Variations Of Pomegranate Juice Phenolics And Healthcare Function Properties During Processing And In Vitro Digestion

Pomegranate fruit and juices received great interest for their health benefits, due to their highpolyphenols content and related antioxidant ability. Because peel has more polyphenols than aril, twoimportant problems have to be addressed at first to develop high quality pomegranate juices. One is how tochoose peel amount, which has a positive correlation with total polyphenols, antioxidant ability, bitternessand color density of the juice. Moreover, variety，maturity，processing technology and fruit storageconditions influence the best dosage of peel. Another is whether peel addition really improve juicepolyphenols bioavailability and in vivo function, because only the juice polyphenols released from foodmatrix are bioaccessible and active in the gut, and in the upper gastrointestinal tract (UGI) they will undergoa series of non-biological physical and chemical changes and enzymatic hydrolysis then become morebioaccessible and active, which may be influenced by peel tannins and other substances.In present study,3pomegranate cultivars (Jingpitian, Sanbaitian and Suanshiliu) of Lintong, Shaanxi,China were used to prepared pomegranate juice (PJ) and other samples. The sample’s physicochemicalcharacteristics, polyphenols compositions, sensory properties and antioxidant capacities were measured tostudy the effects of variety, peel proportion, fruit storage and processing on the phenolics profile andfunctional property of the products. Then, PJs were digested in an in vitro UGI model to study theirpolyphenols contents and several in vitro functions changing trends in the UGI.The results show that aqueous ethanol extracts of rind (ER), aril-mesocarp-epicarp juicing marc(EAME), aril-mesocarp-epicarp mixture juice (AMEJ), and aril juice (AJ) had different polyphenolscompositions. Total polyphenols content (TPC), total flavonoids content (TFC), and total tannins content(TTC) of them were all in the order of ER>EAME>AMEJ>AJ, total anthocyanins content (TAC) of themwere in the order of EAME>AMEJ>AJ>ER, and punicalagin content of them were in the order ofER>AMEJ>EAME>AJ. Peel addition significantly promoted PJ’s TPC and TFC but decreased its TAC.TPC and TAC increased a little by color protection and enzymolysis, but decreased by clarification,filtration, and sterilization. SSC and total sugar content (TSC) of PJs increased by color protection,enzymolysis, clarification, filtration, but decreased by sterilization. Fruit storage for2months increasedtotal acid content (TA) but decrease polyphenol content, antioxidant activity and sensory score of juice.The antioxidant activities of the4products were also very different. Comparing at same dosages ofTPC, total antioxidant activities (TAA and TAA intensities) of them were in the order of ER>AJ>EAME>AMEJ, total reduction capacity (TRC and TRC intensities) of them were in the order ofAMEJ>ER>EAME>AJ, ABTS+scavenging capacities (ARS and ARS intensities) of them were in theorder of AMEJ≧ER>AJ>EAME, DPPH scavenging capacities (DRS and DRS intensities) of them werein the order of ER>AMEJ>EAME>AJ.SJFA (storable juice of JPT aril) had higher TAA than SJFAME (storable juice of JPTaril-mesocarp-epicarp mixture), but SJFA had lower TRC, HRS, DRS, ARS of SAS than SJFAME. Thisindicates peel addition can effectively promote juices radical scavenging capacity.Results of the synchronization study of15kinds juices (3serials of S1, S2, S3, S4, and S5juices madefrom whole arils+0,1/4,2/4,3/4and4/4peel mixtures of JPT, SBT, and SSL respectively) showed thatSSC of most of SSL juices decreased while, SBT and JPT juices were fluctuated along with increasingpeel amount. Processing slightly influence SSC of PJs. TA of the3serial juices always showed the order ofSSL>JPT>SBT although TA of JPT and SBT juices increased but TA of SSL juices decreased when peelamount increased. TA of JPT and SBT juices increased but SSL juices did not vary after processing. TSC ofthe3serial juices were always in the order of JPT>SBT>SSL. Increasing peel amount, TSC decreased withdifferent extent for different varieties because peel contains less reducing sugar than aril and differentvarieties had different peel: aril: seed (w/w/w). Juice color and polymeric color densities were roughly inthe order of JPT≧SSL>SBT. They increased with increasing peel amount. The sensory scores of the3varieties S1and S3juices had certain difference, and SBT S1and S3had higher composite score than JPTand SSL S1and S3. Peel addition mainly deepen the color, increase bitter taste and slightly change aroma ofPJs, and little decrease composite scores of JPT and SBT juices but increase that of SSL juice.TPC of the3varieties Juices were roughly in the order of SSL>JPT>SBT, juice TTC of them were inorder of SBT>JPT>SSL, while, juice TFC of them were similar with each other. TPC, TFC and TTCsignificantly increased with increasing peel amount. Processing significantly increased TPC in most caseswhile, TFC remain stable. Processing increased TTC of JPT and SSL juices but did not change TTC of SBTjuices. Juice TAC of the3varieties were in the order of SSL≧JPT>>SBT. TAC decrease with increasingpeel amount. Processing had no effect on TAC. S1and S3juices of different varieties had very similar UVscanning spectrum and HPLC chromatogram，which indicates phenolics constitutes of aril juices andaril-peel mixture juices of different varieties had little difference. In addition, ellagitannin was the mainconstitute in all juices. AMEJ had more than200times higher punicalagin than AJ, which indicates peeladdition greatly increase juice’s punicalagin content.Antioxidant activities of the3varieties juices were roughly similar. TRC, DRS, and O-2scavengingcapacities (SAS) of them increased gradually along with peel addition. In most cases,25%of peel additionhad greatly increased TRA,50%of peel addition had greatly increased DRS, and75%of peel addition had greatly increased SAS.Fruits storage at4°C for2months increased juices’ SSC and decreased TA and TSC but improved theirprocessing stabilities. Fruits storage increased TPC, TFC and TTC of all fresh aril juices of the3varieties,while, TAC of SSL fresh aril juice increased but TAC of JPT fresh aril juice decreased. Fruits storageincreased TPC, TFC and TTC processing stabilities for both S1and S3juices of the3varieties, andincreased TAC processing stabilities for JPT juices while, decreased for SSL juices.JPT juices (JFA and JFAME), net aril juices (JPTAJ, SBTAJ, and SSLAJ) and aril-peel(whole arie+1/2peel) juices (JPTPJ, SBTPJ, and SSLPJ) polyphenols, antioxidant ability, nitrite elimination andnitrosamine inhibitory ability and anti-inflammatory ability variations in in vitro UGI model showed that,TPC, TFC and TAC of both JFA and JFAME decreased in the4stages of simulated digestion-absorptiondue to dilution and loose. Taking out the dilution effect, polyphenols lost was limited, even increase ingastric and intestinal stages, especially for JFA. TPC of JPTAJ, SBTAJ and SSLAJ were much lower thanTPC of JPTPJ, SBTPJ and SSLPJ respectively. TPC gradually reduced in digestion process and very littleTPC remained in simulated serums. TPC of APJs reduced faster than AJs, TFC of JPTAJ and SBTAJgradually decreased and very little TFC remained in simulated serums. While, TFC of SSLAJ, JPTPJ,SSLPJ and SBTPJ decreased at oral and gastric digestion stages, but greatly increased in intestinal stage,and certain proportion of TFC remain in simulated serums. TTC of AJs lowers than TTC of APJs. They allgradually decreased along with digestion process. TTC of APJs decreased more quickly than that of AJs. Inall simulated serums, TTC were very low. Taking out the dilution effect, juice polyphenols loses for allvarieties were limited. In oral, gastric and intestinal digestion stages, TAA and TRC reduced significantly.In simulated serums, TAA of JFA and JFAME increased as compared to their gastric digestion sampleswhile, TRC of them reduced by50%. Taking out the dilution factor, TAA and TRC loses were limited,even increase in some stages, especially for JFAME.TRC and DRS of APJs of the3varieties were higher than AJs and these differences kept in wholedigestion process. TRC of APJs reduced faster than AJs along with the process. TRC of simulated serumswere in the order of SSLPJ>JPTPJ>other juices. In oral and gastric digestion stages, DRS of APJs changedslightly while AJs increased significantly. In intestinal digestion stage, DRS of all juices reduced by90%.The simulated serums’ DRS of all APJs and SSLAJ were higher, while that of JPTAJ and SBTAJ were lowerthan corresponding intestinal digestion samples. SAS of AJs of the3varieties were higher than APJs. SASof all juices increased gradually in the oral and gastric digestion stages, but decreased in intestinal digestionstage, and increased again in simulated serums. In short, pomegranate juices partly keep their antioxidantactivities during in vitro digestion processing. This is consistent with them actually keep their most ofpolyphenols. In oral and gastric digestion stages, nitrosamine inhibition ability (NIA) of the all juices decreased butNIA of SSLAJ and SBTPJ increased in gastric stage. In intestinal digestion stage, NIA reduced in allsamples except SSLAL. NIA of AJs’ simulated serums were lower than but NIA of APJs’ simulated serumswere equal or higher than corresponding intestinal digestion samples. In oral digestion stage, nitriteelimination ability (NEA) of most juices increased a little but that of JPTPJ and SSLPJ decreased. In gastricand intestinal digestion stages, NEA of all samples decreased. Simulated serums almost had no NEA, exceptJPTAJ serum.In oral digestion stage, the protein denaturation inhibition capacity (PDIC) of AJs decreased about half,while PDIC of APJs increased several times. In gastric digestion stage, PDIC of APJs decreased while AJsdecreased. In intestinal digestion stage, PDIC of all samples increased dramatically. The simulated serumsof AJs remain higher PDIC than that of APJs. In oral digestion stage, xanthine oxidase inhibition activity(XOIA) of SSLPJ significantly higher than that of other samples. In gastric digestion stage, XOIA of allsamples significantly increased except the sample of SSLPJ. In intestinal digestion stage, XOIA of mostsamples significantly increased except the samples of SBTPJ and SSLPJ significantly decreased. Simulatedserums of SSLAJ, SBTPJ and SSLPJ had much higher XOIA, and simulated serum of JPTPJ had a littlehigher XOIA than corresponding intestinal digestion samples. While simulated serums of JPTAJ andSBTAJ had lower XOIA than corresponding intestinal digestion samples.To sum up, the present research proved that different pomegranate products have much different TPC,TFC and TAC. Punicalagin is the richest phenolic compound in them. Peel addition in juice raw materialgreatly increase TPC, decrease TAC, deepen color, and increase bitter taste of the juice, but decrease TA ofSSL juice. Pomegranate storage at4°C for2month can little increase TPC of juices. Clarification, filtrationand sterilization decrease TPC and TAC of juices. During in vitro digestion process pomegranate juicepolyphenols and in vitro function decreased significantly mainly due to dilution effect. Taking out thedilution effect, polyphenols and functions loses are limited, even increase in some digestion stages. AJs andAPJs have certain differences in changing speeds and trends. However, the same kind juices made fromdifferent varieties have closely similar changing trends.