Relationship between lipid peroxidation and fat content in Japanese Black beef Longissimus muscle during storage

Effect of Different Degrees of Deep Freezing on the Quality of Snowflake Beef during Storage

In order to elucidate whether deep freezing could maintain the quality of snowflake beef, three different deep freezing temperatures (−18 °C, −40 °C, and −60 °C) were used in order to evaluate the changes in tissue structures, quality characteristics and spoilage indexes, and their comparative effects on the quality of snowflake beef. Compared to samples frozen at −18 °C, those stored at −40 °C and −60 °C took a shorter time to exceed the maximum ice crystallization zone (significantly reduced by 2–6 h). In terms of short-term storage, samples frozen at −40 °C and −60 °C had better tissue structure and lower drip loss rate than those frozen at −18 °C; significant differences between groups in drip loss were observed between −18 °C and −60 °C. Moreover, a better bright red color and lower shear force were maintained at −40 °C and −60 °C, with significant differences in shear force between the −18 °C group and the other two groups on day 60. Although there were significant effects on the inhibition of lipid and protein oxidation at −40 °C and −60 °C; no significant variation was observed between these two groups throughout storage. A similar phenomenon was found in flavor, with 1-pentanol identified as an important potential indicator of flavor change in snowflake beef during storage. This study demonstrated that −40 °C and −60 °C had favorable impacts on the quality maintenance of snowflake beef compared to −18 °C. These findings provide a theoretical basis for effective stability of snowflake beef quality during frozen storage.

Changes in lipid properties of duck egg yolks under extreme processing conditions

The changes in lipid properties of duck egg yolks during processing may affect the quality of egg yolks. In this paper, various physicochemical and instrumental methods were used to study the changes of lipid characteristics of duck egg yolks under extreme processing conditions such as high salt, high salt-heat synergy and strong alkali. The results showed that both the high salt and high salt-heat treatments resulted in the decrease of the moisture content and the increase of the oil exudation of egg yolks. The iodine value of the lipid extracted from salted egg yolks with or without heat treatment decreased. However, strong alkali treatment increased the moisture content of egg yolks, and the oil exudation increased at first and then decreased. The iodine value of the lipid obtained from preserved egg yolks showed an overall trend with first increase and then decrease, and the saponification value of the lipid got from preserved egg yolks was lower than the lipid got from the raw salted egg yolks. According to the conjugated diene acid value and thiobarbituric acid value, the lipid of egg yolks was oxidized to different degrees under the three processing conditions. At the end of pickling, the fatty acid content of the lipid acquired from egg yolks all increased. Therefore, all three extreme treatments significantly changed the lipid properties of duck egg yolks.

Effects of storage temperature and packaging material on physico-chemical, microbial and sensory properties and shelf life of extruded composite baby food flour

Background

The storability and eventual quality of flour is influenced by the optimality of the storage conditions. The present study assessed the effect of storage temperature on extruded composite flour packed in different packages.

Methods

Oats, soybean, linseed and premix (sugar, salt, Moringa & fenugreek) were blended and extruded. The extruded flour was packed in paper, polyethene and woven polypropylene bags and stored at -18, 25, 35, 45 °C. Moisture content, fat content, water activity, bulk density, aroma, color and microbial load were measured fortnightly for three months.

Results

The physico-chemical and sensory properties of the flour samples were significantly (p < 0.05) affected by the storage temperature and packaging material along the storage period. The highest moisture content (4.02 g/100g) was recorded on the 90^th day of storage for flour stored in polypropylene bag at -18 °C. The highest water activity (0.68) was recorded from flour packed in woven polypropylene bags stored at 25 °C for 45 days and flour packed in paper bags at days 15 and 45 at 35 °C, whereas the lowest aw (0.18) was recorded for samples stored for 90 days at 45 °C packed in polypropylene bags. Flour samples packed in polyethene bags retained their moisture content. The highest bulk density (0.61 g/ml) was recorded on day 0 and it decreased gradually where the lowest value (0.51 g/ml) was recorded for flour samples packed in polypropylene for 90 days at -18 °C. The highest fat content (9.4g/100g) was recorded at day 0 and it decreased slowly during the storage period where the lowest value (8.2g/100g) was measured from flour samples packed in polypropylene for 90 days at 45 °C. None of the treatments had a microbial load exceeding the standards which could be attributed to extrusion of the food samples. The highest aroma and color liking scores were recorded on the 90^th day of storage for woven polypropylene packed flour at 25 °C and for polyethylene packed flour at -18 °C, respectively. The predicted shelf life was 17 months for samples packed in polyethene and kept at 25 °C and 6.2 months for samples packed in polypropylene and held at 45 °C.

