Effect of heat treatments on the phytic acid content of maize products

Processing of maize (Zea mays L fresh and dry) for the production of various traditional products results in the loss of phytic acid. Fresh mature corn contains less phytic acid (1·71 g kg^?1) than dry corn (7·15–7.60 g kg^?1). The loss of phytic acid varies from 18·1 to 46·7% for fresh maize and from 11·5 to 52·6% for dry maize respectively among the heat treatments given. From a nutritional viewpoint, consumption of maize as chapati and after roasting in a sand bath or on charcoal will improve the availability of minerals.     

玉米油脱臭馏出物酶法甲酯化的研究

以固定化脂肪酶Novozym 435为催化剂,以叔丁醇为反应体系的溶剂,催化玉米油脱臭馏出物中的脂肪酸进行甲酯化反应,确定最佳反应条件。结果表明,脂肪酶添加量为80 mg/g,反应温度55℃,反应时间为20 h,醇料比为1.5∶1,叔丁醇添加量为6%,此时酯化率可达到96.84%。每次反应后的脂肪酶用丙酮处理,可循环使用7次,活性无明显降低。     

Effect of defatted maize germ flour addition on the physical and sensory quality of wheat bread

Maize (Zea mays L.) processing produces large quantities of defatted maize germ (DMG) that is being used mainly for animal feed. The objective of this study was to exploit use of this nutrient-rich by-product in bread by replacing wheat flour at 5-20 g/100 g levels. Breads prepared with wheat-DMG flour blends were analyzed for loaf volume, density, instrumental dough hardness and bread firmness, Hunter color (“L”, “a”, “b”, chroma, and hue angle), and selected sensory attributes. Loaf volumes decreased significantly, from 318.8 ml to 216.3 ml, as the DMG flour supplementation was increased from 0 to 20 g/100 g; a similar effect was observed for bread specific volume. Increase in dough hardness (7.56-71.32 N) was directly related to increase in DMG flour levels. Instrumental firmness values were significantly higher for breads containing DMG flours, 61.58 N in 20 g/100 g DMG bread versus 32.84 N for the control bread, made with wheat flour only. The control bread was lighter in color, as shown by higher “L” values, than those having DMG flour, with chroma and hue angle values significantly higher in treatment breads. In general, no differences were observed for the sensory attributes of crumb color, cells uniformity, aroma, firmness, mouthfeel, and off-flavor in breads with up to 15 g/100 g DMG flour, while the overall acceptability scores showed a mixed pattern. The results of this study demonstrated that acceptable quality bread could be made with DMG flour addition at ≤15 g/100 g.     

超声波辅助萃取玉米胚芽油的研究

利用超声波辅助有机溶剂提取玉米胚芽油。选取正己烷为最佳浸提溶剂,研究了超声波辅助提取的液料比、时间、温度、以及超声波频率对玉米胚芽油得率的影响。结果表明,超声波辅助提取的最佳条件为:液料比为10∶1(mL/g),提取时间为50 min,提取温度为50℃,超声波频率28 kHz,在此条件下油脂得率79.19%。     

小麦胚微波稳定化工艺参数初探

研究了微波功率、处理时间、小麦胚原料水分对小麦胚的脂肪酶活力及其储藏稳定性的影响。结果表明,微波处理可钝化小麦胚的脂肪酶,有利于小麦胚的储存;水分在微波稳定小麦胚过程中起着重要的作用,适当提高水分有助于小麦胚吸收微波能量,加快酶失活速率,提高小麦胚储藏稳定性。     

Effect of acid whey on physicochemical characteristics of dry‐cured organic pork loins without nitrite

The present study deals with the effect of acid whey (AW) on physicochemical properties of non‐nitrite organic dry‐cured pork loins. The loins were divided into three experimental batches: with the curing mixture (C), with sea salt (S) and with sea salt combined with AW (SW). The evolution of physicochemical properties, colour, fatty acid profile and microbiological quality were assessed at 0, 30 and 90 days of refrigerated storage. Physicochemical parameters of dry‐cured organic loins were significantly (P < 0.01) affected by treatment, storage time and the interaction between them. Sea salt in combination with AW was the most successful at reducing the browning reaction involved in the formation of dark colour in dry‐cured loins. Significant reduction in a* value (P < 0.05) caused by replacement of curing salt by sea salt has been less pronounced in sample with AW. Storage diminished (P < 0.01) initial differences in profile of SFA, MUFA and n‐3 induced by treatment method. AW added to uncured loins was able to protect PUFA against oxidation comparable to nitrite. The highest count of lactic acid bacteria (LAB) in dry‐cured loins with AW was accompanied by their lower pH (P < 0.05).     

