NSString *input = @"Sodium Nitrite E250 is a food additive ...";
for (NSString *str in @[ @"E100", @"E101", @"E1500" ])
    if ([input rangeOfString:str].location != NSNotFound) {
        // do something
    }

NSArray *ary = [NSArray arrayWithObjects:@"E250", nil]; // String Data to find in String
NSMutableArray *aryFoundData = [[NSMutableArray alloc]init];

for (int i=0; i<ary.count; i++) {
    NSString *str = @"Your String E250";
    if ([str containsString:[ary objectAtIndex:i]]) {
        [aryFoundData addObject:[ary objectAtIndex:i]];
    }
}

// Now aryFoundData contains all the data which are available in string

NSString *testString = @"Sodium Nitrite E250 is a food additive that gives cured meats, such as ham E103, bacon, hot dogs, frankfurters, smoked fish E1255 corned beef, their characteristic red colour and flavour.";

NSRegularExpression *regex = [[NSRegularExpression alloc] initWithPattern:@"E\d+" options:0 error:nil];

[regex enumerateMatchesInString:testString options:0 range:NSMakeRange(0, testString.length) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
    NSLog(@"%@", [testString substringWithRange:result.range]);
}];