Conclusions

Woven polypropylene flour bags could be laminated or have a polyethylene liner, so that the flour does not absorb moisture. Shelf stability of the flour can help its successful marketing and distribution.

Effects of dietary hop (Humulus lupulus L.) β-acids on quality attributes, composition and oxidative stability of pork meat

BACKGROUND

The effects of dietary levels of hop β-acids on physical attributes, lipid oxidation and chemical composition of pork meat were evaluated. Thirty-two castrated male pigs obtained from a complete block design feeding experiment (6.23 ± 0.42 kg initial body weight (BW) to 20.45 ± 0.95 kg final BW) and fed diets supplemented with 0, 120, 240 or 360 mg kg^-1 hop β-acids during 35 days were slaughtered to sample longissimus dorsi muscle for meat analysis.

RESULTS

No effects (P > 0.05) of dietary hop β-acids were observed on meat physical attributes. Quadratic effects (P < 0.05) of hop β-acids were observed on lipid and protein contents and on thiobarbituric acid-reactive substance (TBARS) values of meatballs, whose equations allowed the estimation of dietary hop β-acid levels of 176, 169 and 181 mg kg^-1 to provide up to 16.20% lipid reduction, 1.95% protein accretion and 23.31% TBARS reduction respectively.

CONCLUSION

Dietary hop β-acids fed to pigs might reduce lipid, increase protein and reduce lipid oxidation without affecting physical attributes of the pork meat. © 2017 Society of Chemical Industry.

The Relationships between Muscle Fiber Characteristics, Intramuscular Fat Content, and Fatty Acid Compositions in M. longissimus lumborum of Hanwoo Steers

The objective of this study was to investigate the relationship between muscle fiber characteristics, intramuscular fat (IMF) content, and fatty acids composition in longissimus lumborum (LL) muscle from Hanwoo steers. The LL muscles were obtained from four quality grades (QG) carcasses and subjected to histochemical analysis. There were significant (p<0.05) differences in fiber number percentage (FNP) and fiber area percentage (FAP) of muscle fiber types among muscles from four QGs. Both FNP and FAP of type I increased while those of type IIB decreased with increasing QG from QG 2 to QG 1⁺⁺ (p<0.05). Also, with increasing QG, the saturated fatty acid (SFA) proportion decreased while monounsaturated fatty acid (MUFA) increased significantly (p<0.05). IMF content was positively correlated with both FNP and FAP of type I, but negatively correlated with those of type IIB. The proportions of SFA and MUFA were significantly (p<0.001) correlated with both type I and IIB composition. These results implied that muscle fiber type composition is an important factor influencing fatty acid composition in LL muscle of Hanwoo steer.

Increased intramuscular fat improves both 'chewiness' and 'hardness' as defined in ISO5492:1992 of beef Longissimus muscle of Holstein × Japanese black F1 steers

It is considered that high-fat beef is more 'tender' than low-fat beef in Japanese consumers. However, 'tenderness' which has been an important beef characteristic, has not been commonly defined. ISO5492:1992 provides internationally established items for sensory texture analysis with simple definitions, and the items classified under 'chewiness' and 'hardness' as defined in the international standard are characterized as useful texture descriptors for beef. The aim of this study was to investigate the effects of intramuscular fat on beef texture using the ISO5492 texture vocabulary. Longissimus muscles were harvested from Holstein × Japanese black F1 beef steers with different intramuscular fat levels and were subjected to sensory tests by a trained panel using ISO5492:1992 texture terms. Correspondence analysis indicated that the intramuscular fat level was related to both 'chewiness' and 'hardness' and the intensities of these characteristics decreased as intramuscular fat increased. These findings suggest that intramuscular fat improves both 'chewiness' and 'hardness' as defined in ISO5492:1992.