Shelf Life Study Of Raw And Roasted Almonds For Chinese Market

Due to the strong geoclimate constraints and brief harvest season,the storage and transportation of almonds becomes an important part of the global sales.Its storage quality and shelf life is significant.In this research,we investigated the changes in moisture contents,textural properties,lipid oxidation(free fatty acids(FFA),peroxide values(PV)and conjugated dienes(CD)),volatiles and sensory quality of raw California almonds(packed in sealed PE bag and unlined carton)and roasted almonds(packed in sealed PE bag and sealed vacuum PE bag).under different temperature,humidity,and shelf life,and concluded with the shelf life of almonds.The study was also expected to provide a theoretical basis for the storage of other nut products.Raw almonds were stored for 660 days and Roasted almonds were stored for 360 days.The results are as follows:1、The changes of moisture contents and textural properties:The moisture contents of raw almonds packed in unlined carton presented a tendency of an increasing trend except at 35℃.At the same temperature,the higher the relative humidity,was the faster the moisture content of almonds rose,but the hardness and brittleness were quite on the contrary.The change of moisture contents of raw almonds paceked in sealed PE bag was not obvious.But its textural properties became worse.It is not apparent for the changes of moisture contents and textural properties of the two types of roasted almonds.2.The changes of lipid:At the same condition,the higher relative humidity,was the faster free fatty acids of raw almonds rose.It showed no significant influence of different temperature,humidity and packaging conditions on the roasted almonds.The peroxide values of raw almonds increased firstly and then decreased during the storage,the conjugated dienes increased with the increasing temperature.The peroxide values of raw almonds at 4℃ and 15℃was stable.The conjugated dienes increased with the increasing temperature.As to the roasted almonds,peroxide values and conjugated dienes both increased,and the conjugated dienes were affected significantly by the temperature and humidity.3.The changes of volatiles:volatile components of almonds were extracted by headspace solid-phase microextraction and were identified by gas chromatography and mass spectrometry(GC-MS).An DVB/CAR/PDMS,a temperature of 80℃,adsorption time of 15 min and 5:1 split ratio were determined as the optimum adsorption conditions.44 volatile compounds and 7 major aroma volatile components were identified in raw almonds and 56 volatile compounds and 14 aroma volatile components were identified in roasted almonds under the optimum adsorption conditions.The total volatiles of almonds firstly increased then decreased followed by an increase and finally decreased.The unlined carton was not appropriate for relatiling volatile of raw almonds.There was no significant difference between the two styles of packing.It was favorable to accumulate the flavor at 4℃ and 15℃.4.The changes of sensory quality:The acceptance rates initial baseline of raw and roasted almonds were 66.9%and 96.3%,the sensory score initial baselines were 67.9 and 76.2,and the thresholds were 47.6 and 58.3,The sensory quality decreased as the temperature and humidity increased.The sensory quality of raw almonds packed in sealed PE bag was better than that packed in unlined carton.The sensory quality of roasted almonds packed in sealed PE bag was better than that packed in sealed vacuum PE bag at low temperature.While it showed an opposite tendency at high temperature.In conclusion,the quality of raw almond packed in sealed PE bag was more stable.The different packing methods had little impact on the roasted almonds.We recommend that the sealed PE bag should be chosen for the roasted almonds considering the cost.The quality of almonds was the most stable at 4℃.It was acceptable that the almonds stored at 15℃and relative humidity in 50%.