热处理和碱处理对可食性大豆分离蛋白膜性能的影响

研究了热处理和碱处理对可食性大豆分离蛋白(SPI)膜性能的影响。对成膜液进行适当的加热和调节pH可以提高SPI膜的抗拉强度(TS)和伸长率(E),降低水蒸气透过系数(WVP)。调节成膜液的pH到9,在70℃加热20min,所得到的膜机械性能和阻湿性能最好。     

Effect of Iberian × Duroc genotype on composition and sensory properties of dry‐cured ham

BACKGROUND: Dry‐cured ham quality from three different Iberian × Duroc genotypes was studied: GEN1, Iberian × Duroc1; GEN2, Duroc1 × Iberian; GEN3, Duroc2 × Iberian. GEN1 and GEN2 are reciprocal crosses, while the difference between GEN2 and GEN3 is the Duroc sire line. The line Duroc1 (DU1) was selected for the manufacture of dry‐cured meat products, whereas the line Duroc2 (DU2) was selected for meat production with low carcass fat. RESULTS: Dry‐cured hams from all genotypes had similar chemical composition. However, intramuscular fat of dry‐cured hams from GEN3 was more unsaturated than that from GEN2, while GEN1 was intermediate. Lipid oxidation, measured as 2‐thiobarbituric acid‐reactive substances (TBARS) and hexanal content, was similar between genotypes. The colour of hams was affected by genotype; hams from GEN2 showed higher lightness (CIE L*), while those from GEN3 had a less intense colour (lower a* and C*). Texture measured instrumentally did not differ between genotypes; however, in the sensory analysis, panellists considered hams from GEN3 more fibrous, while those from GEN2 were considered juicier. Hams from GEN3 were also perceived as saltier and more acid. CONCLUSION: Genotype affected the quality of Iberian hams, with those from GEN3 being of lower quality, and this genotype was considered less suitable for the manufacture of Iberian dry‐cured ham. Copyright © 2007 Society of Chemical Industry     

Influence of starter cultures on the generation of antioxidant nitrogen compounds in Iberian dry‐fermented sausages

The purpose of this work was to investigate the influence of a starter culture on the generation of nitrogen compounds with antioxidant activity during the ripening of Iberian dry‐fermented sausages. Starters P200S34 (P. acidilactici M200 and S. vitulus RS34) and P198S34 (P. acidilactici MS198 and S. vitulus RS34) were used to make the Iberian dry‐fermented sausages ‘salchichón’ and chorizo; then, the physicochemical and microbial properties were determined during the ripening process. The oxygen radical absorbance capacity (ORAC) assay was employed to evaluate the antioxidant potential of the nitrogen extracts obtained during ripening of the sausages. This activity was correlated with the most relevant compounds detected by HPLC‐ESI‐MS in the final ripened extracts. Although a relevant part of the antioxidant activity was attributed to the predominant natural nitrogen fraction, the microbial population found in fermented sausages and the fermentation conditions significantly influenced the low molecular weight nitrogen profile and antioxidant activities. Inoculation with the starter culture P200S34 increased free amino acids and amines, such as methionine and tyramine, but other nitrogen compounds also increased the antioxidant activity of the low molecular weight nitrogen extracts. Thus, these starter cultures in Iberian sausages can contribute to delaying oxidative changes during storage.     

Enhanced thermal and antibacterial properties of cross‐linked waxy maize starch granules by chitosan via dry heat treatment

Cross‐linked starch was synthesised using chitosan as cross‐linking agent via a dry heating method. Thermal properties measured by DSC showed transition temperatures increased as compared with that of native starch (P < 0.001), which might indicate the starch and chitosan molecules interacted with each other. XRD demonstrated that the crystalline pattern of the starch remained the same, but there was slight change in the crystallinity degree after the cross‐links. The significant reduction of solubility, swelling power and transparency (P < 0.001) indicated that the cross‐links restricted the starch granules swelling and molecules leaching. Agar diffusion test showed that chitosan‐cross‐linked starch had excellent bacterial growth inhibition, and its antibacterial activity was stronger against Gram‐negative bacteria than against Gram‐positive bacteria. Its antibacterial activity was further confirmed using liquid broth method. Thus, the cross‐linked starch may be directly used in the food formula for protecting food as a natural antimicrobial ingredient.     

Quality characteristics of a non‐fermented dry‐cured sausage formulated with lemon albedo

Dry‐cured sausages were treated with two types of dehydrated lemon albedo (raw and cooked) at five concentrations (0–100 g kg^?1 in 25 g kg^?1 increments). Several physical and chemical analyses were made during the drying stage, and compositional, textural and sensory analyses were conducted on the finished products. The addition of albedo improved the nutritional properties as a result of fibre addition and may have beneficial effects due to the presence of active biocompounds as evidenced by a decrease in residual nitrite levels and delayed oxidation (based on TBARS values). The sensory properties of samples that resembled the control sausages were those that contained up to 50 g kg^?1 dehydrated raw albedo and 75 g kg^?1 dehydrated cooked albedo. Copyright © 2004 Society of Chemical Industry