Effect Of Ultra-high-pressure Treatment On Physical Properties And Volatile Compounds Of Butter

Butter is one of the most important products of dairy industry, and also the essential raw material of slap-up bakery products. However, with low content of mid-short chain fatty acids, which have dairy flavor characteristics, the aroma of natural butter is insufficient. Coupled with the high cost, butter is often replaced by margarine. To aromatize butter and make it a dairy flavoring base, is conductive to upmarket the product as well as reduce the cost. For this, ultra-high-pressure?UHP? treatment technology was applied on butter and, UHP effects on physical properties, volatile compounds and thermal stability of the butter were studied. It would be helpful for finding new ways to aromatize dairy products and accelerating the application of UHP treatment technology on dairy products.Conclusions were drawn as follows:?1? Natural butter was mainly composed of more than 80% of fat, 15% of water and a small amount of protein. There was very a little content of free fatty acids, mainly exist in the form of fatty acid ester.?2? The melting point, crystal form, solid fat content, and texture of butter were impacted by pressure change, while little influence on acid value. As pressure increased, butter melting point went from rise to decline, and up to more than 6o C increase at 200 MPa.Butter crystal form shifted from typical ?' form to the mix of ?' and sub ? forms. It tended to be ? form with better thermal stability and higher melting point, mainly, however, ?'form. Solid fat content and hardness of butter at low temperature were significantly reduce and the spreadability were markedly improved by UHP treatment. There were the same texture improvements at 100, 200, 300 MPa treatment groups.?3? Among all butter samples, respectively treated at 100, 200, 300, 400, 500 MPa for 10,20, 30 min, the 100 MPa with 20 min treated group owned the best fragrance enhancement effect.?4? UHP technology could promote the release of mid-short chain fatty acids in butter with a 8.24% increase compared to natural butter, while the effect was not so well as enzymatic modification. Compared with enzymatic modification, technology of UHP treatment and enzymatic modification could further release mid-short chain fatty acids in butter and enhance the aroma. Namely, UHP butter has greater sensitivity of lipase?Novozym Palatase 20,000 L?.?5? The main volatile compounds of natural butter concentrated in ketones, esters,lactones, heterocycles and aromatic compounds?about 70%?. As the relative contents of acids, alcohols, lactones and aldehydes all increased after UHP treatment, the butter components became more dispersed and, the fragrance turned to be abundant and gentle.The compounds of 2-heptanone, 2-nonanone, 2-undecanone and n-propyl acetate made great contributions to aroma of natural butter and UHP butter. Besides, aldehydes including3-hydroxy-butanal, heptanal and nonanal were only found in UHP butter. Butyric acid,caproic acid, heptanoic acid, octanoic acid, and decanoic acid as the representative of fatty acids?90%? and esters?8%? together constituted the main components of enzymatic modified butter aroma. Treated with the technology of UHP treatment and enzymatic modification, butter volatile fatty acids could further increase about 5%, accompany with the increase of many other volatile compounds. In addition, acids, esters and ketones made great contributions to a more rich and full butter aroma. There was obviously different in volatile compounds between commercially available buttery essence and butter samples.With simple and concentrated compounds, the aroma of commercially available buttery essence seemed unnatural and less gentle.?6? Cookies made from butter aromatized by the technology of UHP treatment and enzymatic modification, tasted best.?7? Thermal stability in butter could be improved by UHP technology, however, greatly reduced by technology of UHP treatment and enzymatic modification. The worst one came to be commercially available buttery essence.?8? ATR-FTIR spectra display that the main components of butter showed little change after UHP treatment. Due to significant component changes in enzymatic modified butter,the ATR-FTIR spectra were slightly different in the bands of 1800-1700 cm^-1 and1240-1100 cm^-1, especially strong band arising at ¹710 cm^-1, compared with natureal butter. Infrared spectra analysis also proved that components in commercially available buttery essence and butter samples were completely different.