kisutch) in parallel with two diets including natural antioxidants (tocopherol isomers–rich mixture, diet II; tocopherol isomers-rosemary extract mixture, diet III). A comparative study of the rancidity development in the corresponding frozen (−18 °C) products was undertaken. When compared to fish fed with diet I, individuals corresponding to diet II showed a greater (p < 0.05) retention of primary (conjugated dienes and peroxides content) and secondary (anisidine and thiobarbituric acid indices) lipid oxidation compounds that led to a lower interaction compound formation (fluorescence ratio ranges: 0.33–0.50 and 0.55–0.85, for diet II and diet I individuals, respectively); likewise, a higher polyene index (1.99–2.14 and 1.72–1.97, respectively) and lower oxidised taste scores (0.0–0.6 and 0.0–2.4, respectively) were obtained. No effect (p > 0.05) on lipid hydrolysis development (free fatty acid formation) could be found as a result of employing different diets.     

Identification of the aroma compounds in stinky mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation and storage

Identification of aroma compounds in Stinky Mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation (with spices and salt) and storage were analysed by electronic nose (e‐nose) combining with gas chromatography–mass spectrometry (GC‐MS). Among the sixty‐one detected volatiles, thirteen aroma‐active compounds, especially linalool, were identified in stinky mandarin fish according to thresholds and concentrations. Totally, twenty‐four aroma compounds correlated well with the periods of fermentation and storage. Trimethylamine, indole, sulphur‐containing compounds, acetic acid, esters and phenols increased continually, while aldehydes decreased. According to these quality indicators, e‐nose data using principal component analysis showed a clear discrimination of the fermented fish and were in good agreement with the results of GC‐MS. In conclusion, fermentation favoured to retard spoilage and provided new aroma compounds. The technique employing an e‐nose in combination with GC‐MS could compare and identify the aroma and quality of stinky mandarin fish.     

Monitoring colour,volatiles in the headspace and enzyme activity to assess the quality of broccoli florets (Brassica oleracea L. italica cv. Bellstar and Legacy) during postharvest storage

The research objective was to study whether volatile organic compounds released in the headspace could be used to assess the broccoli quality (Brassica oleracea L. italica cv. Bellstar and Legacy) during postharvest storage (23 °C for 7 days) and correlated with colour change and the activity of peroxidase/POD, ascorbic acid oxidase/AAO and lipoxygenase/LOX. Volatile organic compounds were monitored using PTR‐MS. Methanol had the highest concentration compared with other volatiles released in the headspace that significantly increased during senescence. The methanol concentration was approximately 500 ppbv before the broccoli colour began to change from green to yellow. The concentration of methanol in the headspace increased to 1000–1100 ppbv for Bellstar and Legacy when the colour became yellowish. LOX had high correlation (0.91 and 0.83 for Bellstar and Legacy, respectively) with volatiles for both cultivars, but not for POD. Methanol production is proposed as the best volatile marker to assess the broccoli quality.